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Bernoulli Spiral Cam Clamps. Will transform how you use your workbench.
Video of them in action here.
Plans available with the template.
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It's worth mentioning that the shape of the exponential (Bernoulli) spiral has a particular property useful for this application. To wit, there is a constant amount of squeeze applied for a given (small) motion of the clamped board, regardless of what the opening is. The spiral is given as r = r_0 * exp(k*theta), with theta given in radians and r_0 being the starting radius. Small k gives a slowly growing spiral, and large k gives a fast growing spiral.
To calculate your own spiral, here's an expression to run in Excel. Adjust r_0 and k to suit your own table's separation of holes and how hard you want to squeeze (smaller k is harder squeeze but less clamp range).
where k is stored in B1, r_0 in B2, and column A has the angles in degrees. Here's an example:
k = 0.6
r_0 = 1
Implements r = r_0 exp(k*theta*pi/180)
angle (deg) radius
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