Cliff wrote:
On Sat, 19 Feb 2005 14:39:28 GMT, "Bill Roberto"
wrote:


Right out of Bill's calculator, copied from Sandvik technical help:

F = finish requirement represented as non decimal integer i.e. 32 or 63.
R = tool nose radius.

SQR((F*(8*R))/(10(sixth))


So, with the tooling & inserts & feeds he said he's using
what's the best surface finish he can expect (no wipers)
if making only one finish pass? Did he mention how much
stock he had left for a finish pass (DOC)?

Next question: What if he makes multiple finishing cuts
at the same Z? What if he steps them over?

G


The formula calculates the theoretical scallop height for any particular
tool nose radius. The keyword is theoretical. If I have a .03125 radius
on the tool nose and I want a 32 finish my feedrate would be .0028. If I
applied the same formula for an 8 finish my feedrate would be .0014.
Unless the machines spindle bearings runout is less than 80 millionths
of an inch, and the resolver feed back can keep track more accurately
than 40 millionths that 8 finish ain't gonna happen. As GarlicDude
mentioned, achieving a finish better than a 32 on a lathe is dependent
on many other factors than just a scallop calculation.