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PPP MMM
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Everybody has a choice of pitch to follow
Bryce
I still didn't get my calculator out, but the line of your thinking is correct. The only reason why this can be done and get away with it is, that the barrel material is soft (26-30HRC) and quiet possibly it can be distorted on tightening.
If the barrel thread is cut in such a way, that it can be screwed by hand all the way to the shoulder and overcompensate for some 0.006" in the pitch accumulated difference it tells me nothing, but a very loose fit indeed. One can do much closer fit with the same and correct pitch on the both parts bearing all the way through and with the same load on every thread and without the need of "excessive" and uneven material distortion adding extra stress.
If a tap was used to tap a hole in a block of a tool steel and then the block was hardenned to (64-66HRC) a fraction harder than the tap itself one could use the same tap and run it into the tapped hole again with the closest fit possible virtually into the infinity.
One can only wonder, just how deep a same size diameter tap with everything being equal, but a 0.0005" different pitch would go without breaking up somewhere?
I don't think, that it would be very deep.
Shoot better
Peter
,,,,,,,,,,,,,,,,,,,,Peter,
If you had a thread of 7.8 inches you'd have run out of room for the extra thread when comparing 16TPI to 1.6mm pitch.
Obviously you will never have a barrel tenon that long but like you said eventually the "error" would become very obvious. Logically even at around 2 inches in thread length it would fail to fit unless cut very loose.
Bryce
Bryce
I still didn't get my calculator out, but the line of your thinking is correct. The only reason why this can be done and get away with it is, that the barrel material is soft (26-30HRC) and quiet possibly it can be distorted on tightening.
If the barrel thread is cut in such a way, that it can be screwed by hand all the way to the shoulder and overcompensate for some 0.006" in the pitch accumulated difference it tells me nothing, but a very loose fit indeed. One can do much closer fit with the same and correct pitch on the both parts bearing all the way through and with the same load on every thread and without the need of "excessive" and uneven material distortion adding extra stress.
If a tap was used to tap a hole in a block of a tool steel and then the block was hardenned to (64-66HRC) a fraction harder than the tap itself one could use the same tap and run it into the tapped hole again with the closest fit possible virtually into the infinity.
One can only wonder, just how deep a same size diameter tap with everything being equal, but a 0.0005" different pitch would go without breaking up somewhere?
I don't think, that it would be very deep.
Shoot better
Peter
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