The Breakroom > The Water Cooler
Am I the only one ?
DavidA:
Just wondered if anyone else had made this mistake.
I mentioned elsewhere that I have just started using my new XI L mill.
I decided to reduce a bit of steel bar by 1/10" in 0.010" stages, just to get the feel of the machine.
The vertical scale is marked 0, 10, 20, 30 then back to 0.
Anyway, I did my ten cuts and measured it. Too thick. 'Strange' I thought. Then did another set of ten cuts. Same result.
After a bit of head scratching I realised that the scale has 36 graduations, not 40. each of 0.002"; giving 0.072" down per revolution of the scale.
I was incrementing down by moving the scale round by whole numbers, and there are only six graduations (0.012") between 30 and the 0 mark.
Please don't let me be the only one here to have done this. :doh:
Dave.
lordedmond:
Yep your are the only one in the wide world that has done such thing :)
Stuart
Only joking, typical Chinese dials, don't change the screw just bung on the dial to make it look OK
Davo J:
I haven't got that machine but we all make similar mistakes.
It would be worthwhile using a vernier or digital caliper on all axis's to check the dials to see how true they are, and that way you know if you have to compensate for them.
Even on my large Chinese HM52 mill (which is the same as Chester's T mill over their) is out on the down feed collar, but a DRO has fixed that.
Dave
andyf:
It took me a long time to work out why the topslide dial on my Chinese lathe never seemed to get things right. I knew it used the common approximation that 40 thou = 1mm, but the error was far greater than 1.5%. Finally, I realised that the dial had 50 "thousandths" graduations round it, whereas the feedscrew was 1mm pitch. :doh:
Happily, my spindle gear is 40T, so it was easy to skim the marks off the dial and index 40 new ones round it.
Andy
DavidA:
That's the next step. Clamp on a dial guage and check what is actually happening.
Dave.
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