VIDEO: A Closer Look at the SGL Drill

All right. So here we're back to our detailed camera view again. We have a nice 3D model here that we're going to use to kind of demonstrate some things. So one of the first things that I really want to talk to you about is this chisel area in the center of the drill. It seems to be a lot thinner than most drills. It really is Danny and you know that's a really important feature here because you know what do we want to do in terms of this work hardening material? We want to reduce the length of the cutting edges. You know that's a really big factor and when we think about forces, you know there's a lot of different ways that you can analyze drilling force but a lot of let's say tried and true formulas, basic formulas that people use, about 70% or so of the thrust forces in drilling come from the size of this chisel area. Right and that chisel is just that this cross section in the middle where the line it is it is just right where my fingers show in there um and of course a lot of that is because one we've got a zero speed condition right there. We've also got the fact that you know it's not a traditional, let's say normal, cutting edge.

You know we're actually extruding material right here, pushing it out of the way right and that really starts to create a lot of force so if we can reduce the length of that then we see an immediate benefit in the forces. We also see a big benefit in how well the drill can center. You know some people call it wobbling, some people call it walking, but the more that we can get this drill to stabilize and start drilling well on contact, the better. So that's one of the first things that we want to emphasize. Now normally when I see a chisel to get stained like that I think of a weak chise. What did we do to the geometry to make the chisel where you know was able to reduce the forces like you said but also still be strong?

Yeah, that's a great question Danny. So a lot of it has to do with two things. So one is you can just sort of subtly see right here that there's a little bit of shape change, it's very faint in this flank but that gives us some more room here so that we have better extrusion along the chisel. It also helps a little bit with coolant flow coming in here, but then we can start to talk about how the rake angles change. We've got a slide for this later but we can just kind of talk about that that this gash is very unique in that most most gashes around tools have a straight rake all the way across. This is actually not just curved but it's a variable rake angle from one into the other. So it's a little bit it's still a positive rake in this area toward the center but it's a lower rake than it is out here and that really provides a lot of extra strength right here. Yeah that's a nice large radius too. Absolutely. You know if you look down in here you can see from this view especially just how big that radius is and how nicely it flows down into the fluid so that makes better chip flow. Absolutely. I mean this is a very wide flute and it's really designed to work with that gash.