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Key bushing caul sizes

  • 1.  Key bushing caul sizes

    Member
    Posted 01-09-2020 15:19
    I had an interesting experience today, bushing front pins on a 15 yr old European keyboard. I usually, at supply house recommendation, use a brass caul .004" or .005" larger than the pin to bush the front pin. I have been trying to tighten up the front rail bushings when I rebush, to reduce side-to-side slop in the key. Tried sizing the mortise and using thicker cloth. However, I still thought there was more slop than I wanted in a newly bushed key.

    I only had a .129" brass caul on hand, for these .129 European front pins, instead of the slightly oversized .031 I would usually use. I figured I'd just use the .129 caul and see what happened. Actually, if this experience repeats itself I may stop using the oversize front pin cauls altogether in the future. Friction came out right on the money, on the whites, 2-3g, after sitting with the .129 cauls & dosed with VS Profelt overnight. Slightly tight on the sharps, but only needed very minor heated caul (used .129) to hit the friction target. Side to side play is excellent.

    Any other experience regarding non-oversized front pin sizing cauls out there?​

    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------


  • 2.  RE: Key bushing caul sizes

    Member
    Posted 01-09-2020 15:35
    A lot seems to be dependent on the key wood density.  Sometimes just bushing tightly against the caul can enlarge the mortise and once the glue is thoroughly dry your cauls no longer feel like they fit as tight.  I now rebush S&S .160 balance rails with exact size cauls (yes, I realize that you are referring to front mortises) .  Works much better.  Best thing to do is try a sample first and make a decision from that result.  I use the two caul Spurlock method with hot hide glue.

    Deb

    --
    5 Tarr's Lane WEST
    Rockport, MA  01966
    978-546-8428





  • 3.  RE: Key bushing caul sizes

    Registered Piano Technician
    Posted 01-09-2020 20:12
    Mr. Ialeggio
     It's January. RH by you is currently somewhere around negative 12%. Come Spring the RH will return to levels more consistent with carbon based life. When that happens the key wood will swell and the hole that is the mortise will get larger as well. So far so good.  The bushing cloth will also get larger but in a more robust fashion than the key wood. Do you think there will be enough slack in the system to keep your friction levels where you want them?

    ------------------------------
    Karl Roeder
    Pompano Beach FL
    ------------------------------



  • 4.  RE: Key bushing caul sizes

    Member
    Posted 01-09-2020 21:05
    Don't know...good questions.  However I do know this, that as I really refine my skills, I have always been unhappy with the side to side play in my bushing jobs, and have been trying to figure out how to reduce that slop. I do have several keysets where the tolerances were tighter than my usual, by coincidence, and my own piano is probably the tightest I have done. I have never had a friction issue that I know of on any keyset, so, I'm going to say the chances are good, it will be okay. However, on this experiment job (I experiment all the time of projects), I will mention this possibility to the customer, and just go back and re-ease at my cost, should the need arise...an advantage of having no mortgage or outstanding debt.

    Another point to consider, when reducing these clearances, is the choice of the  cloth thickness. I always spend some time making sure the cloth I've chosen for a particular mortise is Mic'd, after playing around with different thickness I keep in stock. So the cloth thickness, relative to the mortise size is consistent, and not overly fluffy from the get go.

    However, I guess we shall see what we shall see.  Point taken!

    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 5.  RE: Key bushing caul sizes

    Member
    Posted 01-09-2020 21:14
    The RH in the shop is actually pretty reasonable, for January in NE...low 30's. As this is a mild winter, and I've been keeping the shop colder, in the high 50's, and sealed the air infiltration well this year...the air changes are down, not to mention the heating costs are down as well. In the past, when I was soldering frames, the shop RH was lower, since I had to constantly flush the shop air of soldering gases. So this one is in my favor...but, nonetheless,  I will pay attention to the RH question when trying this trick in future keysets.

