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5/32-32 Machine screw sizes

fartymarty

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This post was moved from another thread for more exposure. Basically I want more information about 5/32-32 machine screw which I guess is a specialty type size? I have never heard of this size before and I wonder if there are others that I've never heard of. There seems to be plenty of taps and dies available to make this thread but when I try to find a size chart that includes it; or a thread checker kit that includes it, I'm coming up with nada.

back story: I was using some aluminum threaded inserts from Harbor Freight to repair my mower's recoil starter. Either due to the quality of the Harbor Freight stuff, or my ham-handed technique, it resulted in numerous stripped threads followed by drilling them out and finally acceptable (?) installs that lasted only a about a week. I decided that I needed a better install tool and some steel threaded inserts. Not doing a whole lot of research I ordered both from Amazon.

Set up: Two days later after they arrived, I was looking over the threaded inserts and noticed that one of them was "5/32-32"...?...I had never heard of such a size before, but then I don't get out much. I checked the insert against a thread checker and it was closest to a #8-32 but would bind just a bit at the end of the thread and not go on all the way. I tried it on 10-32 and it wouldn't even start. No luck on my metric thread checker either. I have never heard of a fractional size below 1/4" only number sizes. ̶I̶s̶ ̶t̶h̶e̶r̶e̶ ̶a̶ ̶l̶e̶g̶i̶t̶i̶m̶a̶t̶e̶ ̶5̶/̶3̶2̶"̶-̶3̶2̶ ̶s̶i̶z̶e̶ ̶f̶o̶r̶ ̶s̶p̶e̶c̶i̶a̶l̶ ̶a̶p̶p̶l̶i̶c̶a̶t̶i̶o̶n̶s̶?̶ I see from a google search, that there are companies that make taps that size so I guess it is a legitimate size, but I've never run across it before.

Question: Is there a special application for that size that any of you know about?

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edit:I just went to my high school era Machinery's Handbook (1966 17th Edition) thinking that if there was an answer I could find for myself, that it would be in there. No. Closest I could find was a 3/16-32 British Standard Fine screw.
 
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Spacey_G

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I've had situations where a #8-32 screw started but bound up after a few threads that turned out to be M4 x 0.7. (Or maybe it was the other way around).

But 32 threads per inch is closer to 0.8mm per thread, not 0.7mm, so I don't think it's some goofy conversion from a standard metric thread.

That's strange indeed.
 

JR 42

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Yeah, I was thinking weird 4mm thread as well, but no idea.

The "All dimensions are measured manually, there may be measurement errors, please don't mind" isn't the most confidence- inspiring product description. :lol_hitti
 

pstemari

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There's a 3/16”-24 thread that I've seen. Just a wee skooch smaller than a 10-24. Your 5/32" is probably something similar: oddball and/or obsolete thread size.


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GRB

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We had a 7x9' room full of tap cabinets. Literally hundreds of different sizes. Probably $50,000 worth. Never heard of 5/32-32. I'm guessing it is really 12-32 which is very unusual but still does exist. 12-24 is unusual, 12-28 is rare, 12-32 is really rare.

Cheap Chinese supplier with something lost in translation?
 

CallumRD1

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Colorado
We had a 7x9' room full of tap cabinets. Literally hundreds of different sizes. Probably $50,000 worth. Never heard of 5/32-32. I'm guessing it is really 12-32 which is very unusual but still does exist. 12-24 is unusual, 12-28 is rare, 12-32 is really rare.

Cheap Chinese supplier with something lost in translation?

But a #12 screw will have a major diameter of about 0.216" while 5/32" is about 0.156". A screw with a 5/32" major diameter would be somewhere between a #6 and #8 thread.
 
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fartymarty

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5/32"-32 is one of the British Standard Whitworth thread sizes:

https://en.wikipedia.org/wiki/British_Standard_Whitworth

The ​5⁄32 in Whitworth threads have been the standard Meccano thread for many years and it is still the thread in use by the French Meccano Company.

Thanks! I looked for that in my old Machinery's Handbook but it didn't include that size in either the BSW nor the BSF listings.

Still I wonder why the taps and dies that I find in that size use the NS or UNS designation. Just Chinese to Engorish confusionese?
 

Mechanical Noise

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Thanks! I looked for that in my old Machinery's Handbook but it didn't include that size in either the BSW nor the BSF listings.

Still I wonder why the taps and dies that I find in that size use the NS or UNS designation. Just Chinese to Engorish confusionese?

The "NS" standards were superseded by "UNS" but are pretty much the same.

https://www.ring-plug-thread-gages.com/ti-N-vs-UN.htm

I know that most of the Whitworth and US coarse thread pitches are the same for the same diameter. Thread form is a little different, however. Maybe, back in the past, US manufacturers followed the pattern with the 5/32" X 32.

It doesn't seem to have been in popular use in the US but there's probably alot of "just in case" taps and dies in toolrooms.

I wonder if alot of this oddball stuff in assortments is just surplus they're getting rid of.
 
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davethorik

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That is a weird one, can't say I've heard of it either.

As it turns out there are a lot of thread pitches I've never heard of. They had a bunch of weird stuff at work but it was mostly scrapped. Don't remember 5/32-32, but the weirdest I can remember are 1/4-40, 1/2-32, and 11/16-20.

I found one of the 11/16" taps in the scrap hopper and I had to keep it just because it's so weird.
 
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