Finer points on bevel grinding advice?

J

Jcdelamater

Joined
Oct 5, 2022
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40
I’m looking for some pointers on improving my bevel grinding. I’m able to get a good flat surface across most of the bevel but I’m trying to improve a few things.
A few notes on my setup. I’m using a 2x42 belt sander at ~4200 FPM. I have been using zirconia belts, but I’m about to order some ceramic.

Anyone have tips on the following?
  • How to keep the bevel flat near the tip. I’ve found there is less area in contact with the grinder and it’s harder to make sure the knife is flat while grinding.
  • Keeping an even edge thickness across the knife. My edges near my tips (for reasons noted above) and near the plunge tend to be thicker than my middle. I’ve found it challenging to get the last half inch by the plunge ground down without gouging into the blade.
  • My plunge lines could use some tips.
  • Getting a thin edge, especially for kitchen slicers. Anything under .02” I get a bit nervous about burning the edge.
Also how long does it take you to bevel a knife? Just curious for reference.
 
I started on a 2x72 with one speed, fast. I managed to add some step pulleys and slow it down which helped a lot. Now I have VFD and would never go back.
When figuring out how to remove material where you want to, especially near the tip, it helps to run slow, keep a light touch and keep looking closely at the blade after every couple passes to see that you are on the right track.
 
I use your grinder. Look on YouTube for simple modifications you can make. I normally use a simple jig (aluminum angle bar) and clamp the blade to it and raise the workrest a few degrees. Grind edge up. I haven't use zircs, but I do use 36, and 60 grit ceramics and the coarser trizacts. I have done a few freehand too. Just go gradually, look at your work, and dunk in water frequently.

The platen is pretty terrible for plunge lines, but I found the bottom wheel was pretty useful to get it started. Once started, the platen worked ok, but be prepared to do a bit of work with sandpaper or EDM stones.

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Yeah, I know my grinder isn't exactly the best, but this is a hobby and I'm not ready to sink that much cash into a VFD 2x72 or something similar. I switched from a jig to freehand grinding and I'm never looking back. Were you using the edge of the lower wheel to start the line?
 
Yep, just to get something set there, not too deep. Once there is a reasonably defined plunge, it is easier to flatten it out consistently on the platen.

It doesn't take much to thin a tip, so I wouldn't worry about it too much. The gentlest of touches there will even it out. At the plunge is difficult, you may/will get a 2 inch belt bump if you focus too much at that point. Just move back and forth a bit to try and keep it smooth. Also, I like to change my angle of approach if possible. Edge up, 90 degrees to platen, then 45 degrees, then 135 degrees, particularly when changing grits.
 
i mostly stick to kitchen knives so i mostly go plungless or sweeping plunge. if looking for a nice sharp plunge a Bump file guide would make sure its lined up and im not sure about the platen on that grinder but since putting pyroglass platen on my KMG not looking back cooler grind temps and you can put a slight radius on the edges of it for nice plunge
 
For now this is a side hobby that I enjoy but am not putting too much cash into. I'm interested in learning to get the most out of the equipment I have and I'll improve my shop over time.

Thanks all for the grinding advice.
 
I ran what sounds like the same or similar grinder for about 6 years (Craftsman 2x42) so I feel your pain. Like others said, upgrading your equipment will help, but on the bright side, learning how to control a fixed speed grinder will only make you better in the long run.

Check youtube for some good videos about upgrading a 2x42 for knifemaking. The biggest improvement I made was adding a ceramic glass platen, which really reduced the heat buildup and helped with consistent plunge lines.

Don't be afraid to just grind more on the tip, dipping your blade in water every pass. If it's thicker there, it just needs more time spent on that area, which is going to mean more frequent quick passes to keep the heat down. Also, try holding the blade at a diagonal to even out the grind by getting more surface on the platen at a time. Or use the disc sander to even out the grind.

As far as grinding it thin goes, just do light passes and frequent water dips and you'll be fine. Also, don't wear gloves, as this will allow you to feel the blade heating up.
 
It is a bit of an expense but I really recommend a file guide for plunge help. It helps me in more ways than just keeping them aligned.
 
Mark your feet where you stand. It has helped me be more consistent in my grinds. Your muscle memory is based on everything being the same, if you shift your feet, you'll shift your grind. Once you established your pass, you won't have to feel that the tip is flat, you'll know it's flat because you've done it a thousands of times. I agree that the tip is the hardest part to keep consistent. I've screwed up many of them by trying to hard to "feel" what I'm doing instead of being confident and just following through on my pass. Until you get into more advanced grinds, your angle shouldn't really change. Once you've established that your flat on the platen, you just have to lock in that angle as you pull the blade across the grinder...it sounds a bit cheesy, but honestly.....it's all about confidence when you step to that grinder. I learned on a grizzly that had one speed.....and that was light speed!!! Glad I did it, when I got a variable speed with a glass platten...it was like going from 90mph down a bumpy gravel road in an old 3/4 ton truck to cruising down the interstate at 75 in a Cadillac.
 
I run a similar grinder and am starting to grow frustrated with my plunge lines and all the hand sanding since I can't run 400+ grit belts for fear of burning tip/edge. Things improved quite a bit when I installed a piece of high temp ceramic glass on my platen. It gives a sharp edge that the original metal does not. Now if I could solve the belt "wandering" across said glass platen when pressure is applied trying to set plunge I'd be a happy knife maker.
 
J Lensmire said:
Now if I could solve the belt "wandering" across said glass platen when pressure is applied trying to set plunge I'd be a happy knife maker.
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You need more belt tension.