    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 6.  RE: Key bushing caul sizes

    Registered Piano Technician
    Posted 01-10-2020 01:39
    Here are some thoughts/questions/comments applied to the original post and subsequent responses:
    - Jim, what is your source of brass cauls?  One reason I ask is that I've found the Spurlock/Erwin teflon/nylon cauls to vary by some thousandths within a set.

    - As per Debra's point, what type of wood is the keystick fabricated from?

    - Once we get past Mr. Roeder's fanciful bizzaro-world of climate extremes, the approach, and tolerance target depends upon what we know of the ultimate disposition of the piano.  Clearly, as long as we're dealing with wood and cloth, an 'ideal' will only exist in some range of variation.  Karl's (first/last names used interchangeably) last line - "Do you think there will be enough slack in the system to keep your friction levels where you want them? " -  highlights the duality of the issue:  friction vs. slop.  How does each affect the ultimate feel of the action?

    - Jim says he'd "just go back and re-ease at my cost, should the need arise..."  Would you use a heated caul to iron (lay down fibers or compress) cloth or easing pliers (crushing wood fibers)?  There ought to be some difference, in theory at least.

    - Jim also references "choice of the  cloth thickness" . What device do you use to measure?  I have to admit that I don't own a special spring-loaded mic designed for this purpose, but it would help.  Still, careful use of a Starrett 1" caliper, with vernier scale resolving to .0001" suggests significant divergence from the nominal dimensions depending upon the RH conditions.  While there's probably a good argument against it, I seem to have had some occasional success using two different thicknesses in a single mortise.  This is especially useful when employing the two-caul method, as you can compensate for (small) variations occurring during the first side gluing.

    - Would there be any benefit to glue-'sizing' the wood at the front of the key (hide glue or  thin CA)? Could that reduce climate-related dimensional change?

    Lot's of fun experiments.  Thanks Jim

    ------------------------------
    David Skolnik [RPT]
    Hastings-on-Hudson NY
    917-589-2625
    ------------------------------



  • 7.  RE: Key bushing caul sizes

    Member
    Posted 01-10-2020 06:55
    Timely post. I'm rebushing an overdamper with the Erwin two-caul method. The balance rail pin is 0.137" and I'll use the appropriate caul for the final caul, but I've noticed that if I put a 0.137" caul in the current balance rail bushing (with the old bushing) then the play is probably close to what I would have chosen for cloth thickness; that is, it's firm but not tight (and this is true for the rarely-used end keys.) Since the current bushings give loose play, that tells me that I probably want to use a cloth that gives me a fairly tight grip on the caul.  I'd rather end up with bushings too tight than not tight enough.

    ------------------------------
    Don Dalton
    Chester VT
    ------------------------------



  • 8.  RE: Key bushing caul sizes

    Member
    Posted 01-10-2020 08:06
    I have both my own shop made two-step Spurlock style cauls and Pianotek's brass cauls. On this job I used the brass cauls and the Bushmaster, single step procedure, which I finally got to work well and efficiently (used hot hide glue). Even though I have a shop-made .146 pin set, I also have a .146 and .150 Pianotek brass caul set. I prefer the brass cauls to the plastic cauls, and since I bought them, I have always used them to size the new felt with Profelt even if the felt was installed with the two-step plastic caul method.

    <friction vs. slop.  How does each affect the ultimate feel of the action?
    usually my friction levels have been quite low. I am  experimenting with higher friction levels, 11-13.5g, as I pin the shanks now at 4-6g (WNG always)...slightly tight, for tonal reasons. I don't do weight balancing metrics aka Stanwood, or even use the data they generate. Rather, the system is low inertia at the hammer, slightly elevated system leverage, minimal lead, usually none starting mid notes of the 30's, all lead in back of the mid point of the front lever, with elevated DW, in the low to mid 60's in the bass graduating to mid 50's in the treble. So...as I usually work to lower friction specs, I can't answer this yet, as I'm gathering data.

