On Thursday, April 2, 2020 at 4:26:16 AM UTC-4, John Doe wrote:
Michael Terrell wrote:

I've cut them with a fly cutter.

I have a relatively big arm type hole cutter but it won't cut down
to 40mm diameter. The small one probably wouldn't do unless (maybe)
if all edges were extremely sharp.

I already ordered a cheap tungsten carbide tooth (TCT) hole cutter.
Might try that. Using a hole saw after cutting teeth out of it did not
produce a
clean cut. If that is tried again, only two teeth will remain.

For a lower, variable speed drill press, I might chop up my cheap
drill press
and chuck/attach a powerful cordless drill to the spindle on top.
Will see how difficult, attaching the drill to the spindle and
securing it in place.

Instead of trying to make a 40mm bearing housing, another
possibility here is to work with the inner/shaft diameter of 17mm. I
ordered a couple of (pillow block?) bearing holders (UFL003).

Lots of possibilities now.





--

Thanks to the replies.

ah. A 40mm bearing housing...............

I would use a magic marker on the aluminum and then scribe a 40mm circle where you want the hearing. Then use about a 1/4 inch drill to chain drill most of the hole and then finish with a round file . No suitable file, then buy a 3/4 inch dowel and use it with sand paper. With good lighting you should be able to make it close enough to have a press fit.

Dan