Metric threading on lathe

My Jet 1024 can do SAE and metric threading. It can do .75 mm pitch,
but not .7. But the M4 standard pitch is .7!
1. Why in the world wasn't this lathe designed to do .7? There's only 4
or 5 pitches that one needs 99% of the time and .7 is one of them. The
lathe will do about 20 different metric pitches, but not one that is
needed! Unless ...
2. Is .75 close enough?
Thanks,
Bob
Reply to
Bob Engelhardt
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I set up a spread sheet to calculate the pitches using all quick-change gears (5 x 8), as well as all combinations of the gears in the feed train. Jet had shown just the values that were even to 1/8's. E.g., .375, but not 1.6363. Also, Jet just used 3 of the 7 gear combinations.
I found a setting that gives a .703125 pitch. Over the course of 5 threads (normal(?) engagement), it would be off .016 mm. Close enough for me.
That setting is: 30 tooth gear before the 127 & 32 tooth after. Quick change on D1.
I'll post the table to the drop box once I get it formatted to something other than an .xls file.
Bob
Reply to
Bob Engelhardt
It's in the DropBox as "Jet1024gears.txt". I.e.,
formatting link
The original .xls is available by email.
Bob
Reply to
Bob Engelhardt

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