Home Forums Hunting & Shooting Gunsmithing Tap size

Had to drill out a small screw on the firing pin stop for a Winchester model 1890. I used a 3/32 bit. My question is what size tap do I need to use for a 3/32 hole? The original screw was a fine thread.

Thanks

A 3/32 tap.

4-48 unf tap drill is #42, .0935,, 3/32 is .0938 so you are .0003 oversized. Should work,but your 3/32 drill might drill a little over size due to wobble.OD is .112 so you have about .0091 to play with on he radius

40 unc , tap drill is #43, .0890

So go #5 Not Wal Mart bubble pack size but not exactly rare.
Depending on the quality of fit you need of course.
5-40 drill #38 (0.1015")
5-44 drill #37 (0.1040")

Thanks, I know I can find the tap here in town, not to sure about the screw

Thanks again

Or go with the #4 if a loose fit, less that 75% thread engagement, is strong enough. Engineering is all about trade offs.

A 75% thread engagement is considered standard and that's what general purpose tap/drill tables are for. It's a compromise between strength and ease of tapping and assembly. So you can go with a slightly smaller hole for more strength or a slightly larger hole if you don't need the strength.

Ace should have #5 and maybe, doubtfully, a tap/drill set. I know they - some anyway - carry #4 in gun threads but never saw the tap (see Brownells).

4-48 is the closest you will get.

I agree that a little looseness in the threads won't hurt, the screw just has to stay in place. It really doesn't have any stress on the threads.
As an aside, #5 screws are typically used for revolver grip screws so you might have one in the parts drawer.

I use 4-40, I got the tap from Brownell's or Midway and order the screws in thru Fastenal. You may have to order in a pak of 12 or 20 but they aren't going to break the bank. I don't know off the top of my head if 4-40 takes a larger drill than 4-48 or not as I tap a predrilled hole as a modification.

4-40 uses a number 43 drill, .089" and the 4-48 uses a #42 at .093". 3/32" is .09375. A 5-40 uses a .101" drill, #38.

Couldn't find a 4-48 unf tap locally. So I ordered one, should be here by the end of the week.

Another question, what screw do I need to use for this tap?

Thanks

. Evidently you don't have an understanding of how things work with regard to taps and tap drill sizes.

I have probably drilled and tapped more holes in one day than you have in a life time. I am a retired machine mechanic from a large crane manufacturer..

If you drilled a 3/32 hole for a 3/32 tap then you fugged up a lifetime of holes.

you apparently dident understand the question.

The OP drilled a 3/32 hole. He wanted to know what size tap to use in that 3/32 hole. All the other posters correctly recommended a 4-xx tap. You recommend a 3/32 tap. Seems to me you are the one who’s not understanding something.

Try getting a sense of humor.

Well Darn, you need a 4-48 screw. And if you have a large hole, Brownel's has over size taps and screws in many sizes. They will fix a bugged hole. I have taps from 0.80, 0.90, 1-72, 2-56, all the forties and 48's. Standards and metrics.

Thanks, to all who replied.
Yes, I figured I needed a 4-48 screw, but just needed to verify it thanks.