Brass cutting tools cnc/industrial mode

[petertha]

I'm getting much better results in my home shop environment drilling brass & its evil cousin bronze with dubbed drills. I have a dedicated set now with the rake angle altered (reduced) and that made all the difference in the world. No more snatch & grab surprises. The chips look distinctly different.

But then I got thinking - brass gets drilled & reamed & tapped by the cubic mile every day in cnc/industrial world, yet I have yet to see specific 'altered geometry' drills for these kinds of materials. They vary by composition (HSS, carbide, coating...) by geometry (point angle, flutes, length) but you never see rake angle = X degrees like insert cutters. Why is this? I mean the machines are more solid, more coolant, more speed & feed control than home shop environment. But a drill is a drill & they must want to avoid breakage & related problems like the plague.

 

[JimDawson]

If there is little to no backlash in the machine, then trying to control the grab is not so important. The machine just won't let it grab because the drill bit can't pull the carriage into the work.

 

[benmychree]

Back in the day, there were "brass drills" they had straight flutes, like a wood cutting "push drill" uses; no dubbing necessary. Some hard bronzes do not need drills dubbed, call it "yellow steel", such as 954 bronze.

 

[KMoffett]

Bits for plastics has the same "dubbed" cutting edge. However, the point angle is 60°. I have some of these, but never tried them on brass.
https://www.mcmaster.com/catalog/124/2495
For brass I've always just ground off the sharp edge. The McMaster0Carr page doesn't indicate the rake for their "Bits for Aluminum, Brass, and Bronze "

Ken

 

[petertha]

. The McMaster0Carr page doesn't indicate the rake for their "Bits for Aluminum, Brass, and Bronze " Ken

Yes, I've seen similar references. I thing that pertains to the flute angle relative to drill axis to help chip evacuation pathway on gummier materials. Parabolics are another flute style. But no mention of altered tips. Huh - must be a machine rigidity & alignment thing when it comes to cnc's. Or maybe they switch over to single point boring tools sooner rather than rely on bigger drills where the problem might be aggravated.

 

[P. Waller]

PCD tools are often used in the mass production of non-ferrous metal parts such as brass, bronze and aluminum components. They can be ran far faster and longer then carbide tools. I suspect that the tool geometry is not what you would assume, also the manufacturers are not likely to publish such data publicly.
The only way to find out is to buy a $500.00 drill bit and see if it works better (-:
I have never used a PCD drill but regularly use inserts for lathe work, also ceramic inserts for hard turning that work a charm.
I would not try using a hard turning insert on a SB 9a lathe that was made in 1945, this would likely end in tears.



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