Thread specs - S&W windage screw

[Old School Big Bore]

I bought a couple of S&W windage screw/nut kits and the threads on both screws are off-spec. They start into the collar on a sight blade, but will not screw all the way through it. I bent one almost to its break-off point trying to install it before I figured out what was wrong. I have emails in to Brownells (the source) and S&W (the purported manufacturer) but who knows how long an answer will take (I have not had good response from either of them in the past), so I'm posting this question here - what die do I need to true these screws up and get my blasted installations finished? Anyone have the specs on this screw? It's the common K/L/N windage screw.
Yes, I'm sure it's the screws at fault, I tried them in new and used S&W blades and in a Weigand blade and with new and used nuts. Luckily, on the rush installation I was doing when I discovered this, I had drilled out the staking on the old screw and nut and was able to re-use them. I have a six-pack of kits on back order at Brownells and hopefully this will have been cured by the time I get them. BTW one user had posted about the same problem on Brownells page, so 'you would think' that between S&W and Brownells they would be trying to solve this.

[Old School Big Bore]

OK, heard back from S&W - get this - THEY SAY THEY DON'T KNOW WHAT THREAD THE SCREW IS - if they don't, who in the world DOES?

[slughammer]

Well today is your lucky day! I went into my kit of stuff and found (2) short blades that I have replaced with taller blade kits.

I think I figured out what is happening. There were (2) different thread pitches that S&W used. Old sight from 1948 has about a 3-48 thread, new sight from 1989 has about a 3-76 thread.

Hope this helps.

[Catshooter]

Old School,

Of course Smith knows what the thread pitch is. The idiot you were talking to doesn't know, that's all.

I don't have a sample of the screw under discussion, but if it would help you can mail it to me and I'll measure it for you. I'll even mail it back! :)


Cat

[9.3X62AL]

It has been several years since I've bought any new Smith & Wesson product, and a good part of the reason for same is illustrated above--absolute bottom-feeder customer service. I HAVE bought new Ruger firearms recently, though, and Ruger's customer service has much to do with those decisions. I just won't feed companies that treat customers with antipathy and disregard, but will happily support makers that take care of me in fair & reasonable fashion.

[Old School Big Bore]

Thanks, guys. Slug - the parts involved here are all current-generation, and the problem with the screws is that the pitch and/or diameter slightly CHANGES about 2/3 of the way down the screw toward the head. They thread into the blades and nuts just fine for about 2/3 of the length, then bind up. The fault is definitely in the screws and not the blades/nuts. If I just knew what thread they are supposed to be, I could get a die and chase the threads. Although these two screws cost me nine bucks each, what I'm leery of is that when the six kits I have on back order at Brownell's arrives, they will be the same way.

[Catshooter]

I'm glad you posted that the diameter seems to change part way down the screw Old School. I'll check for that when they get here.

I have taps/dies down to 0-80. I wouldn't be at all surprised though that they are some odd size. Might not be. We'll see though. There are some pretty hard to find sizes in the firearms world. Comes from the fact that pitch and diameter sizes weren't standardized here until what, the '20s? I'm not sure. Was a bit before my time. :)

I borrowed a 7/32x40 die today from a friend. I've got the tap but I can't find the die for nothing. That's the size of the aperture for the Lyman peep sights.


Cat

[Old School Big Bore]

I wrote back to S&W stating that I was puzzled that NO ONE there knew the thread, and that I was wondering how in the world they MANUFACTURED THE SCREW without that info...the smarmy answer I got back was that 'We don't divulge specs'...Really? I'M A SCHOOL TRAINED S&W ARMORER! Who should have access to the stinking specs if not me? Of course they included a phone number where I could ORDER MORE OF THEM... as if !

[cwheel]

Any good machinist with a micrometer and a thread pitch gage could figure pitch and OD out fast. But if you are looking for a tap and die to fit, they are most likely specials. Gun industry is famous for using non-standard threads for ever, some even end up as special order and pricy. Keeps some people from making repair parts for their products. Of course check Brownell's, MSC is another good supplier for some of these in the specials section.
Chris

[Catshooter]

Well cwheel, as far as the "good machinist" part goes I can't help you there! :) But he is sending the parts to me to see if I can help him out.

The pitch gauge concept is interesting. One that reads to 80 thread per inch and starts at 1 won't have 80 leaves. They skip around quite a bit. A lot of pitches just never got used and some pretty weird ones can be pretty common. For example, ever put a garden hose on? Then you've used an 11.5 pitch thread.

One of the reasons the gun industry is using some weird ones is that a lot of gun parts pre-date thread standardization in America. And sometimes the part just needed a finer/coarser thread than normal. Then again there is the making part duplication difficult for others. :)

Threading and fasteners use is quite the study.


Cat