Guide to fix bevel grind lines

F

Foot Patrol

Joined
Mar 5, 2013
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88
I am having troubles making consistent straight bevels on my knives. I have a KMG grinder that I use the table to grind off of. I am right handed. My bevels pulling to the right start straight but as I get higher the bevel starts to bow in the middle and I can not get it to straighten out. The harder I try to straighten it out, the worse it becomes and ends up wavey. The plunge to bevel sweeps up and looks good until I start to fight to get straight.

On the left side pull, my plunge line goes higher and drops almost immediately down a few mm before straightening out. On this side the bevel is very flat and does not sweep up as it gets to the knife point. Trying to have matching bevel lines is nearly impossible at this point.

Has anyone posted a guide for new makers that shows typical grind patterns/problems with possible solutions to work on? The guide could have pictures that a knife maker can look at and say that is my problem with suggestions on what to do to improve the grind.
 
Sometimes the answer is just as simple as practice, practice, practice. First thing is try to grind your weak side first and when you are happy with that it will be easier to match it with your more confident side. Obviously you don't want to grind one whole side then do the other whole side. You'll probably end up warping the blade. But progress up each side evenly then when you are nearing the top of your grind finish your weak side first then follow with your strong side. Next, technique counts. Stand with your feet approximately shoulder width apart with knees slightly bent. Have your grinder set up at a level that is comfortable. Lock your elbows at your sides and use your legs to shift your weight and shuttle your upper body side to side. Now you will need to pay attention to how you are applying pressure to the blade against the belt. You will remove metal where you are applying pressure. If your line is bowing up in the middle you are applying more pressure there than in other areas. It is the same by the plunge or anywhere else. Remember, you don't have to take it all off in a few passes. Take your time until you get the hang of it. When your line starts getting wavy a good thing to do is stop for a minute and regroup. Clear your mind of frustration, take a couple of deep breaths then approach the grinder again. Often the answer to a wavy line is go LIGHTER with your pressure on the belt. Concentrate on making consistent passes, pulling straight across the belt and lift the tip off the belt before it runs off the edge. If your grind is very wavy and you need to catch up in certain areas to get the line straighter then you can work the low areas carefully until you get close. Place your thumb of your support hand (not the one holding the tang) behind the part of the blade that has a low spot. Carefully place the blade against the belt but don't apply any pressure. The blade should just be skimming on the surface of the belt. You want to feel the blade settle flat against the belt. Start your pull. As you approach the area with the low spot start gently applying pressure there. If you grind edge up then the top of the grind will be at the bottom of the blade, right? Ok, that is where you are placing your thumb. Apply pressure at the bottom of the blade as you pull that spot across the belt. You can also use your pulling hand to apply pressure where you need it. Then do full length pulls to clean it up and tie it all together. Others will have their own techniques but that is what works for me.

Fred will be along shortly to explain the virtues of the bubble jig. :D
 
Great description I4Marc. I am a newbie as well. I have ground maybe 8 blanks out now. Haven't finished any as with each one I do I can see such improvement that the previous ones the previous are not worth HT!

One thing that helped me with issues like yours was (just like I4Marc said) to apply pressure where you want the steel removed. It doesn't seem like that would make a difference as you have the whole thing flat against the grinder right? But in reality the belt is bunching and your angle is likely off a little etc. Afterwards concentrating on a straight pull as well. I use mostly a disc grinder as I just have a Craftsman 2x42 I use just to profile and knock the initial corners down but even with the increased surface area of the disk to steel contact it takes some straight pulls to even things out. Also I grind edge up so I can see if there is a gap between the edge and the belt/disc I know I am pulling the bevel up towards the spine instead of primarily reducing the edge thickness.

So far I should have just +1 on Marc's posts ha!
 
One thing that is often not brought up is the need for a good sharp belt. Pressing harder here or there won't allow for an even cut. I also recommend using mild steel to practice with. It's a lot cheaper. Frank
 
i4Marc said:
Sometimes the answer is just as simple as practice, practice, practice. First thing is try to grind your weak side first and when you are happy with that it will be easier to match it with your more confident side. Obviously you don't want to grind one whole side then do the other whole side. You'll probably end up warping the blade. But progress up each side evenly then when you are nearing the top of your grind finish your weak side first then follow with your strong side. Next, technique counts. Stand with your feet approximately shoulder width apart with knees slightly bent. Have your grinder set up at a level that is comfortable. Lock your elbows at your sides and use your legs to shift your weight and shuttle your upper body side to side. Now you will need to pay attention to how you are applying pressure to the blade against the belt. You will remove metal where you are applying pressure. If your line is bowing up in the middle you are applying more pressure there than in other areas. It is the same by the plunge or anywhere else. Remember, you don't have to take it all off in a few passes. Take your time until you get the hang of it. When your line starts getting wavy a good thing to do is stop for a minute and regroup. Clear your mind of frustration, take a couple of deep breaths then approach the grinder again. Often the answer to a wavy line is go LIGHTER with your pressure on the belt. Concentrate on making consistent passes, pulling straight across the belt and lift the tip off the belt before it runs off the edge. If your grind is very wavy and you need to catch up in certain areas to get the line straighter then you can work the low areas carefully until you get close. Place your thumb of your support hand (not the one holding the tang) behind the part of the blade that has a low spot. Carefully place the blade against the belt but don't apply any pressure. The blade should just be skimming on the surface of the belt. You want to feel the blade settle flat against the belt. Start your pull. As you approach the area with the low spot start gently applying pressure there. If you grind edge up then the top of the grind will be at the bottom of the blade, right? Ok, that is where you are placing your thumb. Apply pressure at the bottom of the blade as you pull that spot across the belt. You can also use your pulling hand to apply pressure where you need it. Then do full length pulls to clean it up and tie it all together. Others will have their own techniques but that is what works for me.

