Cutting a curve on a metal disc.

[GTV16v]

I need to cut a curve on one side of a 30mm diameter aluminium disc. No idea if the cut has a name but imagine it has to sit on a pipe.

One way to do this I suppose would be to mount the disc perpendicular to a face plate on a lathe and use a boring tool. The only problem here is that my mini lathe has a maximum radius of about 80mm and I need the radius to be about 150mm ( I've not measured it precisely yet, but that is close ). Unfortunately I don't have a mill ( yet ).

Any ideas as to how I can achieve this?

Thanks.

[Dave54]

If you want to do what I think you do, basically a curved chord (is there such a thing?) on the circle, and it's a "one off" then unless it has to have engineering type accuracy I'd probably mark it, cut the waste off and file the curve. If it needs to be more accurate, you could fit it using engineer's blue and careful work with a fine file.

[GTV16v]

That's certainly a possibility.

Another thought I had was to cut a disc of the correct diameter, put sandpaper around the edge and mount it on something that rotates ( bench grinder would be far to fast I think! ) and then feed the workpiece at a tangent.

If all else fails, it may be easier to flatten off the surface it's mounting to!

Thanks.

[Dave54]

The thing I always find is that unless you have several the same to do, then making jigs and so on takes longer than the actual job would with hand tools. At least ally is soft to file.

[Hitch]

If i'm imagining this correctly, sounds pretty easy.
Rough it out with a coarse file or even careful grinding, then finish off with a half round file.

How good does the fit need to be, should be able to achieve a very close fit with careful use of hand tools....