Re: [CAD_CAM_EDM_DRO] Re: Machine flex; How much is to much?

Leslie M. Watts wrote:

>I measure about 0.001" deflection or less per hundred pounds
>force on my shop machine spindles. I design metal capable cnc
>stuff to be about the same. These are light industrial machines
>similar to Bridgeport etc.
>
>Typically this is non-linear with initial deflections being
>a little less stiff and larger ones more stiff. That is normal
>for ball and roller bearings.
>
>A light duty drill press is often ten times softer.
>I would think a mill drill would be somewhere in between.
>
>Perhaps someone could measure one with a strong fish scale
>and indicator. Most of the deflection is probably due to
>the column.
>
>

The real important measure is the complete stiffness around the
entire structure from tool, through spindle, head, column, base,
saddle and table, back to the workpiece. I think the spindle and head
are pretty fair on my mini-mill, but the saddle and table are really
sloppy. The cutter seemed to be standing nearly still, but the
workpiece was really wobbling when I did some light aluminum
milling on it last night.

Jon