Milling MACOR!

metalmadness · Jan 22, 2021

Hey,

I have a small batch job in the shop that is made out of Macor material - mica/glass fused ceramic blocks.

They are small rectangular blocks about 25mm across, with a simply rectangular pocket and a thru hole.

My plan is to drill from both sides to prevent chipping on the drill op, and as far as milling goes I have no idea. Theres definitely some online guidance regarding speeds and feeds with carbide.

Anyone dealt with this stuff? Im thinking of running it dry so I don't get this stuff in my coolant system and also, under the way covers.

Milland · Jan 22, 2021

Used to do a lot of Macor and the other machinable ceramics.

Try to use carbide where possible, I'd suggest lighter WOC with a DOC as deep as you can go if profiling. Radius into the work to help prevent chipping, but Macor isn't as prone to spalling off material as some others.

No coolant, use a shop vac with HEPA filters and plaster dust bags. I'd peck drill and watch chip (dust) buildup in the flutes. Keep the vac nozzle close to the cutting zone, but don't foul the cutter.

Macor cleans up pretty well, but I tried to keep oil off it anyway. If using a spindle that drips oil, a M0/spindle off to wipe the spindle nose with a paper towel every so often worked OK.

Wsurfer · Jan 22, 2021

I milled a few parts, nasty stuff. I used food coolant and speeds and feed from the macor web site. Of two identical parts, one was fine, the other had some breakout/chipping on sharp corners. It also chemically reacts with steel, at least with the coolant I was using. Vise surfaces were instantly stained/etched ?. Just a visual thing, just something I hadn't expected. I don't think I'll do it again. I don't like the ideas of ceramic dust inside my machine.

metalmadness · Jan 22, 2021

well, ive gotten through one part just fine using a shop vac w/ HEPA filters for dust management. There was some breakout when finish facing but I think i figured that out.

It finishes really nicely! But honestly its not worth the time to do it. Cool stuff but nasty

metalmadness · Jan 22, 2021

For anyone wondering, I used 4 flute Firex end mills with 35sfm and .002fpt. Can probably bump both of those up to get bigger MRR but the finish may suffer and risk chipping.

Milland · Jan 22, 2021

metalmadness said:
For anyone wondering, I used 4 flute Firex end mills with 35sfm and .002fpt. Can probably bump both of those up to get bigger MRR but the finish may suffer and risk chipping.

Next time try uncoated carbide, the "dead sharp" edge may work better. I've drilled Macor with cobalt drills, so it' not like you need coated carbide to cut it.

And yes, the SFM sounds low for carbide.

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