making a large hole in aluminum bar

[James Baker SD]

I am trying to fabricate a replacement guide holder for a bandsaw and would like to use a piece of scrap yard aluminum (I have it, but do not know its machining qualities yet). It is about 2" x 1.5" cross section and I need to put a large (~30mm) hole through it. What is the best way to do this with limited tooling (I am woodworker, not metal worker)? I have a big, heavy floormount drill press that goes down to about 450 RPM. Doubt I have any drill bits that large. I would be willing to sacrifice a forstner bit if it can do the job without endangering my health. I don't think the hole size is extremely critical. So ideas? thanks.

James

[Troy Turner]

James - Not a metalworker myself, but I'll bet there's one around that would charge a very minimal if any, to bore it out for you. If you still have the old piece, he'd probably be able to make it exactly the way you need it too. Just a thought.

[Izzy Camire]

Aluminum machines pretty nicely. You might consider going to Fastenal if there is one in your area to get the drill bit you want. If that doesn't work order online from Enco. They probably have an inexpensive drill bit. I think I would try more around 600rpm for a spindle speed. Make sure the piece is clamped or at the very least it can't grab and take off when the drill breaks through.

[Ole Anderson]

Use a hole saw if tolerences aren't critical. Lube with WD40 to keep the aluminum from plugging the teeth.

Or go here to get a 30 mm bit with a 1/2" shank: http://kbctools.com/usa/Navigation/NavPDF.cfm?PDFPage=21

[Thomas Hotchkin]

James
I use a General Tool 55 hole Cutter in my drill press all the time. Drill press set to lowest speed, and item well clamped. It cuts aluminum just as easy as wood. I do a test cut on scrap to set cutter for correct size. Does not cut any other metals harder then brass and aluminum. Tom http://www.amazon.com/General-Tools-55-Circle-Cutter/dp/B00004T7P1

[Bruce Page]

Drilling a 30mm (1.181) hole @ 600 rpm thru 1.5” thick aluminum would be fine on a solidly built milling machine. If you’re doing this on a drill press I wouldn’t go any faster than 200 rpm. Make sure the work piece is firmly clamped.

[Ole Anderson]

James
I use a General Tool 55 hole Cutter in my drill press all the time. Drill press set to lowest speed, and item well clamped. It cuts aluminum just as easy as wood. I do a test cut on scrap to set cutter for correct size. Does not cut any other metals harder then brass and aluminum. Tom http://www.amazon.com/General-Tools-55-Circle-Cutter/dp/B00004T7P1

I have used that circle cutter on 1/4" aluminum plate quite successfully to make tapered heavy aluminum washers, but I think you will run into trouble trying to use it on aluminum 1.5" thick as you may with my suggested hole saw. Your best bet is a twist drill at a slow speed using WD-40 or Tap-Magic as a lube. I hope you have a real heavy duty drill press. A mini mill would be a better bet.

[James Baker SD]

I have used that circle cutter on 1/4" aluminum plate quite successfully to make tapered heavy aluminum washers, but I think you will run into trouble trying to use it on aluminum 1.5" thick as you may with my suggested hole saw. Your best bet is a twist drill at a slow speed using WD-40 or Tap-Magic as a lube. I hope you have a real heavy duty drill press. A mini mill would be a better bet.

I have the old 15" Powermatic Beast. Pretty heavy, but only goes down to 400 RPM (5 speed, pulley/belt drive). I measured the shaft of the band saw and it is 25mm, so 1" hole will probably work for me. The aluminum bar I want to drill thru is 1.25" thick. I have a pretty heavy X-Y vise bolted to the Powermatic's table.

Would it help to drill a 1/4" hole first, then 1/2" etc and not try to do it all at once?

Thanks.

[Mel Fulks]

denatured alcohol works well to help drill aluminum, I have no idea why. We used to keep some in a squeeze bottle next to the drii press.

[Bruce Page]

A 1/2" pilot hole would help a great deal. Use your quill stop screw and feed the bit a little at a time when you're getting close to breaking through with the 1" drill. The stop screw will prevent the bit from grabbing and locking up.

[James Baker SD]

Looking at bits online and wondering what size to get. I measured the shaft with a vernier caliper and it looks to be 25.0 mm. I originally thought a little clearance from a 1.0" hole would be good, but I test fitted a piece from a telescope drive that measured 1.00" inch hole and it was more loose than I really wanted. So now I wonder what drill should I buy? Seems I could go for exact and get a 25mm drill, but maybe it will be too tight to fit. Alternative is a 63/64" drill which comes out to 25.003mm which would have a little clearance. I will drill and tap holes for set screws to hold the new piece to the steel shaft.

What's the recommendation? Thanks.

[Brad Pickens]

Just mark your layout and take it to a machine shop--it will take them five minutes to cut it, won't cost you much (certainly less than the cost of an appropriate drill bit), and they are equipped to do it safely.

[Carl Beckett]

You said size wasn't critical, so I suggest just drilling a bunch of smaller holes around the perimeter until it drops out and then filing the edge smooth. No need to go out and buy something you would use only once.1/2 " bit, some oil, and a drill press will work fine

[Ole Anderson]

Carl, what kind of recommendation is that? I thought the whole idea of having a shop is to collect tools that will do a job correctly once then sit around forever, just waiting to maybe be used once more.:)

By the way, the bit he needs is less than $10 at KBC. http://kbctools.com/usa/Navigation/NavPDF.cfm?PDFPage=20 (63/64"), although I would just get a 1", more likely to be needed in the future. I have a number of these bits, they work fine and yes I would drill a pilot hole.

[Carl Beckett]

Carl, what kind of recommendation is that? I thought the whole idea of having a shop is to collect tools that will do a job correctly once then sit around forever, just waiting to maybe be used once more.:)


lol Ya.... the farmer in me will just never go away Im afraid. I would be embarrassed to admit all the different things I have used as a 'hammer'......

[Ole Anderson]

Yea, I have a set of oversize pliers handed down to me by my dad. I can't recall how many times he said "Ole, get me the big pliers". They look like someone took a ballpien to them they got used as a hammer so many times. And now I have so many hammers I can barely count them. Still, every once in a while, those pliers get used to tap on something.