Utility Knife Blades

[RobinW]

I would be delighted if Rhino could provide some set up settings and angles. I have just got my SVM45 and done some spokeshave blades as posted elsewhere, including my scary moment!

I didn't have time to do it properly, but I also had a go with a trapezoidal utility knife blade, 0.75 inch deep.

If I pushed the blade against the stops inside the SVM45, I didn't have enough blade protrusion to use the angle master. If I mounted the blade protruding a bit more, there was barely enough for the angle master and also when sharpening, the tips of the blade were flexing. This resulted in the centre area of the edge being ground more than the tips, so a slightly concave edge. (Not a critical point on a blade which will probably just be used for somewhat imprecise work!)

I couldn't get the jig set up so that I was grinding the full depth of the original bevel. I was in danger of grinding the front of my just paid for jig! I did manage a very small depth bevel, on both sides, and it was certainly sharp.

Strongly advise that anyone trying small width blades to sharpen away from the edge  - see my scary moment elsewhere!

[Herman Trivilino]

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 can't figure how that's possible.  You must be grinding at a very large bevel angle.

[Elden]

I messed around with a blade from a Husky folding utility knife. It is a little smaller than the regular size utility blade. It is marginally workable in the SVM-45. I have barely gotten into the jig along the way. If the blade is positioned perfectly (quite a ways out from the stops), the wheel doesn't get into the jig.

I had to shim the blade as the thickness was too thin for the jig to clamp the blade. Used a couple thicknesses of thin cardboard for clamping. The shims need to be a little thicker as the blade could still move at times, hence the wheel getting into the jig.

The bevel angle is very close to the original bevel. I used the permanent marker approach.

If I was really serious about doing utility blades, I would probably make a permanent shim that would form an extended stop for the back of the blade to be against, as well as for the thickness.

I think the regular size blades should be easier done due to the larger width of the blades.

[RobinW]

I have spent some time today trying a couple of utility blades. They are 0.63 mm (0.024") thick; 61.5 mm (2.42") the long side of trapezoid, 33mm (1.3") short side of trapezoid and 19mm (0.75") front to back.

The bevel is 2.52 mm (0.1") wide.

As the blade is 19mm front to back, when it is inserted fully into the SVM45, the amount protruding is 6mm ( 1/4 ").

Setting the SVM45 to the zero position on its adjustable stop, and moving the universal support bar up and down it was not possible to align the back of the blade bevel with the stone (as per Tormek instruction sheet). This was due to the SVM45 fouling the wheel. So I made the best bevel contact I could with the SVM clear of the wheel. There is insufficient blade protruding to use the angle master properly. Marked the bevel with marker pen and started up the machine. The front edge of the bevel started to shine up. Turned the jig over to do the other side, and lo and behold, it started to grind the sloping face of the SVM45!!!!!!

Reset it so that the angle was slightly steeper and both sides of the SVM would be clear of the wheel and had another go, and got bevels about 1mm wide.

I got a re-sharpened blade, but wasn't convinced it was as good as an original. There is some difference along the edge of the blade due to the freehand element involved when using the SVM45.

I then started doing a technical drawing to see what minimum angle could be achieved using the same utility blade without fouling the SVM45 on the wheel. Then it occurred to me what is the original bevel angle that I am trying to match?

With blades 0.63mm thick, and a bevel width of 2.52mm, this calculates as 7.12 degrees or an edge angle of 14 - 15 degrees.

I don't think it's worth the effort considering the price of new blades, but I know I can get out of a hole if I was stuck for a usable blade.

[Herman Trivilino]

With blades 0.63mm thick, and a bevel width of 2.52mm, this calculates as 7.12 degrees or an edge angle of 14 - 15 degrees.

There's a microbevel that you can't see with the naked eye.

