Re: Z axis on the knee, how practical????

A couple of comments regarding this topic -

1) - While the gas struts might work, a possibly better way that I've used on some retrofit projects is to mount a couple of long stroke air cylinders (available from surplus sales outlets) and connect them to an air tank that is supplied by a pressure regulator - The tank and regulator are available at most of the "farm supply" type of stores and are quite inexpensive - As long as the volume of the tank(s) is significantly larger than the volume displaced by the cylinders the force applied is close to linear and can be regulated to match the load on the knee - In addition the location of the mounting brackets can be chosen to minimize the eccentricity of the load on the vertical dovetail slide which reduces the wear factor significantly - Not what I would use for drilling a lot of small holes as it's sort of like making popcorn by holding the pan an shaking the stove, but good for many applications -

2) - To run the quill up and down without the problems of deflection inherent in an arm attached to the nose of the quill or the difficulty of running both manual and CNC when attaching to the depth stop fitting, one of my customers rigged a ball bearing thrust package that bolted to a tapped hole in the top end of his drawbar - The ball screw was rigged as an "overarm" attached to the head casting and produced thrust coaxial with the quill - To convert back to manual operation just run the quill up and remove the bolt - Use an open end wrench rather than a box wrench to work the drawbar - (He was using an Erickson #30 quick change adapter and didn't have to work the drawbar that much anyhow) - The main drawback to this method is the additional headroom required - Some might also consider this to not pass the "laugh test" but it works quite well -

Roland Friestad
c/o Cardinal Engineering, Inc.
2211 155th Street
Cameron, IL 61423
USA
Phone - 309-342-7474
E-Mail - cardinal.eng@...


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