Using the WM-200 Angle Master for Knives

[SparkyLB]

I received my SVM-45 knife jig a couple of days ago.  I can't seem to wrap my head around what seems to be a pretty direct concept. 

If I have a knife and I desire two, symmetrical bevel angles of 20° for a total included angle of 40°, I place my Angle Master on the BLADE (because the bevel is too small to get a good visual).  To what desired angle do I set the Angle Master?

I know on a single-bevel tool such as a chisel, the edge angle and bevel angle are the same.  I also know on a knife with two, symmetrical bevels, that the edge angle is the sum of the bevel angles.  What throws me off, is the depiction in the Tormek user's guide that shows the "edge angle" is an imaginary line continued from the bevel, but the WM-200 can not rest on this imaginary line, but must rest on the blade.  I know, I overthink things.     

I suspect that I simply set my WM-200 to 20° and let the mechanism sit on the circumference of the wheel and the blade itself, then flip the knife and do the same.  Then when it comes time for the stropping wheel, I keep the 20° dial in place, but change from 250mm to 220mm.  Is this correct?

Thank you, all!

I pray I'm the only silly man who struggles with this problem.   

[cbwx34]

I received my SVM-45 knife jig a couple of days ago.  I can't seem to wrap my head around what seems to be a pretty direct concept. 

If I have a knife and I desire two, symmetrical bevel angles of 20° for a total included angle of 40°, I place my Angle Master on the BLADE (because the bevel is too small to get a good visual).  To what desired angle do I set the Angle Master?

I know on a single-bevel tool such as a chisel, the edge angle and bevel angle are the same.  I also know on a knife with two, symmetrical bevels, that the edge angle is the sum of the bevel angles.  What throws me off, is the depiction in the Tormek user's guide that shows the "edge angle" is an imaginary line continued from the bevel, but the WM-200 can not rest on this imaginary line, but must rest on the blade.  I know, I overthink things.     

I suspect that I simply set my WM-200 to 20° and let the mechanism sit on the circumference of the wheel and the blade itself, then flip the knife and do the same.  Then when it comes time for the stropping wheel, I keep the 20° dial in place, but change from 250mm to 220mm.  Is this correct?

Thank you, all!

I pray I'm the only silly man who struggles with this problem.

You are correct, if you want a 20 dps (degrees per side) angle, and you're going to set the  AM (Angle Master) on the side of the knife, in a perfect world, you would set the AM at 20 deg.  I'm not sure what picture you're referring to, I've attached one that may help.



But, I say "in a perfect world", because in the real world, the AM does not account for any blade taper from the spine of the knife to the edge.  (See this thread).  So, you have to adjust for that too.  That is why I recommend you consider using a calculator to set the angle for knives... (there are examples in my signature)... it automatically accounts for this, and sets the correct angle.

[SparkyLB]

Thank you, cbwx34.  I am referring to the picture in the introductory portion of the manual.  I think it might be first picture in the book.  I don't have the manual at the moment, but it's the pic. where alpha and beta are defined.  I was focusing on the wrong image.  Your picture directly answers my question.  Thank you. 

I appreciate your point that by design, the entire blade is sometimes beveled tapered for strength, notwithstanding the bevels ground at the edge to make it cut.  That would certainly change the bevel angle one is shooting for.  I'm quite new.  I'll look into the calculators.   

With every post I learn quite a bit.  There are many very sharp folks who contribute!

[aquataur]

(I´ll add to this thread. No point in opening a new thread on the very subject.)

I recently got into setting the Tormek with calculated values (T-USB) and I was puzzled how far off the angle master was. I had no explanation for that.

Now at least since Vadim entering the scene, you folks talk about fractions of a degree. I wondered how a blunt device like the angle master with controls that coarse can cater for this.

I now realize that I had used it intuitively (wrong) on the face of a knife with back-taper, fairly to the mid of the knife´s side.

There is not only (as mentioned earlier) an error introduced by the thickness of the blade (increasing with thickness), but also by choosing the wrong reference point:

As a matter of fact, probably only the most inner point of the unit, where the black plastic, the knife´s edge and the stone meet, is of any concern. In other words, measuring on the bevel (such as on a chisel that is straight throughout), which you would think has a consistent angle along its bevel, is wrong by a mile.
(thats what I did).

