[_Lou_]

The attached part requires a 0.194" thru hole with a 0.349" counter bore at a depth of 0.25". The material is steel and I will be using carbide spot drills, drills and end mills.
My question is, should I drill the thru hole and then peck cycle with an 11/32" End mill (within tolerance), or should I use a 3/16" (.1875) end mill and use a circular milling cycle to bring the counter bore to the correct size? I know plunging with an end mill is usually a bad thing, but I will already have a thru hole so I was hoping I could get away with it.
I will be holding the part in a 4 axis chuck on a vertical mill (coolant).

I have almost a 1,000 of these to do and would obviously like to have the quickest program possible but don't want to burn out my tools.

Thanks!

[djr76]

If you can drill it with screw machine drill then interpolate the hole with the 3/16 end mill, it would only be 2 tools and probably the quickest. Cam software would be able to tell you the cycle times of any variable you described.

[underthetire]

Back in the olden days, we used a counterbore tool or ground flat bottom end mills, just plunging a standard end mill down a hole is not going to leave a flat bottom..

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[Jim Dawson]

I avoid plunging with an endmill where possible, but with a pilot hole it will work OK. But....... as underthetire says, a counter bore would be the best tool to use. They are piloted and are designed for making counterbores.