Hello folks. OK so I've been using a 1x42 belt grinder to sharpen my various edged tools so about 4 years now and I consider myself quite good at it. One problem I have though is with burr production. I understand why being that the belt it always edge trailing so obviously the extra metal is going to collect at the edge. Especially when there are chips I'm removing you can develop a pretty big burr. As I progress with the belts it's continuously gets finer until a combination of cork, end grain pine, and with a cork or felt belt with green compound removes it very nicely. The problem is I don't always want to finish on a 15u belt. I wouldn't mind a toothier edge sometimes. If I go right from a 120 grit ceramic to a 16u trizact it doesn't seem to Polish the edge much but nicely deburrs the edge. Only I see on many posts people stopping at say 400 grit and some don't even use a polishing belt. If I don't finish with a loaded polishing belt the burr isn't going anywhere or finish on anything coarser than a 16u belt. Both steps are needed for me. What other or same experiences are there? Thanks
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Belt grinder sharpening and the dreaded burr
- Thread starter Vicv
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if i am understanding you correctly , you are saying you can not remove the burr unless you use a polishing belt, and you don't understand how the people using 400 grit can remove a burr. forgive me if i misinterpreted it. in my experience, i have noticed if i go progressively lighter in pressure once i get a burrs, the piece of metal connecting the burr to the blade gets very thin and falls off. my last few strokes have the blade just barely touching on the abrasive. i think if you continually remove metal from the blade, you are making new burr. by using super light pressure you only abrade the burr that is hanging over the edge, because the burr is curled over from when you did the other side. thats how i do it anyways, i am looking forward to learning more.
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I have sharpened both edge leading and edge trailing on belts and currently, and doing edge leading (edge up into the belt). This is nice because I can see the light glint from the dull edge and when it disappears. Woodster has it right in that you need to get lighter and lighter on the finishing passes. I normally stop at 120-220 grit then go straight to a leather belt w/ compound which fully removes the burr, in combination w/ cutting across grain into a piece of wood (after I have weakened the burr a bit w/ a few passes per side on the leather belt). Hope this helps!
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Sorry bud, I would never recommend anyone, regardless of experience, use a edge leading technique on a belt grinder.
As to the burr,
Is a belt grinder, the burrs are going to be huge no matter what. Spending excessive time trying to reduce the burr on the belts is just wasting steel.
My machine sharpening method involves a 1x42 Norton Blaze 120 grit ceramic belt to set and sharpen the bevel. After this a leather or paper wheel can be used to polish off the burr resulting in very sharp factory style edge. Now, because the burr can be problematic on softer steels I add in a deburring step between grinding and polishing. I use a fine Scotch Brite deburring wheel, it's firm and fits on my bench grinder so it just like using my polishing wheel. This "Softens" the burr and "melts" the appearance of the grind marks in the edge which makes polishing easier and offers more consistent results.
As to the burr,
Is a belt grinder, the burrs are going to be huge no matter what. Spending excessive time trying to reduce the burr on the belts is just wasting steel.
My machine sharpening method involves a 1x42 Norton Blaze 120 grit ceramic belt to set and sharpen the bevel. After this a leather or paper wheel can be used to polish off the burr resulting in very sharp factory style edge. Now, because the burr can be problematic on softer steels I add in a deburring step between grinding and polishing. I use a fine Scotch Brite deburring wheel, it's firm and fits on my bench grinder so it just like using my polishing wheel. This "Softens" the burr and "melts" the appearance of the grind marks in the edge which makes polishing easier and offers more consistent results.
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How come? I have never heard of any examples of a belt grabbing and throwing any blade but I may be wrong. I always do my regrinds like this (as does almost any knife maker when they are setting the bevels) and I have done hundreds of knives in this manner w/ out it ever even feeling like it would grab. To me it is simply not a concern. This also may be because I am going extremely slow compared to most grinders, only running about 500-1500 fps but even when I have played around w/ it at faster speeds it has not been an issue.
Do you have any reference or experience that this has happened to you?
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I only grind edge leading whether grinding bevels or setting edges. I find it much easier to work the belly and tip when they can be seen, with the wrist turning down. How do you reference the edge angle when using an edge trailing technique? Is the belt reversed, moving away from you, or is it rotating towards you?
