Measuring an internal thread - Printable Version +- MetalworkingFun Forum (http://www.metalworkingfun.com) +-- Forum: Machining (http://www.metalworkingfun.com/forum-5.html) +--- Forum: General Metalworking Discussion (http://www.metalworkingfun.com/forum-6.html) +--- Thread: Measuring an internal thread (/thread-1523.html)

Measuring an internal thread - f350ca - 07-22-2013 Needed to make a 55 x 2 mm nut for a hay rake. How do you measure an internal thread? The shaft wasn't available so I had to make a test shaft that I used the 3 wire method to measure then cut the internal thread using the test plug to check the PD. Is there a beter or easier method? In this case he needed the part, none available in north america and an unknown delivery time from Germany. RE: Measuring an internal thread - TomG - 07-22-2013 Greg, To do it properly you would need a go-no-go thread plug gauge, but one that size would probably cost you $300 or more. The way you did it will work fine. I usually make my gauges to the upper extreme of the tolerance to ensure that the internal thread ends up large enough. Tom RE: Measuring an internal thread - f350ca - 07-23-2013 Thanks Tom, thought there might be gauges that were thread specific. A pain to machine a test plug for a one of nut but guess thats the business. RE: Measuring an internal thread - Mayhem - 07-23-2013 C'mon Greg, you know the rules: It didn't happen without pictures! RE: Measuring an internal thread - f350ca - 07-23-2013 Oops, he picked it up still warm off the lathe, needed to get back to being a farmer out standing in his field. or something like that. RE: Measuring an internal thread - TomG - 07-23-2013 I recently cut a special thread using this very technique. It was a .900-32 3B thread, so I calculated the pitch diameter of the external thread and made a gauge to the high side of the 3A tolerance, then cut the internal thread using the gauge to size it. Worked like a champ. Tom RE: Measuring an internal thread - Mayhem - 07-23-2013 [attachment=5708] RE: Measuring an internal thread - dallen - 07-23-2013 ones things for sure once you make the gauge you will have it for the next time. RE: Measuring an internal thread - TomG - 07-23-2013 Not me, it went right back into the scrap bin. If I ever need to make another .900-32 thread, I'll just crank out another gauge. It might be nice to have some standard sizes on hand though, maybe even a go-no-go version of them. Tom RE: Measuring an internal thread - f350ca - 07-23-2013 The nut is off making hay but here's the test plug. As per Tom its back in inventory.