Greetings all; I am aware that making a measurement where the motion of the dial indicators stem isn't perfectly aligned with a motion of the axis and its effects on the trig of such measurements.
I have measured the x axis of this lathe quite a few times, and arrived at an X scale that moves it 1.000 inches according to a dial indicator. However, when carving metal it doesn't seem to be correct. For instance, the motor pulley I took off the OEM 3/4 horse has a .750" bore, but the 1 hp motor on it now has a 7/8" (.875") OD shaft, and a nominally 1" larger pitch diameter, so I undertook to bore the OEM pulley to .875" yesterday, by first boring it out what I thought was .1000", which should have taken it out to .850". But I didn't get .850", more like .824". And had to make about 6 more swags to actually get it to fit the spare, identical motor. Since I've no clue what the tpi or tpmm is on that nominally 8mm screw driving the X carriage, I have simply adjusted the scale value until an inch of drive, moved it an inch indicated, with perhaps .0002" of fuzz in reading the dial. Thats a Grizzly mechanical dial I have something over a $100 bill in. I would assume it hasn't a scale error anywhere near that gross. I bought a digital scale I was going to put on the tailstock barrel but haven't found one of those infamous round tuits yet because I'll have to figure out how to machine a mounting flat on a barrel shaped casting that I could believe was true to the barrels axis of motion. So its loose and has more than enough travel for measuring the X motions on this old Sheldon. Is it possible that commanding a 1" step move from the axis step move generator is not getting a true 1.000 move, or that this mechanical dial indicators scale, 10 full needle turns supposedly = 1.000" isn't an inch by that large an error? This isn't a .1% error, more like 10%! FWIW, I am using another copy of that screw in the X drive of TLM, and am having similar errors, which preclude arriving at the correct size without a lot of sneaking up on the correct fit. How would you guys go about calibrating this, and be assured that the error you measured was real and not a measurement error? I can put this new scale on the x long enough to verify the mechanical dial I suppose, but again, its digital and I'd have to take somebodies word for it as to its long scale accuracy over several inches. But I was born only 1 state line from Missouri. So theres a wee tiny bit of show me blood in me, by osmosis if no other way. What can I do to nail this down? Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
