Supercharged Sherline Spindle - Part IV, Motor Mount

5 Bears Home Homebrew CNC bench mill

In the previous installment, we have been machining the motor mount, to be attached to the spindle foreplate.

The 1/4" leadscrew is visible in this view, but the brass nut is absent.

You can vaguely see the holes above the leadscrew which attach this assembly to the pair of RSR12 trucks on the spindle foreplate. The holes next to my thumb will mount the motor.

The brass nut is nothing more than a rectangle shaped as shown, and drilled/tapped 1/4 X 20, the pitch of the leadscrew.
After the brass nut was tapped, I mounted it to the little leadscrew, and temporarily positioned it like so. A pair of #10 SHCS is resting on the brass, head down, in an attempt to get a rough position for the holes.

Note the notch I miled in the motor mount assembly to gain access to the ultimate location of these screws.

With the brass nut secured to the foreplate, the motor-mount assembly was free to travel left and right approx. 3 inches, more than enough to service and tighten the belts.

Not being pleased with the boxy shape of the motor plate, I tossed it on the big mill and did a bit of contouring.

Here, the foreplate, c/w motor mount assembly, is being attached to the Z axis backplate with six 5/16" SHCS. In addition to these six screws, there are four 0.187" dowel pins which ensure that the foreplate mounts to the backplate in truth.

I bored a large hole in the motor mount assembly to gain access to the upper-right hand 5/16" cap screw, being tightened in the photo.

On the right is the little handwheel....

...and another view of the RSR12 rail and trucks. These appear small and light but have vast strength, and easily hold the motor mount plate and motor with no flexure at all.
The motor and spindle are mounted, and the dual-belts installed. I temporarily wired a 5.5A "Dart" DC motor controller, and tested the assembly. No problems up to ~8,000 no-load RPM.

There is room above and to the left for a pneumatic drawbar, which is on my short-list for "next" projects.