Need advice on drilling holes in Aluminum 1

[nicholr]

I need some advice on repetitively drilling holes in aluminum.

Here's my situation - I have a 2.75 in dia. 2014-T6 aluminum piece that I am drilling 12 holes radially around the piece. The holes I'm drilling are .126-.128 dia by .205-.215 deep. I have a machine that uses a Suhner drilling unit to drill the holes. The Suhner drilling unit uses air pressure and a hydraulic check cylinder to feed in the drill. The drill is turning at about 5000 RPM. I am currently using a 3.2 MM cobalt drill bit with a standard 118 deg point.

My questions are - 1) what would the best drill bit to use? Coated? High helix? Different type of point? 2) I've been doing this operation dry but have noticed some build-up of aluminum on the drill point. Should I try some sort of coolant? Is a coolant really necessary?

Thanks for any advice!
Lee N.

 

[TVP]

Standard twist drills are often used for drilling Al when the depth is less than 6 diameters. Deeper holes should be drilled with high-helix drills as they clear the chips more effectively. Since the depth of the hole that you are drilling is quite shallow, it is not imperative that you use a coated tool or use a cutting fluid. If you want to experiment with cutting fluid, kerosene, kerosene & lard oil, and soluble oil emulsions are the best choices.

 

[JDana]

We drill aluminum all the time, and used to have a Suhner drill. We found that 3 flute carbide Hertel drill worked best for us. Coolant is pretty much needed if you drill with any speed, as aluminum likes to gum up on the tool.

 

[scottmaha]

we drill aluminum all the time. we machine 2024, 6061, and 7075 - all T-6. we use guhring drills exclusively. we have tried everyone else, but guhring has proven to be the best. for your application, i would recommend guhring's series #552 drill. this is guhring's GT80 parabolic flute drill. we have guhring coat our drills with "molyglide". this is a soft coating that is ideal for dry drilling in aluminum below 5 diameters deep. since you only have 5000 rpm available, it does not make since to use cobalt or carbide drills. the #552 is HSS and has a bright finish with polished flutes. if you run carbide in aluminum at to slow of a rpm you will experience cold welding of the aluminum to the drill and ultimately breakage.

this is what works for us.

good luck

 

[pirko]

Dear Nicholr,
this is teoretical problems. Alu making dirty on sharps between 300-600 Celsius. You must go down or up this temperature. Best for you (productivity) is go up. You must use about 15 000 RPM. On this moment you will have not problems. We use milling tools 40 mm dia and 7 500 rpm without cooling. If you use this cutting speed you will not problems. You must recalculate from this cutting condition.
If you have more problems contact me I have more experience with High spee cutting in Aerospace Industry. Good Luck. Libor