Bernoulli Spiral Cam Clamps

comments (1) March 5th, 2012 in Jigs

GarageWoodworks GarageWoodworks, member
thumbs up 13 users recommend

Bernoulli Spiral Cam Clamps.  Will transform how you use your workbench.

Video of them in action here.

Plans available with the template.

posted in: Jigs, WorkBench, bench, jig, clamp

Comments (1)

Filtersmith Filtersmith writes: 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
0 1.0000
5 1.0538
10 1.1104
15 1.1701
20 1.2330
25 1.2993
30 1.3691
35 1.4427
40 1.5203
45 1.6020
50 1.6881
55 1.7788
60 1.8745
65 1.9752
70 2.0814
75 2.1933
80 2.3112
85 2.4354
90 2.5663

Posted: 11:46 pm on May 20th

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