Re: [CAD_CAM_EDM_DRO] Renishaw, digitizers

In a message dated 1/11/01 7:48:28 PM Hawaiian Standard Time,
jmelson@... writes:

<< 3 conical depressions (like a countersink) would work as well, and might
be a lot easier to make and be sure they were on target. In fact, you
don't even need cones! 3 holes with well-chosen diameters so that they
sat part way down on the balls would work quite well.

Jon >>
Group,

I designed a version that uses a ball from a heim joint. About a 3/8" unit
would be good . The probe shank is pressed into the center of the ball. I
have a cylindrical housing that has a delrin bottom plate. Into this, I would
have three setscrews set so the probe runs deads true by spinning with a dial
indicator, The three screws would then be locked and connected to a 3 input
"and" circuit. The trick is to make the fit of the ball to the cylinder bore
about .0005 clearance. A light spring would press the ball/probe down from
above. I checked the quality of several ball joint balls and they do vary.
You must get one of aircraft quality if possible. They have much better
roundness and squareness of the face to bore. This design may need to be
sealed to work properly, a tiny bit of grit will make it unreliable.

I will post a drawing if there is interest.

Peter
THRD, Inc.