Importance of Blade Flats

tito

tito

Joined
May 30, 2006
Messages
670
I've been working on larger blades this year, and have run into problems keeping my blade bevels (flat grinds) straight that I don't have on smaller (less than 6") blades. I'm thinking the problem may be related to how flat I can get the profiled blank on my platen. Does anyone else have this problem for large blades? Should I look into a flat grinder, or should I make some kind of grinding guide - I know there are some out there, like the bubble grind attachment. Any advice is welcome.
 
tito said:
I've been working on larger blades this year, and have run into problems keeping my blade bevels (flat grinds) straight that I don't have on smaller (less than 6") blades. I'm thinking the problem may be related to how flat I can get the profiled blank on my platen. Does anyone else have this problem for large blades? Should I look into a flat grinder, or should I make some kind of grinding guide - I know there are some out there, like the bubble grind attachment. Any advice is welcome.
Click to expand...

practice
practice
practice


seriously, I do all of my grinding freehand on a flat platen (unless I'm going for a hollow grind, then it's freehand on a wheel)

lock your elbows into your ribcage
move with your legs


practice on some scrap wood or the big paint stirrers until you can run a good flat bevel, then work on turning the piece so that you maintain the flat bevel into the tip

don't give up, it DOES get easier


one other HUGE error that a LOT of guys make when learning how to grind is pushing a belt way beyond its useful life.
trust me, I understand that belts are expensive, but your grinding will be MUCH easier and cleaner with a fresh sharp belt
 
The 9" variable speed reversing disk grinder is the answer to your problem. It flattens, it straightens, it slices and dices and is the best thing since sliced bread. I spend the majority of my time grinding on the disk. It will make all of your work cleaner and crisper.

Mike Quesenberry
ABS Journeyman
www.quesenberryknives.com
 
Thank you both for your advice.

Mike Quesenberry said:
The 9" variable speed reversing disk grinder is the answer to your problem. It flattens, it straightens, it slices and dices and is the best thing since sliced bread. I spend the majority of my time grinding on the disk. It will make all of your work cleaner and crisper.
Click to expand...

I was afraid of that.
 
Mike Quesenberry said:
The 9" variable speed reversing disk grinder is the answer to your problem. It flattens, it straightens, it slices and dices and is the best thing since sliced bread. I spend the majority of my time grinding on the disk. It will make all of your work cleaner and crisper.

Mike Quesenberry
ABS Journeyman
www.quesenberryknives.com
Click to expand...

Do you use a horizontal or vertical disk grinder? Thanks!
 
Mike Quesenberry said:
The 9" variable speed reversing disk grinder is the answer to your problem. It flattens, it straightens, it slices and dices and is the best thing since sliced bread. I spend the majority of my time grinding on the disk. It will make all of your work cleaner and crisper.
Click to expand...

So why are there seemingly endless threads on which 2x72 belt grinder is the best tool for the job....and so many knife maker swear by them?
 
The 2X72 and 9" disc grinder are tools to get the flat surface prepared for finishing, but will always leave some ripple. The disc grinder does do a good job getting it pretty flat, though.

If you don't want your blade to look like a fun house mirror, you need to hand sand them after the grinder work is done.

Using abrasive paper on a hard backing block ( micarta or corian work well), clamp the blade to a sturdy surface and hand sand to as flat as you can get it ....using long strokes. Do this at 220 grit. Then take the blade to your surface plate. It can be any flat hard object, but a granite surface plate is the tool of choice by those who truly want FLAT. Attach a sheet of 220 grit to the plate with a spritz of water or tape it down, and sand the flat surfaces. Look at the surface and see where the high and low spots are. Continue until the surface is flat. Then finish going up the grits using the sanding blocks. At any time you want to check the flatness, just put a piece of the current grit on the flat plate and check for high and low spots.

Stacy
 
Farmer Phil said:
So why are there seemingly endless threads on which 2x72 belt grinder is the best tool for the job....and so many knife maker swear by them?
Click to expand...

Phil

The 2x72 is great for hogging off the majority of the stock. But if you want something really straight and really flat the disk is superior. The surface area I get when finish grinding on the disk is 7 - 8 inches compared to 2" on the belt. When I come off the belt and look at a blade and it looks flat, then put it on the disk it highlights every single high and low spot. I come off the disk using 320 grit and then start hand sanding. If you try to go any finer without the rubber backing pad you can end up tearing the paper. The disk I use is the flat 0 degree model in steel, some guys prefer the slight angle on theirs. I also put a slight radius on the outside of the disk so I can run it into my plunge area. You also have to consider my nature I am extremely picky about my grinding and knifemaking in general. I think Nick Wheeler says it best, "Being good isn't enough".

Mike Quesenberry
ABS Journeyman
 
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I made a micarta backed palm sander tool which I heard from Mr. Dave Larsen. It works like charm...
 
I use a 6x48 table sander that has a PG cast iron deck, no flex. It is run by a one horse motor, and does a good job on flat grinds. I wouldn't be without one, as it is also great for flattening grip stock and tangs.
 
i have only been using my kmg for all my grinding.reading this thread i see the value in getting a disc grinder. i plan on putting one together. how important is it to have variable speed on it? i still have my delta 1x42 with a 6" disc grinder on it. im thinking about trying the disc for my flat grinds--do yall thik the delta will work for smaller knives. ofcourse the delta is only one speed.how important is it to have the motor be reversable? when you say 1hp with 3 phase- what does that mean. i know you have to get an ada[pter for the 3 phase but why get a 3 phase in the first place--is a 3 phase the part that allows for variable and reversable functions?-thanks marekz
 
Stacy - I would have to disagree that the disc will always leave a ripple. It may on a long length of blade that you have to move, but when you can cover then entire flat on the disc, you can get it flat and fine enough to go to a buffer.

As for the large blades, try hollow grinding one first and then flatting it. Some folks will say that's heresy, but it's much faster for me and I spend much less time on the platen getting things uneven ;)
 
marekz said:
i have only been using my kmg for all my grinding.reading this thread i see the value in getting a disc grinder. i plan on putting one together. how important is it to have variable speed on it? i still have my delta 1x42 with a 6" disc grinder on it. im thinking about trying the disc for my flat grinds--do yall thik the delta will work for smaller knives. ofcourse the delta is only one speed.how important is it to have the motor be reversable? when you say 1hp with 3 phase- what does that mean. i know you have to get an ada[pter for the 3 phase but why get a 3 phase in the first place--is a 3 phase the part that allows for variable and reversable functions?-thanks marekz
Click to expand...
Yes,the variable speed is important. I run mine usually about half speed.The reversing enables to grind both sides of the blade with the disk turning down. I tried the same thing on my Delta 1 x 42 and it's kinda scary when it wants to throw a knife in your face. The 3 phase motors are the ones that can be reversed and vari the speed. I use a KB motor speed controller rated for my 1hp ac motor.
 
I've found that I have the same trouble grinding flat grinds on my ceramic platen, and I also think that it was from the small 2" working area. Then I strarted using a granite flattening plate after rough grinding, but that took A LOT of time. Now I use a palm sander with micarta backing the sandpaper, like galladuin, but I read about it on Bruce Evan's site, I think. I still check things out occasionally non the flattening plate, just to be sure everything is still working right.

Todd
 
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