Removing large amounts of material?

[JRouche]

I had the piece clamped in place, but also had my hand on it-

There might have been a reason my hand was there- I don't remember. I only did that once.

Learn once, like from D or learn twice and up in the ER like me. Take your pick, I have done both. JR

[darryl]

Don't make the mistake I did when trepanning. I had the cutter set for the diameter of the hole I was making, 6 inches I think it was. I had the piece clamped in place, but also had my hand on it- with lots of clearance from the cutter I thought. Thank goodness I had a slow speed set. As the cutter swung around it went across three of my fingers, taking a divot out of each one. I yanked my hand out of there so fast that it only cut across once. That took about a year to heal up, probably because of the cutting fluid I think.

There might have been a reason my hand was there- I don't remember. I only did that once.

[Bented]

At home I have the offline conversational software for a Trak lathe that I use at work.
Wrote a program just now for dung and giggles.

From 1 1/2" to 4" X 1.05" long, beginning at 4.06" puts a nice .030" x 45 deg. chamfer on the front.

The first screenshot is the start point and turning parameters, DOC, feed rate, spindle speed and so on.

The second screenshot is the tool path, the time estimate of 0:2:15 is a bit optimistic (-;

[RMinMN]

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!

With the Bridgeport and rotary table you have an easy way to make the part using a small diameter end mill so you don't turn the part into chips but....if you learn to trepan you have gained a skill too and some parts might be easier to trepan than to attach to the rotary table without damaging the middle of the part to be cut out. I like the idea of having a nice piece left to use for another project.

[RB211]

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

I do not get the potatoe chip reference, where’s the sandwich to go with them?

[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?

[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!

[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.

[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.

[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.

[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.

[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.

[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

[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.

[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.
.

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.