If something is that critical, it should be adressed by the maker so clear that it is beyond any doubt - which it isn´t.

A chef´s knife may have a single bevel (the edge bevel) approaching a millimeter in size. How can somebody possibly set a meaningful angle using the anglemaster on that?

Needless to say, my recent knifes (since I adopted Vadim´s protocol and setting the angles by calculating T-USB) were sharp at last.

Blessings to you guys who provide those programs freely.

[tgbto]

Not to beat a dead horse, but to underscore what @cbwx34 said : It would be OK for the AngleMaster to just be a tool for a quick-yet-very approximate setting of the angle.

What is not OK is the fact that it introduces a systemic error of half the blader taper angle.

It is well suited to single-bladed tools with a flat back such as chisels and planer blades. It should be avoided for all knives with a tapered blade where it can't fully rest on the edge.

[aquataur]

Short and concise.

I wish I had this information before I ruined all those knives.

[Ken S]

I wish I had this information before I ruined all those knives.

I don't quite understand. I have seen pro and con thoughts about the Anglemaster. I like it for broader, flat tools like chisel backs and plane blades. I have mixed thoughts about using it with knives, although I have seen two Tormek masters use it quite adeptly with knives.

I can't quite see how using an Anglemaster would have "ruined all those knives".
If one knife was not turning out as expected, why would one proceed with other knives before correcting the situation?

I do not intend to sound critical. I have made many errors and only hope to spare others some of my numerous pitfalls.

Ken

[Dutchman]

...
 why would one proceed with other knives before correcting the situation?
I do not intend to sound critical.
...

You are very mild in your response.

[aquataur]

With "ruining" I was probably over-egging the pudding. Their sharpness was less high than my disappointment.

f one knife was not turning out as expected, why would one proceed with other knives before correcting the situation?

Way back then (probably ten years ago) I did not have knowledge of all that great information (like setting the t-usb and all that) and all I had was the anglemaster - and I was obviously misunderstanding the information on how to use it, letting alone that it does not work well on knives from a start.

So it was quite obvious, that something was wrong, unfortunately there was no clue as to what.
So how can one possibly correct something that was not knowingly recognized as wrong, and not knowing of any other path to pursue?

As I said above, the manual should clearly explain the mechanism and the do´s and don´ts. Maybe it does today, but it didn´t back then. It is not enough to show a picture, which you can mis-interpret, you have to understand why.

I am a teacher, and preparing learning material is my daily work. People have to unterstand the underlying mechanisms and not mindlessly repeat a sermon, or they will never be able to react to an unforeseen deviation from the manual.

I have, after intensive study of this all, found a way to get my knives sharp, but this is not something you can automatically expect from somebody buying such a high-priced solution unbiased.

[cbwx34]

I agree with aquataur, and I've brought this up before.  This is an issue that Tormek should address, but as far as I know, they've done the opposite.

If you're given a device and told "this is how to set the angle", and don't realize the math behind it, (or more simply, how it works), you believe that it is giving you the correct result.  I did it, and I'm betting almost everyone else has too... more than once.

Of course, by now you know my answer.... <cough>calculator<cough>    (Perra's device will be another solution.)

[tgbto]

Thing is, it's not that it "doesn't work", rather that it throws the bevel angle off a couple degrees.

This shouldn't change a razor into a screwdriver, and fortunately the amount is always the same for a given knife. *But* :
- a 2.5 dps (5° total) difference is precisely the difference between being in the "carving knife" or "kitchen knife" category in the Tormek Manual, and to be consistent the target range should be much bigger than whatever error is built into the system
- if say, you have very good eyes and measure 35 degrees total (17.5 dps) with the WM-200 on a knife with a 4° total blade taper angle, then you will actually sharpen it at 31 total (15.5 dps). And next time you use the WM-200, if you haven't taken note of whatever the initial setting was, you may think it's 30 degrees,  and actually sharpen it to ... 26 degrees total. Not a good road to go down.

[3D Anvil]

I'm sure most of you know this already, but there is a pretty easy way to measure the angle of the primary grind.  It requires an electronic angle cube, which can be had for around $15.  All you have to do is zero the angle cube on a table, place the flat of the blade on the table, and then place the cube on the blade to measure the combined bevel angle.  Divide that angle by two and subtract that amount from desired edge angle and set the angle master to that number to get the desired angle.