    <Would you use a heated caul to iron (lay down fibers or compress) cloth or easing pliers (crushing wood fibers)? 
    Probably pliers, as if it tightened up, and as the felt was minimal (1.0mm), it would indicate I needed a little more room in the mortise.

    I measure cloth thickness with a non-spring loaded micrometer. However, I don't read off the felt alone, as that creates a point load and gives a false reading. Instead, I take two 3/16" or so parallel sided wooden shims, and sandwich the felt between them, to take the reading. This avoids a point  load. I then subtract the mic reading of the two shims from the total measurement. This gives consistent readings.

    Regarding sizing to control wood movement...I size, but not to control movement...wood moves...go with it. I like to size, because I can apply the glue hot (160 deg) and relatively thin, if the wood isn't instantly soaking all the water out of  the glue. This way there is no bleed through, and I get consistently excellent adhesion.



    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 9.  RE: Key bushing caul sizes

    Member
    Posted 01-10-2020 08:11
    On choosing felt, its a judgement call, based on past experience. I don't usually use Spurlock's shake the key method to choose felt, but more just pull the caul out and gauge the resistance. Too tight, means too much felt. Too much felt can't be eased sometimes, as was discussed in Terry's thread a month ago or so.

    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 10.  RE: Key bushing caul sizes

    Registered Piano Technician
    Posted 01-10-2020 08:23
    I'm not quite clear on this point:

    "I prefer the brass cauls to the plastic cauls, and since I bought them, I have always used them to size the new felt with Profelt even if the felt was installed with the two-step plastic caul method."

    Does this mean you glue the bushings in completely (and let dry)  and then soak them with Profelt and reinsert the brass cauls?

    If so, do you use the same size caul you used for the bushing step?

    ------------------------------
    Eric Johnson [RPT]
    [Eric Johnson Pianos]
    [Westport] [CT]
    www.ericjohnsonpianos.com
    One year older and dumber.
    ------------------------------



  • 11.  RE: Key bushing caul sizes

    Member
    Posted 01-10-2020 09:56
    <Does this mean you glue the bushings in completely (and let dry)  and then soak them with Profelt and reinsert the brass cauls?

    Yup. Same bushing size as well with the Profelt.  I usually gently heat the brass cauls before inserting them in the Profelt soaked already glued bushing.

    Pianotek does it differently. Pretty sure they treat the felt by soaking it in Profelt, and hanging it on a line to dry, before gluing the felt into the mortises. I experimented with their procedure years ago, and tested adhesion of pre-Profelted felt...adhesion was fine. I don't do that, because I don't bush often, and usually don't know what felt I will be using until starting to bush...so it times out better for me to do it this way.

    Doing it my way, you have to move fast, so the Profelt does not loosen the not-quite-cured new glue joint between wood/felt.

    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 12.  RE: Key bushing caul sizes

    Member
    Posted 01-10-2020 10:02
    I stared using the exact caul and oversizing the cloth by .5mm. Dale Erwin said the glue shrinks and draws the cloth in tight. . I measured it using The cloth from Jurgen. You measure the mortise,, subtract the caul,, Thats the amount of cloth needed after drying. Add .5mm and divide in half for the cloth size. That gave me tight front bushings
    If you use too much pressure on the intermediate caul,, you squeeze the glue into the cloth and it shrinks more. If you don't oversize the cloth, the cauls fall out when you turn the keys over.
    Since I didn't always have the right intermediate caul, you size the cloth to that caul and recompute the other size cloth you need.
    I takes two days to completely dry and shrink

    ------------------------------
    Keith Roberts
    owner
    Hathaway Pines CA
    209-770-4312
    ------------------------------



  • 13.  RE: Key bushing caul sizes

    Registered Piano Technician
    Posted 01-11-2020 11:14
    Since the topic of VS Profelt has come up, I have to admit I'm somewhat of a skeptic, or at least agnostic, especially as it seems to be touted as a magic bullet by many.

