Pianotech

Hi all. I am rebuilding a Mason B grand which has 7mm diameter agraffe threads. A colleague refinished the plate and removed the agraffes and returned them to me for polishing. He claims that there were no shims (and that they were kept in the correct order, which I now question). I have never known there to not be agraffe shims. 

None of the agraffes line up perpendicular. Not one. So, the claim that there were no shims and/or the order was maintained at this point I disbelieve. Ok, done with my grousing. 

I need to install shims, but the 7mm thread diameter is larger than what I can purchase from supply houses, which is 17/64 (.266"). 7mm imperial equivalent is .276". 

Does anyone have suggestions of where I can source them? TIA.

The threads in an agraffe are never at the same starting point in every one. Take a handful of agraffes and try them all in the same threaded hole and they will all line up a little differently. Refinishing the plate probably changed the depth of the agraffe holes so even if your colleague returned them in the original order the new paint thickness is probably the culprit for them no longer lining up. 

Shims are probably the preferred way to go, but Isaac Sadigursky taught me a method to align the agraffes that does not involve shims. Agraffes are made of brass, which is pretty soft. The bottoms of them are not flat but have a slight wedge shape to them so that they may be sort of tightened/squished down to the desired height and alignment. What Isaac did was to glue some not too coarse sandpaper to a piece of wood and drill a hole through it at the same diameter as the agraffe screw threads. He would then put the offending agraffe into the hole and gently sand the bottom of it. The flat surface of the wood guaranteed that the sanding would provide an evenly sanded surface, with no bumps or angles. He would sand just a small amount off, try the agraffe in the hole, and repeat until it lined up perfectly. As Isaac used to like to say, "It works."

Hi all. I am rebuilding a Mason B grand which has 7mm diameter agraffe threads. A colleague refinished the plate and removed the agraffes and returned them to me for polishing. He claims that there were no shims (and that they were kept in the correct order, which I now question). I have never known there to not be agraffe shims. 

None of the agraffes line up perpendicular. Not one. So, the claim that there were no shims and/or the order was maintained at this point I disbelieve. Ok, done with my grousing. 

I need to install shims, but the 7mm thread diameter is larger than what I can purchase from supply houses, which is 17/64 (.266"). 7mm imperial equivalent is .276". 

Does anyone have suggestions of where I can source them? TIA.

Hi all. I am rebuilding a Mason B grand which has 7mm diameter agraffe threads. A colleague refinished the plate and removed the agraffes and returned them to me for polishing. He claims that there were no shims (and that they were kept in the correct order, which I now question). I have never known there to not be agraffe shims. 

None of the agraffes line up perpendicular. Not one. So, the claim that there were no shims and/or the order was maintained at this point I disbelieve. Ok, done with my grousing. 

I need to install shims, but the 7mm thread diameter is larger than what I can purchase from supply houses, which is 17/64 (.266"). 7mm imperial equivalent is .276". 

Does anyone have suggestions of where I can source them? TIA.

Hi all. I am rebuilding a Mason B grand which has 7mm diameter agraffe threads. A colleague refinished the plate and removed the agraffes and returned them to me for polishing. He claims that there were no shims (and that they were kept in the correct order, which I now question). I have never known there to not be agraffe shims. 

None of the agraffes line up perpendicular. Not one. So, the claim that there were no shims and/or the order was maintained at this point I disbelieve. Ok, done with my grousing. 

I need to install shims, but the 7mm thread diameter is larger than what I can purchase from supply houses, which is 17/64 (.266"). 7mm imperial equivalent is .276". 

Does anyone have suggestions of where I can source them? TIA.

Dave Conte and All,

I think I understand the predicament. I also think, most respectfully, several of the respondents do not fully understand the predicament. Let's start at the beginning.

First: Dave Conte: is this a vintage M&H model B? If so, it will have employed vintage, flat-bottomed agraffes. The replies you are receiving suggest these agraffes were/are modern, conical-bottomed agraffes with the sacrificial crush ring permitting them to be lined up, by slight over-rotation, perpendicular to the unison centerlines. I do not believe this is the case with your M&H B, so the comments that refer to same may not be helpful.

Next: I have never been aware of any plate refinishing process that distorts the dimensions (depths) of the drilled pockets that receive the agraffes in the plate's agraffe aprons. Thus, those elevations have not changed, unless the refinisher painted the floors of the pockets. If this is the case perhaps removing this paint (ugh) would solve your problem. 

Next: We need to discuss so-called "string leveling" via agraffe height. There are (typically) 36 threads per inch on an agraffe stump. An agraffe is a bi-directional device, meaning we can accept its correct rotation in the plate either at zero degrees to the unison centerline or 180 degrees to the unison centerline. Translation: we aren't concerned if the "front" or the "rear" of the agraffe is perpendicular to the unison centerline. Thus, the agraffe now effectively possesses 72 threads per inch. If we divide 1 inch by 72 we arrive at (rounded off) 0.014". This means that assuming the pockets drilled into the plate are all at the same elevation (okay, cut me a little slack here) no unison string height from one note to the next is more than .014" out of elevation alignment with its neighbor. I am not aware of any manufacturer who installs agraffes one at a time, measures its string hole height(s) above the keybed, makes corrections as necessary by shimming or brass removal, and then moves on to the next. I think we can therefore deduce that a deviation from one unison to the next of .014" is acceptable in our industry for design, manufacture, and regulation purposes of a grand piano. Thus, I don't believe any manufacturer or rebuilder needs to concern him/herself with "leveling" adjacent strings/unisons via the agraffes. We have bigger fish to fry. I don't even think it's practically possible without some sort of laser detection. (If Fazioli uses something like this, more power to them. I know Steinway does not.) And how precise is the hammer line, or the surfaces of the tops of the hammers? How precise is the let-off, and on and on? If we're within .014" on all this we're doing pretty well. Also, BTW, I know of no current manufacturer who uses modern crushable agraffes who removes them, one by one, to remove brass from the conical shell - they merely over-rotate until the agraffe is perpendicular, or try that agraffe in a different hole to see what results. That's the beauty of the design. 

