Lengthwise belt finishes on kitchen knives

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Hubert S.

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Dec 14, 2019
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I am trying to get a lengthwise belt finish on a little honesuki knife I am working on and I am really struggling to get the crosswise scratches out. I am wondering what sort of belt progression I should use. I have been finishing the blade crosswise up to a Trizact A30 and I can hand sand those scratches out with 400 grit paper in a couple of minutes. My goal was to finish the blade with a "very fine" Scotchbrite belt lengthwise, but that does not take the A30 scratches out. The cork belts I have (220-1000) do not work either. I am using a contact wheel for grinding lengthwise, but have also tried a felt lined platen without success (the wheel seems to work a lot better). The blade has a convex grind on it, if that matters. I thought maybe my Trizact belt was contaminated, but a brand new one gave me the same results.

I would really appreciate some pointers for belt progression and/or techniques to get a consistent belt finish in the lengthwise direction. Would starting with coarser Scotchbrite type belts work for this, or do I have to go back to coarser trizact belts after switching direction?
 
Scotch brite belts aren't going to remove any scratches so your scratch pattern needs to be going lengthwise before you blend with the scotch brite.
I hand sand to a clean 400 grit and follow with the scotch brite using the bottom of my contact wheel.
 
E.Carlson said:
Scotch brite belts aren't going to remove any scratches so your scratch pattern needs to be going lengthwise before you blend with the scotch brite.
I hand sand to a clean 400 grit and follow with the scotch brite using the bottom of my contact wheel.
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Thank you, Erik. I looked at some tables that showed the very fine Scotchbrite belt equivalent to 220-320 grit, so I figured it should get A30 or ~800 grit scratches out. It gets most of them, but not all. I thought I was really doing something wrong. It is kind of funny now, I hand sanded the blade lengthwise four or five times to try different belt combinations because I wanted to figure out how to get the lengthwise finish straight from the grinder!

Is there a big difference in surface finish between the very fine and the super fine Scotchbrite belts? Do you go straight from 400 hand sanded to superfine?

One other thing I have tried is going from lengthwise hand sanded to a cork belt finish, but I could not get a consistent finish on the contact wheel. There always seemed to be some areas that looked more polished than others. Maybe that's my technique. Otherwise, I really like the cork belt finish and would probably prefer it over the very fine Scotchbrite, but the Scotchbrite seems to be a lot more forgiving.
 
I followed the clean 100 grit finish with a vertical medium-fine-super fine and it worked good (no visible horizontal lines anymore).
 
I dont even see a huge difference between the coase and super fine, which are the only 2 I have. Scotch brite belts are great for blending to a consistent finish so I use them for all my kitchen and plunge less blades lengthwise.
Cork belts are better for width wise machine finishes, especially when you want to keep grind lines and transitions crisp. Scotch brite belts tend to muddy these up a bit. Be sure to properly break in your cork belts as they aren't ready to use as they come to you. It takes longer than you would think to get them broken in. Use the search to find a thread discussing break in.
 
FredyCro said:
I followed the clean 100 grit finish with a vertical medium-fine-super fine and it worked good (no visible horizontal lines anymore).
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I wonder what's different, I can't get 800 grit scratches out with my very fine Scotchbrite.
 
E.Carlson said:
I dont even see a huge difference between the coase and super fine, which are the only 2 I have. Scotch brite belts are great for blending to a consistent finish so I use them for all my kitchen and plunge less blades lengthwise.
Cork belts are better for width wise machine finishes, especially when you want to keep grind lines and transitions crisp. Scotch brite belts tend to muddy these up a bit. Be sure to properly break in your cork belts as they aren't ready to use as they come to you. It takes longer than you would think to get them broken in. Use the search to find a thread discussing break in.
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Thank you, I'll stick with the very fine belt then.

I think my cork belts are broken in, I get a really nice finish grinding across the blade. I think the cork belt does not have enough give to conform to the convex blade like the Scotchbrite does, that's probably why I can't get an even finish.
 
Hubert S. said:
I wonder what's different, I can't get 800 grit scratches out with my very fine Scotchbrite.
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Do you work with enough pressure on the scochbright belt (you really need to push hard imho)? Did you alternate the angle while grinding to make sure your progression up to 800 was good? Coarse, medium and fine make visible difference for me, not so much difference between fine and super fine in my opinion. Haven't tried ultra fine. Try taking the blade with a magnet and really push hard into the belt, make the belt run fast.
 
