1920's BSA under lever thread form?

[Geoff555]

Hi chaps, I have tried searching and got 400 pages of nothing really revailent, maybe its the way I tell it!
All I want is to find what thread is used on BSA underlevers (1926) example, loading tap cover plate screws,STD33 Knibbs number.
BSF?
.165" diameter approx. ( worn )
I need something with the same thread 3/4" long for a rifle repair.
Thank you for any help you may be able to give.
Cheers.
Geoff.

[chieffool]

You have put this under GENERAL. Just raise anything you want to know as a question under the COLLECTABLE section ... And you will generally find anyone with a relevant answer will chip in.

[martin bingham]

evening,
There is a thread on the vintage bsa forum about piston washer screw sizes and the technical info in that should help,the Bsa cycle adds a bit of history to your predicament.
all the best

[angrybear]

Hi chaps, I have tried searching and got 400 pages of nothing really revailent, maybe its the way I tell it!
All I want is to find what thread is used on BSA underlevers (1926) example, loading tap cover plate screws,STD33 Knibbs number.
BSF?
.165" diameter approx. ( worn )
I need something with the same thread 3/4" long for a rifle repair.
Thank you for any help you may be able to give.
Cheers.
Geoff.

How many TPI & is that the bolt or the hole size ?

5/32 is 0.1562", or 11/64 is 0.1719"

Could be 2BA.

[Geoff555]

Hello thank you, the bolt measures .165" ish, oval and worn. TPI , fine, impossible to count as there is nothing left. Sorry but I could not find the thread on the BSA forum, will try again.
Cheers.
Geoff.

[DAVALI]

If you can access the female thread that you wish to find out the thread pitch then sharpen up a piece of hard wood to fit the female thread and screw this in it should give you some idea of the pitch, having that will give help in identifying what thread you have,

Dave.

[Benelli B76]

Hello thank you, the bolt measures .165" ish, oval and worn. TPI , fine, impossible to count as there is nothing left. Sorry but I could not find the thread on the BSA forum, will try again.
Cheers.
Geoff.

Really old BSA used "Bicycle Thread" bolts, but I think in your case they would be using BA which is an obsolete set of threads up to 0BA (around 6mm). Yours is probably a worn 2BA 0.185 inch dia 31.36 TPI. If not it will be 3BA 0.1614 inch dia 34.79 TPI. These bolts are still available, also taps and dies. I have worked on old Webleys that use BSF threads and there is the smallest, 3/16 - 0.1675 inch dia 32 TPI.

Baz

[kamyonsofor]

Hi I have a Bsa "D" type and our local factors were prepared to size a bolt for me ,if I took the beast in for them to look at another idea someone with a early Meccano set I think they were BA screws /bolts.

[Geoff555]

Hello thank you chaps, what a minefield, some were 37 TPI no not a misprint 37. In the end as the rifle is very non standard then I cheated and tapped it out to 5mm.
Give you some idea as to what I was up against was what should have been identicle holes had a mixture of bolts rammed in hence stripped and over sized holes etc.
Thanks for the tip about using wood as a measure, useful that.
Thanks again.
Cheers.
Geoff.

[noz1]

Really old BSA used "Bicycle Thread" bolts, but I think in your case they would be using BA which is an obsolete set of threads up to 0BA (around 6mm). Yours is probably a worn 2BA 0.185 inch dia 31.36 TPI. If not it will be 3BA 0.1614 inch dia 34.79 TPI. These bolts are still available, also taps and dies. I have worked on old Webleys that use BSF threads and there is the smallest, 3/16 - 0.1675 inch dia 32 TPI.

Baz

BA threads are not obsolete.

[Benelli B76]

BA threads are not obsolete.

I said on the post you can still get them, in fact I have hundreds in stock. Let me know who actually uses them in manufacture today, I would be interested in contacting them ?

Baz