Recommendation? Thin blade using silicon carbide paper

C

Craig James

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Oct 30, 2018
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219
Ladies and gents,

Bit of context - I have a series of old kitchen knives that are far too thick behind the edge, I’d like to have a go at thinning them.

Problem is I have none of the kit you’d typically use I.e no belt sander, wheel or particularly coarse stone (diasharp coarse is as coarse as it gets for me). As this is likely to be an infrequent occurrence I don’t necessarily want to invest heavily.

I was thinking of getting some 120grit SiC paper and giving it a go.

Any thoughts / experience using this method would be welcome, including how to effectively mount this on a flat surface.

I did consider purchasing the washboard system but if I were to go down this route I’d probably settle for an extra coarse stone such as the manticore although I think shipping to the UK would cost more than the stone!

Thanks in advance

EDIT: I should add that achieving an aesthetically pleasing result is not a success criteria!

EDIT2: Maybe I’m barking up the wrong tree here and you’ll just advise me to spend 50quid on the Shapton Pro 120...
 
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I don't see why it wouldn't work. I have a Dexter Russel "vegetable clever" that I've been playing around with thinning on a Norton medium Crystolon (SiC). The blade is definitely scratched but I can work on smoothing that out once I have things where I want. Going slow so as not mess anything up. Every few sharpenings, I'll give a couple thinning passes. I lay the blade flat and then raise it up maybe around five degrees.

Maybe the experienced folks will have a different or better take.
 
I don't think ceramic paper would remove enough metal. I'd look for a few sheets of wet dry SiC sand paper with the cloth backing in 100 and 300 grit. Lay the knife flat and lift the spine a thumb nail thickness and work it until it looks thinner. DM
 
I'll suggest looking into using aluminum oxide grinding belts cut, laid flat and glued to a hard surface (board, bench edge, etc). I've used blue zirconia-alumina belts in 3" x 21" size for this, in 120-grit. The zirc-alumina is a very tough grit and won't break down like the SiC paper's grit will. Can do a lot of work with one belt. The belts have a diagonal seam in them; cut the belt at the seam and lay it flat. Glue it down with something like contact adhesive (spray is easiest).

For pocketknife-sized blades, SiC paper at 220/320 grit on a hard surface works fine. But for much bigger blades, I think the alumina belts are the way to go.

AFTER you do the thinning on the coarse alumina belt, then the SiC paper can work very well to refine the finish to something you like. For example, something around 220-400 grit leaves a nice satin finish emulating a lot of factory knives' finishes.
 
Thanks all for the input, Obsessed I actually have some belts in the garage so will give that a go - will need to get some contact adhesive tho
 
For what it's worth, if thinning the whole blade from spine to edge, or nearly so, is the objective, then the belts work well in that job with all their length and grinding surface area. Down the road, if some thinning behind the edge is the goal, then a SiC stone (Crystolon, etc) or the coarse side of a Norton India combination stone can work well for common kitchen cutlery. I've used my Norton IB8 India stone (Coarse side) for this, thinning the edge on an older Chicago Cutlery 10" chef's knife. I do the maintenance sharpening on the Fine side of the same stone, or also with a pocket-sized Fine India in the same grit.
 
Silicon Carbide wet/dry will work well enough, start with 80 grit wrapped around a steel plate or a brick. Clean it off frequently with an eraser or synthetic wine cork. Get it where you want it and move to 120, then 320, 600 for a nice satin finish.

It won't be quick, but most kitchen knives are low Rockwell, it won't be too bad.
 
I might get a Crystolon - cJB8 for £35 on eBay - I’ve never used an oil stone before. How quickly do they wear and how easy are they to lap?

I assume it would get the job done quicker despite the similarity in grit?
 
Norton's IB-8 will do it. They run about 25$ here delivered. It will wear more than a India but cuts faster and will work on any steel. I doubt you'll notice the wear from one kitchen knife. After 20, yes. They are not difficult to lap. I have rubbed them on a flat area of concrete with
water. DM
 
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The coarse side of a norton jb8 is what I use to remove metal fast, like thinning and shaping, fixing broke tips, lowering spines, etc.
The fine side is an added bonus.
 
Obsessed with Edges said:
I'll suggest looking into using aluminum oxide grinding belts cut, laid flat and glued to a hard surface (board, bench edge, etc). I've used blue zirconia-alumina belts in 3" x 21" size for this, in 120-grit. The zirc-alumina is a very tough grit and won't break down like the SiC paper's grit will. Can do a lot of work with one belt.
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I have some big Busse-kin wood chopping knives with relatively thick edges that are time-consuming to thin out. I've seen you recommend these belts before and would like to try them out. Would you please tell me where you buy them?

