Does anyone know if the tang screws on high and low walls which are supposed to be 12-28s are undersize in diameter or off pitch? I ask because the 12-28 hole in the lower tang for the tang bolt won't accept a modern 12-28 bolt. I know the supposed 10-36s that hold the lower tang in are undersize and off pitch. Is this a general condition? I am putting a block between the upper and lower tangs to use with a stock bolt. Lest there be distress on the forum I'm working on a beater to get it into shooting condition.

One of the Winchester books mentions that several of the original screw sizes were slightly off the modern spec, and I have found that to be true. The closest modern equivalents are 6-48, 3/16-36 and 12-28, but the original holes usually will be found to be very tight on the modern standard screws. On a custom rifle or beater I frequently run a modern tap into the old holes, because some of the poorer-quality replacement screws will be found to have the modern threads.

Please be advised that an original case-hardened threaded hole will not willingly accept a modern tap. You must either use original-spec screws or else anneal the hole before retapping. If it starts squeaking don't try to force it.
Good luck, Joe

I had a friend that HATED odd ball screws. He was inclined to drill and tap EVERYTHING to 10x28 with the thought that if he was in the boon docks and stripped a screw he could just buy a screw. It is sacrilegious to a collector to even think of something like this but to a pragmatist it makes absolute sense. 

I really dislike oddball screw sizes, also, but just "grin and bear it" and go thru the sometimes ridiculous efforts needed to replace a screw with the correct one (swearing as I go... . One I particularly like is the tang screw size for Stevens ( who in the heck thought up a 4x40 screw size as being suitable?).

It makes about as much sense as modern parking lot layout.

Dale53

Leadball;
Thanks for the correction (I was dithering between 5/40 and 4/40 but as usual, the wrong decision was made ).

However, 5/40 is a dandy screw size to use when drilling your mould handles on new moulds (every brand that I have had sooner or later come loose). Drilling them right thru the ferrule and handle solves that little problem. Others use various glues for the same problem. I have a loose handle now and will try high temp silicone that someone suggested. It'll be easier but we'll see if it equals the screw method in longevity.

Dale53

40rod;
         I use accu-glas also-seems to work fine- I drill a 3/16 hole about 3 inches back from the ferrel to allow glas and air to escape --have not had one loosen yet.  leadball

Well, a 35-1/2 pitch threaded hole with a 36-pitch screw would only start getting sticky after 25-30 turns or so.  You only have to turn in the tang screws 3 or 4 turns if I recall.  People who rebarreled Japanese rifles had to approximate the thread size and generally got a decent fit, even with a 16 TPI barrel in a 16.9 TPI receiver.

I remember my one trial at making a smaller nonstandard screw with a standard pitch.  It was the lever screw on a Ballard and I'd found a die with the right number of threads but too small an opening.  No problem, sez I to myself; that's what that screw that bears on the cutout place on the die is for.  I turned it in real  tight, put it on the screw blank (painfully cut and polished by hand on a Unimat lathe) and started threading.  About 3/4 of the way through the process, there was a loud "PINGGG!!!" and the two pieces of the die launched out of the die stock to opposite ends of the garage.  I could see that my costs for nonstandard and ruined taps and dies could get pretty high pretty quickly.

I'll tap a ruined hole with a standard tap if it comes to that, but just grit my teeth and thread out to the original specs if that's what I'm missing.