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Originally Posted by
g-codeguy
.....Picked up a used Hardinge not long ago that came with a knurling tool I hadn't seen before. Looks like you cut with the edge of the tool, and feed in from Z-axis.
I know that pitch and diameter are tied together, but that knowledge doesn't seem to help me much....
I have not knurled on a CNC but in the past have done plenty on Turret and Center lathes.
To comment on your second point yes there is a relationship between the knurl spacing and the diameter; you can consider the knurl and the workpiece to be a pair of gears so you have to fit an integral number of bumps around the workpiece. But at the same time your workpiece is changing diameter because the bumps come up as the hollows go down. I suppose it would be possible to calculate a 'pitch diameter' for the knurling and make that your starting diameter; I nearly always did it by trial and error.
Regarding feeding in from Z that is how we did it on turrets, both straight and diamond knurl; it wasn't really feasible to do anything else. It also seemed to be easier and I always figured it was because the knurl was working on a smaller area of metal. If you come in on X the knurl touches across the entire face and is distorting the workpiece simultaneously on the full width of the knurl; coming in from Z means it is plowing through into the workpiece only on the leading edge.
On a center lathe I would come in at the end of the workpiece with the cross slide and have the knurl overlapping just a small amount. This would start the knurl and get everything in synch and then I would traverse along with the carriage.
Sometimes I found the knurl would start to cut a double start with the knurl rollers spinning twice as fast as they should be; you could see the different appearance on the work when this happened. I would back out and start again. This would leave a poorly knurled section at the end but generally after knurling I would re-chamfer the start end to remove the sharp burrs that the knurl pushes out on the end.
Incidentally starting from the needs a bit of chamfer before knurling to allow the knurl to ride into the part.
Regarding holding +/-0.001" when knurling I don't see how that is possible. Also if the picture that was posted is the part being done I don't see why it is necessary, the knurl is on the handle of a screw-in alignment pin. It would be a very sensitive hand to detect a couple of thou difference in diameter.
An open mind is a virtue...so long as all the common sense has not leaked out.