What thread size is this?

[rawbutter]

I recently bought a Clippard MAR-1 LPR to use on a project, and this is the adjustment knob. Since the knob is pretty tall, I want to replace it with a set screw so the whole thing will fit inside a frame. However, I can't figure out what thread size this is.

All the thread sizes on the LPR are imperial, and the knob thread has a 5/16" diameter and about 40 threads per inch. But I can't find 5/16-40 screws anywhere. I can only find 5/16-18 and 5/16-24, but the TPI here is much higher. (All the threads pictured on the screw are only 1/2" long.)

[WORR13]

u checked with a thread pitch gauge? possibly metric? alot of older paintball stuff has special or 'one off' threading

[rawbutter]

I did, but my thread pitch gauge only has 5/16-18 and 5/16-24. It also has more threads per inch than M8-1.0. So it must be some other non-standard size.

[WORR13]

really need gauge to match it up. possibly 32, 36, 40? -ive seen in paintball parts. maybe stop by machine shop and ask, if you can find one nowadays

[WORR13]

you could check it against a ruler (steel rule) too. if you have one that goes down to 32"nds or smaller. need good eyes and patience --haha

[Macdave06]

Not any help on the threads but now I know how to get a complete brass front end on my 97.

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[Jordan]

Keep in mind those Clippard LPRs require limiting input pressure to 300psi.

[rawbutter]

What Jordan said. Also I have yet to figure out how to get this thing apart, so I'm not sure if it can be rebuilt.

[RuleOfSines]

They might have cut it to a non-standard size to achieve a certain turns-per-psi or something like that.

[Brokeass_baller]

5/16 UNEF is 32. So, I'd run out to a local hardware store and try out a 5/16-32 bolt, or whatever you can find.

If that ain't it, it must be custom geometry, but I can't imagine they'd need anything finer than that.

[Brokeass_baller]

Are you sure that's 1/2 of threads and not, like, 9/16 or something? Just judging from the photo, it looks a little longer than half an inch, and that extra 1/8" can throw off your guestimation.

[rawbutter]

The bolt is longer, but the threaded part is only 1/2 inch. I measured with calipers. But I'm going to give those UNEF screws a shot anyway. I think that's the best bet so far.

[MrBarraclough]

At my local hardware store, about the only things with a 40 TPI pitch are labeled "gun screws." A lot of firearms applications use weirdly tight threading. Maybe you'll find a set screw of appropriate threading if you look at firearms-specific hardware.