Figure out a way to tension the belt tighter. I used to use a crappy 4x36 belt sander with a super weak spring tension device. I added a bigger spring and added some washers to push the tensioning wheel up higher... It worked. Kinda.

I eventually gave up and built a 2x72.
 
I run a 2x42 as well and Upgrading the platen is pretty easy. I used a piece of angle iron and a piece of ceramic glass. It helps substantially with consistent plunges. The standard platen is junk really, It’s not FLAT which is just another thing to fight when grinding the bevel. If you really want to stay cheap I’ve seen some people use ceramic tile pieces from big box stores. Just make sure there’s a ledge for the glass or tile on the platen for safety.
 
I'll defiantly upgrade my platen as that has been an annoyance. I've tried to flatten mine but it does not like to stay flat, and the rounded edges are a pain. I know there is a way to increase the tension as I've had the wandering belt issue also.
 
Jcdelamater said:
I'll defiantly upgrade my platen as that has been an annoyance. I've tried to flatten mine but it does not like to stay flat, and the rounded edges are a pain. I know there is a way to increase the tension as I've had the wandering belt issue also.
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Are your blades ground with distal taper? I know my grinding became a lot easier and more accurate when I started grinding the distal taper right after profiling the blade. Using a grinding guide will give you accurate plunge cuts. Starting the plunge using a sharp file is beneficial as well. It makes the belt drop into the cut made by the file on the first pass across the belt. Keep at it; it gets easier as you go.
Fred
 
I've done a few kitchen knives with somewhat of a distal taper, but I did this as part of my beveling. Do you grind the taper across the whole surface of the unbeveled blade and then grind your bevel?
 
In order to grind a blade that has a good cutting geometry the bevels have to be thinned as you move from plunge to tip. It can be thinned by applying more pressure forward, as you grind towards tip, or you can grind distal taper into the blade blank before you start grinding the bevels. If distal taper is ground first its far easier to keep the grind lines parallel to the spine. Grinding the bevels without distal taper you are fighting to keep the grind lines level and at the same time you are trying to thin the belly of the blade just behind the tip. Doing this will really help you with that problem where the thickness of the blade is different along the grind lines and the edge.
Using layout blue spray both sides of the profiled blade. Let it dry. It's best to use a welders magnet to attach the profiled blade to, it keeps you from scorching your fingers. Use a 100 or 80 grit belt. You want to apply just the slightest pressure towards the tip, slight pressure, the ricasso of the blade almost touching. Keep the grind line across the blade even as it moves towards the plunge area, which you have marked. Turn the blade over and do the same thing to the other side. Scribing a centerline along the blank will. help you to keep the taper even. What you are trying to end up with is two flat surfaces from plunge to tip. Since this is just a hobby for you; make yourself a grinding clamp that which you can clamp at the plunge lines. It will make your life a lot easier. Use a piece of mild steel or scrap for your first try. It won't take you long to get the hang of it. Regards, Fred
 
Thanks for the explanation on creating a distal taper Fred.Rowe Fred.Rowe , but grinding the bevel is my struggle. Using the bubble jig I get a consistent bevel angle, but if there's a distal taper, then the grind line creeps closer to the edge as the blade thins (I hope that makes sense).

It seems I can't use the bubble jig on a distal taper, if I want the grind line to follow the edge. Instead the angle of the blade to the belt has to change as I approach the tip. In other words, if my angle at the plunge line is 4 degrees, by the time it get to the tip it might have to be 2 degrees - to get a constant bevel width.

I'm I thinking of this correctly?

So I end up blending the whole side with a convex grind or hand sand it. That hides the effect.

P.S. I love my bubble jig and never sharpen a blade without it!
 
Sando said:
. Thanks for the explanation on creating a distal taper Fred.Rowe Fred.Rowe , but grinding the bevel is my struggle. Using the bubble jig I get a consistent bevel angle, but if there's a distal taper, then the grind line creeps closer to the edge as the blade thins (I hope that makes sense).

It seems I can't use the bubble jig on a distal taper, if I want the grind line to follow the edge. Instead the angle of the blade to the belt has to change as I approach the tip. In other words, if my angle at the plunge line is 4 degrees, by the time it get to the tip it might have to be 2 degrees - to get a constant bevel width.

I'm I thinking of this correctly?

So I end up blending the whole side with a convex grind or hand sand it. That hides the effect.

P.S. I love my bubble jig and never sharpen a blade without it!
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Sando,

It's not the distal taper that causes the change in angle as you grind towards the tip. It's the fact that,, in upswept blades you are dealing with a spiral as you grind along the belly and tip of the blade. If you take a blade and grind distal taper along it's length and then if you could cut the blade down the center line of the spine splitting the blade in two pieces; each side would be independent of the other which would cause no issues as you ground each bevel That distal taper is not an issue when you are sharpening, for the same reason. Think of doing this with a planner blade for a good reference.
If you could move the BJ along each segment of the bevel from plunge to tip then it would be accurate. But since it's sitting at the plunge, it does not follow.
When I grind a blade that has been ground with distal taper and I'm grinding at 4 degrees, I make no change in position but pull straight thru the tip and belly establishing that 4 degree bevel until the spiral starts. Once the bevels are set, remove the grinding clamp and use the flat bevel, to finesse the belly and the tip. There are many variables taking place once the edge starts moving away from parallel with the spine. Whether the tip rises or the spine drops, the only flat area from edge to spine is at the plunge and forward until the PT point on tangent begins.
The Bubble Jig is a very simple device, but believe it or not, it took me two years to design it so it would function with most any grinder set up and I got it clear in my own head how it would function. I came from a surveying and builder background which is how it came about when I found I could not get the results I wanted.
Happy grinding, Fred
 
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