Edge Angle

[Ric Albano]

What am i doing wrong?

1) I set my 10" Wenger chef's knife at about 17 deg which is about what i found as the factory edge using the sharpie.

- Using my left arm it grinds the edge almost right on the original bevel, but when i reverse the jig to flip the knife and use my right  arm the edge appears to be grinded about half a mm more than the factory bevel and it is noticeable when you compare the two sides under the light

- The tip is more evident the edge angle is off as one side looks more grinded than the other and looks off center

3) On a few knives i noticed the edge closer to the handle of the knife (ricasso) is deeper into the blade or rounded into the blade of the knife than the rest of the edge

Help!

[Mike Fairleigh]

The knife jigs don't center the blade exactly on the center axis of the jig, and the thicker the blade, the more off-center the blade will be.  This is the only true flaw I can see with the current knife jigs.

[Jeff Farris]

KSMike is right. The fact that the blade is not perfectly centered shows up in extremely thick blades, and also in extremely thin blades.

In cases where it is critical that the bevels be exactly the same, take the knife out of the jig and turn it over, when switching from one side to the other.  It will be necessary to reset the angle, but the adjustment should be minimal.

[tb444]

Also note that not all knives are ground symmetrically, or designed to be. Following the factory bevels on each side is a good start. putting a 50/50 edge on a 70/30 ground knife can lead to steering issues, but these types of edges tend to appear on japanese double bevel knives

[RJM]

Folks,

As much as I hated to admit this to myself: In my opinion, Tormek does not truly have a Knife Jig. A jig is a type of custom-made tool used to control the location and or motion of another tool. A jig's primary purpose is to provide repeatability, accuracy, and interchangeability.  A jig is often confused with a fixture; a fixture holds the work in a fixed location. A device that does both functions (holding the work and guiding a tool) is called a jig. An example of a jig is when a key is duplicated, the original is used as a jig so the new key can have the same path as the old one.  There are many types of jigs, and each one is custom-tailored to do a specific job. Some are made to increase productivity through consistency, to do repetitive activities or to do a job more precisely.

I am sure that there are many of you who will disagree with the above definition.

For the most part I enjoy the Tormek. Having said that, I can assure everyone that if you take the craftsmanship out of knife sharpening using the Tormek you will have a mess.

To everyone, Please have a blessed New Year!

[jeffs55]

I agree and wondered what I was doing wrong all this time. Come on Tormek! For this kind of money we should get more. Like a real jig.

[Jeff Farris]

By RJM's definition, you would need a different "jig" for every knife you own or sharpen for someone else. Does that really sound practical to anyone? In my opinion, the Tormek jigs, including the knife jig, do exactly what RJM defines as the purpose of a jig, that is to control the motion of the workpiece (knife) and its relationship to the cutting material (grindstone). Does the knife jig control the knives absolutely, in a manner where the user is just a replacement for a servo motor? No. Does it provide the means to sharpen every blade ever designed from the tiniest pen knives to samurai swords? No. But, it does give you the means to control a huge range of sizes in a manner where most errant motion is minimized if you use the jig as it is designed.

There's still some craftsmanship involved in sharpening a knife on a Tormek. You have to pay attention to what you are doing, you have to follow directions, and you have to practice a few times before you can do it perfectly.

Going back to Ric's original issue, Although Mike brought up the issue of centering, I don't think that is Ric's issue. A Wenger chef's knife should be of a thickness that would be very, very close to centered in the jig. From what Ric has written I think he is not rocking the jig on its axis, but is shifting it laterally. That is what I most commonly see when someone says "the angle gets wider at the tip".

[Justin]

There's still some craftsmanship involved in sharpening a knife on a Tormek. You have to pay attention to what you are doing, you have to follow directions, and you have to practice a few times before you can do it perfectly.

I agree that the knife jig does actually perform as a jig, but it's certainly not the best solution for the problem. The problem with a knife edge is that can be seen as a "dynamic edge", in so much that almost all knives curve and to differing degrees. The answer to the problem is if the knife edge is always at the correct angle whenever presented to the stone. At the moment i am leaning toward the idea of the tool rest or the base of the scissor jig being the basis for a much more reliable jig.  IMO!!

[Jeff Farris]

At the moment i am leaning toward the idea of the tool rest or the base of the scissor jig being the basis for a much more reliable jig.  IMO!!

For some exotic profiles you might be right (although I don't see how a platform is a better solution). But, for the vast majority of knife profiles, the knife jig is the correct tool to keep a consistent bevel along a curved edge.

[Justin]

For some exotic profiles you might be right (although I don't see how a platform is a better solution). But, for the vast majority of knife profiles, the knife jig is the correct tool to keep a consistent bevel along a curved edge.

The reason i like the tool-rest idea is because ALL focus is at the point of contact with the stone. As long as the blade is flat on the rest it can only cut at the set angle. This removes all problems with the angle drifting near the tip of the blade. The problem i see with the knife jig is that the angle is only governed by centre point leaving the extreme ends open to error.

[Herman Trivilino]

When I think of jigs I think of the devices I use with my table saw to make precise repeatable cuts at the right place and at the right angle. No matter how well the jig is designed, the operator's role is crucial.

And no matter how well a jig is designed the work I do with it can almost always be beat with a production-quality machine designed to do the same thing faster and better.

Things are always a trade-off between faster, better, and cheaper. You can have any two of those, but only at the expense of the third.

[Jeff Farris]

The reason i like the tool-rest idea is because ALL focus is at the point of contact with the stone. As long as the blade is flat on the rest it can only cut at the set angle. This removes all problems with the angle drifting near the tip of the blade. The problem i see with the knife jig is that the angle is only governed by centre point leaving the extreme ends open to error.

Your concept only works if the blade is flat. With a blade that tapers (as most do), your pressure points and points of contact with the plate will alter the angle.

I'm also guessing that you haven't actually set a table on the machine with an angle appropriate for a knife blade and tried this yet. Unless the table is very, very narrow (like the width of the stone) interference with the case or handle is a constant problem. Also, at the thin angles desired on knives, the table has to be very thin at the edge or the gap between the table and the grindstone is significant.

[Justin]

Your concept only works if the blade is flat. With a blade that tapers (as most do), your pressure points and points of contact with the plate will alter the angle.

I'm also guessing that you haven't actually set a table on the machine with an angle appropriate for a knife blade and tried this yet. Unless the table is very, very narrow (like the width of the stone) interference with the case or handle is a constant problem. Also, at the thin angles desired on knives, the table has to be very thin at the edge or the gap between the table and the grindstone is significant.

Yes blades with funky bevel/profiles could cause a problem, it does on the Edge pro but is do-able.

Not sure what you mean "table" is that the tool rest? True i haven't set it up as i'm still unsure what is the best piece of kit to purchase without wasting money. I have used the knife jig but unfortunately really didn't like it, hence looking to manufacture an alternative.

[Ric Albano]

What technique would you suggest then, where

"the angle gets wider at the tip".

rocking the jig on its axis, but is shifting it laterally

I lift my elbows straight up causing the tip to lift.  If i glide the knife laterally the tip widens without sharpening

[Justin]

What technique would you suggest then, where

"the angle gets wider at the tip".

rocking the jig on its axis, but is shifting it laterally

I lift my elbows straight up causing the tip to lift.  If i glide the knife laterally the tip widens without sharpening

Here's Jeff demonstrating/instructing use of the knife jigs. Move to 4m:40s point, does this answer your question?

http://www.youtube.com/watch?v=fYURcwkKGPs