While facing a faceplate today I thought about how metal is milled and
wood is turned. In milling a rotating cutter is forced into sliding but
firmly held metal. In woodturning a sliding but firmly held tool edge is
forced into rotating wood.

Consider a horizontal milling machine doing what machinists term
peripheral milling and we term spindle turning. In climb or up milling
the work moves in the same direction that the cutter is revolving and is
forced toward the holding vise as it slides through the cutter. It
produces a smooth surface and wispy swarf. In the more conventional down
milling, the work is moved against the direction of the rotating cutter
and is forced away from the vise. This mode can produce a ridged surface
and chippy swarf if the work isn't held firmly.

Now consider scraping and shearing wood. In scraping the edge is moved
in the same direction as the revolving wood as the tool slides along the
rest. It can produce a smooth surface and delicate shavings. In
shearing, a tool edge is moved against the direction of the rotating
wood and if not controlled can produce a scalloped surface and distorted
shavings.

Machinists and woodturners know that there are other important
considerations that make down milling of metal and shearing of wood
usually preferable to up milling and scraping.

I know that my strained analogy is of no account and boring to many
(most) of you. I thought it interesting and I hope I got it right, but
if not somebody please correct my ups and downs for the sake of future
generations of woodturners.


Turn to Safety, Arch
Fortiter



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