Thumb strap screws

[LesJessop]

The 32-button Lachenal (made c. 1860) I recently posted had no thumb straps, so I've started making replacements.  I've sourced most of the materials, the only problem being the screws holding the straps to the ends: each strap needs two 1/4" #1 gauge screws and one 1" #1 gauge screw. I bought the small screws from the Vintage Screw Company, but they could not supply the long screws.

 

I sent e-mails to Concertina Spares and to Steve Dickinson, but got no answers. A search of the internet has turned up a seller who has 25 mm #2 screws, but I hesitate to use bigger screws. Maybe if I was an engineer and had a lathe I could make my own, but I'm not, I don't and I can't !

 

Do any of the members have two spare screws (maybe from 'breakers') they could supply me with ? Or alternatively, make helpful suggestions as to a solution.

 

 

 

 

 

[Lappy]

Have you tried 

 repair@squeezeboxgarage.com  ?

 

[alex_holden]

AFAIK those screws haven't been made for decades and are like hen's teeth now.

[LesJessop]

The owner of the Vintage Screw Company made a similar comment about the rarity.

 

I've just looked at the squeezebox garage website, where I see "We CANNOT supply the long pinky-rest and thumb-strap screws for English concertinas". So, I guess they must get a lot of people asking about them !

[alex_holden]

I have in the past used a modern metric machine screw that was about the right diameter and the same head style but shorter, and glued a threaded insert into the support post for it to screw into. I turned the inserts myself from brass rod but you might be able to buy them because people often use them to add threaded holes to plastic 3D prints. Not original but it worked and didn't look obviously wrong. I think I also screwed the support post to the action board so it wasn't relying on just the glue joint.

[Theo]

This UK supplier has No2 x 1" in brass which will do the job.

 

https://www.screwsline.co.uk/product/wood_screws/brass/countersunk_head/slotted/?id=1484

[Clive Thorne]

14 hours ago, alex_holden said:

I have in the past used a modern metric machine screw that was about the right diameter and the same head style but shorter, and glued a threaded insert into the support post for it to screw into. I turned the inserts myself from brass rod but you might be able to buy them because people often use them to add threaded holes to plastic 3D prints. Not original but it worked and didn't look obviously wrong. I think I also screwed the support post to the action board so it wasn't relying on just the glue joint.

An alternative source is to buy nylon&brass PCB Supports of required thread (mainly metric, but some UNC in the states?

Then hack the nylon off, and you're left with the (knurled) brass inserts. Ideal for pressing into a suitable hole with a bit of glue.

[LesJessop]

Many thanks for these suggestions. I had seen that some firms offer shorter #1 gauge screws, but it did not occur to me to extend the support post. As a first step I've ordered some 1" #2 screws, and will decide which route to follow once I've seen them.

[Nigel Champion]

This thread reminds me of a fine concertina player/repairer, Harold Green, here in New Zealand a few decades ago.  His day job was as an industrial lathe operater.  He was asked on his retirement what farewell gift he'd appreciate most.  He asked for the lathe he'd been using and they agreed. 

 

He kept the monstrous beast in his garage purely for turning out these 1g screws and concertina end-bolts!!!

[d.elliott]

Please remember the purpose and design of the 'support post' or pillar. The pillar should have a clearance hole through it for the long thin '0' gauge structural wood screws to pass through,  so that they anchor directly into the action plate and pad board, not engaging into the pillars. If you increase the gauge of the wood screw then you need to open up the diameter of the pillar clearance hole accordingly. if you screw into the pillar then you can cause the glue to fail between pillar and action plate and the screw will cease to perform it's function. A full length screw passing through a clearance hole is important. Over length screws are often clipped off and filed smooth under the pad board

 

All the forces of playing, of opening & closing the bellows are transmitted through the finger slides and the thumb straps. The long screws exist to transmit those forces through the action assembly into the action plate and pad board.  The idea of the long screw passing through the pillar is to sandwich the action box cover between the screw head and the shimmed (with card) pillar top through what is effectively a spacer into the heart of the instrument. This ensures that playing forces by-pass the delicate fret work. Where the pillars have come adrift or the card spacers have been lost it is not uncommon to see local fretwork cracking taking place. Cracking generally can occur in old dry hardwood as the wood moves with changes of humidity and with time.  However incorrect support and the transmission of forces through the fret to the peripheral bolts can do a lot of damage.

[Jake Middleton-Metcalfe]

I have often wondered how those 1" #1 wood screws were actually made, whether it was something like a capstan lathe and basically like making bolts but with a coarser thread die or if it was actually done in a completely different way. If it's the former then it might be worth someone trying to make/have made a die and make their own screws as this problem comes up for people again and again. 