Fred will be along shortly to explain the virtues of the bubble jig. :D
Click to expand...

This post has helped me more with understanding the problems that are associated with my technique more then anything else I have read. Thank-you so much.
 
Outside of fresh belts, a truly flat and rigid platen, and grinding skills, one thing that seems to be forgotten is the usefulness of hand tools. Do the bulk removal with your KMG, then fine tune with draw filing and sandpaper until your grinding skills are up to par. You'd be surprised how easy it is to turn ugly into the opposite when things aren't moving at blazing speeds.
 
Grasp the tang

Place your thumb directly in the center of the tang

Apply pressure with your thumb and pull straight across your belt....using the thumb as the key point of determining pressure and the direction you want the grind to go using the opposite hand to guide the end of the blade.

Now grind...holding elbows to your sides, do not let your elbows leave your waist. Use your hand with thumb pressure and place your blade on the belt now use your hips to move your hands...LIKE A MACHINE...pulling the blade across the face of the platen.

Now do it to the other side

You are getting waving uneven grinds because the is what your hands and body are telling the knife to move across the platen as you grind.

Set up the body to move straight across the platen and the grind will follow that line of movement.
 
I4Marc thank you for such a thorough explanation. I grind with my blade up. I have tried to apply pressure with my support hand and some time it works. I know that the more I practice, the more I will get the feel of it. I will have to concentrate on shifting my weight while keeping my elbows in. I was taught this but once the grind starts, I seem to be focusing on the bevel and not my technique. BTW my platen is smooth clear/yellowish plastic resin.

AVigil I do pull with my right hand just like you say and the grind is much better. I believe I have to work harder at my left hand pull as I know I do not put as much thumb pressure on the tang of the blade. My support hand comes more into play here.

Weebus I try to correct my bevels using course sandpaper. In some cases this has been extremely productive and the bevels look more uniform. At this stage, I am trying to learn from my mistakes and am trying to find way to fix my short comings.

Frank I have been trying to use a slightly worn belt to start the grind and then move to a newer belt. I understand that starting the grind with a fresh belt may damage it and I will get more life from it once I can start to work the bevel up. I have to admit, I have not always switched the belt right away. Once I do I can tell how much more steel can be removed with far less pressure.

All in all, I want to thank all you gentlemen for your advice. BF is a great place and I am learning so much from being here.

Scott
 
I am new to the knife making world. I have been struggling to find an answer to my bevel grinding issues. This thread has helped a lot. Its nice to find some people willing to share there tips and secrets. There are other enthusiasts in other fields that you can not get any info out of without paying them. This is awesome. Glad to have so many helpful people out there.
 
Foot Patrol,

Can you post a picture of your platen? I think the plastic/resin platen may be part of your problem. You should have a steel platen or steel lined with a specialized glass. See the link below. Slow down so you can concentrate on your technique. Make sure you keep your elbows in and don't lock your knees. Even these days I catch myself and have to remember to bend my knees a bit. Practice on junk steel until it starts to feel more natural. Frank is right. I did forget to mention fresh, sharp belts. When I try to get too much mileage out of a belt I start to fight with the grind. When I put a fresh belt on I immediately get better cutting, cooler blades and clean crisp grind lines.


http://www.onedayglass.com/pyroceram.php

http://usaknifemaker.com/grinders-s...aten-liner-flat-platen-1-x5-x-0-192-1750.html
 
I4Marc here is a picture of my platen. The platen appears to have 2 pieces of glass that have been glued onto a metal base. You can see the 2 pieces by light line in the middle of the platen. The platen does collect some gunk under the belt and deposits it onto the platen. If you need to see a side picture, let me know.

Foot

glassplaten_zps29263956.jpg
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FP,

My concern was that you had a plastic platen which would not wear very well and result in poor grinds. Apparently you have a glass lined metal platen. This is good. It looks like you have some excessive wear at the left edge of the platen. Do you have any gouges or low spots on the face of your platen? You really need a very flat surface.
 
I4Marc,

I don't have low spot but I need to figure out how to get rid of the gunk buildup at the top section of the platen as it is causing slight high spots. Two weeks ago I really noticed it when I was trying to freehand with Bruce's guide. At the time I was able pick off several large flakes.

There is also excess glue on the sides of the platen where the glass platen and metal base interface. I need to sand this off if I want to free hand with the guide as it can interfere with good vertical alignment.

Foot
 
I have a metal platen and use a razor blade to carefully scrape off that black residue. I suppose you could try acetone on a cloth or brake cleaner?
 
I4Marc you are a genius!!! The acetone removed it in short order. I was afraid to use a razorblade as I did not want to scratch or damage the platen.

Thank you for all your help.

Scott
 
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