How to make a cam lock device

Im building a sheet metal brake and am looking at ideas to hold the
clamp part of the brake in place. I came across this web site where
the builder is using a cam lock to hold the clamp in place.
formatting link
(scroll down a little bit)
Looks like a nice idea but I dont know the background to building a
cam type device.
Anyone have hints, plans or drawings on how to build one??
thanks! Aaron
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A cam lock is simply a rotating ellipse of increasing radius which translates into a constant radius circle (sorry-redundant). Anyway, a cam lock can be designed to apply a certain fixed force through the transition to circle, or it can be spring loaded, thus the clamping force can be adjusted by varying the spring preload. A work-holding toggle clamp is a good example. JR Dweller >
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JR North
Won't argue with that, since I don't understand it.
I'd suggest contacting the guy who made the device with an eccentric; I bet he'd be more than glad to help you. Another way to do it is with a 4-bar linkage as used in a toggle clamp (per JR's comment) or a visegrip. Just study a Vise-grip for a while, see if that turns on any lights for you.
Reply to
Don Foreman
While the elliptical shape may be the best, a simple round with an offset hole in it will also work well. The offset of the hole from the center of the round stock will be 1/2 of the total clamping distance. The round is a lot easier to make as a custom part.
-- Bob May Losing weight is easy! If you ever want to lose weight, eat and drink less. Works every time it is tried!
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Bob May
Just a note -- a circle can be considered a special case of the ellipse.
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Jim Wilson
two thoughts:
does it have to be camlock? how about a simple screw-down device.. a gearbox could speed this up if you're bending alot of work and/or working with alot of thicknesses.
you could link two small gearboxes and have one handwheel close the entire brake down.
re: camlock -- camlocks aren't all necessarily positive lock designs.. that is, your cam doesn't have to directly contact your work. use a cam-follower type design and you can move the cam off (or further away) from the work. imagine a disk with a circular slot milled in it. put a pin through it, off center, and attach a simple handle/lever. then, turning the 'handle' 360degrees will swing your follower (riding in the milled slot) through the offset distance. the follower can be as simple as a dowel pin (ok a big dowel pin) on the top 'jaw' of your brake. play with positioning it before bolting it in to avoid the (not so sweet) "sweet spot" -- the point where the cam can 'slip' and unlock.
hope some of that helped, -tony
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Thanks for that tip! I made a rack to hold a bicycle inside my van and decided to make the 'quick release' component to hold the front fork. I made a circular piece and offset the hole. The clamping force comes on quick and holds well. I eyeballed it to be somewhere in the 1/2 distance range. Next time I'll measure.
Aaron, all high-end bicycles have a cam lock quick release mechanism to hold the wheel on the bike, front and rear. Check it out for an example.
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