Diy 4th axis rotary table using 100mm chuck with minimal backlash

[kingcreaky]

Hi.

I tried making a 4th axis using one of these cheap rotary tables off the bay

RDGTOOLS 100mm TILTING ROTARY TABLE & 100MM 3-JAW CHUCK | eBay




problem is, even if you exclude the stepper motor coupling, remove that altogether... one hand holding the input shaft, and the other on the chuck, you notice atleast 1mm of 'backlash' play.... unless you 'lock' it... which of course when used the way its intended (as a rotary table) is fine... but as a 4th axis its not.

so.... need a new plan... I need an accurate way of controlling a 100mm chuck from a stepper motor with minimal backlash


can anybody make any recommendations?

ive noticed this
CNC 4th Axis Rotary Table (100mm / 4 inch) with Flying Leads | eBay

the description says

Maximum backlash (all rotary tables are tested to be within this spec): 20 arc minutes
Typical backlash (most rotary tables are shipped within this spec): 15 arc minutes

but im not as clever as most on here... can anybody advise if 20 arc minutes equates to around 2mm of backlash? on a 50mm diameter? so...???

any advice etc would be very much appreciated, so thanks in advance