Also, considering the size of these knives and the amount of metal I need to remove (patience isn't one of my strong points when it comes to removing knife metal), should I go to a lower grit than 120? I'm not too worried about scratches (I often use 50-60 grit sandpaper and stones to reprofile). I have no use for smooth, refined, polished edges and any scratches will eventually be removed by finishing at 400-600 grit.

Thanks!
 
MtnHawk1 said:
I have some big Busse-kin wood chopping knives with relatively thick edges that are time-consuming to thin out. I've seen you recommend these belts before and would like to try them out. Would you please tell me where you buy them?

Also, considering the size of these knives and the amount of metal I need to remove (patience isn't one of my strong points when it comes to removing knife metal), should I go to a lower grit than 120? I'm not too worried about scratches (I often use 50-60 grit sandpaper and stones to reprofile). I have no use for smooth, refined, polished edges and any scratches will eventually be removed by finishing at 400-600 grit.

Thanks!
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The belts I used were bought at (now defunct) Sears, under their own Craftsman branding. They're just an example of what can be used. For what you're doing, any aluminum oxide belt made for grinding metal (at least) should work well enough. If you want to go lower in grit for your purpose, I see no reason that couldn't work for you. Should be able to find adequate belts at the home centers or hardware stores (ACE, etc).

I emphasize belts labelled as compatible for grinding metal, as opposed to using belts made primarily for sanding wood only. Many of those wood-sanding belts will also be aluminum oxide, but the grit may not be optimized for metal grinding, i.e., with sharper-edged grit, tougher/more durable bond, etc. Grit intended for wood sanding will often be more blocky & rounded, and won't cut metal nearly as well. May not be as strongly bonded to the backing, either.
 
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MtnHawk1 said:
I have some big Busse-kin wood chopping knives with relatively thick edges that are time-consuming to thin out. I've seen you recommend these belts before and would like to try them out. Would you please tell me where you buy them?

Also, considering the size of these knives and the amount of metal I need to remove (patience isn't one of my strong points when it comes to removing knife metal), should I go to a lower grit than 120? I'm not too worried about scratches (I often use 50-60 grit sandpaper and stones to reprofile). I have no use for smooth, refined, polished edges and any scratches will eventually be removed by finishing at 400-600 grit.

Thanks!
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I sent you a PM.
Edit: It looks like you have your PM's turned off.
Check out Pop's knife supply for good 2x72 belts.
 
I recently tried the purple 3M Pro Grade Precision paper and I was impressed. It is a waterproof sheet with Cubitron II grit which seemed about as aggressive as the SiC Wetordry I usually use but it lasted longer. I was able to complete the mild thinning of a Forgecraft butcher knife with half a sheet of 80 grit. My favorite feature is the "no-slip" backing that allowed me to use it without adhesive on the unpolished side of a granite floor tile; between the long life and quick changes this could save a lot of time.
 
Obsessed with Edges, thanks for your reply and, in particular, your great advice (below) about using belts specifically designed for grinding metal (I assume/hope this info also applies to sandpaper). Most sandpaper I see in the 50-60 grit range is only for wood, and sometimes both wood and metal, but rarely, if ever, do I see it for metal alone. Regarding this, I find it annoying that sandpaper manufacturers often do not state what kind of abrasive they use, although I think most of it is aluminum oxide. I've been using 50 grit emery cloth for reprofiling with good results. I think that product is designed more specifically for metal.

I enjoy experimenting with different abrasives to see which ones are the best. This isn't too expensive and makes the rather tedious job of freehand reprofiling more interesting.

Obsessed with Edges said:
I emphasize belts labelled as compatible for grinding metal, as opposed to using belts made primarily for sanding wood only. Many of those wood-sanding belts will also be aluminum oxide, but the grit may not be optimized for metal grinding, i.e., with sharper-edged grit, tougher/more durable bond, etc. Grit intended for wood sanding will often be more blocky & rounded, and won't cut metal nearly as well. May not be as strongly bonded to the backing, either.
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Thanks again for this info! :thumbsup: I would have made better abrasive choices in the past if I'd known this.

flatblackcapo, thanks for the info and website but I freehand reprofile and 2" belts are too narrow for big knives.

Mr.Wizard, the 3M website said the sandpaper you mention is a ceramic mineral. I've never heard of sandpaper made of that before. Will check our further. Thanks!
 
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