Boys I need some help.
My old Mauser came with a Williams rear sight but without the aperture.
I've got a spare Lyman but it won't thread in more than 1/2 a turn, or so.
They are supposed to be threaded the same. 7/32-40
Any ideas short of chasing the threads?
It might be simply a case of too much paint in the threads.

Here's a bit of useful information that will save you money and may solve your problem. 7/32-40 is a special thread that is hard to find and costly, #12-40 on the other hand is a common fine thread size that is commonly employed with lock hardware. It is commonly available and is not a costly item. There is only .002" difference in the major diameter (outside diameter) of the two threads, not enough to make any difference. I learned this lesson several years ago when I was considering making sight aperture discs. Hope you find this little kernel of information interesting and of use. MSC Industrial Supply and McMaster-Carr both carry #12-40 taps & dies, you would want a bottom tap to go in the shallow hole in the Williams sight. Inexpensive carbon steel tap & die will work fine for a one time job, no need for High Speed Steel.

gunswizard,
Thank you.
That's the kind of information I'm looking for.
John

Here's the project.

I have a 7/32-40 tap. (Easy to find if you know where to look- model railroading emporiums. I paid $7+change for it.) PM me if you want to borrow it.

Will do.
Thank you for your help.

Would this be more expensive than the taps, dies and fuss?

https://williamsgunsight.com/product/williams-twilight-aperture/

Takes all the fun out of it....
Midway has them for $9.95 but shipping jumps it up.
I bought a new one from Graf for $8.95 when I ordered brass and slugs for the 8x57.
It was a Lyman that won't thread in. It's supposed to work according to the Lyman web site.

Got a strong lens to check for a rolled thread or some other tiny catastrophe?

Well it's not the sight itself.
It's the new, just purchased aperture.
The thread start has a burr.....
Return, or get out the file???
It only cost eight bucks.....

Not the burr.
Diameter of this one - .0221
Diameter of the one that fits - .0198

I have several Lyman 57 SML Tang peeps, and a few Williams, The Williams Apertures will thread right in the Lyman’s perfectly, But a Lyman Aperture will NOT go in the Williams.

Agreed.
Yet their web site chains they will.
The caliper says they won't.

Victor Machinery Co. has 12-40 taps and dies at reasonable cost. I've been buying machinist's tooling from them for several years. They list the 7/32-40 tap on the website, but not the die.

www.victornet.com

Jerry

I talked to a local friend who is supposed to have a tap that will work.
If not I'll check into these sources.