Photos Why is There a Curve in My Plunge Lines

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Lurch01

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Jan 4, 2015
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m2Idbhe

vpK64pU.jpg


Often when I cut a bevel the plunge line will curve neatly around to the top of the bevel instead of being a crisp 90 degree angle. Any idea what causes this?

It looks cool but I don't know why it happens and I can't control it. I'm using a jig and I've tried every combination of blade position I can think of and pondered the geometry but I really don't get it.

Anyone run into this before?
 
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There’s two things that could be causing that, first is you have a 2” belt bump in the middle of the blade which means as your approaching the belt your making contact with the edge away from your plunge first or putting too much pressure on that side and the second thing is you may not be spending enough time at the plunge to create a sharp plunge versus the faded plunge line, there isn’t anything wrong with what you have minus the belt bump and a lot of makers shoot for a faded plunge it just comes down to esthetics, I prefer a straighter plunge as it is easier for me to keep the same blade geometry from the ricasso to the tip and I like how it looks. So things to try are make sure the blade is sitting flat on the platen and not tilting one way or another and spend a bit more time or pressure where the plunge is. One reason I don’t like jigs is I can’t feel the grind the same way you do freehand, it takes longer to learn freehand grinding but I think it’s a very good skill to have if you plan to be making knives for awhile. Once you learn it it stays with you as it’s all muscle memory.
 
I had this going early in the free hand grinding of a couple Bowies. If you play with it, you will discover that you can lightly torque the blade as you approach the plunge from the tip. Basically pressing that corner into the platen. You can control how abrupt or square it is at the top.
I run the belt just over the edge of the platen. If you are lucky, you can get it to look just how you want.
 
I’ve found belt position to be the cause of this. If I let the belt overhang the platen, I get a curved plunge line as shown in your picture. If I keep the belt completely on the platen, I get a straighter, more crisp plunge line.
 
Lurch01 said:
m2Idbhe

vpK64pU.jpg


Often when I cut a bevel the plunge line will curve neatly around to the top of the bevel instead of being a crisp 90 degree angle. Any idea what causes this?

It looks cool but I don't know why it happens and I can't control it. I'm using a jig and I've tried every combination of blade position I can think of and pondered the geometry but I really don't get it.

Anyone run into this before?
Click to expand...

I'll trade you? My unintentional skill of making them square vs. your unintentional skill of making them fade.
 
You can help control that by the overhang of the belt.

Also you are starting at the plunge and going toward the tip, try the other way and from the flat move into the plunge .
Also, on the tip side of the platen always keep the blade off the platen a tiny bit to avoid that 2" mark on the blade.
 
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i think it looks great. i hope you can get the other side to match :D the closer you ground to the ricasso, the more angle you used. thats how it happened. jim siska ( rip) was known for his swooping plunges. most people find them difficult to do . consider it a blessing :thumbsup:
 
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