I can only clamp at the heel, now tip is too wide!

This topic has 11 replies, 5 voices, and was last updated 06/07/2013 at 9:43 pm by cbwx34.

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06/05/2013 at 1:23 am #11985
cbwx34
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Ever have this problem? The only “flat spot” or good clamping position on the knife is near the heel, but doing that will mean the bevel at the tip can get too wide.

The tip I found (pun intended) is to angle the knife down in the clamp. As you can see on my high dollar custom knife, ( 🙂 ) marking the knife with a Sharpie and checking…

… clamping the knife horizontal, the marker starts getting removed near the shoulder of the bevel, as the stone approaches the tip. This would result in a wide bevel. However, tilting the knife down, the marker is now removed at the edge of the bevel, along the entire length. The key is still used to position the height (top or bottom). The straight portion of the blade stays the same angle along the entire length (the same as if it was clamped horizontal).

You can make a note in your log to indicate this, for example: “clameped at heel, tilted down so tip is at bottom of ruler.” Or, use an angle gauge and measure the angle.

Just a little tip on clamping and tips! 🙂
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- AngleKnife.jpg
06/05/2013 at 3:06 am #11986
Ken Buzbee
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Great tip, Curtis. I’ve had to do that exact thing many times. (refer back to the picture I posted of my Spyderco Balance)

Ken
06/05/2013 at 6:54 am #11992
cbwx34
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Thanks Ken.

So, how does this work? Here’s my theory (theory because I’ve done no math to confirm this).

The pivot doesn’t “know” horizontal, it just knows the relationship between itself and the knife. So, take a look at this picture…

While the angle doesn’t change on the straight portion, the angle change does change at the belly/tip area, and how much it changes is based on the distance from the center, or in this case, when the rod is perpendicular to the straight portion. So, in the top photo, the knife is properly placed, and the distance from the rod (I left the stone off just for a better view) to the belly/tip area isn’t that far. In the second photo (sorry it’s a bit crooked), the knife is clamped at the heel, and you can see the distance to the belly/tip area is longer, resulting in a greater angle change. But tilt the knife (3rd photo), place the rod perpendicular, and you can see the relationship is once again close to the belly/tip area.

Now, just need a math guru to come along and prove (or disprove) it…. :dry:

As always, check where you’re removing metal before you start grinding away… you can’t put it back! :woohoo:
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- AngleKnife02.jpg
06/05/2013 at 8:37 am #11995
Ken Buzbee
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No mathematical support but I think you’ve got it spot on.

Ken
06/05/2013 at 10:56 am #11997
Phil Pasteur
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Just from a logical level this works. When the angle changes at the tip is due to it being further from the pivot, if you move it closer to the pivot.. which tilting it does, it will reduce the change. Makes perfect sense.

I think Anthony’s proof showed that, depending on the radius of curvature of the tip, an almost perfectly consistent angle should be achievable with proper placement of the blade heel to tip.

So then if both methods work. my only question would be what is the advantage of doing the tilt method over placing the knife in the jaws as in the first picture to achieve an acceptable average angle over the entire length of the blade? The downside of tilting would be that it is harder to document the process for repeatability than by using the pins on the depth gauge on the spine and measuring vise to tip length.
06/05/2013 at 2:16 pm #11998
cbwx34
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… my only question would be what is the advantage of doing the tilt method over placing the knife in the jaws as in the first picture…

…The only “flat spot” or good clamping position on the knife is near the heel, but doing that will mean the bevel at the tip can get too wide…

(The knife in the picture is just to demonstrate the technique.)
06/05/2013 at 11:26 pm #12006
Phil Pasteur
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OK…
I just have not found a knife that I could not get securely in the clamp using one of the methods discuseed previously here, at the proper location to minimize agle variation over the lenght. That is, using chamois, foam tape, moleskin, or some of the other materials that folks have had success with.

I don’t question that the tilting thing would work. It seems that it just adds more variables that are more difficult to duplicate at a later date.
06/06/2013 at 2:54 am #12022
cbwx34
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I don’t question that the tilting thing would work. It seems that it just adds more variables that are more difficult to duplicate at a later date.

OTOH, it might be easier to duplicate on some knives. An option to consider.

Give it a try, before merely dismissing it. Never know unless you do.

Edit: In fact, if I may quote you from another thread…

Scientists “prove” things by experimentation. You need to [strike]get some plates and[/strike] conduct first hand experiments…
👿 :silly:

There are many paths to sharp…. 🙂
06/06/2013 at 10:47 am #12045
Phil Pasteur
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Remember, just brainstorming. Sort of thinking out loud.

Cost/benefit ratio sort of thing. I still am not sure why I would do this if I can clamp the knife in the more traditional way. I don’t need to prove to myself that it will work, as I accept logically that it will.

Admittedly, I am notoriously hard to move once I get something that works. That being said, if I run across a knife that I just can’t clamp up properly using my established methods, I will keep this in mind.

You are absolutely correct about there being many paths to sharp!
😉
06/07/2013 at 10:32 am #12069
Geocyclist
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Unless I am thinking of something else I thought this covered before, the post that shows the a circle/arc of the arm travel.

This is what I do. So far I always mount the knife “straight” (no tilt = flat part is parallel to base). I lay a stone on the flat part of the blade in line with vice. The stone is all the way down at the bottom of the arm. I mark the stone where it touches the edge with tape. I move the stone (still keeping it all the way down) along the edge. I try to get to adjust mounting so that the tip is about the same “length” as flat part. By “length” I mean measuring distance from edge to pivot by using the stone as a measuring device, i.e. the tape mark. This works as a measuring device as long as you don’t slide the stone up the arm (thus making your ruler longer).

Therefore the bevel should be equal/uniform when the flat is equal distance as the tip. Another way to think of this is if you mounted a sheet of paper(a flat “plane”) in the vice you could draw a circle with your stone. So what ever gets the greatest portion of the edge in this circle (by tilting or moving further back or both) should get the bevel as uniform as possible along the entire edge.

In the end it this still drives me crazy. I think it comes down to some trial and error and “best fit”. I think “theoretically” if you get the “tip” and flat the same distance the bevel would be even – but only at the tip. The belly would be slightly different; a few if any knives have belly that is perfectly circular in shape.
06/07/2013 at 12:58 pm #12070
Mikedoh
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Thanks GeoC

I recall the former discussion. This description offers a slightly different visual image. I’ll give the stone tape a go should I run into
difficulty.
06/07/2013 at 9:43 pm #12085
cbwx34
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This description offers a slightly different visual image.

Exactly!!! :woohoo: Same concept… different approach.

Thanks for the input everyone.
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