Taper turning....steeper or less?

Sean S · Sep 5, 2004

Hi everyone,

I have a CNC lathe that turns tapers in degrees of angle.
In the case of say...a self holding taper (but also curious about self releasing), if my calculations for degrees of angle come out to 5 decimal places and the CNC has input for 3 decimal places...would you round up, or round down for the input?

That is to say... would you choose a hair steeper or a hair less steep assuming the machine could actually produce that level of difference.

To that end, do what decimal place do you think it matters at all?

Thanks for the input
Sean

johnoder · Sep 5, 2004

In real terms, one thousandth of a degree amounts to less than .00002" per inch in relation to C/L of spindle. Can you measure that?

John

rke[pler · Sep 5, 2004

.0005 degrees is .0000087 in one inch. I don't think it matters which way you go with the rounding, or even truncation.

Sean S · Sep 5, 2004

Good point guys...I should have thought of that.

Let me then change my question to ask...

At what decimal place would it actually matter and at that point, would you round up or down?

Sean

Dave K · Sep 5, 2004

If you have any means of measuring an angle very accuratly, I would round it off in the direction that your angle is off. If your shooting for 5 degrees, and the lathe actually cuts 4.9876 degrees, I would round it up. Also depends on the tolerance of the angle. If the tolerance is +or- .5 degrees, and your chasing .xxxx degrees, your wasting your time. Kind of like adjusting .0002 to hit right in the middle of your .015 tolerance part.

toolmakerjim · Sep 7, 2004

i was taught in the process of turning a taper to chalk at three equidistance points along the taper and then apply a gage to verify contact.
if the chalk mark is disturbed equally at all three points your taper is good, i wish the power would come back on at my shop this is fun but makes no money...jim

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Taper turning....steeper or less?

Sean S

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johnoder

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rke[pler

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Sean S

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Dave K

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toolmakerjim

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