Milling counter bores

[g huns]

I need to mill several large(to me) counter bores for cores in a mold cavity. The through hole, appx. 2 inches, is already wired through. The counterbore is about 2.5 inches, with a flat on one side tangent to the 2 inch diameter. How do I mill out just the counterbore area. I would like to start at the 2 inch diameter and spiral outward, but everything I tried want to start at the center, lots of wasted passes. This seems like it should be pretty simple, what am I missing?

[Gary]

can you use a pocket spiral and then do a toolpath trim with another offset contour. This would let it spiral out you could do a contour with multi passes but the stepovers are straight into the stock.

[Chipmakr]

If you will draw another circle in the center of your pocket (representing a theoretical boss) and chain it as well as you other geometery a pocket tool path would do what you want. Just choose the size of the center circle accordingly for your tool size.

 

I just tried it with true spiral and a .2 step over and it worked like a charm.

[g huns]

How do you trim a toolpath with a contour? Never liked the multi passes because of the stepovers. Should have mentioned, using .250 endmill with .015 corner radius and cutting S-7 50-52rc. I just used morp-spiral pocket .1875 stepover and .003 depth cuts. So I cut a little air.

[Gary]

No I should have said a pocket toolpath and and offset arc or just draw a smaller one and use that to trim your pocket toolpath. Just program it with small spiral step out and trim what you don't want. hth Gary

[HevyMetl]

Greg,

 

Something that I have found that works well with this application is contour/ramp and change your ap and ae accordingly for ramp cutting. You then can just take it in multiple passes like a regular contour. The only places you should cut air with this one is the flat section where it is already wired out.

 

.25 coated carbide I would start off with full effective Ø stepover with .005"doc per rev and 6112 rpm @ 24 imp with a 4 flute cutter.