The Leading Manufacturer Of CNC Knee Mill Retrofit Hardware and Retrofit Kits  


Z On the Quill or Z on the Knee?

You the customer have a very important choice to make when choosing a CNC Knee Mill

The big question is Z on the Quill or Z on the knee?

Yes, Z on the knee affords more travel however, your Z axis moves may not be square enough for your tolerancing.

The head can be trammed so that it is exactly perpendicular to the table and you can bore straight holes in your work. When boring from the  knee your holes may not be straight.


If your knee is not scraped exactly square to the X&Y table your X or Y Axis position will be lost when the table is raised or lowered. (See Example Below)

If you need to do CNC work at an angle the Head can simply be trammed to that angle with a sine bar and proceed with your job.

When using the knee the part needs to be swung, this means purchasing an expensive sine plate to rotate the part and hold it securely.

The lubrication points on the knee are very sparse, the knee was never intended to be used in this fashion. If it is not lubricated enough you could possibly wear your machine out prematurely.

Something to think about: Check the tram on a rigid head mill or a machining center, they are never in tram close enough to match plates with dowel pins.

A Jig Bore uses the quill for precise Z Axis machining and the head can be moved or positioned and reclamped to accommodate different tool lengths.

We are not saying your mill can be a jig bore, but if used properly you can get very close! Ask a toolmaker that has used a knee mill and they will tell you that you can get very close if used properly.


Your quill is always available for manual use when using Z on the knee, however our Z Axis Quill Drive gives you the best of both worlds accuracy in the CNC mode and manual capability with feed back in the Z Axis while in the manual mode.

This is our opinion and you will have to make your own choice

Thank you!

(c) Copyright 2003 {Elrod Machine}. All Rights Reserved.