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Broadwood lyre bolts

  • 1.  Broadwood lyre bolts

    Registered Piano Technician
    Posted 03-27-2020 14:55
    Hi all,
    A customer was gifted a Broadwood grand that I believe to be from 1895 (#44604). The lyre has 3 mounting elements: positioning dowels and a cam that are present and functioning, but missing bolts. A metal receptor is clearly visible 3" into each of the two bolt holes, and the lyre thickness indicates I need something about 6" long.
    Before I venture to a hardware store, can anyone recommend what thickness of bolt should work, and whether a modern threading is likely to work? I'd guess the diameter to be .5" or less.
    thanks!

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    Scott Cole, RPT
    rvpianotuner.com
    Talent, OR
    (541-601-9033
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  • 2.  RE: Broadwood lyre bolts

    Member
    Posted 03-27-2020 18:53
    You may be dealing with metric threads so I would get several SAE and Metric. You could probably get a fairly accurate bolt size by trying some wood dowels up into the threads or just get various diameters  to test out. If you have a really good hardware store you may be able to get what you need. I have used Fastenal in the past because they carry some stock and get other stock quickly. wow 5 " diameter is pretty huge . Take some pictures !!!!!

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    James Kelly
    Owner- Fur Elise Piano Service
    Pawleys Island SC
    843-325-4357
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  • 3.  RE: Broadwood lyre bolts

    Member
    Posted 03-28-2020 02:49
    It’s very possible that they are Whitworth threads. I restored a 1845 Broadwood that had many missing and defective bolts. Whitworth threads have a 55° angle instead of 60°. Luckily I have a lathe so I ground a cutter and made them. Any machinist should be able to do this once they learn about the thread. It might be easier to just find a conventional bolt that enters a good distance before jamming and then getting a tap for that size and tap out the threads in the piano. Since the threads are very similar to Imperial threads the tap will cut through an existing thread every once in a while but at least the bolt will be usable with minimal loss of strength. Whitworth was the first to propose a unified system of threads. Before him a nut and bolt had to be a matched pair and had to be kept together for their lifetime.

    Glen Hart
    970-250-9596




  • 4.  RE: Broadwood lyre bolts

    Member
    Posted 03-30-2020 14:47
    Retapping is a recourse. I used to have a BMW motorcycle (sigh) and a mechanic overturned an oil pan 10 mm bolt. It fell out and I noticed an oil streak leading to the curbing at a stop sign. Fortunately it just happened.  I was told to use a  ¼" x 20 tap and install that bolt, it worked.

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    Regards,

    Jon Page
    mailto:jonpage@pianocapecod.com
    http://www.pianocapecod.com
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  • 5.  RE: Broadwood lyre bolts

    Registered Piano Technician
    Posted 03-29-2020 14:51
      |   view attached
    I had to re-mount the legs on a Broadwood here in Temple about 3 months ago. Do you think the bolts were something like this? (Attached)

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    Kevin Fortenberry
    Registered Piano Technician
    Temple, Texas
    806-778-3962
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  • 6.  RE: Broadwood lyre bolts

    Member
    Posted 03-29-2020 15:19
    You will not find that puppy at home depot....

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    James Kelly
    Owner- Fur Elise Piano Service
    Pawleys Island SC
    843-325-4357
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  • 7.  RE: Broadwood lyre bolts

    Member
    Posted 03-29-2020 15:45
    Bolts, not wood screws were mentioned. The length might be appropriate.

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    Regards,

    Jon Page
    mailto:jonpage@pianocapecod.com
    http://www.pianocapecod.com
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  • 8.  RE: Broadwood lyre bolts

    Registered Piano Technician
    Posted 03-30-2020 14:26
    Exactly! I went a little different "direction" on this Broadwood. I used really nice coated & hardened lag bolts. Drilled new hole including drilling insets with forstner bits (of which I went ahead & invested in a new set of. At Lowes I was able to get a whole new set for like 35 bucks. I LOVE forstner bits & find them invaluable. But I digress....)

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    Kevin Fortenberry
    Registered Piano Technician
    Temple, Texas
    806-778-3962
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  • 9.  RE: Broadwood lyre bolts

    Registered Piano Technician
    Posted 03-30-2020 15:13
    update: I've tried a couple of bolt sizes from a local ACE. The 1/2" diameter seems appropriate and the threads begin to engage but quickly jam.
    Threads are 13/inch on the bolt--perhaps 12 per inch would do the trick?

    Here's another possibility: Say I can't procure a proper bolt and have no way to retap. Would it work to simply plug the hole and use a large wood screw instead? The hole in the lyre itself is 9/16".

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    Scott Cole, RPT
    rvpianotuner.com
    Talent, OR
    (541-601-9033
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  • 10.  RE: Broadwood lyre bolts

    Member
    Posted 03-30-2020 23:45
    To start with, are you absolutely sure that the plate threads are not metric? If they are there's no problem, but if not then read on.

    Half inch bolts will come with either 13 tpi (threads per inch) UNC or 20 tpi UNF threads.  You won't find a 1/2" bolt with 12 tpi unless it was custom made.  Unified National  and Whitworth share the same tpi in all sizes except 1/2" where the Whitworth uses 12 tpi for coarse and 16 tpi for fine. The difference in the systems is in the thread shape and height which is why the re-tapping can work except for 1/2" bolts.  If the plates that the bolts thread into can easily be removed I would replace them with new plates with 1/2-20 UNF. (but I'm set up to make such things). UNF threads can be tightened tighter and are stronger than UNC threads.  If I were you I'd first try to run a 1/2-13 UNC tap through the plates and see if you can then thread the bolt through the plates.  If that doesn't work, and it probably won't because you have 1/2" bolts, and especially if the original is 16 tpi, then you're not out anything but a little time.  The easiest would be to remove the mounting plates and install 1/2" T-nuts if the wood is solid enough. Otherwise, K. Fortenberry's idea of filling the holes and using lags should work perfectly fine. Hardware store dowels are worthless so you must be able to make non-longitudinal grain plugs or the lags will continually loosen and eventually strip out. If the lag is 1/2" OD then you need a 1-1/4"OD plug minimum.  That's an expensive plug cutter and as usual, the budget and value of the instrument will make the decisions for us.  I hope this is useful information. 






  • 11.  RE: Broadwood lyre bolts

    Member
    Posted 03-30-2020 23:50
    Could you remove the plates and install threaded inserts into the holes to accept the ½" bolt?  I've done that on an old grand where the screw holes were just gone. I might have had to bore the holes a bit to accept the inserts.

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    Regards,

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