The easiest way to see what a split point is would be to look at a semi-big one, say 3/8 to 1/2, with a magnifying glass and compare it with a regular one. It will say on the label if it is or not. I don't know how well I can explain it, but here goes.

First, the benefit of a split point bit is that it is a lot less likely to skate across a metal surface before it finally finds a purchase. Of course, you can just use a punch to start a little dimple to avoid that but the split point (SP) saves time.

The angle is different between standard and SP, not sure why, I believe it is 135 degrees for SP and 118 for standard, 118 looks sharper. The drill doctor has a little gauge built in to the front -- you hold the bit up to it to determine the angle, though it can be a little hard to see. It has a grinding setting for each angle. You chuck the bit into the 6 jaw chuck, there is a centering device to get the flutes in the proper relation to the cams on the front side of the chuck. For both standard and SP, the initial procedure is the same -- you rotate the chuck in one of the openings, the cams give the proper angle on the flutes.

The standard bits are done at this point. The SPs go into another opening and the back side of each flute, the non-cutting side, is ground at a steeper angle, fairly steep actually, on each side, so that when you look at the bit straight towards the head you see a sort of cross effect, and the normal little wide spot between the flutes, about 1/16 or so wide on a 3/8 bit (I'm guessing), has been reduced to almost a point. The point prevents the skating. You have to be careful on the SP part -- the first stage is pretty easy -- the SP part requires a delicate touch and frequent examination with the magnifying glass.

I wish I was a better metalurgist, but I don't believe I've had trouble with any of the different type bits, cobalt or otherwise. I recall from a tool maker friend of mine years ago, that you don't want to get the metal too hot when you sharpen tools. Of course, most guys know this -- you keep a water plunge nearby. I don't know how many times though, when grinding a pitted wood chisel down, I've gotten impatient, didn't quench it soon enough, and produced a discolored part which usually means you've reduced the quality of the temper somehow.

Even after numerous passes in the Amazing New Drill Doctor (pat pending -- I ought'a be selling the damn things at state fairs), the bits never seem to get hot. Must be the diamond wheel. Perhaps the grinding wheel method is what limits the type of metal that works well, that is, certain metals might get too hot or be too hard for a standard grinder to adequately handle, again, I'm guessing.

I might have to check one of those out. Might be easier than the gauge on the D.D. Does that measure the cutting angle of the flutes or the angle of the overall point to the shaft? The latter is what I need.

And now, ONWARD....into further discoveries!!

__________________
Te futueo et caballum tuum

1986 300SDL, 362K
1984 300D, 138K