S&W 59 Windage Screw

Chewy

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I have a model 59 9mm in blue that has had the rear sight (lollipop type) broken for years. No new parts are available and the used ones look horrible. I saw somewhere that a person used a 2.5mm screw from local hardware store, but it has the wrong thread pitch. It goes in a couple of threads and then binds. My 38 cents down the drain. The original mics out to 2.5mm. Does anyone know the correct thread pitch? Any other replacement screws or complete rear blade assemblys that would work? With a machine shop in the basement, I may just make a whole complete rear blade and screw from scratch, but I thought that I would try the easy way first.
Thanks in advance! Charles
 
Real close. Mine doesn't have the hole in the head for click adjustment. I was at Numrich yesterday, but I did my search for rear sight, not windage screw. That will work. Thanks Charles
 
Probably not metric.
2.5mm is 0.098 inch which is the max major dia of 0.0983 of a #3 screw, the thread pitch options for #3 are #3-48UNC and #3-56UNF. The M2.5 screw comes in either a 0.45 or 0.35 pitch which would be either 56.44 TPI or 72.6 TPI. So a #3-56 is real close to a standard M2.5-0.45p. They would probably screw together a bit before they bind.
 
Whether Starrett, B&S, Lufkin, Winchester or S&W, you cannot depend on thread diameters or pitches in standard configurations or combinations. They all operate toolrooms capable producing any cutter desired. Part of it is to confound consumers, so the story goes "They employ proprietary threads to protect products and parts inventory."
More often there are design considerations they wish to utilize. You rarely see thread depths 1.5x thread diameter, for example. All decent sights use threads delivering a specific minute of angle division /or multiple of, especially for windage. Another is liability, long before the game for attorneys. They'd certainly prefer hardware grade fasteners not used, and lessen off-site assembly boiler rooms.
I've smithed for Weatherby, 2 Orange County shops, and Adult Ed also in Orange County. You'd be amazed what people bring in to 'try'.
 
Update: I ordered the screw, nut and being a big spender, a new rear dotted blade. The #3 and 2.5mm screws are close but the TPI are different. They will go into my hardware collection. For the last couple of years from time to time I Goggled the rear sight. I never tried the windage screw by itself. My son started this when he took gun to gunsmith who also tried for a couple of months to fix. Looking forward to get put back together and sighted in. Thank you all!! Charles
 
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