This tool mount is for the MPCNC.

Additional mount for better rigidity -especially for long cylindrical spindles.

Rational:
I love the MPCNC, but was quite frustrated that the tool mount was relatively short, a significant contributor to slop in the XY directions in my opinion. Perhaps it has been fixed with the latest design (Primo MPCNC) I'm not sure. I keep seeing all these spindles held from the base only - it's not good. The problem is that the tool mount is only 120mm tall. Furthermore, it only has 100mm between mounting points. On top of that, the 100mm is effectively much reduced, because you usually need to mount the spindle at least 25mm higher than the bottom hole to account for collet, shaft and cutting bit. So you end up with only about 70mm of effective distance between top and bottom mounting points. (Keep in mind the machine has been designed with 120mm of distance between bearings on the Z axis). This means we are only getting around 58% of the available holding distance. I think that's a considerable source of slop in the XY directions, -especially if there is any flex or slop in your mounts -and there likely is.

This extra mount lets you clamp your spindle much higher, allowing tall spindles to be clamped at the very top and bottom. End to end, base to bit, this results in a much better machine, in my opinion.

Please check the photo and see what you think.

Installation
It's a bit fiddly, but no more so than when you built your MPCNC.
Print two mini nut traps, one for each tube.
Print one Extra Tool Mount.

Mark the location on the Z axis tubes where you want to fix the extra mount.
Take the tubes out of the Z axis. and drill two additional holes in the tubing. Use of a vise and drill press is recommended, but I used a hand held drill and the drill guide to drill the tubes successfully - it just takes a little care, so print the guide if you need it.

Put 4 m4 nuts (7mm flat to flat through center) in the back of the tool mount. They should be a tight fit, but if they are too tight or too loose, put a nut on a bolt, hold it with pliers and heat it on a flame, you can then lightly press the hot nut into the plastic (keep it straight, inline with the hole of course!)

Put 20mm m4 bolts in the two holes from the front of the tool mount.

The Nut traps have been designed with filleted holes that self-locate a little, so one at a time, insert the nut trap in the tube from top, relatively level with the original nut traps and push it the correct distance in. should then be able to screw in the bolts. For me, each one went in first try.

Monoprice

Select Mini

No

No

0.3mm layer height

25%

Print with 3 or 4 wall skin