belt sanders fatal flaw?

W

winguy7

Joined
Nov 30, 2013
Messages
23
Alright I'm new here and new to knife sharpening, for the most part. I have researched about every way possible to sharpen and the various techniques for each. Also I am a Machinist that grinds my own tooling every day, so I have a good eye for it. I've been needing a decent system to sharpen axes and knives, since I already have one of the grizzly 1x30 sanders that's what I decided to use. However after some short use I can't see why anyone would want to use one. I started by sharpening mora (m2000 I think) cheapy tackle box knife. I got it hair popping Sharp easy enough, but wanted to play around with different angles to see if I could get it sharper. But could very quickly tell that the edge of the blade was no longer straight. Not the angle but the very top of edge. It had high and low spots (wavy feeling). To me this is caused by the belt on the sander not having a constant back pressure. Meaning that with every pass some spots on the edge get more sanded than others. Creating thicker spots on the blade that under normal sharpening will eventually become high spots. I wish I would of seen that coming, and have never seen it mentioned before. Just wanted to see what everyone thinks about sanders in general. Heats not a problem for me, just the lack of a truly flat surface to put an angle on the blade is what bothers me. Anyway I'll be using water stones from now on. Are the Norton stones any good?
 
Last edited:
Also, you could try to use the portion of the belt closest to the wheel where there is less slack.
 
Sounds like your pressure isn't even. I had a similar problem when I was new to sanders too, but quickly learned consistency.
 
Why dont you put some backing under the belt?
Wouldnt that solve the problem?

One more question? How were you planning to change mora edge angle? it is scandi grind - one proper angle only.
 
I don't ever use the platen for sharpening. Using the platen is the only time I've had problems, but I learned that after trying it once.

If you are indeed using the platen, take the advice from above and either remove it, push it all the way back, or try the belt above it.
 
I used klingspor belts starting with 400, 600, and then 800. The platen is off, and I beefed up the tension spring in the back with a heavier one. Also I loosened the bolts on the rear pulley when putting on the belts and then tighten them back down so that there is no slack at all in the belt. Probably right about only being one right angle for the Scandinavian grind, it never did get any better with different angles. That just brings me to another problem though. I do not see how you could get anything other than a convex grind using a belt sander. To me lighter pressure will just make the effects less noticeable, and that over time of sharpening a single knife with one will lead to the same results. Like I said I was just playing around with it. I wasn't concerned about ruining the knife. Anyway just my thoughts on it. Glad to see all of yours as well.
 
I love my Kalamazoo belt sander I get exelent result, one secret I fined is to use very light pressure
let the belt do the work
I use 3M Trizact™ Sharpening Belts with amazing result
 
I have found that I like to use the platen. I glued some thick buffalo leather to it. It gives me a slightly less convex. In any sharpening setup, practice is paramount.
 
When I grind a edge on the platen I find the angle I am wanting for the knife I lock my elbows and make a three passes. I don't look at the edge until I do all three. The key is keeping yourself locked in and you can't do that by inspecting the blade every pass. Flip it over and repeat. I use the platen mostly. If you like convex try putting a thin felt backing on your platen with a J flex belt and you can do it on the platen as well. This is what works for me but may not for you.
 
That's a good idea. I can see how you would get a less convex edge doing that. Not that I think there's anything wrong with a convex grind or bevel, I prefer one.And I know practice helps, but for me the belt sander is only going to be good for the kitchen knives. I don't see how using a belt sander you could end up with anything other than some high breed grind with scani, hollow, or any of the other grinds. Seeing as how the micro bevel will always be convex. I also see that you could get these same bad results with stones however. It would just depend on your technique. For example I watched a video of some "master" Japanese knife sharpener who was going back and forth with a large kitchen knife. Only on one section of knife though, and then moving to the next. He was clearly not counting stokes, and even mocked the technique of pulling the knife toward you in one even stoke. To me the jokes on him though. Unless you either have the whole blade on the stone at one time when you're pushing and pulling, or count your strokes with the different sections of blade you will get those same high and low spots. Yes the knife will be sharp and its faster, but I think that eventually those spots will form. I'm glad that people do get the results they are looking for with the sanders, I just thought I would throw it out there as something to watch for. I'm probably over analyzing this its just that I grind cut-offs, drills, taps, turns, facer's, recess's, etc. every day. They have to be perfect to work right and it makes you a little anal about these things.
 
Last edited:
One other thing I don't like about these little 1x30 sanders is that no matter how thick the backing on the paper is, the middle of the belt is always going to be the part that's doing the most metal removal. Seeing how the pulleys are convex themselves. Making it impossible to get your bevel straight near the handle. Bigger more professional sanders with wider heavier paper might not have these problems. I guess it just depends on their design.
 
