Blade angle on the vise

[developer (ChrisB)]

Newbie here, purchased the PP1 last month personally from Bob Nash here in Nevada, a peerless and most pleasant experience.
Added the 800/1000 on his advice and did so far 7-8 knives. The number of Band-Aids used since then bears witness to the efficiency of the system.
Over the years I have used almost every sharpening system (seriously!) and later got rid of them. My free hand stank to high heavens.
I’m very happy now with the results.
The marks on the base rod are hard to see, so they were never used, preferring instead to use the angle cube, making sure every time that both sides are symmetric, no problem here. But something strange popped up. It turns out that by attaching said cube to each side of the blade (and the unit is perfectly level and both vise tightening screws at the minimum turn) the readings are very different(!), like a 1:4 ratio.
I can not figure out what is causing this. On the other hand may be it is irrelevant, given that each arm is adjusted to the cube readings.
I have a notion that this subject was brought up somewhere but can’t find it again.
If there is a more educated user in south Clark County, I’ll be ready to sweep your shop in exchange for tutoring.
Thanks in advance.

Working to make knife.wickededgeusa.com a great forum!

[developer (ChrisB)]

Are you using anything to wrap around your blade when you clamp it in the vise? This happens with fully flat ground knives where there is no flat surface for the vise to hold. What needs to be done in that case is to wrap the spine with a thick layer of tape, a piece of leather, chamois, something to fill the gap and compress with the vise around the blade to keep it centered.

Working to make knife.wickededgeusa.com a great forum!

[tcmeyer]

thenolden: I’m trying to understand what you mean by a 1:4 ratio. I finally inferred that you are reading maybe 0.9 degrees high on the left side and 3.6 low on the right. As MesaCranker suggests, this is probably just the result of the blade clamping up out of plumb – very typical for Full Flat Ground (FFG) blades. You can try to reclamp the blade using tape, leather or whatever, trying to get closer to plumb.

Or you can simply adapt to the situation, as you already have readings from the sides of the blade that tell you how far off of plumb you are. For instance, using the 0.9 and 3.6 degrees I posited, you know that one face of the blade is 2.7 degrees displaced from the other side. You can confirm this by holding one side flat against a flat surface, then after zeroing your AngleCube on the surface, check the top face of the blade by placing the AngleCube on it.

Knowing the angle between the two sides is important, because now you know that each face is offset from the centerline of the blade’s cross-section by 1.35 degrees. If the blade were plumb in the vise, you’d see 1.35 degrees on each side, with the left high and the right low. Since you are getting 0.9 degrees on the left, you know that the centerline is leaning 0.45 degrees to the left. To match your bevels, set your left rod angle 0.45 degrees below your intended angle, and set the right rod angle to 0.45 degrees above your intended angle.

Dealing with the confusion caused by FFG blades has been the main driving force behind the move to the Gen 3 vise, which solves the problem completely. More or less.

Of course, if I misunderstood your problem in the first place, this is all just so much hooey.

[tcmeyer]

I made this a separate comment so as to not fully flummox anyone like me, who has ADD and whose eyes glaze over when a comment runs too long.

I’m a firm believer that the Gen II vise is fully capable of meeting the needs of the hobbyists here. That said, you should clearly understand how the vise works. Here’s a few starter points:

1. The left jaw is stationary and the right jaw holds the blade against it.

2. The right jaw is floating

3. The top screw is used to set the distance between the stationary jaw and the floating jaw. Do not use it to apply clamping pressure.

4. The lower screw is a JACK screw. It pushes the lower part of the floating jaw away, causing it to rotate about the top screw and creating clamping pressure at the blade. This is the heavy work.

4a. Do not over-tighten either screw. One half turn past contact with the lower screw should be more than enough. If it doesn’t, there’s something wrong with your clamping technique. Consider using tape. Small blades only need a quarter-turn.

5. Use the top and bottom screws to evenly clamp the blade between the jaws. Properly set, the floating jaw should make contact over its entire area against the blade. The tightening process may tend to move the lower part of the floating jaw away from the blade,

6. Never mount a blade with jaw contact only at the bottom of the jaws (along the spine). It may pop out of the jaws unexpectedly.

For FFG blades, I try to hold them flat against the left jaw. A blade with 3.5 degrees of displacement between sides would ideally be mounted with the left side plumb (flat against the stationary jaw) and with the bottom of the right (floating) jaw kicked out about 3.5 degrees from vertical.

To visualize all this, put your key into the lower position (just makes this easier). Then insert the blade into position in the vise. Reaching over the top of the blade with your right hand, pinch the two jaws together so that they are both flat against the blade. This is a good time to set the position of the top screw. In any case, note the position of the floating jaw. Try to set your screws to emulate this position. It may take several tries as you mount a blade until you find the correct position of the floating jaw.

[developer (ChrisB)]

Thank you, thank you to both respondents.
First I’ll try the tape trick and then report the results.
Separately I’ll print out tcmeyer’s response, read it again very carefully and try to apply his very detailed instructions. It’s heart warming to see how devoted people are to the furthering of sharpening theory/practice and then share freely with others.
I didn’t mention on my initial posting that all the practice was done on decent (not beaters) kitchen knives.
Thanks again.

Working to make knife.wickededgeusa.com a great forum!

[tcmeyer]

I’m sorry, but I should have made clear that the method described by me for clamping and sharpening FFG blades is a matter of preference. The principle of using the vise, however, is not.

I recommend using a lubricant such as gun grease or anti-seize on the threads of both screws and on the tip of the lower (jack) screw. If you use anti-seize, use it sparingly – it will drive your wife nuts. It is also good practice to flatten or even polish the end of the lower screw, so as to remove sharp points which might dig into the surface of the floating jaw – a process called galling. Some newer vises have steel inserts to prevent such galling. Even so, it couldn’t hurt.

This has all been covered thoroughly in earlier threads, but I figured it was worth repeating. And I like to preach.

[developer (ChrisB)]

I hope this doesn’t come up too long. And also honors the replies received so far.
I just don’t get it..
I have at home a true 0 degree surface, verified at different points every time it’s used. I leaned 4 wide blade kitchen (Coricama, Sabatier, Eskilstuna, Forgecraft) knives, one at a time, making sure that the side lies perfectly flat against said surface. Using the the angle cube fully resting on the side, discovered to my surprise that not a single knife tapers equally on both sides. .
And not only that, but each reading is different when the same blade is propped on a perfectly level WE vise as compared to said perfectly level surface(?!).
Everybody knows that but me.
Now I can’t understand how this brings compensations on the angle of each arm when using the WE, given that the angle measurement is done just on relation to each side of the apex, which may not be the geometrical vertex of the blade but still creates an isosceles triangle for the cutting area. Which in turn doesn’t seem to be very relevant when one considers the single bevel knives (scalene) and/or the amazing results obtained by gifted free handlers who could never dream on working on a 0.5 degree tolerance.
I’m certainly not trying to be contrarian. An explanation/correction is appreciated. Or do like my wife and prove me always wrong.
Thanks for listening.

Working to make knife.wickededgeusa.com a great forum!

[Author]

Posts