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11-14-2012, 08:45 PM #1
Clausing Colchester 15 " failure to cut 6 TPI
I have a english model lathe and have not been able to cut 6 TPI. I made sure that the drive gear had 36 teeth as stated on the placard.
11-15-2012, 08:25 AM #2
Sorry to hear that.
Have you cut any other size threads successfully prior to this attempt?
11-15-2012, 06:41 PM #3
No! I have not tried other thread pitches. When I first tried to cut 6 TPI, I got 12, and then changed drive gear to the correct 36 tooth one and ended up with 10 threads. Also noticed that the lowest speed is 37 RPM, which seems fast for short tight threading. Thanks for showing concern.
11-15-2012, 07:54 PM #4
Not personally familiar with your lathe but apparently in your first try, the lathe spindle was turning twice as fast in relation to the feed as you intended. (or same difference: gearbox shaft was turning half as fast as desired compared to spindle)
If there is a compound set on the spider, you may be able to transpose two gears. (swap the large driven, with the smaller driver, to speed up the gearbox). For instance the gear on the gear box, with the one on the compound that is driving it so long as the ratio between them is 2:1
If not, look for a gear to go on the gearbox input that has half as many teeth as the one that was on in the first try. (leaving the gearbox at same setting & other gears the same).
11-15-2012, 08:18 PM #5
Dose the gearbox have the correct driven gear?
Is the colchester a triumph, they have a high low selector for gearbox feeds. Gives 1:2 or 2:1 change.
11-16-2012, 05:35 AM #6
Great points you brought up. I have looked for a speed change lever that I have on my Lodge and Shipley lathe. There are only two choices of gears on the gear box and as I said before, I changed to the 36 tooth gear as requested on the placard. Maybe if I call a dealer, they would help with the gear problem.