Sharpening Snafu's

C

Cushing H.

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Jun 3, 2019
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On a recent thread some have spoken about using their grinder to sharpen their blades (and there are some videos out there also advocating this). so, just for yucks, I used one of my trial blades to try sharpening on the grinder. I used a new 220 grit ceramic belt, very slow speed on the belt, and targeted a 15 degree primary bevel.

What I ended up seeing (and feeling) was periodic single-particle scratches extending 1/4 inch (or maybe a little more) up the secondary bevel. (this was not "wandering" on the angle on my part, it was very discrete single scratches pretty clearly associated with specific locations on the belt.) If this was a knife I cared about I would be using some pretty colorful language right now - but again this was an experiment.

So Question: for those that have sharpened on your grinder, have you seen this problem, and how do you avoid it? Is it just a poor quality belt (it is "Red Label" abrasives from Amazon)? Do you dress the belt before sharpening to make sure it runs uniformly without standout grit? I am not thinking of this as a primary way of sharpening ... but if it can be done, I would like to know what the tricks are....

(BTW - I spend years sharpening on my 1x30 Harbor Freight sander, and never saw this particular effect.....)
 
i find that happens with new belts. some of the fresh grit pieces are taller and leave tiny swipes on the blade,above the secondary edge. also, a thread or fuzzy edge hanging off the side of the belt will do the same thing. i use a worn belt, so all the tall grits have been knocked down. you can also try gator belts.
 
Thank you john. Yeah - i keep looking at the gators. I am going to pick up several when i am at Pops in two weeks.
 
I tape my blade and leave only a very small gap between the tape and the edge.

For putting an edge on the grinder I have a specific belt only for that a Norax Engineered ceramic U936 220 grit. Run it slow
They are about $12.25.

They run cool and run flat. No bits fly off and no stray strings.

It is like using sharpening stone on the edge.

I take the edge down to almost forming a burr then go to an edge pro and set the edge.
 
C Cushing H.

No, it unlike other belts. The abrasive is laid down in little flat blocks. The belt is smooth and flat. Very high tech stuff.
 
I'm guessing your primary bevel was close to 15 dps (maybe 10 dps) and so the low angle was causing those issues. I sharpen with new belts all the time and never have issues with that.
 
Cushing H. said:
Sounds like they are worth trying. Thank you!
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The are Norton's version of a trizac. It's worth getting a couple to see if you like them better than 3M Trizac belts. Trugrit has them.

As for the tape you can tape up the blade and then cut through it to sharpen. This helps protect against slips.
 
Storm W said:
The are Norton's version of a trizac. It's worth getting a couple to see if you like them better than 3M Trizac belts. Trugrit has them.
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There are several "Trizact" belts. There are 337DC aluminum oxide aka Gator, 407EA structured silicon carbide, 307 structured aluminum oxide, 953FA Structured ceramic.

The 953FA structured ceramic are similar to the Norax 936.

These are not similar to the popular Gator belts which are aluminum oxide.
 
AVigil said:
There are several "Trizact" belts. There are 337DC aluminum oxide aka Gator, 407EA structured silicon carbide, 307 structured aluminum oxide, 953FA Structured ceramic.
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Yeah - ive been starting to see and recognize the different versions. In playing with different abrasives in general i am seeing real differences. The ceramics and, especially, the silicon carbide seem, for lack of a better description, somehow “harder” ... or maybe the variation of grti size in a single belt is greater? In any event, the finish they leave versus an equivalent AO belt is very different, with seemingly deeper scratches... ceramics are great for material removal, but i am coming to the conclusion that the AO based belts seem better for refining and finishing (from an surface appearance perspective, not a material removal perspective)

For sharpenng (as discussed in other threads, a little micro serration is good - maybe that is why you like your ceramic based norax?
 
great suggestion mr vigil. next time i will tape the whole blade and sharpen it that way. i hate going back to the buffer with a sharp edge on the knife.
 
After reading the headline, the question that came to mind was precisely how sharp do you want your snafu to be? :p
 
I went to my grinder today, and took a close look at that 220 grit belt I had used. Sure enough - there was a big bump in the grit, standing somewhere between 1/32 and 1/16 of an inch off the otherwise relatively uniform surface of the belt :(. Bad belt? Is this common - Do you guys inspect your belts for such defects before using (esp. for sharpening) ... Seems to me this is more extreme than some of the grit particles being a little bigger than the rest on the belt???
 
jdm61 said:
After reading the headline, the question that came to mind was precisely how sharp do you want your snafu to be? :p
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I was going to come out with some witty remark about the SNAFU being some obscure knife used to shave the hair on the back of a fly ... BUT it turns out there really is such a thing: The Peter Rassenti SNAFU 2.0 folder:
upload_2019-9-2_11-23-10.png
 
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