FredyCro said:
Do you work with enough pressure on the scochbright belt (you really need to push hard imho)? Did you alternate the angle while grinding to make sure your progression up to 800 was good? Coarse, medium and fine make visible difference for me, not so much difference between fine and super fine in my opinion. Haven't tried ultra fine. Try taking the blade with a magnet and really push hard into the belt, make the belt run fast.
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The 800 grit finish I put on was pretty clean I think, just a few lengthwise pulls by hand with 400 grit removed all scratch marks. For the Scotchbrite, I am using the bottom of a contact wheel and pull the blade up towards me with gentle pressure. I have tried the felt lined platen with a bit more pressure. The net effect was that it washed out the edge at the choil and still left some scratches. I may try it on a different blade in the future, but I think I will finish this one with 400 grit by hand and then Scotchbrite.
 
I've never had success with scotchbrite actually removing scratches that are the opposite direction. The couple times I've tried the vertical wheel finish I first got all the scratches going in the correct direction with a 220 belt on the wheel but I never continued trying it to get to a point I was happy with the finish.
 
Id suggest trying the coarse or medium scotchbrite then follow up with your finer scotch brite, the medium will work for changing the direction of the scratches as long as the low belt scratches are gone. That might give you better results and medium pressure does work a bit better than light pressure.
 
Joshua Fisher said:
Id suggest trying the coarse or medium scotchbrite then follow up with your finer scotch brite, the medium will work for changing the direction of the scratches as long as the low belt scratches are gone. That might give you better results and medium pressure does work a bit better than light pressure.
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Thank you, Joshua. I am 100% certain I do not have any low belt scratches as I can get rid of the vertical scratches with 400 grit by hand very quickly, but the Scotchbrite cannot get all of them out.

I am curious now, both you and Fredy seem to have success, so it looks like there is a chance to skip hand sanding all together. Can you tell me what belt progression works for you and where you make the switch in direction? What speed do you use for the Scotchbrite belts?

Also, is there any appreciable difference between the 3M belts and others? I saw Pop's offers surface conditioning belts at about half the cost of the 3M belt I got from Trugrit. I need to order some other stuff from Pop's anyway so I'll probably get a coarse or medium belt from them and see how it goes.
 
Hubert S. said:
Thank you, Joshua. I am 100% certain I do not have any low belt scratches as I can get rid of the vertical scratches with 400 grit by hand very quickly, but the Scotchbrite cannot get all of them out.

I am curious now, both you and Fredy seem to have success, so it looks like there is a chance to skip hand sanding all together. Can you tell me what belt progression works for you and where you make the switch in direction? What speed do you use for the Scotchbrite belts?

Also, is there any appreciable difference between the 3M belts and others? I saw Pop's offers surface conditioning belts at about half the cost of the 3M belt I got from Trugrit. I need to order some other stuff from Pop's anyway so I'll probably get a coarse or medium belt from them and see how it goes.
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I use the surface conditioning belts from Pops for production work and they are great, I’ve used both those and the 3m belts and can’t tell a difference. I use medium pressure with a slow speed, I normally only run my grinder at 30% but before I had a variable speed motor I used them fast and they worked just as well, I just like the slow speed for extra control. I do all belt finishes on my knives but usually leave them going the width of the blade versus lengthwise, my progression is 50, 120 trizact then the medium conditioning belt all post ht, for blades with a hamon or Damascus I go up to 600 in the trizact then the blue fine conditioning belt and as long as I spend the time on the grits working up it leaves a very fine scratch pattern. I recently taught a class making forged integral knives and one student made a small santoku and polished the entire blade, we used 36 grit belts to rough in all the grinding and on the bolster where it transitioned to the blade we were able to change the direction of the 36 grit scratches with a medium surface conditioning belt using the top idler wheel to smooth out the bolster to blade transition, it did take a bit of work and would have been faster to go to finer belts first but we only had a few grinders and belts available.
 
I finish my kitchen knives to 220 on the grinder, then a sanding pass using 400 on the diagonal, then finish with 600 on a lengthwise stroke. Then I do a light pass with an extra fine surface conditioning belt. Works out great. I've never had much luck taking scratches out with the conditioning belts myself. I just use them for general blending.
 
