thread identification

[angus]

hi
i have a bit of a puzzler

i am missing a screw from a williams rifle sight... its 0.138 diameter, so either 9/64 or 3.5mm
and either 0.5mm pitch or 48tpi

the books i have dont really give me a standard thread.....

any idea's as to what thread  it is ?

[Pete.]

A 3.5mm screw would have an OD of 3.48mm so the OD of 3.505 suggests an imperial size. Also M3.5 typically comes in 0.6 and 0.35mm pitches, which would work out at 42.3 and 72.5tpi, so there's no metric equivalent close to your 48tpi.

[angus]

sort of worked that bit out for myself..... the sight came from America, so guess it will be nothing standard!

[John Rudd]

It doesn't necessarily have to be a standard thread.....
I've known threads to be made as "specials" .........There' no reason why you can't make any thread the size you want....

[philf]

hi
i have a bit of a puzzler

i am missing a screw from a williams rifle sight... its 0.138 diameter, so either 9/64 or 3.5mm
and either 0.5mm pitch or 48tpi

the books i have dont really give me a standard thread.....

any idea's as to what thread  it is ?

Angus,

It looks very much like a 6-48 UNS to me. (Which is 6 gauge in neither UNF(ine) or UNC(oarse) but UNS(pecial).)

I don't know where you would get a die to make a screw in the UK. They come in kits of taps & dies for gunsmiths in the US:

http://www.brownells.com/gunsmith-tools-supplies/general-gunsmith-tools/taps-dies/tap-die-kits/tap-die-kit-no-1-prod713.aspx

Cheers.

Phil.

[Bluechip]

 
I think the Metric Series is getting as confused as Inch threads. I have some 3.5mm x 0.5mm myself.
 
Not where I got them, but  ....
 
http://www.fish4parts.co.uk/Tools.1099/Thread-Insert-Systems-%252526-Cutting-%25252F-Tapping-Tools.10930252/Thread-Cutting-Taps.10930332/Metric-Fine.10930333/M3.5-x-0.5mm-Pitch-Straight-Flute-Second-Tap.100690.html?osCsid=jrjn1tqdhj5fhh6tbdssuvn8k5
 
Dave BC

[Pete.]

hi
i have a bit of a puzzler

i am missing a screw from a williams rifle sight... its 0.138 diameter, so either 9/64 or 3.5mm
and either 0.5mm pitch or 48tpi

the books i have dont really give me a standard thread.....

any idea's as to what thread  it is ?

Angus,

It looks very much like a 6-48 UNS to me. (Which is 6 gauge in neither UNF(ine) or UNC(oarse) but UNS(pecial).)

I don't know where you would get a die to make a screw in the UK. They come in kits of taps & dies for gunsmiths in the US:

http://www.brownells.com/gunsmith-tools-supplies/general-gunsmith-tools/taps-dies/tap-die-kits/tap-die-kit-no-1-prod713.aspx

Cheers.

Phil.

I think you're right, since the TPI matches and only 3 thou out on the OD from his measured size:

http://www.muzzlecouplings.com/measuring_thread_size.htm

http://www.ebay.com/bhp/6-48-screws

[Jonny]

Still the most common thread used in US, theyre still on UNC, UNF but slowly changing over to metric.
Taps and dies quite common here too and cheap because no one wants them about £4 delivered for an 8-32 HSS tap last month for US, dies about the same.

Sure the 48TPI is about right?
Williams I would have thought 6-32  or 8-32 if measured the threaded hole.

[75Plus]

6-40, 6-48 and 8-40 are common sizes found in US made firearms and have been for at least a century. Here is the inventory of a Master Gunsmiths 142 pc. screw assortment from Brownell's, one of the top gunsmithing parts sources in the US.

 Master Gunsmith Screw Kit-142 Kit

Contains 10 each of 14 premium 3/32” hex style scope and base screws. These difficult to find screws are favored non-slip replacements for slotted screws. Set includes tweezers and thread size gauge/shortening jig.

Kit Contains:

#6-40 Fillister Head (3/8, ½)

#6-40 Oval Head (1/4, 3/8)

#6-48 Fillister Head (1/4, 3/8, 9/16)

#6-48 Oval Head (1/4, 3/8)

#8-40 Fillister Head (1/4, 3/8, ½)

#8-40 Oval Head (1/4, ½)

[angus]

Still the most common thread used in US, theyre still on UNC, UNF but slowly changing over to metric.
Taps and dies quite common here too and cheap because no one wants them about £4 delivered for an 8-32 HSS tap last month for US, dies about the same.

Sure the 48TPI is about right?
Williams I would have thought 6-32  or 8-32 if measured the threaded hole.

the measurements are of the other locking screw.... definitely seems to be 4-48.... a mate of a mate thinks he has some... time will tell

[philf]

the measurements are of the other locking screw.... definitely seems to be 4-48.... a mate of a mate thinks he has some... time will tell

Angus,

4-48 is much smaller OD than you originally quoted and is a standard UNF thread and is only 0.118" c.f. 0.138" you originally quoted.

6-48 UNS is 0.138".

Phil.

[angus]

sorry philf my keyboard isnt typing what i meant!!!

i have 6-48 UNS written on my desk!