I use stiff backed belts running over a glass lined platen to set and sharpen edges. I prefer using a platen more than a slack belt because the slack belt or convex edge is hard to reproduce. A convex edge is altering ever time the edge contacts the belt. There are so many variables, pressure, location and angle of approach are hard to control and reproduce. Convex edges can be very sharp just not reproducible. If a knife goes to another owner they will find the edge hard to duplicate.
Using a set and controllable angle relative to the flat platen to set an edge or to sharpen it can be produced at any time by anyone who knows the angles used.
I use a 2 X 72 belt grinder at its slowest speed and use a Bubble Jig to control the set angle. Here's a video showing a swedge being ground at a set angle. I use the same basic technique for and sharp edge. [video=youtube_share;ohA9ZJctAXY]http://youtu.be/ohA9ZJctAXY[/video]
 
That is a much nicer setup. More controllable, and I do like the idea of using the platen better. I guess I'm just saying that for me the harbor freight and grizzly sanders are not going to cut it. The platen on them is a joke and pulleys need to be flat. I think for 150- 250 I can get a really nice set of stones that are way more controllable. Instead of spending a lot more to get a nice sanding set-up. Probably should of called this fatal freight flaw instead. They have their uses, I just don't see knife sharpening as one of them.
 
Sharpnessis said:
I have found that I like to use the platen. I glued some thick buffalo leather to it. It gives me a slightly less convex. In any sharpening setup, practice is paramount.
Click to expand...

I did the same thing with leather on the platan for the odd times I use it. Mainly for setting a bevel or heavy removal. It is much more forgiving than belt on metal.
Practice is a large part of using the sander. Over time you can make small adjustments to correct things like recurve blades, uneven tips and grinds etc.
 
winguy7 said:
That is a much nicer setup. More controllable, and I do like the idea of using the platen better. I guess I'm just saying that for me the harbor freight and grizzly sanders are not going to cut it. The platen on them is a joke and pulleys need to be flat. I think for 150- 250 I can get a really nice set of stones that are way more controllable. Instead of spending a lot more to get a nice sanding set-up. Probably should of called this fatal freight flaw instead. They have their uses, I just don't see knife sharpening as one of them.
Click to expand...
A lot of quality sharpening supplies can be purchased for the price of a good 2 x 72 belt machine. I'm a full time maker and so have them in my shop as part of the knife production but if I was not in that position I would look to the good stones available as well as the diamond units.

Good luck in your search, Fred
 
Thanks Fred, I was just thinking of the drill grinder we have at work. If someone could modify one of those to chuck up a knife it may be the ultimate sharpener. Of coarse this is really just hopes and dreams, I believe it costs around 20k. I'll try and get a picture of it to post later. Maybe then you can see why I'm so particular(spoiled) when it comes to grinding.
 
As you can see there are many ways to use this small fixed speed belt sanders. I don't care for the speed they run at.
I use a 2 x 72" at about300- 600 rpm depend on belt and what I am sharpening.

Since you are a machinst you shouldn't have any trouble setting up one of these with step pulleys for a adjustable speed.
www.cootebeltgrinder.com I have one of these that I purchased many years ago and two other variable speed 2 x 72 machines. The belt grinders will do a excellent job on a Axe of hachett as well.
 
I purchased the Kalamazoo 1x42" and find this does a great job sharpening all of my knives. I use x-weight belts and have added a custom made SS platen to mine which is adjustable. I sharpen between the openings in the platen. The speed of getting a quality mirror edge is so much faster then stones. I still use water stones along with diamond stones from DMT. Most of my best edges are achieved using the belt grinder. Best of luck using what ever method you choose. This just works well for me. Have also been a machinist for over 40 years. Yea I'm old. :D

P1010001-1_zpsf1c35d79.jpg~320x480
 
winguy7 said:
For example I watched a video of some "master" Japanese knife sharpener who was going back and forth with a large kitchen knife. Only on one section of knife though, and then moving to the next. He was clearly not counting stokes, and even mocked the technique of pulling the knife toward you in one even stoke. To me the jokes on him though. Unless you either have the whole blade on the stone at one time when you're pushing and pulling, or count your strokes with the different sections of blade you will get those same high and low spots.
Click to expand...

I respectfully disagree. With blades that have seen use, sometimes a LOT of use, some portions of the blade will be more dull than other portions. If you only do completely even strokes, covering the entire blade length with the same amount of grinding, one of two things will happen:

1. You'll never get the really dull areas sharp because the rest of the blade is sharp and you stop.
2. You'll get the whole blade sharp, but you'll needlessly grind away lots of the rest of the blade, WAY after it was already sharp.

The Japanese stroke that you describe above allows you to focus grinding on the areas that need it more than others. When I do this, I get to spend the right amount of grinding on each area. Enough to get the whole length of the blade sharp. However, I don't focus on one area for too long. Maybe 15 or so strokes in one area, followed by 2 or 3 passes across all sections of the blade. That way I don't form any "high or low" areas as you are describing. Then back to focusing on the area, or areas that still need grinding. The Japanese stroke is one of the great techniques of sharpening. I wish I had learned it MUCH earlier in my sharpening career.

Brian.
 
You must log in or register to reply here.
Back
Top