Imperial Lyre Box Screw

Discussion in 'The Rehearsal Room' started by 2nd tenor, May 5, 2017.

  1. 2nd tenor

    2nd tenor Well-Known Member

    I have a Boosey and Hawkes instrument that came to me without a screw in its lyre box. Thinking that it might be handy to have a functioning box I contacted a couple of spares suppliers who assured me that their part would fit and work in my B&H. The supplied parts didn't fit so I measured a couple of things (thread diameter and pitch) and used the information to identify the thread type used. I now have a (roughly 1/2" long) 4 BA screw in the Lyre box (sourced it off of eBay), I couldn't get a knurled head head Screw but plain slotted will work for me - assisted by some small handy tool, be careful not to over tighten. The British Association or BA standard for threaded parts is something that was commonly used in the past, it is no longer in common use - expect older instruments to have Imperial (inch based) rather than Metric (millimetre based) threads on them.

    I hope that the 4BA size details above are a help to someone who finds themself in a similar situation and, of course, that this post actually shows up when someone searches for the deatails in a few years time. What worked for me might not work for someone else, but it's a start.
    Last edited: May 5, 2017
  2. Jack E

    Jack E Well-Known Member

    With motor bikes, 2T, I think they didn't start switching away from Whitworth and BA threads until the 1970s - and plenty of smaller and more specialist companies stayed with them well after that. The good news is that model engineers still use BA screws, and screws, washers and nuts are still readily available in steel, stainless steel and brass in sizes down to 12BA - which is 1.3mm diameter. It's also worth bearing in mind that, if your lyre screw is a BA thread, your water valve screws and nuts are probably BA threads, too.

    If any of the threads get damaged, model engineers' suppliers also sell BA taps and suitable tap wrenches.

    With best regards,
    2nd tenor likes this.
  3. 4th Cornet

    4th Cornet Active Member

    This is an interesting thread...


  4. 2nd tenor

    2nd tenor Well-Known Member

    :) . I didn't realise that my interest in all things engineering was contagious. The original post was more intended to be a statement of information for those who might at some time need it rather than anything else, a way of giving back something to the on-line community and potentially helping some future reader. A while back someone started a thread about valve alignment. That's a subject of limited interest but by using it, and further developing some of the ideas in it myself, I've worked on a couple of instruments and improved how they play - some topics don't appeal to the majority of members but they still have value.

    tmp seems a bit quiet at the moment, I guess that there comes a point when existing members have said what they want to about any particular subject. However, if anyone has repair expertise to share and wants to start a thread on keeping older instruments in good working order (ready for playing) then I'd follow it with interest.
    Last edited: Jun 13, 2017
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  5. 4th Cornet

    4th Cornet Active Member

    It is indeed a useful post. I hope mine wasn't taken as being sarcastic as that wasn't the intention :S
  6. MissBraz

    MissBraz Active Member

    hahaha love this !!! Much appreciated from this engineer!!
    4th Cornet likes this.
  7. Tom-King

    Tom-King Well-Known Member

    It can never hurt to have information out there - good on you for sharing.

    I would, personally, have not bothered searching for that and simply used a lyre that clips onto the bell (and I do anyway - my Bb and Sop don't have a lyre box, by choice - I prefer the music that little bit further away) but I'm sure it'll come in useful to someone at some point in the future - this is where forums like this are much better than facebook, it's easier to search back and find information like this.
    Jack E, 2nd tenor and 4th Cornet like this.
  8. 2nd tenor

    2nd tenor Well-Known Member

    Update, for the record.

    By chance a friend's Besson (maybe 1990's? maybe UK built?) ended up with me for a bit of basic maintenance. I noticed that the Lyre Box screw was missing, to my surprise it too takes a 4BA by 1/2" screw.

    Thanks, I'm happy to share information; in the past others on tmp have been kind enough to answer my questions so offering a bit of data back to the forum seems an appropriate thing to do.

    On a Cornet, Flugelhorn or Trombone ( :) ) that off of bell mounting is an option, but if you happen to play a Tenor Horn, Baritone, Euphonium or Tuba then a different route is needed.
    Last edited: Aug 12, 2017
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  9. Jack E

    Jack E Well-Known Member

    I would imagine the reason they stuck with the BA thread is that it greatly simplifies the stocking and supplying of spares, so your customer can just order "a lyre box screw for my Besson tenor horn", and be sure to get a part which fits.

    Also, if you already have the necessary drills and taps to produce a BA thread, why throw them away to buy metric replacements, and incur the cost of modifying all the production drawings, parts lists, and arranging for the stores to stock both items? With its small thread and large, knurled head, the lyre box screw can't be bought off the shelf from bulk suppliers of threaded fasteners, anyway - just like the water key screws with their long shank and short thread, it's not used anywhere else in industry, so even if you switched to a metric thread, it would still have to be specially made.

    One of my favourite points about the Land Rover I used to own was the way they didn't change any part unless there was a damn good reason for doing so, but worked on the lines of, "If it ain't broke, don't fix it." Mine was a 90, built in 1986 - but some spares for it were compatible with models dating back to the late 1940s!

