Originally Posted by
runcyclexcski
Hi all --
Mo has been discussed here a while back, but I thought I could get some job-specific insight. This is for my own lab, not manufacturing/production. So I have the time, but I do not have $$$$ to invest into this.
I need to make 5 parts out of pure Mo sheet, 3 mm thick. Each part is a rectangle 35x62 mm, with 40+ holes ranging in size from 1.25 mm to 2.0 mm. The 1.25 mm holes are then tapped 0-80. The parts are used as heat sinks in microscopy which experience excursions from -80C to +40C while epoxy-glued to borosilicate glass. The choice of Mo is due to corrosion resistance, low heat expansion, good conductivity, relatively low cost (compared to say Ta), and relatively ok machinnability. Tried Al, numerous SSs, Ta, Ti, Invar, W and none had all of the above properties in one material.
I just made one of these on a Sherline mill. The part came out OK, it took about 5 hrs, and I am not looking forward to repeating this for 4 more. So I am wondering if there is anything I can do better. I glued the original 3 mm 100 x 100 mmplate to a 10 mm flat Al plate, used RPMs and feeds I would normally for Steel and Ti. There was not much heat/smoke, just very fast wear of the drills and mills. Used TiN-coated centre drills for drilling holes and a 4mm 2-flute carbide endmill. No other drills b.c the part wast thin enough, and the centre drills went through. For 1 part, used up 10 drills and 3 mills. Tapping was OK b.c. the threads were shallow.
Any specific drill/mill brand recommendations? Special oil? Can these be laser-cut instead? Tried water jet (outsourced), it formed bubbles and delaminated. For now, I ordered a 2mm plate instead of 3 mm, just to make it a bit less epic.
Thank you all in advance!