So with all this, where does Dave Conte stand? As we know, the agraffes in vintage M&H pianos are oddballs. Short of drilling out the plate's agraffe holes, tapping them for modern inserts, installing the inserts, and then installing modern 7/32" or 1/4" agraffes with sacrificial crush rings, Dave will need to remove brass material from the bottom of each vintage M&H flat-bottomed agraffe so that when it snugs into the plate pocket it will be perpendicular to its unison centerline. And if the vintage M&H agraffes possess 36 threads per inch, he'll be within .014" of adjacent unison elevation, and for the most part all will be well in the world.

David G. Hughes, RPT

Baltimore Chapter

Hi all. I am rebuilding a Mason B grand which has 7mm diameter agraffe threads. A colleague refinished the plate and removed the agraffes and returned them to me for polishing. He claims that there were no shims (and that they were kept in the correct order, which I now question). I have never known there to not be agraffe shims. 

None of the agraffes line up perpendicular. Not one. So, the claim that there were no shims and/or the order was maintained at this point I disbelieve. Ok, done with my grousing. 

I need to install shims, but the 7mm thread diameter is larger than what I can purchase from supply houses, which is 17/64 (.266"). 7mm imperial equivalent is .276". 

Does anyone have suggestions of where I can source them? TIA.

Thank you David Hughes for that very elaborate and informative answer to Dave Conte's original question.  I learned a lot from your answer, but I did want to add to it if that's okay.  Specifically about what is being done to achieve accuracy with the modern Steinway grand and what can reasonably be expected.

Steinway is installing agraffes into a plate that is cast using no-bake casting (past 5 years), and machined using CNC machinery for (among other things) the location and surface of the agraffe holes.  With the depth precisely set as a reliable baseline, our process is as follows:

Turn in the agraffe using a breakaway torque of 9-11nm and observe where the agraffe stops.  It MUST stop between [1o'clock 7 o'clock] and [2 o'clock 8 o'clock]

If it stops too early or too late, it must be changed out. (similar to what Geoff recommended earlier in the thread).  Since Steinway is a manufacturer, we are able to have many more agraffes on hand than necessary for a single piano and this process is not only practical, but also efficient.

The agraffe which has stopped naturally in the "green zone" is then finished by tightening square to the string (3 o'clock 9 o'clock)

What this process allows us to do is rely on the depth of the agraffe hole set by the CNC machine and the agraffes themselves which are machined to tolerances of +/- 0.001"

I'm going to use the same back of the napkin math here, but since the correct stopping position is 1 out of 12 possibilities instead of 1 out of 2 possibilities, the 36 thread/inch agraffe combined with the process of swapping them out til one stops in the green zone means that we effectively have 432 threads per inch to work with.  This is a little more than a tolerance of 0.002"  (another way of expressing this is to say +/-0.001") 

Once we get the agraffes tightened in this way, they end up with a consistency that is much closer to +/-0.002" (which includes the variances in the agraffes themselves) all without the need for a laser level.

Any tolerance in the depth of the agraffe hole resulting from the CNC machining of the plate would be added to the figure I just came up with, but I would honestly be surprised if it were more than 0.001"

For anyone reading this who happens to be in New York on a weekday morning, email me in advance of your visit and I'd be happy to attempt to arrange a factory tour to show you what I just described along with many other things

Dave Conte and All,

I think I understand the predicament. I also think, most respectfully, several of the respondents do not fully understand the predicament. Let's start at the beginning.

First: Dave Conte: is this a vintage M&H model B? If so, it will have employed vintage, flat-bottomed agraffes. The replies you are receiving suggest these agraffes were/are modern, conical-bottomed agraffes with the sacrificial crush ring permitting them to be lined up, by slight over-rotation, perpendicular to the unison centerlines. I do not believe this is the case with your M&H B, so the comments that refer to same may not be helpful.

Next: I have never been aware of any plate refinishing process that distorts the dimensions (depths) of the drilled pockets that receive the agraffes in the plate's agraffe aprons. Thus, those elevations have not changed, unless the refinisher painted the floors of the pockets. If this is the case perhaps removing this paint (ugh) would solve your problem. 

Next: We need to discuss so-called "string leveling" via agraffe height. There are (typically) 36 threads per inch on an agraffe stump. An agraffe is a bi-directional device, meaning we can accept its correct rotation in the plate either at zero degrees to the unison centerline or 180 degrees to the unison centerline. Translation: we aren't concerned if the "front" or the "rear" of the agraffe is perpendicular to the unison centerline. Thus, the agraffe now effectively possesses 72 threads per inch. If we divide 1 inch by 72 we arrive at (rounded off) 0.014". This means that assuming the pockets drilled into the plate are all at the same elevation (okay, cut me a little slack here) no unison string height from one note to the next is more than .014" out of elevation alignment with its neighbor. I am not aware of any manufacturer who installs agraffes one at a time, measures its string hole height(s) above the keybed, makes corrections as necessary by shimming or brass removal, and then moves on to the next. I think we can therefore deduce that a deviation from one unison to the next of .014" is acceptable in our industry for design, manufacture, and regulation purposes of a grand piano. Thus, I don't believe any manufacturer or rebuilder needs to concern him/herself with "leveling" adjacent strings/unisons via the agraffes. We have bigger fish to fry. I don't even think it's practically possible without some sort of laser detection. (If Fazioli uses something like this, more power to them. I know Steinway does not.) And how precise is the hammer line, or the surfaces of the tops of the hammers? How precise is the let-off, and on and on? If we're within .014" on all this we're doing pretty well. Also, BTW, I know of no current manufacturer who uses modern crushable agraffes who removes them, one by one, to remove brass from the conical shell - they merely over-rotate until the agraffe is perpendicular, or try that agraffe in a different hole to see what results. That's the beauty of the design. 

So with all this, where does Dave Conte stand? As we know, the agraffes in vintage M&H pianos are oddballs. Short of drilling out the plate's agraffe holes, tapping them for modern inserts, installing the inserts, and then installing modern 7/32" or 1/4" agraffes with sacrificial crush rings, Dave will need to remove brass material from the bottom of each vintage M&H flat-bottomed agraffe so that when it snugs into the plate pocket it will be perpendicular to its unison centerline. And if the vintage M&H agraffes possess 36 threads per inch, he'll be within .014" of adjacent unison elevation, and for the most part all will be well in the world.

