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Thursday, October 17, 2013

CNC mill conversion - Part 4

Y axis spacer
While the X axis motor mount gets attached directly to the right side of the moving table, the Y axis motor mount connects to a spacer block, which in turn connects to the front face of the moving table. 

As always, the process started with a rough piece of metal that had to be cut down to its plan dimensions, and squared.

Raw material

Squaring one side

insert surfacing video

Finished stock

With the stock now in a usable form, I reproduced the bolt holes, and the ballscrew pass-through hole onto the part. 

Locating the Y axis with an edge finder

Holes center-drilled

1/4" holes drilled all the way through

Reaming the ball-screw pass through hole

The spacer houses two sets of bearings whose purpose is to support and guide the ballscrew. 

Ball bearing races

As you can imagine, the tolerances are getting much closer for the bearing surfaces, and a slow and methodical approach to their milling was necessary. I chose to use a boring bar held in a boring head to machine these countersunk surfaces.

Boring head set

The boring head is a fantastic tool, capable of high precision IF you know how to use it. I knew how, in theory, but the few times I had the opportunity to actually employ it, I was not very happy with the results.

However, I was eager and hopeful to experiment with different cutting surface angles, feed rates, and depths of cut, and this time around I got a lot better results, indicating that either my technique is indeed improving, or that I just lucked out. More boring practice will be required to settle this argument.

Finishing the bearing recess

Finished recess

Inner bearing surface

Ball bearing race

Outer bearing surface

This process had to be repeated on the back side as well, before the spacer could be considered done.

Finished Y axis spacer

I put all the parts I've made for the Y axis together, to give you a better idea of how they all fit.

Ball-screw with spacer and motor mount

Same thing as viewed by the stepper motor

Lead screw and hand wheel will be replaced by the ball-screw and stepper motor

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