screws, bolts and fasteners used on vintage TE

[tatel]

In my current case, I need to identify this set screw used on  F931B knobs.

I can undo most of them with a 1.5 mm hex key, but there are some more tight where the key slips.

Diameter seems to be 3.5 mm, so perhaps this is a metric set screw and the matter is I need better quality metric hex keys. Long is about 4.78 mm which looks a lot like 3/16 however. Then this would probably be an imperial screw and I would probably need a set of imperial hex keys, particularly a 1/16" one. I'm getting it anyway, but it would be nice to have confirmation about what kind of screw this is.

From a more general point of view, it would be nice if a compilation of different screws, etc, used in vintage Fluke, HP, Tektronix, (put your favorite brand here) could be made,with links to providers if possible, and compatible replacements. A little bit like the sticky threads on this section. Alas, I have been unable to find much about this matter in these useful threads.

[mikeselectricstuff]

imperial allen keys go down to 1/64" increments

[HalFoster]

Google Wiha hex key sets: 35392 Metric, 35393 Imperial.  Amazon has them and they are what I use for all set screws.

[tatel]

1/64" increments? Wow, fine fine tangerine.

In looking at this: https://www.amazon.com/Bondhus-16936-Balldriver%C2%AB-L-wrenches-BriteGuard/dp/B000E7ZQ8U/ref=sr_1_15

Hoping they will be good enough.

[George Edmonds]

If it is 3.5mm OD it could be 4BA which used Imperial keys

George Edmonds

[TimFox]

A detail about inch-dimension hex keys ("Allen wrenches").
Almost all standard sizes are binary-fraction inches, but there is one extra at 0.050" in many sets.
0.028" and 0.035" sizes are also found in sets.
(e.g.,  https://www.mcmaster.com/7158A4/  )
American turn-counting dials for Helipots often used small spline (or Bristol) wrenches, along with other knobs, with a quite-different hexagonal- or four-fold symmetric cross-section.
See  https://mgs4u.com/product/ss-508-bristol-spline-l-key-kit/

[BrokenYugo]

#6-32? https://www.engineersedge.com/screw_threads_chart.htm

[tatel]

After looking at the vernier of mi caliper through a printer loupe, I would say diameter is 3.46 mm +/- 0,02 mm

From https://en.wikipedia.org/wiki/British_Association_screw_threads 4BA has 3.60 mm outside diameter. 6/32 and 6/40 both have 3.5052 mm outside diameter and I'm unable to find anything closer to 3.46 mm so I'm going to try 6/32 set screws.

This AliExpress seller seems to be one of the cheapest and one can choose between 304 stainless and 12.9 steel. https://www.aliexpress.com/item/1005007168325606.html

Another Ali seller: https://www.aliexpress.com/item/1005006097897350.html

And one from Ebay: : https://www.ebay.com/itm/185383761203

Not really sure if 304 stainless would be better than 12.9 steel.  I guess, to avoid rounding the hex socket heads, on these little set screws, one should choose a good steel alloy. 12.9 sounds like plenty. When I was into speleology, we used metric 8 machine screws made from 8.8 steel to hold the ropes in pits. Would be 304 stainless tougher than 12.9 steel? Or would it be better because it wouldn't rust?  What would you choose?

I'm attaching a pdf with some pomona screws that at first glance looked as if they could be used on some Fluke devices to fasten covers, etc, but after a close-up look, that seems to be wrong.

If after some repair you happen to know what screws could be used in any vintage device, could you please report about it?

[Hamelec]

see table

[BrokenYugo]

304 is bubblegum compared to 12.9 or A574, quenched and tempered alloy steel.

[tatel]

Wow, what a difference. 12.9 it will be.

[Kleinstein]

With such small screws it is unlikely to find a high strength version like 12.9. So if offered at Ebay of Ali.., chances are that it is not the claimed strength. Still sometimes excess inventory lots of special parts end up there.
Normal such small screws are more 5.6 grade or similar.

For 304 stainless, this is only the chemical composition. The actual hardness can vary a lot, depending on the degree of cold working. So it can be rather soft, but also quite hard.

[BrokenYugo]

While quality is obviously not guaranteed on AliExpress, afaik 12.9 or some similar flavor of hardened chromoly is standard for all those little black oxide socket head screws, at least by US standards.

[Hamelec]

Normal such small screws are more 5.6 grade or similar.

I dont think so, a lot of Set screws are hardened and tempered

[CatalinaWOW]

Do be sure to buy known high quality tools.  Dimensional accuracy on lower grade sets is often uniform across the size range.  And what is a negligible error on the larger sizes makes smaller sizes nearly or totally unusable.

[Overspeed]

Hello

Under 1/4 inch of OD the US system change of ''name'' the 8-40 or 6-32 or ...

first number is the size ( OD ) 2 other are the pitch ( number of thread per inch )

Check Brownell's gun parts that common screws to plug sight hole on gun

Regards
OS

[Hamelec]

here is a more or less complete overview of threads (sorry, most of it is in German)
http://www.mikroskopfreunde-nordhessen.de/dateien/Gewindetabellen-2011-12.pdf
hf