David G. Hughes, RPT

Baltimore Chapter

Hi all. I am rebuilding a Mason B grand which has 7mm diameter agraffe threads. A colleague refinished the plate and removed the agraffes and returned them to me for polishing. He claims that there were no shims (and that they were kept in the correct order, which I now question). I have never known there to not be agraffe shims. 

None of the agraffes line up perpendicular. Not one. So, the claim that there were no shims and/or the order was maintained at this point I disbelieve. Ok, done with my grousing. 

I need to install shims, but the 7mm thread diameter is larger than what I can purchase from supply houses, which is 17/64 (.266"). 7mm imperial equivalent is .276". 

Does anyone have suggestions of where I can source them? TIA.

Thank you David Hughes for that very elaborate and informative answer to Dave Conte's original question.  I learned a lot from your answer, but I did want to add to it if that's okay.  Specifically about what is being done to achieve accuracy with the modern Steinway grand and what can reasonably be expected.

Steinway is installing agraffes into a plate that is cast using no-bake casting (past 5 years), and machined using CNC machinery for (among other things) the location and surface of the agraffe holes.  With the depth precisely set as a reliable baseline, our process is as follows:

Turn in the agraffe using a breakaway torque of 9-11nm and observe where the agraffe stops.  It MUST stop between [1o'clock 7 o'clock] and [2 o'clock 8 o'clock]

If it stops too early or too late, it must be changed out. (similar to what Geoff recommended earlier in the thread).  Since Steinway is a manufacturer, we are able to have many more agraffes on hand than necessary for a single piano and this process is not only practical, but also efficient.

The agraffe which has stopped naturally in the "green zone" is then finished by tightening square to the string (3 o'clock 9 o'clock)

What this process allows us to do is rely on the depth of the agraffe hole set by the CNC machine and the agraffes themselves which are machined to tolerances of +/- 0.001"

I'm going to use the same back of the napkin math here, but since the correct stopping position is 1 out of 12 possibilities instead of 1 out of 2 possibilities, the 36 thread/inch agraffe combined with the process of swapping them out til one stops in the green zone means that we effectively have 432 threads per inch to work with.  This is a little more than a tolerance of 0.002"  (another way of expressing this is to say +/-0.001") 

Once we get the agraffes tightened in this way, they end up with a consistency that is much closer to +/-0.002" (which includes the variances in the agraffes themselves) all without the need for a laser level.

Any tolerance in the depth of the agraffe hole resulting from the CNC machining of the plate would be added to the figure I just came up with, but I would honestly be surprised if it were more than 0.001"

For anyone reading this who happens to be in New York on a weekday morning, email me in advance of your visit and I'd be happy to attempt to arrange a factory tour to show you what I just described along with many other things

Dave Conte and All,

I think I understand the predicament. I also think, most respectfully, several of the respondents do not fully understand the predicament. Let's start at the beginning.

First: Dave Conte: is this a vintage M&H model B? If so, it will have employed vintage, flat-bottomed agraffes. The replies you are receiving suggest these agraffes were/are modern, conical-bottomed agraffes with the sacrificial crush ring permitting them to be lined up, by slight over-rotation, perpendicular to the unison centerlines. I do not believe this is the case with your M&H B, so the comments that refer to same may not be helpful.

Next: I have never been aware of any plate refinishing process that distorts the dimensions (depths) of the drilled pockets that receive the agraffes in the plate's agraffe aprons. Thus, those elevations have not changed, unless the refinisher painted the floors of the pockets. If this is the case perhaps removing this paint (ugh) would solve your problem. 

Next: We need to discuss so-called "string leveling" via agraffe height. There are (typically) 36 threads per inch on an agraffe stump. An agraffe is a bi-directional device, meaning we can accept its correct rotation in the plate either at zero degrees to the unison centerline or 180 degrees to the unison centerline. Translation: we aren't concerned if the "front" or the "rear" of the agraffe is perpendicular to the unison centerline. Thus, the agraffe now effectively possesses 72 threads per inch. If we divide 1 inch by 72 we arrive at (rounded off) 0.014". This means that assuming the pockets drilled into the plate are all at the same elevation (okay, cut me a little slack here) no unison string height from one note to the next is more than .014" out of elevation alignment with its neighbor. I am not aware of any manufacturer who installs agraffes one at a time, measures its string hole height(s) above the keybed, makes corrections as necessary by shimming or brass removal, and then moves on to the next. I think we can therefore deduce that a deviation from one unison to the next of .014" is acceptable in our industry for design, manufacture, and regulation purposes of a grand piano. Thus, I don't believe any manufacturer or rebuilder needs to concern him/herself with "leveling" adjacent strings/unisons via the agraffes. We have bigger fish to fry. I don't even think it's practically possible without some sort of laser detection. (If Fazioli uses something like this, more power to them. I know Steinway does not.) And how precise is the hammer line, or the surfaces of the tops of the hammers? How precise is the let-off, and on and on? If we're within .014" on all this we're doing pretty well. Also, BTW, I know of no current manufacturer who uses modern crushable agraffes who removes them, one by one, to remove brass from the conical shell - they merely over-rotate until the agraffe is perpendicular, or try that agraffe in a different hole to see what results. That's the beauty of the design. 

So with all this, where does Dave Conte stand? As we know, the agraffes in vintage M&H pianos are oddballs. Short of drilling out the plate's agraffe holes, tapping them for modern inserts, installing the inserts, and then installing modern 7/32" or 1/4" agraffes with sacrificial crush rings, Dave will need to remove brass material from the bottom of each vintage M&H flat-bottomed agraffe so that when it snugs into the plate pocket it will be perpendicular to its unison centerline. And if the vintage M&H agraffes possess 36 threads per inch, he'll be within .014" of adjacent unison elevation, and for the most part all will be well in the world.

David G. Hughes, RPT

Baltimore Chapter

Hi all. I am rebuilding a Mason B grand which has 7mm diameter agraffe threads. A colleague refinished the plate and removed the agraffes and returned them to me for polishing. He claims that there were no shims (and that they were kept in the correct order, which I now question). I have never known there to not be agraffe shims. 

None of the agraffes line up perpendicular. Not one. So, the claim that there were no shims and/or the order was maintained at this point I disbelieve. Ok, done with my grousing. 