Metalhead0483 said:
I finish my kitchen knives to 220 on the grinder, then a sanding pass using 400 on the diagonal, then finish with 600 on a lengthwise stroke. Then I do a light pass with an extra fine surface conditioning belt. Works out great. I've never had much luck taking scratches out with the conditioning belts myself. I just use them for general blending.
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Same. I crosshatch 220 after initial 120 bevel grinding, then lengthwise 400, then sometimes a fine SB on top of that, sometimes a few strokes by hand. I use a 40 duro 8" wheel, and I also prefer AO belts over trizact for this application.
 
Metalhead0483 said:
I finish my kitchen knives to 220 on the grinder, then a sanding pass using 400 on the diagonal, then finish with 600 on a lengthwise stroke. Then I do a light pass with an extra fine surface conditioning belt. Works out great. I've never had much luck taking scratches out with the conditioning belts myself. I just use them for general blending.
Click to expand...

Same. I crosshatch 220 after initial 120 bevel grinding, then lengthwise 400, then sometimes a fine SB on top of that, sometimes a few strokes by hand. I use a 40 duro 8" wheel, and I also prefer AO belts over trizact for this application.
 
I ordered a medium and super fine conditioning belt from Pop's and tried them on a knife that I finished with a trizact A30. The medium took the A30 scratches out very quickly, but the finish was not really great. The super fine belt, however, fixed that right up and gave me a nice satin finish. I did try to get the A30 scratches out with the super fine on the second side without using the medium belt first, but that did not work and left some scratches in the other direction. The medium belt got those out very quickly as well and then I went back with the super fine. This was the first blade that I was able to get a decent finish on without any hand sanding, so I'm pretty happy about that. I am a bit disappointed in the quality of the medium belt, though, it has the worst wobble of any belt I have ever used, I'd say around 1/8". Maybe it's just a fluke, the super fine belt runs true and there is not really any difference I can tell compared to the 3M belt.
 
I end up hand sanding all of my kitchen blades but I set up hand sanding with length wise grinding on my 14" contact wheel.
I grind the bevels on both hard and felt platens to create a hybrid full flat/convex profile.
My grit progression is ceramic 50 then 80 on the flat platen down to around 0.03" followed by felt platen grinding. I use ceramic 80 and 120, then 3M gator belts A300, A160, A100, A65. All of this is perpendicular grinding.
Then I switch to length wise grinding on the 14" contact wheel. For AEB-L I can usually go to gator belts starting at A300 and on down to A65 or A45 then on to hand sanding which is really just refining things and doesn't take very long. If I'm using a higher alloy steel I usually start length wise grinding with ceramic 120 then to A300 gators and on down.
 
Robert Erickson said:
I end up hand sanding all of my kitchen blades but I set up hand sanding with length wise grinding on my 14" contact wheel.
I grind the bevels on both hard and felt platens to create a hybrid full flat/convex profile.
My grit progression is ceramic 50 then 80 on the flat platen down to around 0.03" followed by felt platen grinding. I use ceramic 80 and 120, then 3M gator belts A300, A160, A100, A65. All of this is perpendicular grinding.
Then I switch to length wise grinding on the 14" contact wheel. For AEB-L I can usually go to gator belts starting at A300 and on down to A65 or A45 then on to hand sanding which is really just refining things and doesn't take very long. If I'm using a higher alloy steel I usually start length wise grinding with ceramic 120 then to A300 gators and on down.
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What is the reason for going down in grit when you switch to the trizact?

I have noticed that the trizact belts seem to want to give a different convex curve on the felt platen than the ceramic belts, or maybe I'm not using the right amount of pressure. I tried a J-flex AO belt on the felt after the ceramic and that seemed to conform much better to the bevel. I have not tried lengthwise grinding on a contact wheel with coarse grit, I'm afraid I'd mess that up in a hurry. I have a drawer full of blades I messed up, I think I can find something in there to try this out on.
 
Hubert S. said:
What is the reason for going down in grit when you switch to the trizact?

I have noticed that the trizact belts seem to want to give a different convex curve on the felt platen than the ceramic belts, or maybe I'm not using the right amount of pressure. I tried a J-flex AO belt on the felt after the ceramic and that seemed to conform much better to the bevel. I have not tried lengthwise grinding on a contact wheel with coarse grit, I'm afraid I'd mess that up in a hurry. I have a drawer full of blades I messed up, I think I can find something in there to try this out on.
Click to expand...

I switch to a coarser grit when going from perpendicular grinding to horizontal grinding because getting rid of the perpendicular scratch marks at that point with a similar grit that I left off at would take more time. Structured abrasives aren't as aggressive as ceramics or fresh AO belts so bumping up the grit size isn't a problem.
 
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