Fred
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Thanks for chiming in Fred. In either case the belt is always rotating toward me from the top of the sander and going down over the platen plate. I have a reverse switch on my vfd but when I try it on my belt sander it won't track right w/ out modifying the tow of the tracking wheel (I have heard).
Either in edge trailing (edge down) or edge leading (edge up) it begins as an estimate and I fine tune my technique to where I know it is + or - 1 dps as verified on the Wicked Edge. Then repetition trains muscle memory so it is no longer that difficult. I still have to go back and reprofile some I did not get thin enough once in a while, but I have only recently switched back to going edge leading. I have went back and forth over the years hehe. To get the basic angle I can, with the grinder off, put the edge perpendicular into the belt/platen, then cut that angle in half which will be about 45 dps, then cut that in half again and that is roughly 22.5 dps. Then I just go under that a little bit and train and there ya go! =)
Rotating towards me. I watch for a full glint of a burr along the entire edge. I like edge trailing because I can see the distance between the spine and belt to keep it even. I always use light pressure as I sharpen on the slack part between the platen and top pulls. If I push much it increases the angle as the belt deflects so I always use light pressure unless I'm removing chips from a lawnmower blade or something. What I mean is I can only seem to get the burr small enough to remove if I finish on a 15u or finer belt. If I stop with say a 120 the burr just never really goes away regardless if I go to cork, felt, leather belt or wood. The burr is super soft and just moves around like metal powder clung together. When I finish on a high grit belt I can watch the little glints fly of the edge. I always test with my thumb nail. If the burr is still there the edge slides off. When it's gone the edge digs in. Another way to really tell is the whack the edge into a maple board. If the burr was removed completely the edge is fine. If not I'll see a glint looking straight at the edge. Hope that makes sense
pjwoolw
Sharpening guy
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If you finish on a leather belt with white compound then run the edge through a wine cork your issue will disappear. Three passes on each side of the edge for a total of six. As long a you go 400 or higher, silicone carbide belts work the best in my experience in the 400-600 range, then finish on your leather belt you will get a relatively burr free edge. You may want to give linen belts and CBN a try rather than the higher grit Trizact or whatever belts in higher grits your using. Wheels in my view are really a waste of money and time when you do the same thing better on the belt grinder you already have. Not that wheels wouldn't work. I just don't see the need.
I use a cork coaster about 6" diameter and 3/8" thick. Never have used plain sic belts besides the 15u 3m micro finishing belt. I use trizact after 120 grit. I wrecked my leather belt a year ago and replaced it with felt one. I'd love to find a 1x42 linen belt. The felt is loaded with green compound from Lee Valley. I should've mentioned well made carbon knives are no problem of course usually use Waterstones on them. It's the cheap German and Chinese soft stainless makes a difficult burr
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Keeping with the original statement of edge sharpening with a belt sander edge leading into the belt.
It can be dangerous because the belt can be cut by the sharp edge causing it to come flying off and possibly being cut by the knife. I doubt it's going to grab and fling it like a buffer but I don't want to be the one to find out. I have had a belt "blow-up" using an edge leading sharpening method, it happened once and a lesson was learned.
I don't thing grinding out blades has the same concern. I'm sure grinder speed plays a role too.
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I had a recurve edge pull into the outside of the belt doing some leading edge work at moderate speed - trashed the belt. Works OK for flat and outside curve, but when working on a powered belt leading or trailing, I found I always had to use some secondary means of burr removal anyway. Now I use them trailing to be on the safe side.
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If the edge contacts the belt at different angles of approach the edge leading technique can be challenging. If a constant angle is maintained I've never encountered this problem. If an edge is getting close to sharp and the spine is lifted, bad things can happen. Like most operations in the shop its using proper technique that makes it work.
Never sharpen on a slack belt, edge leading, for many reasons.
Never sharpen on a slack belt, edge leading, for many reasons.
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Interesting. Yeah I'm sure speed does play a roll. I have had one belt break on me, but it was a cheap belt at fast speeds... I don't remember which technique I was using. Now I use only high quality belts and I use 'em like they were free haha. Even if a belt were to pop on me it would not be dangerous at the speeds I usually work with.
You are so right Fred. I have noticed stuttering if I put the edge/spine into the belt perpendicular and tilted a little upwards at the contact point, so if I am hogging metal off at a perpenticular angle I make sure either to be either at 90 degrees or tilted slightly down.
