Help me identify some old screws?

[rvt]

Help me identify some old screws?

Exciting bank holiday monday ;)

I often get given lenses to repair or modify. It's not uncommon to find that someone has either tried to have a go at it themself and got in a mess, or that simply someone has used the wrong fitting screw driver at some point in it's life. This often results in the odd screw looking a mess or sometimes being completely unusable.

These are from lenses from the 60's, 70's usually. Sometimes early 80's. There is a common one that i come across, but I'm stuck on what exactly it is. Ideally I'd like to order a hundred or more just so I have them spare. So here we go..

Head diameter seems to be about 2.48mm.
Thread diameter seems to be about 1.63mm.
It seems to be 6mm long.

I found this site. Am I looking for M1.6 6mm screws?

I'm a little confused as I assume because of the age of the lenses most would be imperial. Would that be a problem here?

Thanks for your help. I hope your day has been as exciting as mine :P

[trevoratxtal]

Hello
I found this site. Am I looking for M1.6 6mm screws?

I'm a little confused as I assume because of the age of the lenses most would be imperial. Would that be a problem here?

It is possible a BA size (metric/imperial)
http://www.vmyg.org.uk/pages/resources/how%20to%20do%20it/nuts_and_bolts.html
Has a table to compare.
All the best
Trev

[Jasonb]

Can you say what the pitch/tpi is ?

Could well be 10BA as the thread ius more than likely to be a little undersize, 10BA would be 1.70mm

Jason

[rvt]

Trev, Jason - thank you!

I measure the diameter of the thread as 0.64 inches, the tpi as ~68-70 (not very accurate of course)

These are a little less than the 10 BA, but there doesn't seem to be anything else closer. Does that mean that it's likely to be a metric screw or that it's normal to find measurements a little 'off' to 'standard' ?

[mklotz]

A #10 Thury thread has:

diameter = 1.64 mm
tpi = 72.8

This from the FINDTHRD program on my website.  You might want to download it and do some further checking.  It may also be useful for future thread identification.  It's free so you have nothing to lose.

[rvt]

Thanks Marv. I get the impression this might be a bit of an obscure thread/screw to use on a mass production camera lens from the 70's though? Perhaps I am wrong. Hopefully I will get to the answer soon though. I ordered a small batch of 10 AB 1/4" screws to 'test'.

[John Hill]

If I recall correctly many older optical instruments used metric threads due presumably to the German prominence in the field.

[rvt]

Good news! Got some 10AB samples through the post today and they seem to fit well. I was gentle with the threading and it seemed to require no force and I couldn't feel any grinding. It was secure too, not loose. So seems great, thanks to everyone for the advise! I would have just ordered M1.6 screws if I hadn't known, which may have fit, but most probably would have damaged the thread.

This guy was very helpful, I can recommend him: http://www.modern-screws-fixings.co.uk/

If I recall correctly many older optical instruments used metric threads due presumably to the German prominence in the field.

Hi John,

The majority of 'consumer' optical instruments (ie 35mm cameras) are actually made in Japan (Canon, Nikon, Pentax, Minolta etc). Of the German brands out there that do make 'consumer' glass, it's all very high quality though. I will keep that in mind if I come to work on some German glass in the future, thank you!

[andyf]

Hi RVT,

Glad that you got fixed up .

This page http://pages.cs.wisc.edu/~bolo/workshop/thread.html shows a number of threads with major diameters of around 1.6mm. Maybe yours was really a Thury (Swiss, so perhaps used on optical equipment). The BA thread was based on the Thury, and used the same 47.5^o thread angle.  But it's easier to use 10BA than try and find a Swiss supplier.

Andy