BMatthews

With a good thick sulphurated cutting oil and a stoned HSS single point I have no trouble getting a nice shiney result when cutting the annealed drill rod.

The key is setting up the cross and compound slides correctly. I don't know your ability level so bear with me if I repeat the obvious.

You want the compound set at 29 degrees from the cross slide so that the trailing side of the cutter drags lightly on the back side of the thread you're cutting. Also for obvious reasons you want to do your last few cuts a thou at a time. I also find that a final pass with the setting at the previous pass does a nice polish cut run by using the spring in the machine to supply the cutting pressure. Another hint is that I like to run a smooth cut lathe file lightly over the crests to remove the sharp burrs between my last cut and the "polishing pass" which is set to the same as that last pass.

If you try this I think you'll find that it leaves a pretty slick finish.

Oh, one other thing that isn't always obvious. The leading side of the thread cutter needs a little more rake than you think it needs. This is because of the advance rate used in cutting threads. You want enough clearance rake that it makes up for the angle of the thread spiral along with a little clearance for the cut. So the cutting tool ends up with a 10 to 12 degree rake on the leading side. If that's not there you may find that it's dragging the thread just cut along the front ridge as it rotates down and away.

Again, sorry if this is already well known.