This style toolholder has been around since the late 1800's, according to what I read in a forum. Universally approved - "I'll never go back" they say. Yet, not that widely used, I think. A few make their own, as I did. A few buy the $140 - $150 commercial one (Eccentric Engineering).
I think that these could be hugely popular at the right price. $50? And I think that they could be produced very cheaply on a CNC mill. The only tricky part is getting the CAD file, what with the funny angles involved.
Here is a good picture of the Eccentric Engineering one:
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Whattaya think - would the CAD file be that hard & what could they be made to sell for?
Bob