Xitesmai 1 Posted February 24, 2011 Report Share Posted February 24, 2011 Does anyone know the hole size for the M22x.75RH tap for the S12? I've looked everywhere and no engineering site references this size tap, for the size of the drill hole... Quote Link to post Share on other sites
TonyRumore 1,332 Posted February 24, 2011 Report Share Posted February 24, 2011 If you plan on making some sort a threaded muzzle device, the inside bore would normally be machined to the correct diameter with a boring bar in a lathe. The closest drill size would be 27/32" and may or may not work. Tony Quote Link to post Share on other sites
skiboatsp 111 Posted February 24, 2011 Report Share Posted February 24, 2011 (edited) On metric it's easy Subtract the pitch from the O.D. .75mm - 22mm = 21.25mm divided by 25.4 = .8366" round up to .837 inches It's hard to hold precise sizes when drilling plus this is a fine thread and needs a smooth bore to hold a consistant thread percentage. My first choice would be Boring on a mill or lathe, or milling by interpolation Second would be drilling and reaming (this would require an adjustable or custom made reamer) Third would be drilling by carefully sneaking up on the final size with slightly smaller drills If you move too far from these deminsions you loose your optimal thread persentage of around 75 - 85% very quickly. Edited February 24, 2011 by saigatechusa Quote Link to post Share on other sites
Xitesmai 1 Posted February 24, 2011 Author Report Share Posted February 24, 2011 It is for a muzzle device... I think I can use a lathe with a spring center to bore out the threaded portion... thanks for the help guys... Tony, how come it may or may not work...the variation in tolerance of Russian machining? Quote Link to post Share on other sites
skiboatsp 111 Posted February 24, 2011 Report Share Posted February 24, 2011 27/32 is .8438" you ned .842" for 75% thread. If you can hold .8438 plus 0.0 you should be OK Quote Link to post Share on other sites
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