Why are my blades tilted in the clamp?

[Gib Curry]

Thank you Sir. Your post on the knife sharpening class you took inspired me to find a class at the Phoenix Knife Shop, which I am going to take next month. I have never been able to get anything resembling a sharp edge by hand, but the knowledge I am gaining here is starting to make me think I might be able to get closer with some instruction. I also appreciate you saying you fumble with the math. Perhaps you might clear something up for me. In the picture above it shows a cant to the left of 3.2 degree. If I am figuring it right, and that is a big if, it seems to me that in order to address a 20 degree edge correctly I should have the left stone at 16.8 and the right at 23.2. Is that correct or am I off my rocker?

Let us know how the sharpening class goes. I was pleasantly surprised how much it helped me WE sharpening. And it is also true that the WE sharpening gave me something that helped me better myself free hand.

I can’t tell you how happy the other guys jumped in to explain the angle conundrum with FFG blades.

Your question is, obviously, very timely for all of us. Thanks for speaking up.

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Great information everyone…Thanks a bunch.

For Now,

Gib

— Sent via HTC One using Tapatalk.

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For Now,

Gib

Φ

"Everyday edge for the bevel headed"

"Things work out best for those who make the best out of the way things work out."

[Joel Casto]

One thing that I notice on my WE, and I assume all do, that can cause the blade to cant left is the clamping action itself. As the bottom screw is tightened it creates incredible bending (and clamping) force, moving the uppermost part of the clamp jaws to the left. That movement is amplified if the top screw is not sufficiently tightened. Clamp and watch the blade closely as the bottom screw is tightened and you will see the blade rotate to the left as the clamp jaws flex to the left. I don’t see this as a problem. Rather, the point is that the lower screw exerts incredible bending and clamping force and as it does it also torques the clamp jaws to the left. This makes sense – as the bottom of the right jaw moves to the right, the top must move to the left. To limit that rotation, the top screw must be tightened completely, and securely.

I think. Or am I missing something?

[Robert Olmstead]

One thing that I notice on my WE, and I assume all do, that can cause the blade to cant left is the clamping action itself. As the bottom screw is tightened it creates incredible bending (and clamping) force, moving the uppermost part of the clamp jaws to the left. That movement is amplified if the top screw is not sufficiently tightened. Clamp and watch the blade closely as the bottom screw is tightened and you will see the blade rotate to the left as the clamp jaws flex to the left. I don’t see this as a problem. Rather, the point is that the lower screw exerts incredible bending and clamping force and as it does it also torques the clamp jaws to the left. This makes sense – as the bottom of the right jaw moves to the right, the top must move to the left. To limit that rotation, the top screw must be tightened completely, and securely.

I think. Or am I missing something?

Incredible information! And thanks so much everyone for taking the time to respond. I agree that as the bottom screw is tightened it moves the blade even farther. I did some checking with the angle cube attached as I tightened the bottom screw and it definitely moves the blade as it is tightened. I am not worried about the fact that it moves, only how to adjust the stones. Now that I understand that a little better life is moving along nicely 🙂

[Josh]

I have not noticed the blade moving before! I will have to keep an eye on that next time to verify.

One thing that may be the issue is that people are clamping incorrectly… Before you clamp you should make sure that your bottom screw is protruding about the same width as the spine of your knife. then you clamp the top screw as tight as you can. At this point you will notice that the bottom screw is holding the jaw out so that the gap in the middle of the vise is almost parallel the whole way down (it will be slightly smaller at the bottom, but not much). this is when you tighten the bottom screw until the gap is perfectly parallel all the way from top to bottom.

give this a whirl and see what you think…

[tcmeyer]

Having a blade move on you during the clamping process says in big, bold letters that it ain’t being clamped right!

With FFG blades, I always hold the left flat of the blade flat against the left jaw of the vise. This is a positive fixed position that you’ll be able to repeat. Shims and pads and such are not repeatable without a lot of care and measuring.

With the blade held flat against the left jaw, I loosen the top screw and then pinch the top edges of both jaws together, holding them both flat against the blade. I then take up the slack in the top screw, taking care not to move the right jaw. With the top screw very lightly tightened, I run the bottom screw in until it makes contact, then make one-quarter to one-half more turns to tighten the vise. This works with most FFG blades, but thick blades may be beyond the range of the screws.

The following drawing shows the general idea. It shows an FFG blade with a 5.3 degree grind, but that might also be beyond the range of the vise. I have done knives up to 4.4 degrees.

And the blade does not move!

Attachments:

• FFGviseset-up.jpg

[Joel Casto]

Your drawing illustrates my point. As the clamp is tightened the blade leans to the left off vertical as shown in your illustrations. I don’t think it has anything to do with right or wrong, just physics. And it’s not just the blade, the jaws themselves flex to the left. You can clamp a quarter in it and it flexes or leans left.

