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bobbybeef
03-17-2005, 09:54 PM
Hullo All,
I have hack saws and so on but I am seeking to find a quick simple way to cut a few brass circles in one eighth inch brass plate. I want to recover the circles and make cogs from them. I can allow a 5/32 inch hole in the centre but no bigger. The circles are about three inches in diameter.
At present I cut with the electric jig saw and metal cutting blade a rough circle and then centre it in the lathe and true it up.
A minilathe and a minimill are available.A rotary table is also available.

Bi polar hole saws are brutal and perhaps I am not using them properly .Can they be made to do a better job?
Grateful for any help and guidance.
Bobby

precisionworks
03-17-2005, 10:39 PM
A single-point fly cutter http://ustool.com/images/Huge%20images/TP461H.JPEG works well in thin aluminum or thin brass.

Holesaws are grabby in softer materials.

If you have access to a woodcutting bandsaw, it's easy to make a circle cutting jig for these parts.

Al Messer
03-17-2005, 10:57 PM
If these "circles" can have a couple of holes drilled in them without ruining the final product, mount a piece of Plywood to your lathe faceplate. Fasten the "blanks" to the plywood as close to center as you can with a couple of screws. Make up a "trepanning tool" which looks just like a Parting-Off Tool except it has a bit of clearance ground on the bottom of the outside edge. I think it would be best not to have any positive rake on it, but you may have to experiment a bit. Also, I would chuck up a piece of rod in the tailstock drill chuck and lightly set it against the circle to keep it from flying all over the shop when the trepanning tool pierces the far side of the blank. Good luck!

Al Messer
03-17-2005, 11:00 PM
Addendum:

Precisionworks,

I probably would agree with you except this cotton picking computer of mine won';t open the link you posted. I think I know what you are talking about and it should work well in either a lathe or drill press.

psomero
03-17-2005, 11:07 PM
uhh, cut as many squares as you need, make two spuds (one for chuck one for live center in tailstock), squish squares between spuds and take light cuts until they're round?

i've done dozens of discs at a time that way

bobbybeef
03-18-2005, 12:07 AM
Posomero,
Thank you. Sounds good. Whats a spud. Presume its a flat plate pushed in by the tailstock. Please tell me how it works.
bob.
Precisionworks,
I have one of those but the drill in the centre is way too big for my job.
Bob.
Al Messer,
Ys that is an improvement on what I currently do and will give that trepanning a try.
Bob.