Quick check of lathe threading gearing NOPOL

A quick method to check lathe gear selections is to mount a dial indicator to measure carriage travel, and count spindle rotations.
A mark on the chuck or faceplate gives a fairly accurate way to count revolutions. Take the slack out of the geartrain while zeroing this mark, and watch the DI for 1.00" of travel while hand cranking the spindle the same number of turns as the threads per inch you want to cut. Of course, if the count doesn't come out the same for 1" of travel, the correct gears aren't in place (or the quick change box ratio is incorrect).
It works well for me WB
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incorrect).
Given the fact that I have altered the gear setup on my lathe in order to achieve finer feeds, I must dial a 10 pitch thread to chase a 20 pitch. As a result, I always check any thread selected to make sure I'm not thinking backwards. Your system is very good, but slow. I simply pick up the surface to be threaded, then take a shallow pass, which can then be checked against a thread gage, or a scale. The results are easily determined without making a setup of any kind. Assuming you have made an improper selection, when the proper thread is chased, 99-9/10% of the shallow pass will have been machined away, so one finds no evidence it was ever there.
Harold
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"Harold & Susan Vordos" snipped-for-privacy@tds.net

Agree. Take a scratch thread. Check with a scale. If you're wrong, the result's totally obliterated in cutting the full thread. Frank Morrison
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This is one of those things that they teach in the SB "how to run a lathe" book - and likewise one of those things that I never fail to do. That is, to check after the first pass to see that the pitch is correct, one way or another.
The only novice failure this won't catch is somebody fabricating a left-hand thread by mistake.
Jim
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On 22 Nov 2004 02:13:28 GMT, snipped-for-privacy@aol.com (Fdmorrison) wrote:

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If marking or scoring is the fear, I've used a SHARPIE magic marker, held in the tool post .
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