Milling 102

[JeffF]

I'm addicted to this site! You guys do some of the most incredible work. It's just fascinating to see the parts and engines you can produce. Stunning.

As you no doubt know by now, I'm still in the very beginner stage of milling and I am making every effort to learn through books, websites, videos and other sources without driving you folks nuts. But, that said, I can't seem to find infomration on how to do what seems like a very common and simple process.

I have a rectangular piece of aluminum about 1/4 inch thick and roughly 2 inches by 3 inches. I want to round the outside 4 corners. Not a lot, just an eighth inch or so rounded corners.

Do I just hand file them, or is there a special milling bit I should use? Rounding outside rounded corners (both large and small radiuses) seems like something I'll be needing to do a lot, so knowing what tooling I need, and/or what the process is to do that is going to be pretty important.

Jeff

 

[sssfox]

Jeff,

Using a file is good practice and will teach you tool control.
It works well, for small projects.

They make corner rounding end mills in many different radii, but they can be expensive.

You can also do it on a rotary table. You put the piece of metal on the table with the center of the radius over the center of the table.

Of the choices, the corner rounding end mills are the easiest to use and make the most sense from a long-term basis. It depends on how much money and time that you have.

Steve Fox

 

[mygrizzly1022]

Hi Jeff

Round over router bits desinged for wood do a good job on aluminum. 1/2 in shank would be a better choice than 1/4.

Regards... Bert

 

[maverick]

Jeff,
If you decide to file the corners round, be sure to use a radius gage to
keep everything uniform. It doesn't even have to be a store bought
gage, a simple piece of tin can with a suitable shape will work.
Learning to file is not difficult, but like most things you get out of it
only what you put in. You will find a few minutes with a file will sometimes get the same thing done as tricky setup, and much faster.

Regards,
Maverick

 

[Rex]

Round over router bits desinged for wood do a good job on aluminum.

a spritz of WD40 helps the aluminum cutting

 

[SmithDoor]

I heard of using router bits I have never try this but is is low cost over milling cutters. I use milling cutter

Dave

 

[chipenter]

I use router bits on steel and cast iron , but only the end 1\16" they don't like side cutting run them at twice the speed of hss cutters , go as fast as you like on Ally .
If bought in a set they are much cheaper .

 

[JeffF]

Thanks guys, this is very helpful!

Jeff

 

[Forestgnome]

Notice he's talking about rounding the corners of a 1/4" plate. A rounding mill is going to be dicey to use on that unless your vise can clamp the plate vertically very near the cut. Otherwise the plate will flex and cause chatter giving a poor cut. My vote is stay with the hand file. That's the way I'ld do it. To get evenly rounded corners with a file, fit file a 45d bevel to a predetermined distance from the corner on all 4 corners. Then finish rounding the two edges left on each corner.

 

[MachineTom]

That piece would have 4 corners, where 3 planes/axis come together, and 8 edges, or 12 depending, if corner could be counted as a edge, where 2 planes come together. OP said Corner, but I think he means edge. Answers were each directed at the edge solution.

For Corner rounding I use my belt sander, If it is for looks, I blue it and use a template of whatever radius looks good, and scribe it. Quick and easy