Utility Knife Blades

[Herman Trivilino]

I've never had any luck sharpening utility knife blades.  I looked at a new one under the 40X microscope and it has a micro bevel on it that's maybe 0.1 mm wide and has a more refined scratch pattern.  Once you know it's there you can see it as a shiny strip along the cutting edge using magnifying glass or even with the naked eye.

[grepper]

Do you mean the metal handle ones with the thumb button that slides the blade up and down? I've gotten those so they seem sharper than when they were new.  But then maybe I just go use to dull blades!

Must be fun having a microscope!

[grepper]

Herman, you had mentioned that there were some knives that you just could not get sharp, and I'm curious if the microscope showed why.  Do you know what was happening with them?  Are they sharp now?

I think I'm going to have to get a microscope. 

[Rhino]

Utility blades have not been a problem with me.  They have a straight edge like a chisel.  My biggest problem is that they are full of sticky junk (from slicing adhesive tape).  Also, the metal is removeable by grinding and I have no problem putting on a new angle.  Maybe you can try another brand

[Herman Trivilino]

Do you mean the metal handle ones with the thumb button that slides the blade up and down?

Yes.  Made by Stanley.

[Herman Trivilino]

It is fun having a microscope.  It's been a while since I tried sharpening a utility knife blade, so maybe I'll have another go at it.

I haven't been able to figure out why I can't get some knives as sharp as others.  I believe it is due to the fact that some steel is harder  to grind and to form a burr.  It takes more skill to sharpen knives made of these tyes of steel, but I don't know if that's the whole story.

I'll keep you posted as I conduct my experiments.

Last night I remembered I had a knife blade that I hadn't sharpened.  Some years ago my daughter got me one of those Gerber tools that has a pair of needle nose pliers, a saw, screw driver, and so forth all in a small portable device that fits in a belt pouch.

I looked at the knife blade and tested it for sharpness.  It has one small nick near the tip but otherwise would slice through paper but not shave hair too well.  I decided to take the Tormek honing wheel to it.  It made the edge shiny, the scratch pattern remained but as usual the metal between the scratches was smoother.  It improved its ability to slice paper and shave hair.

[grepper]

I haven't been able to figure out why I can't get some knives as sharp as others.

Did you put one of those knives under the microscope to try and see what is actually happening?  I know for me at least, when that happens I stick with a rougher wheel longer, turning the knife frequently.  Sometimes it seems to take a lot longer, even at 300 grit, than I would think.

On very dull knives I get the idea that it's taking a while to actually make the hollow bevel caused by the wheel, and when the thing is not getting sharp I'm guessing that I'm not getting to the actual edge.  It would be so cool to actually see and understand what what happening then.

I will be interested what you find out when you scope one of them! 

[Herman Trivilino]

On very dull knives I get the idea that it's taking a while to actually make the hollow bevel caused by the wheel, and when the thing is not getting sharp I'm guessing that I'm not getting to the actual edge.  It would be so cool to actually see and understand what what happening then.

Yes, Mark, I have verified with the scope that that is exactly what's happening.

However, even when I'm sure I've ground all the way to the edge and eliminated the burr, some knives are just sharper than others.  I'm thinking it's the quality of the steel and edge angle.

To rephrase what Ron Hock said, I've come up with three questions you ask about a knife.

1. Is it corrosion resistant?
2. Is it easy to sharpen?
3. Does it hold an edge well?

You can get an emphatic "yes" to, at best, only two of those three questions.

So, for example, today a friend has brought me a knife to sharpen.  It's obviously highly corrosion resistant as it's a kitchen chef's knife and despite years of use is almost as shiny as chrome and the surface is uniform in appearance with no discolored spots or portions.  It's had it's edge broken off along most of its length because he attempted to sharpened it with one of those cheap devices like you might see on the side of an electric can opener.  But in the places where the edge is not broken it appears to still be pretty sharp.

So my guess is that this is hard and brittle steel meant to hold an edge well.  If my theories are correct this will be a difficult knife to sharpen.  We shall see when I give it a try tonight.

[Rhino]

2. Is it easy to sharpen?
3. Does it hold an edge well?

I miss the hunting knife I had as a kid.  It was rusty.  The leather handle was moldy.  But it was sharp and easy to sharpen.  I sharpened it on the bottom of a crock pot, I sharpened it on a stone in the wild.

The only thing I have like that now is my Gransfor axe.  I used it to chop up 4 lobsters for the fire last year.  I saw it rust right before my eyes in less than 15 minutes in seawater (from the lobsters).  Polished it right up immediately.  Some discoloration but not bad.  I can live with it.

[RobinW]

Herman

What jig do you use for the utility knife blades?

(The amount of blades I've used over the years - short use and then binned - would have paid for a few Tormek jigs!)

[Rhino]

I use the small knife jig for the utility knife blades.  Works fine.  The SVM-45.

[Herman Trivilino]

I use the small knife jig for the utility knife blades.  Works fine.  The SVM-45.

At what bevel angle?

[Rhino]

Regarding the bevel angle, I don't remember but I thought there was no problem if you use the small knife jig and clamp at the first stop.  I hope to have time to check this weekend for you.

I was also thinking, if you want to take a lot of the human skill out of this, you can clamp the small knife jig into the chisel jig.  I'll check this weekend to see if it is possible too.

[Herman Trivilino]

When you refer to the small knife jig are you still talking about the SVM-45 or the new SVM-00?

[Rhino]

I should have been more clear.  I was referring to the SVM-45. 

My utility blades are trapezoidal and .75 inch from the sharp edge to the non sharp edge.

As I said earlier, I remember clamping it to the SVM-45 and sharpening it.  I'll double check this weekend.

I am looking at my utility blade right now.  It is wider (from the sharp edge to the non sharp edge) than my paring knife or about the same as my paring knife.  I certainly sharpen my paring knife many times with the SVM-45 so I don't see sharpening a .75 inch utility blade as being difficult.

I do plan on measuring the angle for you this weekend if I can get to it.  I'll try putting the SVM-45 (with the utility blade) into the chisel jig too.  Just for fun.