From Newsgroup: rec.crafts.metalworking

The principle can be applied to trochoidal tool paths, and I recently
wanted this feature while doing some trochoidal material removal, but
its not a function specifically of trochoidal milling. Not the way I
want it anyway.

I thought of this ages ago, but manual milling of all things brings it
back to mind. I sometimes rough mold blanks on the manual mill. A
common operation is to remove approximately 0.24 inches of material from
most of a blank leaving a boss at one end to be rounded over for a
hinge. In this roughing operation I usually use a 1/2 inch 3 flute end
mill with bright aluminum geometry. I can take 80% axial width of cut
about as fast as I can turn the handle in the climb pass, but only about
40% feels good in the conventional pass to return. On this machine
doing this I get no chatter and the floor of the cut is decent. Better
than good enough for roughing. "Rapiding" back takes the same amount of
time as cutting back, so its just wasted time to only climb cut this
roughing operation.

None of my CNC machines (currently under power) are as powerful or as
rigid as then manual mill. None of them are high dollar VMCs either so
when we get to the obvious answer I'll tell you why its less desirable.
The basic principle in the previous paragraph can still apply.

It might be desirable to be able to set the step over differently for
climb cutting vs conventional cutting in roughing operations. Some
might argue that you just do whichever works best and rapid back to the
start. The Speedmasters only rapid at 150ipm and the Tormach 1100S3
only rapids at 110ipm. That travel time adds up over the course of an operation. It can cost you hours. Now if I could adjust climb and
convention step over (and or feed rate) within a single roughing
operation in many cases the material removal rate would be LOT higher
than only climb cutting or only conventional cutting depending on the application.

On a recent job in a large deep pocket we found that climb milling
didn't chatter with a reasonable chip load, but it chattered like crazy
when conventional milling. It sure would have been nice to adjust the conventional cut independently and cut in both directions instead of
spending a third of the cycle time performing rapids. I have not really
seen this mentioned much in machining circles. Guys who use a half
million dollar machine owned by their boss's bank just count on those
stupid fast rapids, or their machine is so heavy, powerful and rigid it doesn't matter. Hobbyists just live within their limits and puff up
their chest saying, "SEE! it can cut metal," defensively. I'm somewhere
in between.
--
Bob La Londe
CNC Molds N Stuff

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From Newsgroup: rec.crafts.metalworking

On 5/17/2026 11:38 AM, Bob La Londe wrote:

It might be desirable to be able to set the step over differently for
climb cutting vs conventional cutting in roughing operations.

Another operations I do routinely when targeting a hard dimension is
take a modest to heavy climb cut, and then take a zero stepover
conventional cut. This removes the little bit left from deflection of
the climb cut, but is not enough material to cause the conventional cut
to dig in and deflect in the other direction. It also often leaves a
really nice finish and a straighter side wall.
--
Bob La Londe
CNC Molds N Stuff
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