Another thing you could try: Use double stick tape on a faceplate to hold your part. If you don't have a faceplate, use a piece of wood in the 3 jaw chuck a backing plate then use the double stick tape. Use a small object held in place by your center in the tailstock to put pressure on part to hold it tight against the tape. Cut out your part to size. The thickness of the tape should give just enough clearance for your tool not to hit anything it's not supposed to. This way you'll not have a hole or any marks in the center of the part.
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Best way to cut a circle from sheet?
- Thread starter ProfessorGuy
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- Sep 28, 2013
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if you can fit the sheet into a 4 jaw on your lathe, use a trepanning tool (look up some pics online for how to grind one). I've managed 3/8in (or 1/2in, can't remember) on my tiny lathe without too much trouble. It's not fun, but it works 
- Joined
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Several ways will work.Cut the piece out with a holesaw that is oversize. First remove the pilot bit if you do not want a center hole.Then glue the piece to a piece of 3/4" mdf that will go in the chuck.I would use hot hide glue because it will hold and a heat gun removes the piece in a few seconds.Yellow carpenters glue will work too with a piece of brown Kraft paper between the mdf and the work.When done turning the edge to dimension the work will pop off with a screwdriver.If you have hot hide glue it is easier to clean up ,just warm up the work and scrape the residue off.Hot water removes the gummy residue that is left.
Trepanning will work too.Glue the piece the same way as the above method.
Your lathe should be able to handle either method.
mike
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- Jan 19, 2015
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Using the lathe seems to me like the best solution. The motors on those lathes are really small, but something is wrong if your lathe will not cut aluminum without stalling. Are you sure the cutter was sharp, and properly ground? Did it have enough end relief to prevent the bottom edge of the tool from dragging on the outside radius of your cut? I'm not handicapped by such a small lathe motor, but I've cut many circles out of aluminum by hot melt gluing the stock to a face plate made out of plywood, or MDF, and turning the circle on the lathe with fast and easy results. Or make an aluminum face plate that is slightly smaller than your finish diameter.
I would grind a 1/16" wide cutting tool out of a piece of 1/4 x 1/4 steel so that the end looks rather like a 3/16" or 1/4" long parting tool. As you probably know, the end relief angle you would need depends on the diameter of the circle being cut. If my math is right, you need at least a 25 degree end relief angle, if there is no side relief. Side drag on the cutting tool can also rob your lathe of scarce power, so you can grind it with a tiny bit of relief behind the cutting tip, if needed. Feed straight in. If that's still too much load on your lathe, you can try narrowing the cutting tool even more to perhaps 1/32". If the tool is fed straight in, it should still be plenty strong enough to cut aluminum. I've bored the inside of tiny and shallow holes in steel with such a dinky cutter. To cut aluminum, you don't even need HSS. You could grind a functional cutter out of a piece of 1/4" key stock.
You might also try using a cutting fluid. A good cutting fluid for aluminum is one part of any light weight machine oil, like 3-in-1, or any 10W oil, thinned with 3 parts of mineral spirits. That might help a little.
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- Jan 22, 2014
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I found myself faced with a similar problem some time ago on a project that I was working on. I needed to accurately cut 4 - 3" OD X 2" ID circle plates out of .060" thick aluminum. I started by rough cutting the OD's on my floor standing band saw. I trued and finished sizing the OD's by making a disk/sandwich jig to run on the lathe. I then cut the ID's on my woodworking Jig Saw sandwiched between 2 pieces of hardboard. It was like riding a mad bull trying to keep control of them bouncing around when the blade would catch, but I muddled through at my neighbors expense (noisy). I rough finished the ID's with a large sanding drum on my drill press. Then I finished sizing the ID's by holding the parts individually on my lathe by the OD. I tried using hole saws for a couple of these operations but all it wanted to do was burn it's way through.
It was a lot of work and I remember thinking how there must be a better way, but I couldn't figure out any other way to do it. Thin stock is hard to work with anyway you try to do it short of plasma, flame or CNC.
It was a lot of work and I remember thinking how there must be a better way, but I couldn't figure out any other way to do it. Thin stock is hard to work with anyway you try to do it short of plasma, flame or CNC.
I made some round plates for an IED housing (yes, the dangerous type, for scientific use) when i was an apprentice and my master taught me a method that i like to use.
He used two aluminum discs cut from round stock, one set up in the chuck and one loose with a center hole drilled. Both with smooth, dry surfaces and an OD close to the desired measure, as big as possible in other words.
Sandwich your plate to be cut between them, clamp them securly together with the rotating centre and turn to diameter.
Im not at my shop now, but i can take pics later if you want.
He used two aluminum discs cut from round stock, one set up in the chuck and one loose with a center hole drilled. Both with smooth, dry surfaces and an OD close to the desired measure, as big as possible in other words.
Sandwich your plate to be cut between them, clamp them securly together with the rotating centre and turn to diameter.
Im not at my shop now, but i can take pics later if you want.
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[FONT=&]You didn't say if your piece has a central hole in it or how true the finished circle had to be. Since you were initially cutting with a jeweler's saw it sounds like you had to do some cleanup work. There are two methods to rough out a circle that I have used. one is to cut out a square using a hack saw or band saw, then cut the corners off to make an octagon. If you want to get closer yet, you can cut the resulting eight corners. That should bring you fairly close to your desired circle. The second method is t scribe a slightly larger circle on your workpiece and drill a series of not quite intersecting holes on the scribe line. With a 2" circle, you could rough out the part with about 25 holes. You can then use your jeweler's saw to connect all the dots. I have also used an old drill bit in a hand drill to complete the parting by angling the drill bit in the holes to connect them. Either way is fairly quick. I have used both on steel plate over 1/2" thick..[/FONT]
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I use something similar. The driving surfaces are covered in cork and using the tailstock to sandwich the part to turn the OD. Look at videos showing metal spinning. Same way of doing it.
Remember that you can not take heavy cuts. Doing so will either stop the disk turning or the tool will cam it out. Use lots of lube at the cutter to prevent the chip sticking to the tool.
Since the part is Al, do you have a table saw to rough it out? Use a Non-ferrous metal blade to at least cut off the corners. I usually shear off the corners or if it is a casting and rolled to size, I use a round mold and roll it down to size while rotating the part 90 degrees at every pass.
Pierre