I used them on a different machine, my Micro mill so just mounted them on 2020 extrusion which I skimmed just enough to get correct spacing.
http://www.mycncuk.com/attachment.ph...5&d=1456081931
The measurements on mine are 19.2mm to edge of hole which is 38.2mm diameter so from back of plate to centre of motor spindle should be around 38.3mm, side to hole is 13.3mm so edge to centre of hole is 32.4mm. Hope this helps.