Example: if you want an edge angle of 15° per side and the angle of the primary grind is 2° per side, set the Angle Master to 13° to get an actual edge angle of 15°.

Having said that, I don't use the Angle Master for knives anyway, because it's a bit of a blunt instrument even when you apply the correction.  I can't think of a good way to compensate for the location of the plastic bit on the blade.  It needs to be *directly* on the edge bevel to be completely accurate.

[aquataur]

I'm sure most of you know this already,

Well I didn´t I wasn´t even aware of such a device, but I admit I was not regularly browsing this forum for the past years.

there is a pretty easy way to measure the angle of the primary grind.  It requires an electronic angle cube

It became obvious in this context.

It [the angle master] needs to be *directly* on the edge bevel to be completely accurate.

This fact is not as obvious as it should be (as mentiond above), I learned it the hard way.

As I mentioned above, after all questionmarks have been resolved with the aid of you all in this discussion, I dropped the AM for knives. I also don´t see a need for an electronic angle cube. Setting the angle with the T-USB parameter is very easy and works with low-tech tools as it gets.

The problem with a primary bevel is how to grind it on the Tormek. We speak of angles probably below 10dps, which I have addressed here.

I believe the exact angle of a back bevel (primary bevel, relief) is not important, and AFAIK there is no agreed upon numbers for it.
BTW in Perra´s Angle Calculator Lite 1.4 the formulae under Edge and Bevel Calculation lets me estimate the back bevel´s angle quite well.

[Ken S]

When I started with my Tormek in 2009, the handbook and Jeff Farris' videos were our primary learning sources. Here is a link to Jeff's video on sharpening scissors:

https://youtu.be/HGFeBd8ZspM

Note his short cut for setting the bevel angle. Instead of trying to measure the very small scissors bevel with the Anglemaster, Jeff adds ten degrees and uses the broad surface of the jig platform as a reference for measurement.

For those concerned with the hollow grind of the Tormek grinding wheel, Ernie Conover suggests adding three degrees to the Anglemaster setting.

If an error of half the taper of the knife blade is troublesome, why not just correct the Anglemaster setting by two degrees? This should put the bevel angle within tolerance. If this is not close enough, dial in a more exact number.

I would probably use a kenjig or one of the computer apps; however, the Anglemaster can be dialed in for tighter accuracy if desired.

Ken

[tgbto]

Note his short cut for setting the bevel angle. Instead of trying to measure the very small scissors bevel with the Anglemaster, Jeff adds ten degrees and uses the broad surface of the jig platform as a reference for measurement.

Still, as explained, the AngleMaster is questionable even assuming you can measure the edge with sufficient accuracy. Moreover, the scissors in the video seem to be Fiskars one, with mostly untapered blades.

If an error of half the taper of the knife blade is troublesome, why not just correct the Anglemaster setting by two degrees? This should put the bevel angle within tolerance. If this is not close enough, dial in a more exact number.

Because then you have to measure the taper angle of each blade, or else you're adding a random (or at least eyeballed/inconsistent) correction. Why two ? and not 3.5 ? 1 ?

The AngleMaster is Tormek's documented way of *setting* an angle to a knife. Nowhere do they mention the blade taper angle having an impact, let alone how to measure it nor correct for it. It is a bad tool for setting an angle on most kitchen or hunting knives. They even go as far as making videos (such as the one referred to by @cbwx in antoher post) talking about the WM-200 along with knives that obviously make its use problematic.

I would probably use a kenjig or one of the computer apps; however, the Anglemaster can be dialed in for tighter accuracy if desired.

Again, the issue is not one of accuracy : if you use the angle master you're not setting the angle at the desired angle +/- whatever accuracy the tool has. Instead you're setting the angle at the desired angle *minus* half the blade taper angle +/- said accuracy.

The Tormek is intrisically a great tool for setting consistent (and precise enough) angles on most blades, when used properly. The AngleMaster is a *bad* way of using the Tormek to set an angle. Whether some people get sharp knives when using the AngleMaster is irrelevant as to whether or not it can set the apex angle you're targeting. What good is it if you end up with the wrong angle after having spent a lot of time removing metal that should have been left here in the first place ?

I think improving this flaw in the documented Tormek method is both simple and desirable, but we have to acknowledge there is a fundamental issue here, and not make it an accuracy question as was also done in the other "it doesn't matter" video.