Sharpening for push cuts

[UnixDork]

I hope this is the correct place to post a question like this, it seemed to me that some of the testers (or just technical knife nuts) here would know.

Years ago I went to a company that sharpened blades to drop off a diamond blade. This place sharpened everything from scissors to cutter heads for milling machines and who knows what else. On a huge machine in the shop was a ~5' long blade being sharpened. It was mounted in a jig and was being stroked across a stone by the machine. I later found out this was a blade that goes into a hydraulic press for cutting paper. I've always wondered about the particulars of a blade like that considering how high the pressure is when it's forced into a big stack of paper. I did some searching on the net and found out these kinds of blades are made from some typical knife steels (52100 and D2) as well as other not so typical steels and tungsten carbide.

Seeing as how the steel doesn't seem to be too much of a factor, (correct me if I'm wrong) is there a way to sharpen or even bevel a blade to optimize it for push cutting? The blade I saw in that shop looked almost like a planer blade, it was chisel ground.

 

[kamagong]

For push cutting, a highly polished blade is desirable. I'll leave the rest to the experts.

 

[knife saber]

I would think that the finest, thinnest edge you could reasonably get would be the best possible. The other part of any kind of cut is obviously the medium you cut through - in a fairly consistent medium like stacked sheets of paper, using a consistent method of applying force (the hydraulic press), you minimize the variables that can cause unwanted damage to your blade, such as lateral movement, changing density/hardness/abrasiveness of the medium, etc. So the answer is (as it seems to be for all things) the perfect push cutting blade is defined by what is being cut and how it is being cut. Once you have those factors (and all the associated ones) well-described, you can determine what type of edge is best.

 

[V10011011]

I like carrying one scary sharp knife. Its possible to chisel grind it down to 17 degrees and get a surgeon's scalpal of a knife. Style over function.

 

[Grapevine]

Those paper cutting blades are also usually brought down on the stack of paper in a diagonal fashion, like a guillotine, so the action is actually a little more like a slicing cut rather than a straight push cut.

 

[Stockman]

Those paper cutting blades are also usually brought down on the stack of paper in a diagonal fashion, like a guillotine, so the action is actually a little more like a slicing cut rather than a straight push cut.

This is correct, I have 2 Paper Guillotines that use tungsten carbide tipped blades. The paper is clamped first at between 1000 to up to 3000 psi depending on the paper being cut and the blade slices the paper stack in a sideways motion at about a 30 degree angle. The blades are chisel ground with a 22 degree primary and a 20 degree secondry bevel and get sharpened every 2 weeks. The standard steel blade ( not tungsten tipped ) last only 2 - 3 days before they are blunt.

 

[UnixDork]

This is correct, I have 2 Paper Guillotines that use tungsten carbide tipped blades. The paper is clamped first at between 1000 to up to 3000 psi depending on the paper being cut and the blade slices the paper stack in a sideways motion at about a 30 degree angle. The blades are chisel ground with a 22 degree primary and a 20 degree secondry bevel and get sharpened every 2 weeks. The standard steel blade ( not tungsten tipped ) last only 2 - 3 days before they are blunt.

Wow, thanks for the info.

 

[Ebbtide]

Forged from one of those steel papercutter blades


I think it is 1050.
It takes a polished edge really well.
Isn't the technical term for that kind of cut called a shear?