Re: [CAD_CAM_EDM_DRO] Knuth DRO's from Singapore on EBAY - has anyone bought them?

Ted Inoue wrote:

>I've recently stumbled across the following EBAY ad:
>item number 2570941080
>
>They have 2 and 3 axis, Knuth DRO units with glass scales, rated at
>0.0001".
>Looks like a decent unit and the prices can't be beat for the
>features. $549 for 2 axis, $779 for 3 axis, plus $88 shipping charges.
>
>

Note that just because the readout DISPLAYS 4 digits to the right
of the decimal point does not mean it actually has that resolution.

People in the industry have told me than nobody makes actual Imperial
(Inch) scales since the late 1960s! So, all the scales are actually metric,
and they do a conversion to inches in the readout box. Unless you pay
a fortune, the best scales you can get are typically 5 uM, which gives
a resolution of roughly 0.0001969". That is about .0002", but not
EXACTLY .0002". Therefore, if you fiddle with one for a bit, you
will find there are certain readings you CAN'T get to! This drives some
Inch-bound machinist slightly batty.

Jon