    With best regards,

  10. KenIrvin

    KenIrvin Member

    We have several besson Sovereign cornets with missing lyre box screw - does anyone know what size thread this is. Tried 4ba and it is too big so obviously not standard across the Sovereign range!
  11. Jack E

    Jack E Well-Known Member

    It might be a 6BA, Ken - outside diameter 2.8mm, as compared to a 4BA at 3.2mm. You can buy various sizes of BA screws on E-bay starting at about £1.60, or try your local motor factor or hardware store for small metric screws - say, M3 or M3.5 to check them, and the metrics will be very cheap.

    KenIrvin likes this.
  12. 2nd tenor

    2nd tenor Well-Known Member

    I guess that I have to refer you back to my original post in the hope that it will guide your search. The lyre boxes that I found screws for where on larger instruments than Cornets, though I can't see that making a difference it might. If you don't have an engineering or diy background it might well be difficult for you to identify the correct thread yourself and there are many alternatives that could have been used.
    (EDIT including Metric, BA series and the American Unified series - see the Dawkes site for the last.)

    Somehow you need to measure the diameter of the screw hole and that will give you near enough the root diameter of the screw - you could try putting the plain end of some small drills into the hole. You also need to get an idea of the screw's pitch. I don't recall how I did that now but if doing it again I think that I'd be thining down a matchstick (near square) until it entered the hole easily and could be screwed in by lightly deforming the wood, then count the number of turns required to cover some distance and you can work out the approximate thread pitch. Tables of screw root diameter and pitch are available on line, your first answer might not be perfect but it should be near and help you get the right choice the next time.

    I hope that the above is a help.

    Edit. There seems to be an assumption the a screw supplied from a specialist brass music shop wouldn't do the job. Whilst they didn't manage to help me that might not be the case at all for other people. If you haven't tried one then I suggest you do and risk a few pounds - it could save you a lot of time.
    Last edited: Sep 23, 2017
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  13. KenIrvin

    KenIrvin Member

    Thanks Jack and 2nd tenor. i have also tried 3M which were way too small so will have to keep trying
  14. Jack E

    Jack E Well-Known Member

    I've done a bit of digging, based on the fact that 4BA is too big, and M3 is too small.

    The outside diameter of 4BA is 3.6 mm, as compared to an M3.5 at 3.5mm, so you might think that such a tiny difference as 0.1mm (or .004" in Imperial measure) wouldn't be enough to stop a 4BA screw being screwed in; but the pitch of the two threads are also different, with 4BA having a pitch of 0.66 mm as compared to M3.5 at 0.6mm - the combination of larger diameter and wrong pitch being just enough to prevent a 4BA screw going into an M3.5 hole.

    There is an intermediate BA thread, 5BA, but this is very uncommon, except in specialist applications - and it can't be an M.4, as a 4BA will drop straight through that size hole. Equally, if an M3 (O/D 3mm) is too small, then it can't be a 6BA, which is smaller still at 2.8mm; so it looks like your best bet would be an M3.5 screw.

    HTH, and best regards,


    PS - when you establish what size it is, can you post it on here, please? Lost lyre screws seem to be a common problem, and any info on the size that fits your cornets may save someone else a lot of headscratching! :)
  15. Jack E

    Jack E Well-Known Member

    But not as quirky as this one . . .


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  16. KenIrvin

    KenIrvin Member

    Hi Jack
    Thanks for the detailed description of threads.
    I have tried 6BA which is too small, waiting arrival of 5BA.
    It seems Besson changed the Lyre box on the cornet some time after mine was produced (~1992?). I think the newer models use the universal screw readily available.

  17. KenIrvin

    KenIrvin Member

    Finally identified the thread size thanks to Ian Shaw at
    1/8" BSW x 1/2" does the job.
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  18. 2nd tenor

    2nd tenor Well-Known Member

    Obviously I’m really pleased that you have been able to find something to suit your instrument and that you have taken the time and trouble to record your results here. Thank you.

    As and when you feel able to would you please let us know what led you to Ian Shaw and how he identified the size for you. Those details might help others with a similar problem at some future time. Thanks.
    Jack E likes this.
  19. Jack E

    Jack E Well-Known Member

    Good-oh, I'm glad you were able to sort it. I never would have guessed it might be a Whitworth thread - though it's always possible that the original thread was something else, but got damaged, and the hole was tapped for a larger screw to replace it?

    If there's anyone on here who used to work for B & H, maybe they can add some extra info. Either way, I'm sure that this information will prove helpful to others. As I said earlier, lost lyre box screws seem to be a perennial problem.

    With best regards,

  20. KenIrvin

    KenIrvin Member

    Ever the detective.
    I had assumed that the thread would be BA and tried 4,5,and 6 before resorting to Google. Searched for information on thread sizes and information hosted by Model Fixings came up. I sent two photos - one showing thread lenght against a ruler and one clearer photo of the thread, plus the information that 5BA fit but would not screw in. Ian came back to me within the hour with the suggestion of 1/8" BSW (and apologised for not having any screws in stock). Ordered some straight away and Bob's your uncle - problem solved. I don't know anything about their business but given the response from Ian would recommend them to anyone with a small engineering problem.

    The screws fit both my cornets (Besson Sovereign and B&H Regent) as well as a B&H 700 belonging to the band so I assume it is common to all cornets produced before mid 1990's(?)
    2nd tenor likes this.

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