Removing large amounts of material?

[Michael Edwards]

Well, how about buying an Oxy Acetylene torch and cutting the center out? If you are doing a lot of these, this would be the cheapest/quickest method, then a simple lathe job to clean up.

Edit: NVM, OP said aluminum, disregard potato chip pic..
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[MrWhoopee]

Well, how about buying an Oxy Acetylene torch and cutting the center out? If you are doing a lot of these, this would be the cheapest/quickest method, then a simple lathe job to clean up.

Works fine for low carbon steel. Not so much for aluminum, which is what the OP asked about.

[Lee Cordochorea]

If I were doing something like this - and it was a one-off - I'd drill a small hole less than 2" from center, then use a metal cutting blade on my scroll saw to rough out the hole. Second choice would be step-drilling.

Pheh! Who am I kidding? I would forge & weld a ring from a one inch square bar, then machine the forging to shape on the lathe. (Might have to upset over a mandrel after welding to insure adequate thickness.) More folk have scroll saws than have forge furnaces, though. Even more folk have drill bits.

[RB211]

I'd use a CNC mill and just slot it out

[BCRider]

Well, how about buying an Oxy Acetylene torch and cutting the center out? If you are doing a lot of these, this would be the cheapest/quickest method, then a simple lathe job to clean up.

As mentioned by others the OP asked about aluminium. So the oxy-acetylene won't work well. But a plasma cutter on the other hand....

Chain drilling through 1" material around a roughly 3.75" diameter? Then having to still bore or otherwise cut through the webs left? I'll take 15 minutes of grinding a tool bit and doing the treppaning cut any day of the week. I've done some chain drilling over the years. And frankly it's not a whole lot of fun and takes quite a long time and the opening still needs a lot of cleaning up. It would be far faster to grind out a trepanning tool and do the job directly in the lathe.

A good 3.5" hole saw would also cut down on the amount of work. And I like the idea of the chip relief holes too. That was a great suggestion. I'd go with four 1/4 inch holes though to preserve more of the center slug. But that's just my frugal nature.

Helpful hint on grinding out the tool bit. I did the sketch earlier showing a 1/2x1/4 size blank tool to start. But I realize that 1/2 square is far more common. What I've found a few months ago is that a thin zip disc in an angle grinder can cut away the lumps on HSS a lot faster than using the bench grinder and converting all that steel to black powder on the floor. I know it's not the proper tool and the zip disc is slower in HSS than with mild steel. But it's still FAR quicker for removing lumps of waste than grinding all the way with a bench grinder.

[oxford]

A good 3.5" hole saw would also cut down on the amount of work. And I like the idea of the chip relief holes too. That was a great suggestion. I'd go with four 1/4 inch holes though to preserve more of the center slug. But that's just my frugal nature.
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You might get by with the 1/4” holes and it would push through but I think they might want to load up. I was using roughly a 1/2” bit as I didn’t care about the core but you could most likely go smaller than that.

[Dan Dubeau]

As with most things machining, it depends. Quite a few different ways to do it, and the best one depends on your machines, your quantity, your tooling, your experience, your forseen need to do more of them in the future etc (many other variables....). There are no one size fits all blanket answers in this game for how to hold, or how to do a job. It depends.

1" deep in aluminum with a lathe and a boring bar and only one to do, I'd simply drill it out as big as I could, and finish boring to size. You'd be over and done with it before you ground a trepaning tool. 2 to do? maybe, but I'd still drill/bore. 5? trepan probably as I'm a scrounger and would want the slugs for something else . 100? waterjet the blanks from plate. 1000? Pick up the phone and shop around quotes. It depends.

[JRouche]

Example - 1” thick, 6” diameter round plate stock and needs a 4” inner diameter machined through.

My question - What is the best technique for removing all of that material?
Thanks, Rob

Hey Rob.. I would use a quality hole saw. They come in sizes real close to what you need then finish it up with a boring bar or cutter.

I have a few trepanning tools and they would work but the hole saw would work with less setup. Use lots of wd40 or your favorite "red" lube. JR

[BCRider]

You might get by with the 1/4” holes and it would push through but I think they might want to load up. I was using roughly a 1/2” bit as I didn’t care about the core but you could most likely go smaller than that.

I'm sure a few more smaller holes for sure would need more cleaning to make them work. But for the little extra effort the cores would be more usable for other projects. I just hate to see good material turned into swarf if I can save it for something else.

[mtraven]

Hey Rob.. I would use a quality hole saw. They come in sizes real close to what you need then finish it up with a boring bar or cutter.

I have a few trepanning tools and they would work but the hole saw would work with less setup. Use lots of wd40 or your favorite "red" lube. JR

if I didn't have HSS around to grind a trepanning tool, that'd be my go to as well as I have a variety of hole saws. two things to keep in mind:
1)on both the lathe & drill press they tend to over drill, so dont get to greedy with your initial removal, boring another 50k aint no thang.
2)the key is a very slow, consistent feed. as JR said, keep well lubed & chips clear...which, after your past the tooth depth, can really only be done by peck drilling.

and you might consider ear plugs (which I almost never wear)...they make some nasty noises sometimes.

[darryl]

If you don't consider the cost of a hole saw of that size, then I think that's the way to do it. Drilling the swarf release holes makes a lot of difference. Here's another idea- when you mount the blank on the chuck, mark the position with a felt pen so you can reverse the piece while keeping the mark under the same jaw. That lets you go halfway from each side, easing the requirements since you're only going in 1/2 inch now, and your cuts will be close to concentric. Of course you would be leaving enough material to bore clean later, so your hole saw would be undersized. You'll lose some of the diameter of the inner piece, but better that than having binding problems and offset problems from coming in from both sides. That's one of the problems I set myself up for, by trying to keep as much diameter on the cutout as possible. That's always been a false economy. Drilling the swarf release holes reduces the diameter of the cutout, but just accept that.

A tip- before you get the inner piece fully separated out, turn a spot on it so you can easily mount it in a chuck later. That will give you the maximum diameter you can get out of it later, plus it makes it easier to center and hold when you are cleaning it up later for some other use.

[oxford]

2)the key is a very slow, consistent feed. as JR said, keep well lubed & chips clear...which, after your past the tooth depth, can really only be done by peck drilling.

See above. Drill the hole for the chips to fall out of and you can feed until you’re through the other side.

Peck drilling doesn’t really work that well either if the work piece is horizontal. It pulls some chips out but most stay in there. You really need to blast it with air. On the lathe may be a little better with them falling out.

[garyhlucas]

The hole saw you want for this job is a Lenox 3 tooth carbide hole saw. Less teeth for way less torque and big slots to clear the chips. I think you can get them in 2” cutting depth.

[AZHTR]

I do have a Bridgeport and rotary table. I like trying new ways to do things and have not tried trepanning. I will most likely experiment with both the trepan tool and the hole saw (Lennox 3). I don’t make a lot of this type of part, but when I do, my chip pan fills up awfully fast. I do use a fairly heavy boring bar and it works well, it’s just a lot of wasted material.

I appreciate all of the helpful suggestions! As always, this forum is extremely helpful!

[RB211]

I do have a Bridgeport and rotary table. I like trying new ways to do things and have not tried trepanning. I will most likely experiment with both the trepan tool and the hole saw (Lennox 3). I don’t make a lot of this type of part, but when I do, my chip pan fills up awfully fast. I do use a fairly heavy boring bar and it works well, it’s just a lot of wasted material.

I appreciate all of the helpful suggestions! As always, this forum is extremely helpful!

Wait, you have a Bridgeport and rotary table? Dude, why not slot it with a 2 flute and blow the chips out with air?