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Building a Bandsaw Fence #2: Cam

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Blog entry by Rick_M posted 05-25-2017 06:49 PM 955 reads 0 times favorited 3 comments Add to Favorites Watch
« Part 1: Making the rails and gluing up the fence. Part 2 of Building a Bandsaw Fence series Part 3: The end »

Next part is making the cam and what I’m calling the “shoe” (as in brake shoe) for lack of a better term (suggestions welcome).

The original cam template. I made this and it didn’t look right. Probably should have tried it first but I decided to tweak the curve a little and used a logarithmic spiral template by Marius Hornberger.

Tweaked curve, much better looking in my opinion.

Getting the cam to work proved a little trickier than expected. Marius originally used a round cam and they kept popping loose so he remade them as a spiral and problem solved. But my cam based off the spiral is doing the same thing his round cams were doing so I’m not so sure of his solution.

One problem is the “shoe” is not parallel to the rail. (pic above) I assumed it was because the opposite shoe (pic below) was too close so I trimmed some off, then more off, then more off, to the point where it stopped working, but the front shoe was still out of parallel.

I trimmed the front shoe to a 3° angle and glue a shim on the back piece to add back some thickness and it now it works. (No picture but there is or will be a video on Instagram) It still isn’t as smooth as I’d like and I’ve already redesigned it in my head. One problem may be that I used nails as pins as suggested by Fiebach but I suspect they are flexing. So before redesigning anything else I’ll try replacing the nails with something stiffer and see if that helps.

-- http://thewoodknack.blogspot.com/



3 comments so far

View HokieKen's profile

HokieKen

4595 posts in 1015 days


#1 posted 05-25-2017 07:32 PM

Rick, I’ve had a little experience designing cams. Just a guess based on the picture of your template but, the distance between the “locking” point on the cam must be the shortest point on the curve. Just looking at the picture, it appears that the radius going to the 3:00 position from the 12:00 position is closer to the pivot than the 3:00 “locking” point. If that’s the case, then the cam will naturally try to rotate to the point that is the shortest distance from the pivot. You also have to be careful that the locking position is further from the pivot than the unlocked (12:00) position or your fence will never be free to move.

Hope that makes at least a little bit of sense…

-- Kenny, SW VA, Go Hokies!!!

View Rick_M's profile

Rick_M

10853 posts in 2257 days


#2 posted 05-25-2017 08:56 PM

Must be an optical illusion because of the angle. Here is the template I made.

Last night I began suspecting the nails were not up to the task and today replaced them with heavier duty versions and performance drastically improved but there was still some small flex. So I went to 1/4-20 bolts and all flex is gone and the cam locks up tighter than a Pilgrim on her first date. Paint is drying. :)

I’m going to redraw the plans for the fence. Normally I wouldn’t redraw someone else’s plans but the originals are not workable as-is and are really more of an idea. Not sure if I will do them in Fusion (still learning) or make 2D drawings.

-- http://thewoodknack.blogspot.com/

View HokieKen's profile

HokieKen

4595 posts in 1015 days


#3 posted 05-25-2017 09:50 PM

Nice. Yeah, that template looks much better.

-- Kenny, SW VA, Go Hokies!!!

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