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+--- Thread: not sure (/thread-3326.html)
not sure - oldskoolron - 09-23-2016
had a visit from a mate today that was watching me check if my lathe was running true [centre to centre ] anyhows its a enco/grizzly 4003 an I was looking at the manual I have an it shows how to line up a centre point in the chuck [it recommended that I make my own dead centre for it so I did ] and to use the dead centre in my tailstock I put a piece of 40mm bar stock in a pre drilled both ends then mounted it in between the centres .I then ran the dial gauge along it an there was -002 runout which I got by adjusting the grub screws .
now heres my problem im unsure about
all the diagrams in book show top view only an no mention of side view which I found to be out -04
my mate said I have to get it back to close to zero or ill have a taper but to me id only have a taper if the cutting tool was on top
eg' my point is you will get a taer BUT it will depend where the cutting bit is
am I correct or totally wrong im unsure but my mate says even if the cutter is on the side ill still get a taper mmmmm im not that upto date like you fellas as ive said I only started working these machines in the last year or 2
thanks in advance for the answers
RE: not sure - Pete O - 09-23-2016
Yes is will still affect the cut as the tool will not be on centre over the length of the job, your mate is correct it will cause a taper. L.F. Sparreys old book 'The Amateurs Lathe' had a diagram that illustrated this point very well.
If you picture an extreme example of the same thing, say your tailstock was 2" below centre rather than .002", and picture the changing relationship between the tool and the work as the tool moves along, it will give you an idea of the effect.
Also I think a more accurate check would be to take a skim cut of the bar mounted between centres and then check the diameter at several points along the bar.
RE: not sure - TomG - 09-23-2016
Are you talking millimeters or inches? If the height of the centers differs by .04mm, I'd leave them alone, because any taper would be insignificant. If they are .040" off, then that's another story. It won't make much difference on a large diameter, but small diameters will taper quite a bit.
Tom
RE: not sure - Mayhem - 09-23-2016
The way that I got my tailstock lined up was to pinch a razor blade between the two centres. If they are in line in both axis the blade will be perfectly perpendicular to the ways when viewed front on and from above. I had to shim the tailstock to get the correct height.
RE: not sure - oldskoolron - 09-23-2016
im talking metric tom easy for me than imperial .most parts I try to make come out pretty good but im wanting to make a hyralic clutch setup for 1984 to 1999 Harleys and need it to be spoton for the piston
if yous think leave it I will as im only talking bout work bits that will be 3inches long at max
cheers
RE: not sure - Pete O - 09-25-2016
Wasn't quite clear from your post Ron whether it is out by four thousandths or forty thousandths. I think the point of Tom's response is that four thou is okay but forty thou is not.
RE: not sure - oldskoolron - 09-26-2016
sorry imeant 4 thou
RE: not sure - Dr Stan - 09-26-2016
Did you take a clean-up cut on the shafting? If not you really need to do so as it will give you a much better idea as to the amount of taper.