I need to install shims, but the 7mm thread diameter is larger than what I can purchase from supply houses, which is 17/64 (.266"). 7mm imperial equivalent is .276". 

Does anyone have suggestions of where I can source them? TIA.

Thank you David Hughes for that very elaborate and informative answer to Dave Conte's original question.  I learned a lot from your answer, but I did want to add to it if that's okay.  Specifically about what is being done to achieve accuracy with the modern Steinway grand and what can reasonably be expected.

Steinway is installing agraffes into a plate that is cast using no-bake casting (past 5 years), and machined using CNC machinery for (among other things) the location and surface of the agraffe holes.  With the depth precisely set as a reliable baseline, our process is as follows:

Turn in the agraffe using a breakaway torque of 9-11nm and observe where the agraffe stops.  It MUST stop between [1o'clock 7 o'clock] and [2 o'clock 8 o'clock]

If it stops too early or too late, it must be changed out. (similar to what Geoff recommended earlier in the thread).  Since Steinway is a manufacturer, we are able to have many more agraffes on hand than necessary for a single piano and this process is not only practical, but also efficient.

The agraffe which has stopped naturally in the "green zone" is then finished by tightening square to the string (3 o'clock 9 o'clock)

What this process allows us to do is rely on the depth of the agraffe hole set by the CNC machine and the agraffes themselves which are machined to tolerances of +/- 0.001"

I'm going to use the same back of the napkin math here, but since the correct stopping position is 1 out of 12 possibilities instead of 1 out of 2 possibilities, the 36 thread/inch agraffe combined with the process of swapping them out til one stops in the green zone means that we effectively have 432 threads per inch to work with.  This is a little more than a tolerance of 0.002"  (another way of expressing this is to say +/-0.001") 

Once we get the agraffes tightened in this way, they end up with a consistency that is much closer to +/-0.002" (which includes the variances in the agraffes themselves) all without the need for a laser level.

Any tolerance in the depth of the agraffe hole resulting from the CNC machining of the plate would be added to the figure I just came up with, but I would honestly be surprised if it were more than 0.001"

For anyone reading this who happens to be in New York on a weekday morning, email me in advance of your visit and I'd be happy to attempt to arrange a factory tour to show you what I just described along with many other things

Dave Conte and All,

I think I understand the predicament. I also think, most respectfully, several of the respondents do not fully understand the predicament. Let's start at the beginning.

First: Dave Conte: is this a vintage M&H model B? If so, it will have employed vintage, flat-bottomed agraffes. The replies you are receiving suggest these agraffes were/are modern, conical-bottomed agraffes with the sacrificial crush ring permitting them to be lined up, by slight over-rotation, perpendicular to the unison centerlines. I do not believe this is the case with your M&H B, so the comments that refer to same may not be helpful.

Next: I have never been aware of any plate refinishing process that distorts the dimensions (depths) of the drilled pockets that receive the agraffes in the plate's agraffe aprons. Thus, those elevations have not changed, unless the refinisher painted the floors of the pockets. If this is the case perhaps removing this paint (ugh) would solve your problem. 

Next: We need to discuss so-called "string leveling" via agraffe height. There are (typically) 36 threads per inch on an agraffe stump. An agraffe is a bi-directional device, meaning we can accept its correct rotation in the plate either at zero degrees to the unison centerline or 180 degrees to the unison centerline. Translation: we aren't concerned if the "front" or the "rear" of the agraffe is perpendicular to the unison centerline. Thus, the agraffe now effectively possesses 72 threads per inch. If we divide 1 inch by 72 we arrive at (rounded off) 0.014". This means that assuming the pockets drilled into the plate are all at the same elevation (okay, cut me a little slack here) no unison string height from one note to the next is more than .014" out of elevation alignment with its neighbor. I am not aware of any manufacturer who installs agraffes one at a time, measures its string hole height(s) above the keybed, makes corrections as necessary by shimming or brass removal, and then moves on to the next. I think we can therefore deduce that a deviation from one unison to the next of .014" is acceptable in our industry for design, manufacture, and regulation purposes of a grand piano. Thus, I don't believe any manufacturer or rebuilder needs to concern him/herself with "leveling" adjacent strings/unisons via the agraffes. We have bigger fish to fry. I don't even think it's practically possible without some sort of laser detection. (If Fazioli uses something like this, more power to them. I know Steinway does not.) And how precise is the hammer line, or the surfaces of the tops of the hammers? How precise is the let-off, and on and on? If we're within .014" on all this we're doing pretty well. Also, BTW, I know of no current manufacturer who uses modern crushable agraffes who removes them, one by one, to remove brass from the conical shell - they merely over-rotate until the agraffe is perpendicular, or try that agraffe in a different hole to see what results. That's the beauty of the design. 

So with all this, where does Dave Conte stand? As we know, the agraffes in vintage M&H pianos are oddballs. Short of drilling out the plate's agraffe holes, tapping them for modern inserts, installing the inserts, and then installing modern 7/32" or 1/4" agraffes with sacrificial crush rings, Dave will need to remove brass material from the bottom of each vintage M&H flat-bottomed agraffe so that when it snugs into the plate pocket it will be perpendicular to its unison centerline. And if the vintage M&H agraffes possess 36 threads per inch, he'll be within .014" of adjacent unison elevation, and for the most part all will be well in the world.

David G. Hughes, RPT

Baltimore Chapter

Hi all. I am rebuilding a Mason B grand which has 7mm diameter agraffe threads. A colleague refinished the plate and removed the agraffes and returned them to me for polishing. He claims that there were no shims (and that they were kept in the correct order, which I now question). I have never known there to not be agraffe shims. 

None of the agraffes line up perpendicular. Not one. So, the claim that there were no shims and/or the order was maintained at this point I disbelieve. Ok, done with my grousing. 

I need to install shims, but the 7mm thread diameter is larger than what I can purchase from supply houses, which is 17/64 (.266"). 7mm imperial equivalent is .276". 

Does anyone have suggestions of where I can source them? TIA.

David Conte, Daniel DeBiasio, and All,

I failed to mention an important factor in this agraffe elevation conversation - I'm sure you all are well ahead of me.

