U drills

[Erie Fred]

My experience of them is extensive re-grind is not really an option. To make a decent job of it would require removing a good 1/4 off the height to allow the features to be re-ground. But doing so will impede the holes for fixing it into the holder and it may fall below the end of the holder.

Have a look at the image below

View attachment 475001

Below the cutting edge as we look at the insert is curved to give a slight negative rake to aid cutting action and swarf evacuation, and the cuts along the face break up the swarf so it comes off in pieces rather than long strings. If you grind them you loose the rake and the cutting edge moves closer to 90 degrees which makes it incredibly difficult to drill.

You can tickle them once or twice but major grinding to reinstate the rake reduces the strength of the tool. Plus the chip breakers need reinstating too.
Considering they cost £40-£100 each a professional re-grind isn’t going to be cost effective. You’d be better tickling them yourself. Although you find once you’ve done so they don’t perform nearly as well as they did with the titanium oxide coating on them…

Softer stuff will be a different story but the stuff I used to drill it wasn’t worth messing about trying to regrind them. Once they were spent they were binned.

Again, I can't see the OP much ever needing to grind anything.

 

[Munkul]

I use the spmx u-drills from cutwel in the mill, they work great for cnc drilling structural steel plates, inserts are very cheap and they last a long time, a few hundred holes each anyway. Tried one in my lathe once, with a few adapters stack up it was terrible. As Brad says it needs to be very rigidly mounted to work.