Mill vs lathe to cut a disc?

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Frank O

H-M Supporter - Gold Member
H-M Supporter Gold Member
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I have a 6" x 6" x 5/16" plate of 6061 aluminum that I need to cut into a disc 5" in diameter.

I have a mill (LMS 5550) and a lathe (10 x 21 Grizzly G0516, minus the mill section), but so far have probably spent 15x as much time using the mill as compared to the lathe.

I'm therefore wondering if it would be easier to use a rotary table on the mill (I have a small 4" one), or if I should bite the bullet and work on my lathe chops.

Any suggestions on what seems like it would be the easier or better way to go?

Also -- am I right in thinking that, regardless of whether I use the lathe or mill, I'm going to need to drill a hole in the center of the plate for work-holding purposes? Or is there a way to pull this off without doing that?
 
You could trepan on the lathe and stop just short of cutting through, to avoid a center hole. (If your 4-jaw or faceplate will fit the plate.)

On the rotary table, you could glue or tape the plate down to avoid the center hole.
 
Thanks! I learned something new today. (Not counting the web hits on the ancient medical procedure.)

I'll have to look into getting or making a parting or grooving tool.
 
I had a real nice trepan tool that could be used in lathe or drill press; expensive, but it worked quite nicely and accurately, it got sold with my business, and I expect the idiots probably broke it ---
 
Frank O said:
I have a 6" x 6" x 5/16" plate of 6061 aluminum that I need to cut into a disc 5" in diameter.

I have a mill (LMS 5550) and a lathe (10 x 21 Grizzly G0516, minus the mill section), but so far have probably spent 15x as much time using the mill as compared to the lathe.

I'm therefore wondering if it would be easier to use a rotary table on the mill (I have a small 4" one), or if I should bite the bullet and work on my lathe chops.
Click to expand...

Having done this on a part that needed a precise outside diameter except for a 5º bump on my mill with 10" rotary table::

Anything you want round (all the way around) should be done on the lathe; if it fits on the lathe.
 
benmychree said:
I had a real nice trepan tool that could be used in lathe or drill press; expensive, but it worked quite nicely and accurately
Click to expand...

Yes, a web search shows they get really pricey really quickly.

So I guess I'll take a shot at grinding my own. If I'm cutting a 5" diameter through 5/16" plate, any suggestions on the type and dimensions of tool blank to start with?
 
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