The commencement of the thread in the plate's female hole, to my knowledge, is not controlled when the holes are tapped to receive the agraffes. This means we have two variables: where the threading starts on the agraffe and where it starts in the hole. We have now introduced an infinity predicament.

If these two factors could be precisely controlled, and if the (sacrificial crush ring) agraffes were manufactured to exacting standards, and they were torqued down to exacting standards, I think then we could achieve a tolerance of .002" for the string elevation holes from one agraffe to the next in a completed plate.

David G. Hughes, RPT

Baltimore Chapter

------------------------------
David Hughes RPT
Vintage Case Parts
Glyndon MD
(443) 522-2201

Original Message:
Sent: 09-26-2025 16:17
From: Daniel DeBiasio
Subject: Agraffe shims

Thank you David Hughes for that very elaborate and informative answer to Dave Conte's original question.  I learned a lot from your answer, but I did want to add to it if that's okay.  Specifically about what is being done to achieve accuracy with the modern Steinway grand and what can reasonably be expected.

Steinway is installing agraffes into a plate that is cast using no-bake casting (past 5 years), and machined using CNC machinery for (among other things) the location and surface of the agraffe holes.  With the depth precisely set as a reliable baseline, our process is as follows:

Turn in the agraffe using a breakaway torque of 9-11nm and observe where the agraffe stops.  It MUST stop between [1o'clock 7 o'clock] and [2 o'clock 8 o'clock]

If it stops too early or too late, it must be changed out. (similar to what Geoff recommended earlier in the thread).  Since Steinway is a manufacturer, we are able to have many more agraffes on hand than necessary for a single piano and this process is not only practical, but also efficient.

The agraffe which has stopped naturally in the "green zone" is then finished by tightening square to the string (3 o'clock 9 o'clock)

What this process allows us to do is rely on the depth of the agraffe hole set by the CNC machine and the agraffes themselves which are machined to tolerances of +/- 0.001"

I'm going to use the same back of the napkin math here, but since the correct stopping position is 1 out of 12 possibilities instead of 1 out of 2 possibilities, the 36 thread/inch agraffe combined with the process of swapping them out til one stops in the green zone means that we effectively have 432 threads per inch to work with.  This is a little more than a tolerance of 0.002"  (another way of expressing this is to say +/-0.001") 

Once we get the agraffes tightened in this way, they end up with a consistency that is much closer to +/-0.002" (which includes the variances in the agraffes themselves) all without the need for a laser level.

Any tolerance in the depth of the agraffe hole resulting from the CNC machining of the plate would be added to the figure I just came up with, but I would honestly be surprised if it were more than 0.001"

For anyone reading this who happens to be in New York on a weekday morning, email me in advance of your visit and I'd be happy to attempt to arrange a factory tour to show you what I just described along with many other things

------------------------------
Daniel DeBiasio
Technical Education & Support
ddebiasio@steinway.com
718-267-3229
Steinway & Sons

Original Message:
Sent: 09-26-2025 15:06
From: David Hughes
Subject: Agraffe shims

Dave Conte and All,

I think I understand the predicament. I also think, most respectfully, several of the respondents do not fully understand the predicament. Let's start at the beginning.

First: Dave Conte: is this a vintage M&H model B? If so, it will have employed vintage, flat-bottomed agraffes. The replies you are receiving suggest these agraffes were/are modern, conical-bottomed agraffes with the sacrificial crush ring permitting them to be lined up, by slight over-rotation, perpendicular to the unison centerlines. I do not believe this is the case with your M&H B, so the comments that refer to same may not be helpful.

Next: I have never been aware of any plate refinishing process that distorts the dimensions (depths) of the drilled pockets that receive the agraffes in the plate's agraffe aprons. Thus, those elevations have not changed, unless the refinisher painted the floors of the pockets. If this is the case perhaps removing this paint (ugh) would solve your problem. 

Next: We need to discuss so-called "string leveling" via agraffe height. There are (typically) 36 threads per inch on an agraffe stump. An agraffe is a bi-directional device, meaning we can accept its correct rotation in the plate either at zero degrees to the unison centerline or 180 degrees to the unison centerline. Translation: we aren't concerned if the "front" or the "rear" of the agraffe is perpendicular to the unison centerline. Thus, the agraffe now effectively possesses 72 threads per inch. If we divide 1 inch by 72 we arrive at (rounded off) 0.014". This means that assuming the pockets drilled into the plate are all at the same elevation (okay, cut me a little slack here) no unison string height from one note to the next is more than .014" out of elevation alignment with its neighbor. I am not aware of any manufacturer who installs agraffes one at a time, measures its string hole height(s) above the keybed, makes corrections as necessary by shimming or brass removal, and then moves on to the next. I think we can therefore deduce that a deviation from one unison to the next of .014" is acceptable in our industry for design, manufacture, and regulation purposes of a grand piano. Thus, I don't believe any manufacturer or rebuilder needs to concern him/herself with "leveling" adjacent strings/unisons via the agraffes. We have bigger fish to fry. I don't even think it's practically possible without some sort of laser detection. (If Fazioli uses something like this, more power to them. I know Steinway does not.) And how precise is the hammer line, or the surfaces of the tops of the hammers? How precise is the let-off, and on and on? If we're within .014" on all this we're doing pretty well. Also, BTW, I know of no current manufacturer who uses modern crushable agraffes who removes them, one by one, to remove brass from the conical shell - they merely over-rotate until the agraffe is perpendicular, or try that agraffe in a different hole to see what results. That's the beauty of the design. 

So with all this, where does Dave Conte stand? As we know, the agraffes in vintage M&H pianos are oddballs. Short of drilling out the plate's agraffe holes, tapping them for modern inserts, installing the inserts, and then installing modern 7/32" or 1/4" agraffes with sacrificial crush rings, Dave will need to remove brass material from the bottom of each vintage M&H flat-bottomed agraffe so that when it snugs into the plate pocket it will be perpendicular to its unison centerline. And if the vintage M&H agraffes possess 36 threads per inch, he'll be within .014" of adjacent unison elevation, and for the most part all will be well in the world.