 

M2 thread 25mm CS screw with threaded insert inside the pad board under the pillar works quite nicely though I have found.

[fred v]

I would suspect that in these days they would be rolled. Almost all bolts are roll threaded now.

[Jake Middleton-Metcalfe]

6 hours ago, fred v said:

I would suspect that in these days they would be rolled. Almost all bolts are roll threaded now.

Probably going to a business with this sort of setup and giving them the spec of what you need would be a way forwards. I have not ever outsourced this sort of custom fitting so have no idea of cost on that one. Its worth exploring and seeing what the cost of a batch would be.

 

The only thing is its got to be custom as wood screws to exactly that spec are not available off the shelf. 

 

Worth looking into anyway 

[LesJessop]

When I contacted the Vintage Screw Company they said that in response to demand they'd looked for a manufacturer and been quoted a price of $1,500 for 5,000 screws. If anybody wants to look into acquiring a large number of screws then maybe the V.S.C. might put you in touch with the makers ?

 

I assume that in Louis Lachenal's day there would be small specialist workshops in Soho who would turn out screws of any size to order, made using a treadle-operated lathe. 

 

I don't suppose Harold Green left behind a box of 1" #1 screws to his friends ? 

 

Incidentally my solution was, following from Theo's suggestion, to buy some 1" #2 screws and work on reducing their size using files and wet-and-dry paper. 

 

 

 

[Jake Middleton-Metcalfe]

23 hours ago, LesJessop said:

When I contacted the Vintage Screw Company they said that in response to demand they'd looked for a manufacturer and been quoted a price of $1,500 for 5,000 screws. If anybody wants to look into acquiring a large number of screws then maybe the V.S.C. might put you in touch with the makers ?

 

I assume that in Louis Lachenal's day there would be small specialist workshops in Soho who would turn out screws of any size to order, made using a treadle-operated lathe. 

 

I don't suppose Harold Green left behind a box of 1" #1 screws to his friends ? 

 

Incidentally my solution was, following from Theo's suggestion, to buy some 1" #2 screws and work on reducing their size using files and wet-and-dry paper. 

 

 

 

 

That is a fair price assuming variants on these screws would not be needed. If someone bit the bullet and ordered that ... assuming they very carefully studied the old screws across a number of instruments and worked out if there were any variation problems, then they could sell them on to whoever needs them, adding on a margin for their time and the problem would be solved for everyone perhaps for ever. I don't have a spare £1500 to do this though.

 

I mean one could always order less, perhaps only 2000 or even 1000 screws would actually be all that anyone would ever need.

 

The small lathe option sounds a bit more up my street if I could work out a way of making them quickly enough on a small scale, I think a different approach might be needed from making bolt threads though. As people have said thread rolling machines are the industrial way of doing this but those are really big machines I think.

 

Edited July 27 by Jake Middleton-Metcalfe

[Clive Thorne]

3 hours ago, Jake Middleton-Metcalfe said:

As people have said thread rolling machines are the industrial way of doing this but those are really big machines I think.

 Yes they can be very big, and even if a company had one they would need to have a set of thread rolling dies produced, plus the blanks of course.

 

Unless you are absolutely committed to maintaining originality for some reason I would have thought that retapping and using current standard threads or screw sizes would be the sensible way to go. Probably get 100 screws for £10.

 

[Jake Middleton-Metcalfe]

12 hours ago, Clive Thorne said:

 Yes they can be very big, and even if a company had one they would need to have a set of thread rolling dies produced, plus the blanks of course.

 

Unless you are absolutely committed to maintaining originality for some reason I would have thought that retapping and using current standard threads or screw sizes would be the sensible way to go. Probably get 100 screws for £10.

 

 

This is what we are left with really. M2 25mm cs bolt and threaded insert in the pad board it is for me I suppose.

[Stephen Chambers]

On 7/26/2025 at 9:57 PM, LesJessop said:

I assume that in Louis Lachenal's day there would be small specialist workshops in Soho who would turn out screws of any size to order, made using a treadle-operated lathe. 

 

There was at least one, that of a Swiss immigrant who set up as a "small screw and piano rivet manufacturer", and his name was Louis Lachenal - it's how he got into the concertina manufacturing business in the first place!

 

And "family lore" (I interviwed Bill La Chenal, a great-grandson of Louis Lachenal, and his mother Dorothy (“Dee”), when I visited them on 15th March 2000) has it that [Joseph Henry] Nettlefold, the Nettlefold in Guest, Keen & Nettlefolds, was his apprentice.