    -I used it recently to tighten a bushing job for which I was a little dissatisfied: I took several of the more loose keys, applied a little Profelt to the bushings and inserted cauls. In the morning, the bushings had loosened up and practically fell out. These were on fully dried hide glue.

    -In the other test cases (different pianos) where the glue held, I detected no appreciable difference in sizing between treated and non-treated keys. Some have claimed that one can hold off a full re-bushing job by using VS. I'm not sure how.

    -I've tried it in worn damper guide rail bushings. Didn't seem to make a difference.

    Of course, it's possible I'm simply not using it the way in which it's intended. However, there are no instructions included with its use.

    ------------------------------
    Scott Cole, RPT
    rvpianotuner.com
    Talent, OR
    (541-601-9033
    ------------------------------



  • 14.  RE: Key bushing caul sizes

    Registered Piano Technician
    Posted 01-12-2020 07:49
    IME Profelt works best extending the life of new bushings.  As a corrective to worn felt the results are somewhat hit-or-miss, though I typically see at least minor improvement.  As you note, there are no good instructions, but Bob Marinelli at Pianotek pointed out to me that if bushing cloth has been treated with Teflon, Profelt won't penetrate it; if you've used the chemical on a worn set and it made no difference at all, perhaps those bushings had been treated with Teflon.

    ------------------------------
    Kent Burnside, RPT
    Franklin TN
    615.430.0653
    ------------------------------



  • 15.  RE: Key bushing caul sizes

    Registered Piano Technician
    Posted 01-12-2020 09:59
    There has to be some (as in: I don't know how much) remaining cloth fiber material that hasn't been permeated with glue and/or simply worn away.  It's much more likely to have some effect if the set-up involves a somewhat larger mortise with a medium to thick cloth, as opposed to one having a smaller mortise/thinner cloth, i.e. nothing for the VS to work with.
    It would still be useful to have a reminder as to how the product actually works.

    ------------------------------
    David Skolnik [RPT]
    Hastings-on-Hudson NY
    917-589-2625
    ------------------------------



  • 16.  RE: Key bushing caul sizes

    Registered Piano Technician
    Posted 01-12-2020 16:51
    Since I invented the Bushmaster and was the first to make accurate metal cauls available to the trade, I'm a bit partial to the single caul factory method.

    I go oversize at the front rail and same size at the balance rail. I heat the cauls on the lid of the glue pot so they are HOT going in to the mortises.  One thing I have learned is that the longer you keep the cauls in place, the more stable your results will be. I'm talking days...not hours. If you are able to leave them in for 3 or 4 days (I know this is not always possible) you should be pleasantly surprised at the stability.

    Frank Stopa told me years ago that they would leave cauls in the keys on the shelf for months till the keys were to go into the piano.

    I use VS-PROFELT judiciously, usually no more than 1-3 drops if I need to size them. If they are not too bad but just needing little softening and tightening up I will apply a drop or two right at the business point and not use a caul. It will soften and spring up the cloth a  bit and then relax. It takes some experimentation to find the right proportions.

    Pwg

    ------------------------------
    Peter Grey
    Stratham NH
    603-686-2395
    pianodoctor57@gmail.com
    ------------------------------



  • 17.  RE: Key bushing caul sizes

    Member
    Posted 01-12-2020 19:13
    My method is the same as Peter's but I include clamping the front rail. There is a bar clamp behind the capstans, 4 key groupings. Overnight or longer (until I can get to them).  Clamping the front rail insures nice square corners to the felt in the mortice.

    ------------------------------
    Regards,

    Jon Page
    mailto:jonpage@pianocapecod.com
    http://www.pianocapecod.com


  • 18.  RE: Key bushing caul sizes

    Registered Piano Technician
    Posted 01-12-2020 21:38
    Just a follow-up on my earlier post regarding VS Profelt:
    Yes, Pianotek does indeed have some cursory instructions on their website. However, they say it's a "miracle" treatment, and say to soak the bushings.

    Too bad the ingredients aren't listed.