David G. Hughes, RPT

Baltimore Chapter

------------------------------
David Hughes RPT
Vintage Case Parts
Glyndon MD
(443) 522-2201

Original Message:
Sent: 09-25-2025 10:24
From: Dave Conte
Subject: Agraffe shims

Hi all. I am rebuilding a Mason B grand which has 7mm diameter agraffe threads. A colleague refinished the plate and removed the agraffes and returned them to me for polishing. He claims that there were no shims (and that they were kept in the correct order, which I now question). I have never known there to not be agraffe shims. 

None of the agraffes line up perpendicular. Not one. So, the claim that there were no shims and/or the order was maintained at this point I disbelieve. Ok, done with my grousing. 

I need to install shims, but the 7mm thread diameter is larger than what I can purchase from supply houses, which is 17/64 (.266"). 7mm imperial equivalent is .276". 

Does anyone have suggestions of where I can source them? TIA.

------------------------------
Dave Conte, RPT

Piano Technician in Residence
The University of Tennessee
College of Music
Knoxville TN
(817) 307-5656
Owner: Rocky Top Piano
------------------------------

Dave Conte and All,

I think I understand the predicament. I also think, most respectfully, several of the respondents do not fully understand the predicament. Let's start at the beginning.

First: Dave Conte: is this a vintage M&H model B? If so, it will have employed vintage, flat-bottomed agraffes. The replies you are receiving suggest these agraffes were/are modern, conical-bottomed agraffes with the sacrificial crush ring permitting them to be lined up, by slight over-rotation, perpendicular to the unison centerlines. I do not believe this is the case with your M&H B, so the comments that refer to same may not be helpful.

Next: I have never been aware of any plate refinishing process that distorts the dimensions (depths) of the drilled pockets that receive the agraffes in the plate's agraffe aprons. Thus, those elevations have not changed, unless the refinisher painted the floors of the pockets. If this is the case perhaps removing this paint (ugh) would solve your problem. 

Next: We need to discuss so-called "string leveling" via agraffe height. There are (typically) 36 threads per inch on an agraffe stump. An agraffe is a bi-directional device, meaning we can accept its correct rotation in the plate either at zero degrees to the unison centerline or 180 degrees to the unison centerline. Translation: we aren't concerned if the "front" or the "rear" of the agraffe is perpendicular to the unison centerline. Thus, the agraffe now effectively possesses 72 threads per inch. If we divide 1 inch by 72 we arrive at (rounded off) 0.014". This means that assuming the pockets drilled into the plate are all at the same elevation (okay, cut me a little slack here) no unison string height from one note to the next is more than .014" out of elevation alignment with its neighbor. I am not aware of any manufacturer who installs agraffes one at a time, measures its string hole height(s) above the keybed, makes corrections as necessary by shimming or brass removal, and then moves on to the next. I think we can therefore deduce that a deviation from one unison to the next of .014" is acceptable in our industry for design, manufacture, and regulation purposes of a grand piano. Thus, I don't believe any manufacturer or rebuilder needs to concern him/herself with "leveling" adjacent strings/unisons via the agraffes. We have bigger fish to fry. I don't even think it's practically possible without some sort of laser detection. (If Fazioli uses something like this, more power to them. I know Steinway does not.) And how precise is the hammer line, or the surfaces of the tops of the hammers? How precise is the let-off, and on and on? If we're within .014" on all this we're doing pretty well. Also, BTW, I know of no current manufacturer who uses modern crushable agraffes who removes them, one by one, to remove brass from the conical shell - they merely over-rotate until the agraffe is perpendicular, or try that agraffe in a different hole to see what results. That's the beauty of the design. 

So with all this, where does Dave Conte stand? As we know, the agraffes in vintage M&H pianos are oddballs. Short of drilling out the plate's agraffe holes, tapping them for modern inserts, installing the inserts, and then installing modern 7/32" or 1/4" agraffes with sacrificial crush rings, Dave will need to remove brass material from the bottom of each vintage M&H flat-bottomed agraffe so that when it snugs into the plate pocket it will be perpendicular to its unison centerline. And if the vintage M&H agraffes possess 36 threads per inch, he'll be within .014" of adjacent unison elevation, and for the most part all will be well in the world.

David G. Hughes, RPT

Baltimore Chapter

Hi all. I am rebuilding a Mason B grand which has 7mm diameter agraffe threads. A colleague refinished the plate and removed the agraffes and returned them to me for polishing. He claims that there were no shims (and that they were kept in the correct order, which I now question). I have never known there to not be agraffe shims. 

None of the agraffes line up perpendicular. Not one. So, the claim that there were no shims and/or the order was maintained at this point I disbelieve. Ok, done with my grousing. 

I need to install shims, but the 7mm thread diameter is larger than what I can purchase from supply houses, which is 17/64 (.266"). 7mm imperial equivalent is .276". 

Does anyone have suggestions of where I can source them? TIA.

Hi all. I am rebuilding a Mason B grand which has 7mm diameter agraffe threads. A colleague refinished the plate and removed the agraffes and returned them to me for polishing. He claims that there were no shims (and that they were kept in the correct order, which I now question). I have never known there to not be agraffe shims. 

None of the agraffes line up perpendicular. Not one. So, the claim that there were no shims and/or the order was maintained at this point I disbelieve. Ok, done with my grousing. 

I need to install shims, but the 7mm thread diameter is larger than what I can purchase from supply houses, which is 17/64 (.266"). 7mm imperial equivalent is .276". 

Does anyone have suggestions of where I can source them? TIA.

Hi all. I am rebuilding a Mason B grand which has 7mm diameter agraffe threads. A colleague refinished the plate and removed the agraffes and returned them to me for polishing. He claims that there were no shims (and that they were kept in the correct order, which I now question). I have never known there to not be agraffe shims. 

None of the agraffes line up perpendicular. Not one. So, the claim that there were no shims and/or the order was maintained at this point I disbelieve. Ok, done with my grousing. 

I need to install shims, but the 7mm thread diameter is larger than what I can purchase from supply houses, which is 17/64 (.266"). 7mm imperial equivalent is .276". 

Does anyone have suggestions of where I can source them? TIA.

I never use old agraffes, they're too old and I have seen too many break. Especially after being torqued off then back on. Not to mention after seeing the distortion of the hole with a microscope.

Expect Buzzzzzz or POP at the worst moment!

