plunge line

[Bodork]

Can someone explain or show me how to make a plunge line that leans toward the point of the blade? I cant seem to get the grind to straighten out when I try it this way. I guess I'm not holding or moving my stock correctly.

[tomsm44]

Are you talking about a curved plunge line that sweeps up and forward on the blade, or a straight plunge line that leans forward?  The knife below is probably the closest I've done to what you're talking about.  When I grind my blades, I keep the plunge forward of where I want it until I'm almost through, then slowly move it back once the edge thickness is where I want it.  With a very slight overhang on the edge of my grinding belt, it makes a nice straight vertical plunge line like you see on most knives.  On the one below, I set my tracking so that I had probably 3/8"-1/2" overhang on my belt edge.  That gives a bit of a forward curve to the plunge line.  I've seen guys get a more gradual curve, but I'm not sure what technique they use.  I'm thinking it probably involves changing the pressure and angle when grinding near the plunge.  I also did one once with a straight plunge with a forward angle to it.  I grind edge up on a vertical flat platen and I just raised the handle/lowered the tip in relation to the platen to get the plunge line to lean forward.  It was a bit tricky getting it even but it can be done.  I didn't really like the overall appearance, so I never really tried to perfect it myself.

 

[Lin Rhea]

Along with what Matt has said, you can radius the edges of your flat platen. They need to perfectly match if possible. It doesn't take much.

[tomsm44]

Originally posted by Lin Rhea:
Along with what Matt has said, you can radius the edges of your flat platen. They need to perfectly match if possible. It doesn't take much.

So that's how they do the more gradual curves.  I knew that by just letting the belt overhang you have to be very careful.  The slightest pressure on the blade will make the belt dig in at the edge of the platen and mess up the whole thing.  I may have to build me a second platen just for doing radiused plunge lines.

[Bodork]

Thanks guys! Yes Matt, that is pretty much what I am looking for. I usually keep my blade on my table while grinding and pull straight across. When I raise the handle to make the line lean forward, I have a hard time keeping the top if the grind straight to the point of the blade. Maybe In ust need more practice. Mike

[tomsm44]

I've also found that a "forged" finish on the flats makes slight imperfections in your grind/plunge lines virtually invisible.  The key word being slight.  When doing a hand rubbed finish on the entire blade, those slight imperfections might add a couple of hours of hand finishing to sort out.  Some guys can grind good enough to have everything just about perfect before the hand sanding starts, but I don't build enough to stay that well practiced.  That's one of the reasons I tend to do more the style pictured above when I do have time to throw one together.