Cutting A Ring From A Plate

ch2co

ch2co

Grumpy Old Man
H-M Supporter Gold Member
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Jan 9, 2013
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Real lathe newbie here, who has probably a dumb question, but …OK, so how do I explain this. I’m starting out with a piece of 1/2” x 7” x 7” aluminum plate that I was going to bolt through it’s center to a 1” rod that will be mounted in the chuck of my 10 x 22 Grizzly lathe.
I need to end up with a ring 5.5” od x 4.5” id x 1/2” thick from this plate. What type of tool should I use to plunge into the face of the plate that will cut all the way through without hanging up on the walls of the (circular) groove that will eventually go all the way through the plate.
Or is this not the way to go about it? I want to save the center 4”+ disk for another smaller ring.
 
Obtain a 3/16 HSS tool bit, and sharpen it like a cut off tool, square on the end, under cut both sides, back just under half an inch, (and perhaps tapered back from the cutting edge, and cut a tiny groove (Dremel cut off wheel will do) just behind the front edge, and get the tool supported at least as close as 9/16 from the cutting edge.
I would suggest that you put your lathe in it's slowest gear and feed by hand, while continuously applying kerosene or some other liquid with a small brush just ahead of the tool.

Cut both cuts nearly all the way through, then finish the outer cut first.

Were I doing it, I'd put it on a face plate, with the nut at the middle and clamps around the outside or drilled through the corners. Suspended your way it's going to ring like a large bell.
 
another approach would be to turn your od first using the bolt to hold the plate onto the chuck, then use the chuck jaws on the OD and bore the inside to the correct dimensions
 
I have a couple pictures that show the tool in operation. I was making a couple backing plates. Here is the link
Pierre
 
Thank you, each and every one. Tom, great instructions for grinding a cutting tool. Bill, you hit the nail on the head with Trepanning, clicked on a long past memory lost in
the tangle of neurons they call my brain. I've done it many times in wood on a drill press. Coffmajt, this is sort of how I have been doing this, remove all metal that isn't the ring piece that I want, the big problem with this is that for a 5" dia. 1/2" thick ring, I end up with a five gallon bucket of aluminum shavings and 2 hours of cleaning up all the chips.
Pierre, that's almost exactly what I had in mind to do, but couldn't find the kind of cutting tool that I needed. And Savarin, that is EXACTLY what I'm doing. The rings that I'm currently making are for my trusty 105mm f15 Jaegers scope built from scratch after picking it up at an astronomy auction. A fantastic double star viewing wonder. Pictures attached. This is the reason that I bought my little lathe and minimill. . Everything is used or surplus scrap including my lathe and mill that I lovingly try to turn into a functioning piece of equipment. This scope is a keeper. The tubes in the background are for my net project, a 127mm f9 scope.

Thanks again to all.
Chuck the Grumpy Old GuyIMG_3235.jpgIMG_3238.jpg
 
Nice scope! As for the tool, it is a bit tough to spend $3-400 for a couple small jobs. I borrowed the Manchester tool from work, but originally I had ground a HSS tool to do the same thing prior to the shop spending the money. It was a little smaller for only going through 1/4" stock.
Pierre
 
Nice scope. I hope mine performs as well.
 
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