Re: Knee for z-axis control?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, R Rogers <rogersmach@y...>
wrote:

> The cons to using the knee? you cannot accelerate as quickly as you

do with a quill. So it is a bit slower however, not a huge
difference. And you need a larger motor for Z than X and Y.

The knee on a bridgeport will usually lose position if not clamped
when cutting. They may also rock from side to side if the gibs are
not just right, causing chatter on heavy cuts. If your machine is
very worn at all( or dirty) you will not have accurate Z motion. This
can affect bore straightness and drilled holes may not come out
opposite the starting point.

Test yours by putting an indicator on a work piece, parallel to the Y
axis. Clamp the Knee and see how much the indicator dial moves.

If you do this before you invest in a W axis, you may decide that
just a power feed on the knee is a better alternative, and a cnc
quill makes more sense. It does vary a lot by machine.

Fred Smith - IMService