I need to drill two 8mm and one 7mm holes in the sides of 25 Hammond 1550Q boxes.
To save changing bits, I've been using a stepped cone cutter, but I've not found a way to prevent slag building up on the trailing edge of the cutter.
I've tried the fastest speeds, the slowest speeds, slow plunging, rapid plunging, adding cutting fluid to the box and/or the cutter, but to no avail.
Is this slag simply due to the type of aluminium from which these boxes have been made, or am I still not cutting/plunging at the correct speed ?
Worst case I could drill the holes with individual HSS bits, but even with them I've found these boxes clag up the flutes.
Just the material. They'll porbably be cast from pretty much pure alu, which is like machining butter.
I'm guessing you've tried various lubricants?
WD40, or some oil based cutting fluid would be my choice, however you'll probably still have to flick the buildup of between holes.
If i was doing it i would clamp some stops on your drill table to locate your box for the first hole, grind the drill flat bottomish so the drill cuts initially on two points (each flute) use parafin as a lubricant and don't go silly with the revs, just cozz you can cut ally at a fast speed doesn't mean you have too, drill your 25 off @ 7mm. reset your stops and do the 8mm.
Flat bottomish drills are great for brass. Recently I bought a set of Heller cobolt drills, not that I'm drilling hard stuff, I just find they drill a neater hole in half the time as jobber drills, maybe worth a try ?
Good to know I'm not doing anything too dumb :)
Guess I'll just have to persevere and keep the bits clean as I go.
Thanks for the pointer about the drills. I don't have a grinder, so I'll have a hunt for some ready made drill bits.
Last edited by Saracen; 15-09-2013 at 10:07 PM. Reason: Crossed posting from EddyCurrent.
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