Mill question

R

rzw0wr

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I have a not real good mill. Smithy.
I got it about a year ago and finally got it to working ok for what is is.
I have everything adjusted to within .001"

My question or problem is:

When I mill a piece no matter the length I get a .001" taper from end to end.

The taper does not bother me, what bothers me it is that a 2" long piece has this taper and a 10" has the same taper.

This drives me nuts.

I can't see where it would be the table because the taper is is not due to length.
The taper is just always there.

Any ideas?

Thank you,
Dale
 
Perhaps you should strive for plus or minus .002. You'll always be in tolerance.
 
The taper does not bother me. I can live with the .001"

What I don't understand is my it is the same on different lengths of steel.
 
Could it be that the table drops a hair due to a bit of play in the gibs? You start “x” at one position and as you move past centre the table sags that thousandth as the balance shifts. I don’t think it would ever register as a taper, just a fixed amount all the time. Maybe try clamping your part at different locations on the table and see if the condition repeats.

-frank
 
Is the taper always in the same direction?
What tool(s) are you using? End mill, face mill, fly cutter?
Do different cutting tools produce the same taper?

Tom
 
Last edited:
Is it a linear taper or a step change? If you make a cut 5" long, if you measure it at 2.5" is it .0005 off ?
 
Is the end you finish on the smaller size? If so, this could be due to thermal expansion. The cut starts cold, the cutter moves on, the material heats up and expands, gets cut, then shrinks 1 thou after its cooled. Or something in the spindle assembly is getting hot - possibly a bearing?
 
Smithy type machines typically work better as lathes than mills. Check for play in the gibs and table, something is moving around as you cut
or the ways themselves have error. Show us a picture of the error with respect to the machine and cutting direction
-Mark
 
I am wondering when in my lifetime that I would ever have a project that requires a one mill tolerance.
 
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