[Rob]

I've got a pack of Stanley blades (double ended) that I bought with a Stanley knife in 1989, I'm down to the last blade (first side).  I think there were ten in the pack originally.  So 2013-1989 that's 24 years for let's say £5 in cost

Those blades have cut bitumen roofing felt on three shed roofes, cut plasterboard in two house renovations and all manner of woody things over the years

For me, I'll buy new ones when the last one finally expires.  I don't think the Tormek is right for some jobs. This is probably one of them

[Herman Trivilino]

We used to go through them a lot faster than that on a carpentry crew.  It was really the only tool we usually carried that had a sharp edge on it, and so it got used for all manner of things.  A nail can be used, by the way, to change the blades.  No screw driver needed.  Just place the head of a common nail in the screw slot and turn the nail.

I don't believe the Tormek can be used to come anywhere near the sharpness of a new one.  The bevel geometry is complicated, the edge angle is small, and the edge itself is very true.

[grepper]

You may be right Herman that maybe you can't get them sharp as new, I don't know, but they fit into the knife jig just fine as I remember, and I was able to get them very sharp.  They were dull, but now they seem really pretty sharp.  Plenty good enough so you won't think they are dull.  I don't remember it being any sort of a problem.   I don't use them much, so for me it worked out great.

I would suspect if you used them every day and went through a pile of them, it might not be worth sharpening them and just switch them out with new ones.

[Herman Trivilino]

You must have barely inserted them into the SVM-45.  I don't recall having done that, but it was some time ago that I tried to sharpen them.

[Rhino]

Thanks everyone for sharing.

I got the Tormek out.  It was a busy weekend so I did not get to do actual grinding but it help bring back my memory.  I don't have a permanent setup for my Tormek so it takes me a little longer to set up the system.  Another disclaimer, I am just telling you what I did and I in no way recommend anyone follow.  You have to make your own decision as to safety.  Once I saw the system the memory came back.

I used two blades as support (I call them support blades from now on).  Stuck them all the way into the back of the SVM 45.  Then I put the blade I wanted to sharpen between the two support blades.  That gives you enough thickness to clamp.  I clamp about 1/3 of the utility blade (the blade I want to sharpen into the SVM45 only.  Roughly until the U shaped cutout just disappears behind the SVM45 clamp.  You can't really see this because the two support blades would block your vision.  But I am just giving you an idea. 

To align the utility blade with the SVM45, I use a transparent ruler placed against the SVM45 and I align the blade to be sharpened to it.  I won't go into details since you probably have your own aligning method. 

Then I put my SVM45 against my grindstone which I seem to recall is about 243 mm diameter.  I measured about 12 to 14 degrees with my angle device.  Meaning, at least to me, I seem to be able to grind at 15 degree or 20 degree. 

I don't remember grinding with the stone coming towards the blade or away from the blade back when I did it. I did not grind this weekend, just checked the setup. My guess is that I would have ground with the stone coming towards the blade.  Since I can set a 20 or 15 degree angle, it is not a problem.  On my setup, I can flip the SVM45 and sharpen the other side easily.

It was an intellectual exercise and I remember the product being as sharp as a new blade.  But then, utility blades are not ultrasharp.  My kitchen knives are sharper. 

I was not too worried about the fine points of blade angle or symmetric grinding although I think it can be achieved if you measure carefully and grind without putting too much pressure to distort the blade or the clamping setup.  I did it for fun a while back.  Come to think of it, utility blades make good shims.  I'll dull a few used ones the next time to use as shims on my SVM45. 

I will continue to buy utility blades instead of sharpening them.

[Herman Trivilino]

Excellent innovation there, Rhino.  I can see how that would work nicely.  If ever I need to sharpen one I'll do it that way.  It'd be interesting to see what the edge looks like under a microscope.

[grepper]

I've used two strips of metal clamped into the knife jig  to produce an extended thin clamp a bunch of times with small bladed knives.  For the most part it seems to work well enough even though on some blades they have a tendency to pop out.  But then on small blades, I don't find it necessary to have a completely firm clamp, just some assistance from the jig to hold the bevel angle.  It just requires a little practice, skill and understanding the setup, but then it works just fine.

If the SVM-45 was just a little thinner with a less obtuse angle at the end of the clamp, it would solve a lot of the small knife problems.  I guess it's the size that it is for strength owing to the fact that it's aluminum.  I've wondered if a thin, possibly titanium grip for the end of the SVM-45 might work.