[RicknBeachcrest]

I need to drill a 1 1/2" hole in several pieces of 1/2" aluminum plate. I've read where people have used a forstner bit.

Any comments?
Thanks.
Rick

[ger21]

A forstner bit will be instantly destroyed. I'd just use a hole saw. If you need them to be precise, make an MDF template with a forstner bit. Drill the aluminum with a 1-3/8" hole saw. Use a router with a flush bearing bit along with the template to finish the hole.

[keebler303]

hole saw to get to net size, a boring head would get you to perfect size, assuming you have a mill to put a boring head in.

Matt

[kinghong1970]

knock out tool?



never mind... 1/2" plate... wow!

[HorridHenry]

Look at the 2 Piece Titanium Nitride Coated High Speed Steel Step Drills here
Electrical Estimator-software,figures &amp: tracks materials, estimates

The biggest goes to 1&3/8" perhaps you can find a 1&1/2" in the states elsewhere?

[RicknBeachcrest]

Thanks for all the replies.

I didn't think about a hole saw and
I've got a boring bar for my small mill.

So that should take care of it.

Rick

[slowlearner]

personally I would step drill vs hole saw.

[louieatienza]

personally I would step drill vs hole saw.

I'm not sure if they make a step drill with 1/2" steps?

[fizzissist]

Hole saw and a squirt bottle with WD-40 to keep the aluminum from gumming up.

Do this all the time on a manual mill, and follow with a boring head. What to do with the resulting 1/2" thick biscuits is still a mystery, but they come in handy for standing off parts above the table for the occasional odd job.

For thinner plate/sheet stock, the pilot drill will allow you to stack multiple layers. The only caveat is that you need to "peck" and clear chips often so the teeth don't load up. Otherwise, it works great.

[Geof]

You can use a spade drill.

http://www.cnczone.com/forums/genera...uminum%3B.html

[DonFrambach]

I've gone the hole saw route with success. One trick I discovered was to go only part way through with the hole saw but deep enough that the pilot drill went all the way through. Then flip the material over and use the hole saw from the other side.

[fizzissist]

We amassed a collection of hole saws over the years, with a small collection of mandrels. Before I was able to convince people that CNC could make short work of 80% of our hole cutting, hole saws up to 4" was the common way to make big holes in the mill.

The beauty of a hole saw too is that if you have to make a hole that's got a small dia that connects to a larger dia, like the shape of a small pulley that drives a big pulley... as long as you have material for the pilot hole in both sides, you cut those, then angle the plate and mill straight between the tangents of the holes.

....Btw, get the mandrels with the 3 flats on the shank to keep it from spinning.