How to put a 180 degree radius on the edge of a steel plate?

[Andrew TinsleyParticipant @andrewtinsley63637]

Hello,

I have been making a repair piece for a large Victorian church key, A slitting saw worked wonders for the tumbler slots. I now have to make a round profile to the edge of the key. I was going to take a file to do the job, when I started thinking ……… how would you do such a job using machine tools, either lathe or mill?

Is there a simpler way than using a milling cutter in the mill chuck and having the plate mounted vertically on a rotary table? It just seems to be a lot of kit to do what looks like a simple job!

My interest is theoretical and the file is about to be used!

Regards,

Andrew.

[Andrew TinsleyParticipant @andrewtinsley63637]

[mechman48Participant @mechman48]

Hi Andrew

​Use a bench grinder to take the meat off then draw file the rough edge with 2nd cut file … & emery if you wish …

George.

[Jeff DaymanParticipant @jeffdayman43397]

Try googling "corner rounding cutters" – these cutters will round your keys nicely (not cheap though). JD

[KWILParticipant @kwil]

If you really want to, mount plate (or key edge) vertically in machine vice, pass a radius milling cutter down each side. Job done. Radius does need to be = 1/2 plate thickness for your 180 degree requirement.

[Andrew TinsleyParticipant @andrewtinsley63637]

Hello Kwil,

I am afraid that I don't understand your description. Not too well up with engineering terminology. What is a radius milling cutter? I am only really familiar with ordinary milling cutters and specials for cutting say a woodruff key slot.

Come to think, is a radius cutter one that has a curved cutting edge at the bottom of the cutter?

A description of a radius milling cutter may help me out here!

Thanks,

Andrew.

P.S. Thanks George, I did in fact use my bench grinder to get the rough stuff off. A big help as my muscle wasting disease and heavy filing don't go together too well!

[Neil WyattModerator @neilwyatt]

You could cut a groove in some silver steel and make a form tool

Neil

[Danny M2ZParticipant @dannym2z]

These work well – just remember, the curve is a RADIUS so us half the thickness of the key for a smooth curve. **LINK**

* Danny M *

[mechman48Participant @mechman48]

I have a set of these with different cutter styles all carbide tipped…

http://www.toolstation.com/shop/Power+Tool+Accessories/d80/Router+Bits/sd2579/TCT+Router+Bit+Set/p37879

this set has a 'round over bit' that will do the job.

George

​

[JasonBModerator @jasonb]

If you have a blunt milling cutter just grind the cornes off that freehand on the bench grinder so they are concave, which gives a quick and cheap rounding over bit. Did the moulding around the base of this engine that way.

[Andrew TinsleyParticipant @andrewtinsley63637]

Thanks everyone,

As usual I was way behind on working out how to do this job. Lots of useful information and I now know what a radius milling cutter is. Now if I had been thinking router, then the penny would have tumbled!

Thanks again everyone.

Regards,

Andrew.

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