The correct stock size for threading 3/8-16 stud

stioc

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The machinery handbook says .375 for major diameter. I started with a .382 stud but by the time I got some depth to the threads the major diameter changed to .355 - needless to say the nut threads on very loose. So should I've started with say a .4" stud?
 
No, start with .375" diameter and don't cut the threads undersize, as you apparently did; having said that there is nothing really wrong with having the stock a bit undersize, especially for coarse thread pitches. When I single point thread, by the time I am on size with the threads, I generally have to file off the crests of the threads to eliminate burrs, resulting in a undersize major diameter; little thread strength is lost by the insignificant reduction in diameter.
 
Thanks! I figured out my stupid mistake. The nut I was using to test the threading is an M10 not 3/8" :eek 2: Threw me for a loop and I was so proud of myself that I got all the angles and things right, the pitch was correct without looking any of that stuff up.
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We have all done it, some metric and inch sizes are so close is hard to tell them apart especially on french and italian machines and automobiles, they use both system on the same part. Hair pull stuff.
 
I recently had to repair a 2 1/2" steam valve, where the bonnet had broken; the bonnet was held on the body with 1/2-12 studs and nuts, the packing gland was fitted with 1/2-13 studs and nuts; I had tried a 1/2-13 not on the gland studs and assumed that it was all 1/2-13 ----WRONG!
After my discovery, I had to re make my parts to repair the valve, perhaps a half hour's work; "Could be worse, could be raining".
To see where this valve goes, Google "Sturgeon's Mill", and look at our web site.
 
the packing gland was fitted with 1/2-13 studs and nuts; I had tried a 1/2-13 not on the gland studs and assumed that it was all 1/2-13 ----WRONG!
Joseph Whitworth strikes again! Well, not really. Whitworth was first to have accepted standards for fasteners... Still 1/2-12 threads are most
often Whitworth threads. Ask me how I know!

(British cars...)
 
1/2-12 was our standard before World War 1, unless you were dealing with Brown & Sharpe, their standard was 1/2-14
 
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