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I bought a sporterized Japanese 7.7 rifle. It only had one screw left with the receiver. I suspected it was stuck. It took a while to get out and when I did I found the threads were stripped. My question is what size are the threads. They look like 1/4 by 28. But they aren't.I guess they must be metric. Anyone know size they are?
They may be 1/4" screws after all. Mausers have 'em as well. But IIRC, the Type 38 and Type 99 MAY have different thread pitches. But I've no way to check for several days.
Yes k98s use a 1/4 20nc thread. I may end up tapping it out to that. But I would like to keep it orig. if I can. I tryed screwing in another orig. screw and just messed it up a little on the end it wouldn't start. I got a 1/4 28 dye the screw would start but only go about 1/2 turn and stop. Thats why I wounder if something metric would work? I have some new made screws from Midway if I could get the orig. threads cleaned up. Thanks for the help.
1/4x32? I think there may be an old thread that discusses this very subject, maybe a year or two old. Too busy cooking to spend much time on the site today. And the next several days are likely to be worse. But the 1/4" OD is not metric, so it's "gunsmith size". Or "super sercret military magic size". Firearms seem to have required bizarro threads for the longest time.
You can buy new screws mfg. buy Forster. I guess they work I don't remember using any. But I bought three sets for spares. But they don't say anything on the package except For Japanese 7.7 actions.
Japanese Arisaka screws are a one of a kind, however,,,if you plan on retapping the the threads, careful,,you can blow those holes out pretty easy.
if the screws stripped out inside the hole, you can pick the threads and save them...iv seen this done many times, guys trying to fix a buggered hole, and blow the hole out,
iv yet to see one done succesful.
I do not have a T99. But I do have a T38. The trigger-guard screw thread size on this rifle is 6mm dia. x 0.9mm pitch.
28 tpi is 0.907 mm pitch. So a 28 tpi chaser will do, if you can get a suitable 6mm bolt with a long unthreaded portion and turn the 28 tpi on that.
:wave:
Patrick
Not quite Patrick. T99 screws are'nt the same as those for the T38, without getting to technical they're larger in diameter and have a finer thread than T38 screws. Closer to the 1/4x32 Jmoore suggested.
Quote:
Originally Posted by vintage hunter
Thanks for that info. They are probably going to be metric, nevertheless. If someone could provide measurements of an example, maybe one could suggest a near equivalent!
:wave:
Patrick
In a bit of a hurry ATM, but a few quick measurements show that T99 screws do indeed have a major diameter of .234'' or 6mm. Threads are 34 TPI on a standard gage. Have'nt found a match to any known metric gage yet. Have to check later but by butting the 99 screw end to end with a 38 screw it looks like the 38 screw has tapered threads. Maybe just my eyes playing tricks........................
Sounds like 6mm, with 0,75 mm pitch (= 33.87 tpi). This is a metric fine pitch series, used by model engineers among others, and available in the UK, replacing the old 32 tpi series. A specialist tool supplier (not your local DIY store) could get you a die for it. But if you're only going to use it once in a lifetime, just buy a couple of those screws - that will probably be cheaper.
:wave:
Patrick
The screws are not the problem. I've got screws and can buy more if needed. It is the treads in the front of the receiver. This is a bubba salvage if it wasn't one of the uncommon mfg., I wouldn't mess with it. Chuck it think your idea is what I need to try first. It looks to me like bubba got his screw started crooked and then just drove it in with a BFH. When I got the screw out a least the first 1/3 of the threads were gone. It was just smooth on the end. Chuck what do you use for a pick? A dental pick. Thanks to the rest of you guys for your help and ideas. I'm about ready to try anything that sounds like it would work. Thanks again
if the first part of the hole is trashed, heres what i have and would do..counter sink it, over size the hole down to the good threads, and then you can use a longer then needed screw if you have to, if the buggered the hole, then trying to fix it will be tough..if its the rear screw on the action, you may be able to come in from the top side and run a tap from the good threads down to the buggered threads..
if the old screw left meat inside the hole, then a good dental pic or sharp punch, and take your time, picking threads is a labor of love,,,hate rather...
if its the front guard screw...counter drill it, and be done.
Thanks, it's the front screw. I'm going to try picking it first. Then go from there. I'll get back to you with how things work out. I don't have a heated shop to work in and it cold here in central flyover now. So I will probably not work much on that until spring. Right now I'm just getting tools and parts ready to go. Thanks again, Bill
Chuck today we are going to counter bore like you said. A guy on another forum said to cut three grooves in a extra screw and use that as a tap. We tryed that last night. It almosted worked. The grooves let us get the screw started and screw all the way in. But when we unscrewed it the threads were a little distorted. I think the lug is skin hardened and that left a burr on the first thread that was harder than the screw. Today we are going to counter bore enought to get rid of the burr. I'm sure that will fix it. Thanks for the idea.
hope it works out...check your level 2 times, and drill it once..if it doesnt look right,..dont drill it.