[Josh]

Hey Jordan, can you explain this a little bit more? Wouldn’t +1 and a -9 be a spread of 10 degrees? not 8? I just caught this as I did a video on this… maybe you can explain it better lol. Thanks!

[Josh]

As I was thinking about this more, I think you can do it either way…

1. either you can take the higher number and subtract the lower number, then divide that number in half to figure the cant, or

2. you can add the two numbers (1+9 = 10) and divide in half (5) which will give you the target of what each side should actually be at. So the difference between ‘5’ and what it truly is ‘1’ or ‘9’ is a spread of 4 degrees. And you adjust accordingly…

what do you think?

[Roman]

I strongly believe that Jordan’s math is correct. One angle clockwise and second is counterclockwise, so it is positive 1 and negative 9. the sum is negative 8, adjustment is half, meaning 4 per side.
But your method is much more simple. I will try it next time.
Thank you to both of you.

[JS]

As I was thinking about this more, I think you can do it either way…

1. either you can take the higher number and subtract the lower number, then divide that number in half to figure the cant, or

2. you can add the two numbers (1+9 = 10) and divide in half (5) which will give you the target of what each side should actually be at. So the difference between ‘5’ and what it truly is ‘1’ or ‘9’ is a spread of 4 degrees. And you adjust accordingly…

what do you think?

Yeah basically you’re just subtracting the lower number from the higher number every time and dividing in half, then adjust your angles accordingly. I put the positive and negative signs there to give a visual of what you’re seeing when you put the cube on the blade. The result should actually read -8/2 = -4 which technically means that the centerline of the blade is leaning 4 degrees towards the negative direction (left). -8 is just the sum of +1 and -9.

[tcmeyer]

Aargh! The AngleCube gives you the angles relative to a zero, but you can’t treat them as positive and negative numbers! You are reading values which are simply above or below the zero reference. Consider this: If you zero the AngleCube when it’s lying on its side, it will read 91 degrees on the left side and 81 degrees on the right, for an included primary grind angle of 10 degrees. The centerline of the blade is therefor displaced five degrees from the faces. Since the left face says it’s at one degree, that means the blade is leaned 4 degrees toward the left side.

Set your angles at 4 degrees lower than nominal on the left and 4 degrees above nominal on the right.

[Daymon Haight]

So, I have two questions.

1) Would this also apply to other grinds like hollow grounds? As long as the clamps are on the flats?

2)What if the blade cants to the right, instead of to the left? Same math and everything, just for the right side?

I ask because I can’t for the life of me get this ZT 0560CBCF centered or even near centered in the clamp. It’s canted off to the right and you can visually see it. Maybe I’m doing something wrong?

[JS]

I’m not treating the angles themselves as positive and negative numbers but in the sense of a number line where for example 0 is in the middle and everything to the left of zero is negative and everything to the right is positive. No matter how the angle cube is zeroed, measuring this way you’d still get a sum of -8. This method works and the cad backs it up. Everyone may understand it in a different way or have their own way of doing it. As long as the results are the same, then that’s fine. If it’s too complicated then butt the left side flat against the jaws every time and you know that side is always zero. Measure the right side and divide by two. Common sense will tell you to move the left arm inward X number of degrees and the right arm outward or further away.

[tcmeyer]

So, I have two questions.

1) Would this also apply to other grinds like hollow grounds? As long as the clamps are on the flats?

2)What if the blade cants to the right, instead of to the left? Same math and everything, just for the right side?

I ask because I can’t for the life of me get this ZT 0560CBCF centered or even near centered in the clamp. It’s canted off to the right and you can visually see it. Maybe I’m doing something wrong?

My answers: (1) If the flats are parallel to each other, the blade should clamp vertically. If not, then yes, but I don’t think you’d be able to get a valid reading to base it on.

(2) Because the left vise jaw is always vertical, no symmetrically ground blade should ever cant to the right. If it does, it’s not clamped correctly. An asymmetrical grind wouldn’t apply either.

[tcmeyer]

I’m not treating the angles themselves as positive and negative numbers but in the sense of a number line where for example 0 is in the middle and everything to the left of zero is negative and everything to the right is positive. No matter how the angle cube is zeroed, measuring this way you’d still get a sum of -8. This method works and the cad backs it up. Everyone may understand it in a different way or have their own way of doing it. As long as the results are the same, then that’s fine. If it’s too complicated then butt the left side flat against the jaws every time and you know that side is always zero. Measure the right side and divide by two. Common sense will tell you to move the left arm inward X number of degrees and the right arm outward or further away.

If you add +1 and -9 and get 8, you must be adding them as positive & negative numbers. They simply tell you how far on either side of a particular point they fall. One degree to the right and nine degrees to the left. Ten degrees apart.

[Author]

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