Any rules of thumb for eccentric edge clamps?

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CarvedTones

Board of Directors, Vice President
Andy
I am going to make a set of 4 eccentric edge clamps to fit 3/4" round dog holes. I was thinking of going with a mostly round tear drop shape with the post off center to one side (actually both sides; a pair each way since every now and then the direction matters). Anyway, I wondered if there were any good rules of thumb. The math is easy; however far off center I am is half the amount it can adjust. But it seems likely there is a good ratio, like maybe a third of the radius or something, where they hold well but still have a reasonable adjustabl;e range without being too large.
 

Glennbear

Moderator
Glenn
Being geometrically challenged I am going to go with the pattern I found in a wwing mag if I can find the pattern when the time comes. :wsmile:
 

CarvedTones

Board of Directors, Vice President
Andy
My first attempt was far too aggressive, but using a belt sander to make the circle elliptical helps. To go from minimum to maximum adjustment requires a 3/4 turn. If you leave the shape as a circle (plus the "handle" in the other 1/4) most of the change in adjustment takes place in the 2nd of the 3 quarters. You have to ease the arc there. I will have to take a picture tomorrow. I was testing/using just one on a bench hook with staggered dog holes. Murphy helped me pick the wrong orientation first. A righty pushing a gouge/chisel/rasp/plane/etc needs one that tightens CCW, so of couse I was using a CW one which loosened quite often from stock getting pushed right to left...
 

CarvedTones

Board of Directors, Vice President
Andy
A bit of an update. Some home maintenance and taking the kids to the movies ate up a lot of my Sunday but I did spend a little time and again did not take pictures. I wouldn't really want them anyway; I have decided I need a larger one out of softer wood. I was using white oak mostly because that is what the bench hook I was using it on is made of. But the WO burnishes to a hard slick surface that needs a lot of pressure to hold well. Also, my attempts at changing the arc always resulted in a "kink" somewhere that limited adjustability because it would not hold too close to or at that spot. Anyway, tonight I plan to make a 3" round one out of softer wood about 1/2" off center. Another "twist" I will try is not putting a tail/handle on it. That will make it bidirectional. For use on a bench hook, that should be okay.

My other use, which is on a carving stand to hold blanks, will need tails/handles.
 

CarvedTones

Board of Directors, Vice President
Andy
Following up with a little success after various experiments.

I made this:

edgeclamp1.JPG


I turned it and "corrugated" the edge.

It works like this:

edgeclamp.JPG


that little piece of stock was slid in from the right and it is held reasonably firm for carving, planing or whatever as long as the tool is worked from right to left. I decided to leave it with no "tail/handle" so it can work from either side.

This is a useful clamp, but this was largely to learn about them. I plan to do a few other things with them before too long...
 
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