Machinist (?) advice needed

[ar15barrels]

At this point I'd sent the material to someone else to make it, since I'm wondering how easy the OP is to work with.

PIA price is normal price x10.

[ar15barrels]

Sorry, didn't measure the original screw (sent them back) and it's a good thing, otherwise there would be more of the below...

Love the comments...

1. OP doesn't know what he's doing, where to measure from on a caliper
2. Can't use/read a caliper (hard to miss reading 0.1xx on a zeroed out DIGITAL caliper)
3. He couldn't have set his caliper at .10 as we can't see the dial
4. He won't tell us where he's located (ummm, WTF does that have to do with anything asked for input on a post not where a local machinist is that can help me)
5. Measurement after measurement is obviously wrong, even though I don't have this screw in my hand it can't possibly be 40 TPI

I think I've just had my caliper duties impeached!

We are not trying to make fun.
It's just that the measurements you are claiming are NOT jiving with the photos you are posting.
Are you perhaps measuring in mm and shifting the decimal point a digit and claiming inches?

[sonofeugene]

I also think that the OP is setting the caliper at 0.100 when the jaws are closed. Maybe.

And I think you're likely correct. A 12-40 screw.

[ar15barrels]

Here is a 12-40 tap for size comparison:



It looks FINER than his screw:

If we assume he is correct at 40tpi, then the diameter of his screw needs to be smaller.
Maybe 10-40?
Certainly not as small as 8-40:

[Half Cocked]

That thread gauge looks super wonky.

Harbor Freight? Maybe he got his vernier calipers at the same place.

[drkphibr]

Harbor Freight? Maybe he got his vernier calipers at the same place.

Never a shortage of trolls or folks who have to degrade others and their efforts to feel better about themselves or their toys/tools.

And like you've NEVER purchased anything from Harbor Freight. I freakin' LOVE HF. You get exactly the quality (and set your expectations accordingly) you pay for. Great way to save $ for one off/lower end jobs where you're livelihood doesn't depend on your tool brand name.

BTW, the analog/dial caliper is RCBS and the digital is Hornady. Wouldn't give a second thought to using HF calipers either.

[ar15barrels]

Never a shortage of trolls or folks who have to degrade others and their efforts to feel better about themselves or their toys/tools.

Please post a picture of your calipers with the jaws completely closed so we can see your zero and then 3 more pictures like these:





That should end all the confusion over your past dimensions and pictures that were so incorrect and too incomplete to make sense.

[JagerDog]

my attempt at general screw measurements...

Previously you said it wouldn't fit a 3/16 drill gauge.

This makes no sense.

[ar15barrels]

Previously you said it wouldn't fit a 3/16 drill gauge.

This makes no sense.

Several of us are pretty sure his digital caliper is reading -0.100" while the jaws are completely closed.