How do you mill a radius (chamfer) on top & bottom of holes?

[Dave KingParticipant @daveking15982]

How do you mill a 2mm radius (chamfer) on the top & bottom of a hole? I got 18 holes of 2 different diameters that require a 2mm radius chamfer top and bottom of the holes. Is there a tool i can make up or buy to do this job?

[Dave KingParticipant @daveking15982]

[JasonBModerator @jasonb]

If it will fit in the lathe then you could grind a form tool and just use that on the edge of the hole. Much like this but with a bit more relief so it clears the inside of the hole

If it won't go on the lathe then mount on a rotary table and use a 2mm radius corner rounding milling cutter to whizz round the edge. one of these, infact you could also use that as your form tool in the lathe. If the holes are quiet small it may be easier to make a tool like that milling cutter of teh correct dia and just plung in with it like you would a standard countersink

 

J

Edited By JasonB on 08/02/2015 16:40:29

[Dave KingParticipant @daveking15982]

Thank you for your prompt reply. I had thought of your ideas but they don't really help. The only way i could think of a solution was to make up a cutter and mount it in a boring head.

Can i ask perhaps a better question. I am trying to make a flywheel. The drawing calls for a 0.063" radius around the spokes. Which is not a problem with a corner rounding milling cutter until you get to the corners of the spokes which are round. ( R 0.186" & R 0.156&quot.

How would you produce this?

[JasonBModerator @jasonb]

Is that off a "Farmboy" ?

You could spend ages locating the centre of each corner radius on the rotary table and do each one individually but a better way would be to search out or make corner rounding cutters that have the central part equal to the dia of the corners so 3/8" and 5/16" and just plunge in with these ideally before you mill out the spokes but would work OK if you have alreadt done that.

Then once the corners are riounded you can mill and then round the spokes. Flip teh flywheel over to do the other side don't try comming up from below.

Or just file it and blend into the straight spokes should be fine under a coat of paint

[Dave KingParticipant @daveking15982]

Yes its off a Farmboy.

I think you are right. There does not seem to be a easy solution.

I will try to make some sort of tools on the lathe. If i make it them out of silver steel of the correct leed in hole dia 3/8 and a 5/16 and with the 0.064" radius on. Mill it in half (cross section) and harden it. And plunge it into a trial hole and see what happens. (it is only a small radius)

If it does not work I can fall back to the file and blend method!

Many thanks for your help its nice to have some advice before i spend more hours in the garage.

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