Why does increasing speed when taking very light finish cuts help things?

[my65pan]

I always leave at least two light finish cuts.
I guess it would be a pre-finish and a finish cut.

Both of those cuts are at higher speed and slower feed than the roughing cuts.
You are spot on about the tool nose radius. It should be bigger than the feed.

The first, or pre-finish cut, will remove any tool push off that may have been occurring
during roughing. It also allows a test for any taper in the cut that may be going on.

On the finish cut I go for the size, bumping the tool in or out .0005" at a time to eliminate
any taper that showed up on the pre-finish cut.

Rick

This is exactly how I do it! I usually do this same routine at a slightly larger arbitrary diameter first just to see how the tool/material will behave regarding finish and taper when I get to the actual finish diameter.

 

[Maryak]

Hi Guys,

IMHO, a good finish depends mostly on ensuring that the cutting face of the tool is wider than the rate of feed. If this is done, combined with a light, (0.001" - 0.005"), cut then with a little experiment of the speed a good finish is almost a gimme. LH Sparey used the same tool for roughing and finishing. For his finishing cut(s) he lightly ground and honed the roughing (knife) tool and then set it at a very shallow angle to the work so that most of the cutting face rubbed during the finish cut, works a treat.

Hope this helps.

Best Regards
Bob

 

[mu38&Bg#]

I hope I didn't push the topic to far off with my response to Mosey's question on inserts.