[modeleng] Re: Trepanning(?) copper

Hi Dennis,

Try 5 degrees back from perpendicular to the work positive rake. Also, make
sure the side clearances are clearing the cut edge, especially the outer
radius. Otherwise things will rub and get ugly. Also a good idea to clamp
the plate down securely and use a really rigid tool holder bar. Copper is
always sticky to cut. A nose radius on the tool may help, rather than a
parting tool shape square tip.

If the trepanning op doesn't work, you could maybe use a sub plate with a
remote centre of rotation to rotate the plate to be cut past a normal size
small endmill along the cut. The sub plate is bolted to the mill table and a
dowel can be used as the pivot.

Good luck, Jeff Dayman Waterloo Ontario Canada


----- Original Message -----
From: "Dennis Rayner" <dennis.rayner@xxxxxxxxxxxx>
To: <modeleng@xxxxxxxxxxxxx>
Sent: Tuesday, August 31, 2004 3:00 PM
Subject: [modeleng] Trepanning(?) copper


> Hi all,
>
>     I'm cutting 5+" and 7+" circles out of the front and back smokebox
> plates for my Elidir. I'm using my Dore Westbury with a boring head at
> lowest geared speed believed to be about 34 rpm.
>
>     A simple question - what top rake should the cutting edge (a miniature
> "parting" tool) be? Currently I'm using zero (as per brass) and it don't
> seem happy!
>
> Thanks as ever
>
> Dennis
>
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