/diy/ - Do It Yourself

>>1790155
>but shouldn't there be 2-3 different angles cut with that grind?
I put a standard roll point on it The clearance is added by rolling the the drill bit down and away on the grinding wheel. It was done with a purpose built machine under coolant.

It needs clearance on the heel, however you get the clearance is up to you.

"Split point" drills are literally just drills that start out as roll points, then you add in a deep heel relief until you "split" the chisel point from behind.
Its becoming the most popular drill point because the tip of your drill does not cut. It physically has to push material out of the way to get your cutting edge into the material. With a big chisel like in a roll point, it can walk and talk more pressure to get the hole started. Split point less walk less pressure.
Not only that Its very hard almost impossible to do roll points by hard correctly, so its way easier when hand grinding to put a 4 facet or fake split points on a drill. Hence why you are used to seeing it.

I put split points on most everything, but this was a literal 1" bit. You will never be using this without predrilling a hole. The point chisel will never be used, and in real world usage the heel shapes make no difference.
So I didnt bother splitting it.

Pic related is not mine, I would have had these tools rejected for poor finish quality FWIW, but it shows the two side by side (even though the chisel point is fucked up on the roll point for some reason)

>>1574895
This is true
Not only that the roll point needed a steeper angle to cut better.

Look at the tip of a regular roll point. The big chisel point is not sharp, it doesnt really cut. It brute forces material out of the way until the cutting edges can hit and cut. It needed to be somewhat steep.
The ancient powers that be decided that 118 was a good middle ground for strength and angle to actually move material.

The split point, same principle applies, but its chisel is much smaller and walks less. And with the big chisel problem gone, you can put a more shallow angle on the cutting edge.

The shallower angles help cut metal better, all around a better metal cutting drill.

The fact that 118 roll point DOES cut metal ok and it cuts wood ok is why its still around. Even though ideally youd have 135 split points for metal and Brad points for wood.