-chris

Hi all. I am rebuilding a Mason B grand which has 7mm diameter agraffe threads. A colleague refinished the plate and removed the agraffes and returned them to me for polishing. He claims that there were no shims (and that they were kept in the correct order, which I now question). I have never known there to not be agraffe shims. 

None of the agraffes line up perpendicular. Not one. So, the claim that there were no shims and/or the order was maintained at this point I disbelieve. Ok, done with my grousing. 

I need to install shims, but the 7mm thread diameter is larger than what I can purchase from supply houses, which is 17/64 (.266"). 7mm imperial equivalent is .276". 

Does anyone have suggestions of where I can source them? TIA.

I never use old agraffes, they're too old and I have seen too many break. Especially after being torqued off then back on. Not to mention after seeing the distortion of the hole with a microscope.

Expect Buzzzzzz or POP at the worst moment!

-chris

Hi all. I am rebuilding a Mason B grand which has 7mm diameter agraffe threads. A colleague refinished the plate and removed the agraffes and returned them to me for polishing. He claims that there were no shims (and that they were kept in the correct order, which I now question). I have never known there to not be agraffe shims. 

None of the agraffes line up perpendicular. Not one. So, the claim that there were no shims and/or the order was maintained at this point I disbelieve. Ok, done with my grousing. 

I need to install shims, but the 7mm thread diameter is larger than what I can purchase from supply houses, which is 17/64 (.266"). 7mm imperial equivalent is .276". 

Does anyone have suggestions of where I can source them? TIA.

Dave C. 

I haven't been following this whole thread, but one of the metric sizes will supposedly work as a replacement for the MH agraffes. This is something Isaac Sadigursky used to suggest as a substitute on these pianos. 

Years ago there was a thread on reconditioning old agraffes which included polishing out the torus to remove cuts and other irregularities there. I think it was posted by Paul Revenko Jones. It must go 10 years back at least though maybe somebody kept that procedure. 

Otherwise, I agree with David Hughes, especially when it comes to worrying about minor variations in string height. Of course, if one does happen to break oneafter you've installed these, it's a problem getting one that will match the others. But not a problem getting one that will function even if you have to drill out re tap and use an insert. I also agree with D Hughes that drilling out and it using inserts on the whole set would be burdensome. 

I never use old agraffes, they're too old and I have seen too many break. Especially after being torqued off then back on. Not to mention after seeing the distortion of the hole with a microscope.

Expect Buzzzzzz or POP at the worst moment!

-chris

Hi all. I am rebuilding a Mason B grand which has 7mm diameter agraffe threads. A colleague refinished the plate and removed the agraffes and returned them to me for polishing. He claims that there were no shims (and that they were kept in the correct order, which I now question). I have never known there to not be agraffe shims. 

None of the agraffes line up perpendicular. Not one. So, the claim that there were no shims and/or the order was maintained at this point I disbelieve. Ok, done with my grousing. 

I need to install shims, but the 7mm thread diameter is larger than what I can purchase from supply houses, which is 17/64 (.266"). 7mm imperial equivalent is .276". 

Does anyone have suggestions of where I can source them? TIA.

Original Message:
Sent: 9/26/2025 7:02:00 PM
From: David Love
Subject: RE: Agraffe shims

Dave C. 

I haven't been following this whole thread, but one of the metric sizes will supposedly work as a replacement for the MH agraffes. This is something Isaac Sadigursky used to suggest as a substitute on these pianos. 

Years ago there was a thread on reconditioning old agraffes which included polishing out the torus to remove cuts and other irregularities there. I think it was posted by Paul Revenko Jones. It must go 10 years back at least though maybe somebody kept that procedure. 

Otherwise, I agree with David Hughes, especially when it comes to worrying about minor variations in string height. Of course, if one does happen to break oneafter you've installed these, it's a problem getting one that will match the others. But not a problem getting one that will function even if you have to drill out re tap and use an insert. I also agree with D Hughes that drilling out and it using inserts on the whole set would be burdensome. 

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320

Original Message:
Sent: 09-26-2025 18:27
From: Dave Conte
Subject: Agraffe shims

Original Message:
Sent: 9/26/2025 5:32:00 PM
From: Chris Chernobieff
Subject: RE: Agraffe shims

I never use old agraffes, they're too old and I have seen too many break. Especially after being torqued off then back on. Not to mention after seeing the distortion of the hole with a microscope.

Expect Buzzzzzz or POP at the worst moment!

-chris

------------------------------
On the page, it looked....nothing.
The beginning, simple, almost comic.
Just a pulse - bassoons, basset horns, like a rusty squeezebox. And then suddenly, high above it..an oboe, hanging there unwavering, until a clarinet sweetened it into a phrase of such delight.
This was no composition by a performing monkey!!

865-986-7720 (text only please)

Original Message:
Sent: 09-25-2025 10:24
From: Dave Conte
Subject: Agraffe shims

Hi all. I am rebuilding a Mason B grand which has 7mm diameter agraffe threads. A colleague refinished the plate and removed the agraffes and returned them to me for polishing. He claims that there were no shims (and that they were kept in the correct order, which I now question). I have never known there to not be agraffe shims. 

None of the agraffes line up perpendicular. Not one. So, the claim that there were no shims and/or the order was maintained at this point I disbelieve. Ok, done with my grousing. 

I need to install shims, but the 7mm thread diameter is larger than what I can purchase from supply houses, which is 17/64 (.266"). 7mm imperial equivalent is .276". 

Does anyone have suggestions of where I can source them? TIA.

------------------------------
Dave Conte, RPT

Piano Technician in Residence
The University of Tennessee
College of Music
Knoxville TN
(817) 307-5656
Owner: Rocky Top Piano
------------------------------

Everyone,

I just created a rather thrilling, and complimentary, reply to Daniel DiBiaso, but after hitting POST it has not appeared. Maybe it will after a while. Of course, I did not save a copy of it. :-(

Drat. The machinations of this discussion group thingy infuriate me to no end. Then again, maybe I'm just too old!

David G. Hughes, RPT

Baltimore Chapter

------------------------------
David Hughes RPT
Vintage Case Parts
Glyndon MD
(443) 522-2201

Original Message:
Sent: 09-26-2025 20:16
From: Dave Conte
Subject: Agraffe shims

Original Message:
Sent: 9/26/2025 7:02:00 PM
From: David Love
Subject: RE: Agraffe shims

Dave C. 