    ------------------------------
    Scott Cole, RPT
    rvpianotuner.com
    Talent, OR
    (541-601-9033
    ------------------------------



  • 19.  RE: Key bushing caul sizes

    Member
    Posted 01-13-2020 08:03
    The one time I used VS Profelt it softened the glue and they came out.

    ------------------------------
    Regards,

    Jon Page
    mailto:jonpage@pianocapecod.com
    http://www.pianocapecod.com
    ------------------------------



  • 20.  RE: Key bushing caul sizes

    Registered Piano Technician
    Posted 01-13-2020 11:17
    Hi all,
    In our shop we use Jahn-Pianoteille's pre-glued key bushing cloth from Germany. This is what we install when we build new keysets because the results are so consistent.

    Cost for the pre-glued cloth is about $15 USD per keyboard (~3 meters / keyset) but well worth it. The material and method we use saves at about an hour per piano over our old glue pot method. Cloth is from www.jahn-pianoteile.com (stock #17301, 1.3 x 9.5mm). We use Bushmaster and brass cauls from Pianotek. We leave the cauls in overnight for best results.

    There's a short video on my facebook page of the method in use. Of course, we have the advantage of almost exclusively bushing brand new keys we just built with CNC accurate mortises, and always the same size key pins.

    We keep our shop in Michigan humidity controlled with a humidifier set to 35% in winter and dehumidifier set to bring it down to 40% in summer.  So the RH is always in a 5% range. Humidity control is critical for this kind of work.

    -Dean




    ------------------------------
    Dean Reyburn, RPT
    Reyburn Pianoworks
    Reyburn CyberTuner
    1-616-498-9854
    dean@reyburn.com
    www.reyburnpianoworks.com
    www.cybertuner.com
    Facebook: www.facebook.com/dean.reyburn
    ------------------------------



  • 21.  RE: Key bushing caul sizes

    Registered Piano Technician
    Posted 01-13-2020 15:17
    Jim,
    I think cloth thickness choice is maybe more important than caul size choice. It's a question of how you select your cloth relative to your caul. (I've never used brass cauls, always used Spurlock's except for when I made my own prior to him making his plastic ones available - so my experience may vary from yours).

    Part of the choice has to do with the process of cutting the felt with the caul installed (if it is tighter, it is a lot easier to do that without the cloth tending to become displaced or even pulled out). After years of experiment, I have got used to how tight a dry fit should feel, using the caul sizes Spurlock provided (now Erwin), aiming for needing an ironing after removing the caul to get a good, nearly friction free resilient fit.

    Skolnick raised the question of measuring cloth thickness. It requires a standard pressure to get consistent results, so a good quality micrometer with a friction device on the spindle will work fairly well - not for a standard measurement, but for relative thicknesses. I prefer to use a millimetric spring loaded "dial thickness gauge" I got from Jurgen a couple years back - but he doesn't seem to be carrying it any more. I find I can get good enough consistent results with a light touch of the finger. It was like this one.

    ------------------------------
    Fred Sturm
    University of New Mexico
    fssturm@unm.edu
    http://fredsturm.net
    http://www.artoftuning.com
    "We either make ourselves happy or miserable. The amount of work is the same." - Carlos Casteneda
    ------------------------------



  • 22.  RE: Key bushing caul sizes

    Member
    Posted 01-13-2020 22:14
    Fred,
    I agree about the right cloth thickness and the "feel" of the caul/felt in the given mortise. I does take me some time to decide on the appropriate cloth.

    One thing I find interesting to puzzling, that I see in some European bushings from the last 15 years up to very recently on a new German keyset, is that the felt they are installing is, in my opinion, way to fluffy...presumably fluffy because its too thick. The pin becomes surrounded with cloth over time, or even out of the box.

    I don't think I would attribute this to anything other than factory rushing, or "use what you've got...quick" factory syndrome. For felt installations in keysets that should be reasonably upper tier, the application of the cloth sometimes is just sloppy, misaligned and not something I would feel comfortable warrantying in my own work. As well have seen serious, too-much-felt bushing issues, on recent German uprights which otherwise are real nice instruments...but the seizing, and re-seizing keys, leave sour tastes in clients mouth's.

