Need to make a big hole in Aluminum plate

[Investigator]

I have no idea what a RF 30/31 mill is but can you not interpolate such a small hole?

 

[Investigator]

going now to google "interpolate".........

 

[Investigator]

................................

Careful please read this part!
You do not want the center piece to break loose and trap the end mill as you approach the end of the cut. So with leaving 2 small retaining tabs about 180 degrees apart to hold the center plug in place. When done you should have a plug that is cut all the way except for two small areas that you can cut with a small saw and then blend into the rest of the cut.

Or flip before completely cutting through and avoid the sacrificial plate and cut down to about 1/4 to 1/2” left and flip, locate on the center hole again and continue to clear the remaining part but still leave the retaining tabs to hand cut at the end.

Thank you! that is not something I would have thought of.

 

[Jimsehr]

When I made a steady out of alum I made the bottom of steady first . Then I put it on the machine with the hold down bolt snug. Then I drilled steady with a 1/2 drill in a collet by pushing alum into drill with tailstock. That way I knew 1/2 hole was on center of machine . Then I used that hole to center steady on rotary table. I worked from that hole to cut the 3 slots for the steady fingers. Then I cut the center plug out.

 

[JimDawson]

Thinking off the wall here.....

I have a small rotary table. What about mounting it so that I could turn it under the mill head, and cut with an end mill?

That's how I would do it given your available tooling.

 

[tq60]

Rent a hole saw from a rental place or buy one as they are handy to have.

Place wood under it clamped tight to table.

Slowest gear possible and peck drill.

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[Investigator]

I was under the impression that a hole saw cutting that deep in aluminum was a problem. But that does look like the easiest solution. I have several hole saws already but hadn't really considered using one because as I said I thought it was somehow an issue.
I guess going slow and lots of cleaning out of chips would work and might be the easiest set up.

 

[RandyM]

Use a lubricant. I use WD40 for aluminum. You'll still have to clean the chips out of the cutting very often. I think the hole saw is really your best choice.

Another tip for this is to cut half way thru one side and then flip the part over using your pilot hole to line it all back up. This will keep the saw groove from getting so deep.

Good luck.

 

[Investigator]

Another, albeit late thought. What would be the preferred size opening for a steady rest? Put another way, what size stock should I plan on being able to handle?

Talking this through in my head......My spindle is 1.375", so it seems there really is no value in making a steady for smaller than that since it could fit through the head stock and work close to the chuck. I guess making the steady large enough to handle a range from 1.375"-? would be a better plan.
So, 2.5"? 3"? does it matter how much of the fingers are extended past the rest?
Maybe the best design criteria would be what size hole saw I have readily available?

 

[pontiac428]

I cut a hole in 1.5 in aluminum plate with a hole saw... Once. Never again. I'd suggest hogging the hole out with a S&D bit then using a boring head or a fly cutting head in the Rong Fu. Rotary table would work well too.

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