I haven't been following this whole thread, but one of the metric sizes will supposedly work as a replacement for the MH agraffes. This is something Isaac Sadigursky used to suggest as a substitute on these pianos. 

Years ago there was a thread on reconditioning old agraffes which included polishing out the torus to remove cuts and other irregularities there. I think it was posted by Paul Revenko Jones. It must go 10 years back at least though maybe somebody kept that procedure. 

Otherwise, I agree with David Hughes, especially when it comes to worrying about minor variations in string height. Of course, if one does happen to break oneafter you've installed these, it's a problem getting one that will match the others. But not a problem getting one that will function even if you have to drill out re tap and use an insert. I also agree with D Hughes that drilling out and it using inserts on the whole set would be burdensome. 

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320

Original Message:
Sent: 09-26-2025 18:27
From: Dave Conte
Subject: Agraffe shims

Original Message:
Sent: 9/26/2025 5:32:00 PM
From: Chris Chernobieff
Subject: RE: Agraffe shims

I never use old agraffes, they're too old and I have seen too many break. Especially after being torqued off then back on. Not to mention after seeing the distortion of the hole with a microscope.

Expect Buzzzzzz or POP at the worst moment!

-chris

------------------------------
On the page, it looked....nothing.
The beginning, simple, almost comic.
Just a pulse - bassoons, basset horns, like a rusty squeezebox. And then suddenly, high above it..an oboe, hanging there unwavering, until a clarinet sweetened it into a phrase of such delight.
This was no composition by a performing monkey!!

865-986-7720 (text only please)

Original Message:
Sent: 09-25-2025 10:24
From: Dave Conte
Subject: Agraffe shims

Hi all. I am rebuilding a Mason B grand which has 7mm diameter agraffe threads. A colleague refinished the plate and removed the agraffes and returned them to me for polishing. He claims that there were no shims (and that they were kept in the correct order, which I now question). I have never known there to not be agraffe shims. 

None of the agraffes line up perpendicular. Not one. So, the claim that there were no shims and/or the order was maintained at this point I disbelieve. Ok, done with my grousing. 

I need to install shims, but the 7mm thread diameter is larger than what I can purchase from supply houses, which is 17/64 (.266"). 7mm imperial equivalent is .276". 

Does anyone have suggestions of where I can source them? TIA.

------------------------------
Dave Conte, RPT

Piano Technician in Residence
The University of Tennessee
College of Music
Knoxville TN
(817) 307-5656
Owner: Rocky Top Piano
------------------------------

Mr. Hughes, 

You must be slipping mentally in your old age to accept a tolerance as great as .002". This is an outrage! No self respecting piano technician would evef accept such sloppy work! You need re-assess your priorities in life. The performance capabilities of even a Wurlitzer spinet would show up the inadequacies of such variation as you have suggested. I am appalled at your willingness to advocate doing work to such low standards! My respect for you has diminished accordingly.

TIC

Peter Grey Piano Doctor 

Everyone,

I just created a rather thrilling, and complimentary, reply to Daniel DiBiaso, but after hitting POST it has not appeared. Maybe it will after a while. Of course, I did not save a copy of it. :-(

Drat. The machinations of this discussion group thingy infuriate me to no end. Then again, maybe I'm just too old!

David G. Hughes, RPT

Baltimore Chapter

------------------------------
David Hughes RPT
Vintage Case Parts
Glyndon MD
(443) 522-2201

Original Message:
Sent: 09-26-2025 20:16
From: Dave Conte
Subject: Agraffe shims

Original Message:
Sent: 9/26/2025 7:02:00 PM
From: David Love
Subject: RE: Agraffe shims

Dave C. 

I haven't been following this whole thread, but one of the metric sizes will supposedly work as a replacement for the MH agraffes. This is something Isaac Sadigursky used to suggest as a substitute on these pianos. 

Years ago there was a thread on reconditioning old agraffes which included polishing out the torus to remove cuts and other irregularities there. I think it was posted by Paul Revenko Jones. It must go 10 years back at least though maybe somebody kept that procedure. 

Otherwise, I agree with David Hughes, especially when it comes to worrying about minor variations in string height. Of course, if one does happen to break oneafter you've installed these, it's a problem getting one that will match the others. But not a problem getting one that will function even if you have to drill out re tap and use an insert. I also agree with D Hughes that drilling out and it using inserts on the whole set would be burdensome. 

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320

Original Message:
Sent: 09-26-2025 18:27
From: Dave Conte
Subject: Agraffe shims

Original Message:
Sent: 9/26/2025 5:32:00 PM
From: Chris Chernobieff
Subject: RE: Agraffe shims

I never use old agraffes, they're too old and I have seen too many break. Especially after being torqued off then back on. Not to mention after seeing the distortion of the hole with a microscope.

Expect Buzzzzzz or POP at the worst moment!

-chris

------------------------------
On the page, it looked....nothing.
The beginning, simple, almost comic.
Just a pulse - bassoons, basset horns, like a rusty squeezebox. And then suddenly, high above it..an oboe, hanging there unwavering, until a clarinet sweetened it into a phrase of such delight.
This was no composition by a performing monkey!!

865-986-7720 (text only please)

Original Message:
Sent: 09-25-2025 10:24
From: Dave Conte
Subject: Agraffe shims

Hi all. I am rebuilding a Mason B grand which has 7mm diameter agraffe threads. A colleague refinished the plate and removed the agraffes and returned them to me for polishing. He claims that there were no shims (and that they were kept in the correct order, which I now question). I have never known there to not be agraffe shims. 

None of the agraffes line up perpendicular. Not one. So, the claim that there were no shims and/or the order was maintained at this point I disbelieve. Ok, done with my grousing. 

I need to install shims, but the 7mm thread diameter is larger than what I can purchase from supply houses, which is 17/64 (.266"). 7mm imperial equivalent is .276". 

Does anyone have suggestions of where I can source them? TIA.

------------------------------
Dave Conte, RPT

Piano Technician in Residence
The University of Tennessee
College of Music
Knoxville TN
(817) 307-5656
Owner: Rocky Top Piano
------------------------------