Manually milling non-circular curves

There's probably a lot of easy ways to do it, only if we knew what you are working on....
 
I come across the need for curve cutting all the time. My latest project is pickup covers like this one.
If I had the means to make these on my own then I think I’d attempt cutting my own punch and die sets so that I could press these out of 24 ga nickel silver sheet.

A8386D89-D48D-4117-9991-2C2F2C4EC6F0.jpeg
 
All I see there are radii . Maybe I'm missing something because you are showing the part at 45* .
 
westsailpat said:
All I see there are radii . Maybe I'm missing something because you are showing the part at 45* .
Click to expand...

They are covers for a humbucking guitar pickup. Their shape would be properly described as "obround." Think of a rectangle with semi-circle ate each end.
 
Those would be hard to press form. Where the 2 radii meet would tear out.
 
derf said:
Those would be hard to press form. Where the 2 radii meet would tear out.
Click to expand...

Yup, that's why most of the humbucker pickups covers I saw when I was playing electric were square. I don't think they needed to form fit so tight. And because they damped the output a lotta folks tossed them.
 
westsailpat said:
"Obround" ? I have never heard that before . Teach a old dog a new trick , I don't understand .
https://en.wiktionary.org/wiki/obround
Click to expand...
You've got it right there from Wikipedia- a rectangle with a semicircle tangent at each end.
Or, the shape of a milled slot, if you prefer.

At one point, the term was pretty foreign to me. When I started with precision sheet metal fabrication back in 1980, it referred to punched slots. I was calling them ovals, but one of my colleagues corrected me. Obrounds have flat sides, ovals are more like ellipses....anyway, it still sounds strange.
 
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The way I was taught to do this was...
Plunge milling, yes I said it! I know I'm beginning to sound like a fanatic, but hear me out:

If you have a DRO, you advance the cutter to each of the pre calculated points. when you are SURE (by checking your layout or cemented template, then you just plunge down. this is very accurate and doesn't involve any risky moves. Also, you get to lock the X and Y travel to make sure your cut is right.

just sayin'

P.S. I have done lots of non-eccentric cam plates like this from paper templates and a loupe. it works very well!
 
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