    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 23.  RE: Key bushing caul sizes

    Registered Piano Technician
    Posted 01-13-2020 23:37
    I think most of the German manufacturers probably buy their keysets ready made, at least to the extent of a keyframe with bushed keys on it. So they are probably Kluge for the most part, possibly Czech. That is not certain knowledge, but it was the case at Sauter when I was there (along with actions already screwed to frames and hammer sets). Most of the German firms are smaller, so probably wouldn't want to bother with in house key manufacture, any more than making action parts or hammers. Maybe someone knows more specifically about, say, the source of keys for Bechstein or Schimmel.
    Regards,
    Fred Sturm
    "Travel is fatal to prejudice, bigotry, and narrow-mindedness." Twain






  • 24.  RE: Key bushing caul sizes

    Posted 01-14-2020 00:52
      |   view attached
    Interesting discussion.
    I don't do that many key bushings but I have found that for me, dry-fitting cloth into the mortise and putting it on the frame gave me a different result than gluing a bushing in and letting it dry overnight. I found I had to go up several sizes of cloth ( I am talking about  increments of 0.1mm thickness) to get the same snug feel with a glued in cloth bushing.
    Does anyone pre-iron bushing cloth with a clothes iron prior to gluing? That is what I think I will try next time. The goal is to get a good snug fit without too much squishy-ness that can come when thicker cloth (1.4mm ) is called for.

    I will also look into trying the pre-glued strips and will bring some in from Germany, if anyone is interested.

    This is the spring loaded gauge I use for measuring felt. It is worth it for me. I got tired of the inconsistencies of calipers and even my disc micrometer.

    ------------------------------
    Jurgen Goering
    ------------------------------



  • 25.  RE: Key bushing caul sizes

    Registered Piano Technician
    Posted 01-15-2020 11:08
    Some wash their cloth (to shrink it) and then iron it in order to increase density.

    Pwg

    ------------------------------
    Peter Grey
    Stratham NH
    603-686-2395
    pianodoctor57@gmail.com
    ------------------------------



  • 26.  RE: Key bushing caul sizes

    Posted 9 days ago

    I have brought in some of that European Pre-Glued bushing cloth strip material.  It is 1.30mm thick and 9.5 mm wide. The adhesive is heat activated.

    If someone wants to try it out please contact me off list.



    ------------------------------
    Jurgen Goering
    ------------------------------



  • 27.  RE: Key bushing caul sizes

    Member
    Posted 9 days ago
    How do you apply the heat?  Just by using hot brass cauls?

    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 28.  RE: Key bushing caul sizes

    Registered Piano Technician
    Posted 9 days ago
    Hi Jim,
    We use the Jahn pre-glued cloth and to install we use a Pianotek soldering iron with (usually) the same brass caul in the iron as the final brass caul.  Temparature should be about 200 degrees F with a temp control, and use a bushmaster to cut. Then insert the hot iron for about 10 seconds (8 to 12 or so). I like to wiggle the iron in a circle to make sure you get heat everywhere.

    It's easy to tell if you get enough heat, or too much.  Enough means the glue activates well and you can't pull it out easily (without heat or water).  Too much heat and the cloth compresses too much, or way to much heat and you burn the cloth.

    There's a video on my facebook page that shows our procedure for this.

    Since there's only one thickness of this cloth, we vary the caul size and/or how much VS pro felt or water/alcohol mix we use with the iron to achieve a consistent final result.

    -Dean

    ------------------------------
    Dean Reyburn, RPT
    Reyburn Pianoworks
    Reyburn CyberTuner
    1-616-498-9854
    dean@reyburn.com
    www.reyburnpianoworks.com
    www.cybertuner.com
    Facebook: www.facebook.com/dean.reyburn
    ------------------------------