[FlyingElectron]

I'm hoping someone can give some good recommendations on what type of drill bit to use to drill a #5 (0.2055 inch) diameter hole about 1 inch deep into 6061 aluminum.

Obviously I've figured out that I should use a #5 drill bit, but I'm curious if there are any advantages to a 135 degree split point over the standard 118 degree point, and if there are any advantages or disadvantages of cobalt over black oxide or Tin coatings. My machine has a limited vertical stroke, so i will be using screw length bits if that matters. I can spin my spindle up to 8000 RPM but am limited to feed rates of about 0.5IPM before the spindle motor stalls.

The prices at enco are pretty close for all the different drill bits, so I just want to try to pick the most appropriate one.

Thanks All!

[HuFlungDung]

A split point on a twist drill makes penetration of the work easier, so the thrust load on the machine will be lower. But a plain uncoated, polished flute drill is generally recommended in aluminum, although almost any type of drill can be made to work. You'll want enough flute length so that the chips can come up the flute when the drill is getting deeper into the hole, so don't buy something too short. However, a pecking routine can/should be used to clear the drill when it gets into deep hole drilling. In your situation, it doesn't sound like you'll be able to take a proper chip, so the tendency of the drill to clog will be higher, because not much chip flow is coming up from the bottom.

[FlyingElectron]

Thanks for the info! When you say the drill will penetrate the work easier, does that translate into needing less hp to drill the hole? I'm using a 118 degree drill bit right now and I stall my motor if I feed faster then 0.5IPM. Do you think a split point would let me feed faster since it penetrates easier, or is most of the power used to turn the drill bit after penetration?

It sounds like a split point is better then a non split point, is there any reason to not always use a split point drill bit (besides the split point bits costing more)?

Thanks!

[HuFlungDung]

I think it is fine to use a split point grind all the time. Thing is, you need to learn to sharpen that feature on the drill yourself, or you'll be forever buying new drills

The split point will reduce the load on your Z axis motor, but will not decrease the power required to remove the metal. In fact, because it penetrates more easily, it may seem to take a better chip and seem to draw more power, on a marginally powered machine.

[FlyingElectron]

Cool! Thanks for the recommendations. I've got a drill doctor that can sharpen split point, so I think I will be ok on the sharpening front. :-)