Roughing and Finishing

[kb18951452]

What settings are people using for rough and final passes?

Lame as it may be, i have neevr used a rough pass, chosing instead of use my 1/16 taper ballnose from the start, and run at 50 ipm, with a 8% stepover. Thats roughly 1inch per hour (on the jobs i am working)

Wat are yalls rough settings, (for instnce, bit size of rought and finish, and the stepover and pass depth of both)

How are you rezeroning after a tool change?

[Thkoutsidthebox]

You'll find with some more complex or deeper carvings, that not using a roughing pass may result in broken bits when the 1/16" bit hits a section which is too deep for the cutter length. The size of roughing cutter IMHO is dependant upon how complex your carving is...the curves...the grooves etc, and allowing it to rough out areas which a bigger diameter cutter might skip over and hence then break the finishing tool. Someone else might have a more precise formula. I don't think I've ever run without a roughing cut incidentially. I usually use about an 8mm roughing tool.

I zero the Z height off a piece which I know won't change height after the roughing cut, such as an edge.

[Rcnewcomb]

The choice to use a roughing pass is based on how deep the carving is and whether there are adjacent large discontinuities in Z depth. We always run a roughing pass on stone.

For roughing we use a 1/4" or 3/8" end mill at 2 ips for wood and 1 ips for stone.

We run between 3ips & 6ips on the finish pass for wood. Stone is about 1ips to 2ips. We keep the XY and Z feeds the same speed. Most of our finish machining is done with a 1/8" ballnose. We use the Beckwith bits for wood. We haven't found anything else that does nearly as well as these bits. We use coated bits from MCLS for stone as long as the Z depth is no more than 0.5"

FYI: I have a Shopbot PRT Alpha.

For dish designs the 3M sandpaper/scotch-brite attachment for a drill does an outstanding job of cleaning up tool marks. ->Link