For this part, we need

• 2 X 40 mm aluminium spacers
• 1 X 1/4"? x 8 mm flexible coupling
• 2 X 8x16x5 bearings 688Z
• 2 X 8 mm shim, look like thin washers
• 2 x 8 mm lock collar + set screws
• 8 x M5 20 mm bolts
• 2 X C Beam end mount plates
• 2 X M5 55 mm bolts
• 1 X Nema 23 stepper motor
• 1 X 8 mm lead screw 250 mm length

And Bad Boys II playing in the background

Arranged out in order of build

Four of the 20 mm M5's into the bottom block (they're the same)

Bearing fits here

The lead screw needs to be knocked down for about 40 mm in, so with 220 git sandpaper and a cordless drill, finished with 1500, make sure to clean very carefully you don't want grit in the lead screws or bearings afterwards, clean them elsewhere and don't over tighten the chuck on the lead screw, take your time and test often til the bearing is a slip fit.

took me about 40 seconds each side. You do not want the bearing to have side to side movement, it should be snug but smooth on and off.

lower block goes on, four bolts, bottom of the Z is where the gantry plate is.

Always so much swarf in these things so blow them out with air. note orientation of the eccentrics on the plate. make sure its all riding properly and adjust the eccentrics etc here.

Insert lead screw

Lower bearing

Add washer (rounded side towards bearing, flat side towards lock collar) and lock collar.

Flush the bottom of the lead screw to the bottom of the plate

Gently tighten the set screw on the lock collar, don't over do it or it'll strip. Try to think about having the various set screws all face the same way so it is easier to work on later.

Top side next, same as the bottom, lock collar, washer round side towards bearing, bearing and plate. four 20 mm M5's

Adjust so there is no slop in the Z gantry, either by tightly holding up the collar, or by backing off the four M5's holding the plate, and then applying some pressure to the collar up so that it preloads, tighten down the M5's don't over do it, just enough so its not able to move up and down without turning the lead screw

add the coupler, asks for a .5 mm gap , but my lead screw wouldn't get closer than this. Doesn't matter as long as it is not riding on the surface of the plate

Put the 50 mm bolts into the NEMA 23 , have the wires coming out between the bolts.

add the standoffs, and thread into the plate, note the wires are facing towards the back of the gantry.

tighten the coupler to the motor shaft.

And we're done Move it around and test it etc, no slop and not too hard to move, make sure the lead screw doesn't bind.