Lumpy, Bumpy, Hollow Grinds

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Dave Behrens

Dave Behrens

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Feb 25, 2011
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Im having a problem with my hollow grinds that I didnt really have before. I recently moved up from a 3" serrated contact whell to an 8" smooth wheel, and now my hollows are really

uneven even from afar. This is the first time I have used tool rest while grinding as well. I know I'm the problem and not the grinder. Does anyone know what I may be doing or

something I can improve on. I know practice makes (near)perfect but I would really like more specific tips or techniques that have worked for others. Thanks.
 
This is going to vary by maker but sharp abrasives, and a clean pass from plunge to
tip. Try to stay consistent as you go up in grits. My knives are usually hand finished
in the hollow 5-10 min. per side of the blade. The better your grind the better the hand
finishing wil go. This knife has a machine satin finish. A 14" hollow grind.
Ken
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Are you talking about the grind lines or the bevel itself (2" marks)? I have a 6" wheel that came from KMG with a concave surface. It wanted to grind smiley faces instead of a straight line. I saw it after putting a straight edge across it.
 
Go slow, light pressure, with sharp belts. I sit on a barstool and keep my arms in as close to my sides for stability, and I find it helps. Happy grinding!:thumbup:
 
I agree. Sharp belts and light pressure- especially when you start getting to the higher grit belts. Any type of small movement "mistake" I make with higher grit belts tend to be pretty noticeable.

Wow, I never thought to look/ measure the flatness on rubber wheel (good catch David). Not that my wheel is new, but good to know as they should wear after awhile in theory. I know what I am going to check in the next day ot two!
 
I just bought an 8" wheel and concluded that it'll need some dressing to get it where it needs to be. But that conclusion was by my buddy Greg. I have zero experience yet with hollows. Maybe someone can pipe in on how they like their wheels? Sharp edges, rounded, convex surface edge to edge?
I'd guess it's your wheel first off.
 
Brian Ayres said:
Maybe someone can pipe in on how they like their wheels? Sharp edges, rounded, convex surface edge to edge?
I'd guess it's your wheel first off.
Click to expand...

This seems to be a very personal subject. I personally radius the corners of all my wheels (hard to purposely "mess up" a new wheel). The radiusing of the wheels helps with two things; 2" marks and very nice plunges.
 
Radius on the edges please!!
Dave could you be getting some chatter from work rest to bevel, causing ur bumps?
 
I like them with sharp square edges, right at 60 duro, and for the plunge about a 320J Flex
belt tracked just a hair off the edge.
Ken.
 
Tool rest is not the problem. I would venture to say that these "bumps" are showing up when you get to the finer grits. WORD.... (Belt-Bump).

Belt-Bump is more noticeable on a smooth contact wheel, and even more noticeable when using cheaper belts (can we say a thick belt joint on a thin belt?). Belt-Bump will almost disappear when using 3-M Gator belts.

Like folks above said........ Use sharp belts. Worn belts are your worst enemy.

Robert
 
Could it be that going from a 3" to 8" it's harder to stay in the hollow, being the 8" is more shallow. I use a 10" wheel, free hand, and have hard time with my off hand staying in the groove.
 
Its definitley harder to stay in the hollow with a larger wheel, for me its work from
one side to the other trying to keep them symetrical, going slower helps a lot. If theres
one thing that makes me start to feel good about a knife I'm working on its a clean
grind. Must be why you always hear Grind, Fit, and Finish.
Ken.
 
Wow! Lot's of great info. Thanks guys. I think I found the problem, I need to slow down and not press so hard(I'm impatient so, sue me;)). To David66, the whole grind from heel to point, top to bottom is uneven and bumpy, I noticed I have been catching the edge of the wheel while grinding,:D then overgrinding to remove the mark. I have been using sharp belts. I think a lot of this is just getting the feel for my new grinder...we'll see:D. Thanks a lot guys for all of the helpful tips.
 
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