How would you cut this?

[FanMan]

This is a semi hypothetical question, the milling operating I had in mind turned out to be unnecessary, but the question remains: say you need to mill some amount off the side of a workpiece, considerably deeper than wide. For example, maybe 1/8" cut by 3/4" deep. Setup restrictions prevent laying it over and cutting it 1/8" deep by 3/4" wide. Anyway, one could make a shallow cut the full 1/8" wide, advance the spindle, and repeat until the 3/4" depth is reached, or position the end mill at the full 3/4" depth and make repeated shallow cuts with the side of the cutter until the 1/8" is reached.

Which would you do, and why?

 

[Tony Wells]

One question first. Why are you restricted to a 1/8" end mill? Am I not visualizing the cut correctly? A larger end mill would take it in a single pass.

 

[timmeh]

All dependent on size/power of machine and Dia. of cutter to determine how much material to remove per cut.

But regardless of size/power of machine and Dia. of cutter, set cutter short of final size radially-say .010". Work your way down axially in steps-say .200", .200", .200", .140". Leaves .010" in both directions to clean up to size.

Don't take a full 1/8" x 3/4" cut with a 1/8" diameter cutter, it will break.

 

[Tony Wells]

Usually the problem with stepping down in -Z- is that you wear the end mill on the diameter and length based on your step down. Then on the final pass, unless you have the length (and it is not a blind slot, for example) the dullest portion of the flutes will not cut as easily and it can leave a noticeable step at the bottom. However, if you have sufficient flute length, increase your -Z- increment to put the "used" section of flutes below the work so you can expose flutes with little to no wear. Your shoulder or edge of part will more likely be square due to lack of pushoff from the dull end mill section.

 

[tq60]

No mention of end mill size.

Would suggest simular as above in that cutting just less than the 1/8 depth of side cut and plunge in part of the depth and cut the lender and repeat until just short of full depth.

Use a roughing or not so new cutter.

Switch to "good" cutter as finish cutter and first cut to depth then sneak up on the side.

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[RandyM]

Why not a slitting saw?

 

[FanMan]

Right, I never specified the end mill size, I was picturing something 1/4" at least, maybe 3/8 or 1/2". Anyway, this is what I was trying to describe. As I said, I could cut the full 1/8 with the end of the mill and step down, or start at the 3/4" depth and go back and forth across the part until the 1/8 dimension is reached. Assume the workpiece is sufficiently rigid and the end mill flutes are long enough. I know either would work but I'm wondering which would be the better approach, and why.

 

[ddickey]

Plunge mill, leave a few thou for final cleanup then side mill.

 

[tq60]

Some restrictions to consider is part may flex and aluminum may load up.

So one could plunge in but not at full depth so small bites so to speak and bottom of mill is doing the work.

After most of the material is removed leave at full depth of cut then sneak up taking small cuts at high speed to help avoid loading the mill.

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[Jonathans]

What DDickey said, with an endmil greater than 1/2" diameter