ART,
All tests V.028 per posted MachSpindleOct16 on page 55 - reply 559.
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Test #1 was out of curiosity doing a thread test at 404 rpm using the following code:
M98 P0001 L20
M30
O0001
G32 Z-1.9 F.1
G4 P2
G01 X.1
G01 Z0.0
G01 X0.0
G4 P2
M99
M30
So i just did 20 looped passes. Pass #6 and #17 were bad, and the lead increse was .003" / inch.
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Test #2 used code from the wizard.
404rpm/ .1P / 20 passes@.0002"
Pass #14,19 & 20 were visualy observed as bad. I have attached a file which icludes the report for test #2 and test #3.The first pass had a decrease in lead of .0008" /1" and .001" / 1.4" inch. Then there was a correction after pass#1 and pass #14, 19, & 20 were bad visualy and changed the lead to a increase, namely .0035" / inch.
Picture TEST#2 shows the passes at 1.4" along the scribing.
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Test #3 was the same as test #2.....EXCEPT..... I decided to try correctng the pitch and see what would happen.
So instead of a .1P , the modified pitch used was 0.09965 ..... (0.1000 - .00035=.09965 ). So the first 13 passes
showed a decreased lead of 0.001". Pass #14, 19, & 20 were bad and cause an increase in pitch.
This is shown in picture TEST#3.
Picture TEST#3MAG shows a maginfied view at the 1" point of scribing.
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SO three different tests and all had a common .0035" total "range" of lead error. I could shift the location of the error relative to a perfect pitch. Note also that each test had a screwy pass all occuring at around pass #14 or #19 or so. Those screwy passes al seem rather close to what happened n other tests. In the other test that went to 40 passes they seem to occur around pass #15,30,and near 40.
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BTW: I did one additional test. I hate to compare apples and oranges.....but for info ......... It was manualy done on my 30 to 40 year old Rockwell 11" MANUAL lathe. Pitch was .1 @ 10 passes and the change in lead was 0.0003" in 2" of scribing, no variance between lines, single scribed line. Hmm....
all those old belts and pulleys /gears / gearbox, lead screw, half nuts and 23 times more accurate than my CNC lathe!
RICH