As far as sharpening on a slack belt edge leading... I do this a lot as well have have never noticed any issues. Question: when you do a full convex to zero (on a slack belt) how do you finish it? Edge trailing? curious...
I should clarify that I NEVER use my buffing or scotch brite belts edge leading as that causes the obvious problem you listed hehe
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You are so right Fred. I have noticed stuttering if I put the edge/spine into the belt perpendicular and tilted a little upwards at the contact point, so if I am hogging metal off at a perpenticular angle I make sure either to be either at 90 degrees or tilted slightly down.
As far as sharpening on a slack belt edge leading... I do this a lot as well have have never noticed any issues. Question: when you do a full convex to zero (on a slack belt) how do you finish it? Edge trailing? curious...
Josh,
I have a real aversion to slack belt convex edges. This is why: when an edge is placed against a slack belt, the belt gives, with the apex of the cutting edge being the pressure point. Depending on the pressure applied, the belt is moving across the apex at an uncontrolled projection, which to my mind, "Pushes" the apex to the opposite side of the blade. Change sides and it happens on this side as well. The apex moves one way then the other. Its thinning the burr @ the same time the result is a very thin burr thats easy to remove.
The slack belt technique produces a sharp edge, I agree. I just think there are other, better options that exhibit improved cutting characteristics. This type of edge is hard to reproduce on anything other than a belt machine. This is how the mouse pad came into use which has the same effect on the apex. If you think about this technique using a different scenario: suspend the belt between two supports by its ends, now place the blade on this "slack" belt and move the blade along the belt. The belt always angles away from the apex as the edge moves along it.
I'm a flat edge kind of guy
its no doubt because of the Bubble Jig and ERU that I manufacture and use constantly. But I do produce a convex edge in a manner of speaking. If its done on a 2 x 72 belt machine, I grind a "flat" edge on the platen, using a Bubble Jig to control the angle, say 15 dps. Once the burr is created and ready to be removed, I change the angle of approach, making it more acute and in the process the shoulders are rounded making the geometry more efficient. When I sharpen on our wet VS machine, using a Bubble Jig its easy to achieve the rounded shoulders but with a "flat" apex. I love sharpening knives, a little weird me thinks 
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I accidentally turned a folding knife and it caught edge leading into my slotted paper wheel once; it shot right up into my collar bone and fortunately only glanced off result in a minor cut and bruise... Could've been a lot worse though.
So, no more sleeping at the wheels for me LOL!
Everyone has their own way. I also have a gatco and a lansky. I also enjoy my Waterstone. For me it's hard to beat the edge on a German chef knife that a 120 grit belt leaves with only one pass on a 16u belt to knock down the burr then Polish on the felt. But a 2k naniwa aotishi is close. Just takes longer. I like the convex edge but only because it's so easy to put on. I don't think it lasts any longer or shorter than a v edge. Even when I freehand with water stones I still finish on the felt belt. But a knife that would take an hour to freehand out the nicks and dents takes 45 seconds on the belts. And the edge looks better and more even
You are so right Fred. I have noticed stuttering if I put the edge/spine into the belt perpendicular and tilted a little upwards at the contact point, so if I am hogging metal off at a perpenticular angle I make sure either to be either at 90 degrees or tilted slightly down.
As far as sharpening on a slack belt edge leading... I do this a lot as well have have never noticed any issues. Question: when you do a full convex to zero (on a slack belt) how do you finish it? Edge trailing? curious...
Josh,
I have a real aversion to slack belt convex edges. This is why: when an edge is placed against a slack belt, the belt gives, with the apex of the cutting edge being the pressure point. Depending on the pressure applied, the belt is moving across the apex at an uncontrolled projection, which to my mind, "Pushes" the apex to the opposite side of the blade. Change sides and it happens on this side as well. The apex moves one way then the other. Its thinning the burr @ the same time the result is a very thin burr thats easy to remove.
The slack belt technique produces a sharp edge, I agree. I just think there are other, better options that exhibit improved cutting characteristics. This type of edge is hard to reproduce on anything other than a belt machine. This is how the mouse pad came into use which has the same effect on the apex. If you think about this technique using a different scenario: suspend the belt between two supports by its ends, now place the blade on this "slack" belt and move the blade along the belt. The belt always angles away from the apex as the edge moves along it.
I'm a flat edge kind of guy