Shrapnel Phase Two

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Y and Z axes were built over the last couple of weeks. I didn't take a bunch of pics of the progress on the Y axis because it was fairly straightforward. I would, however like to talk about the thrust nut and retainer that I came up with for this machine. It is quite elegant, simple and very easy to construct.


Here you can see the thrust bearing end of the Y axis. The bearing housing is milled in such a way that the bearing has about .2" of play all the way around the bearing. This allows for some adjustment if things aren't quite lined up correctly (which is quite difficult on a homemade CNC mill).

 

A 1/2-10 ACME nut is then machined with a shoulder so that the nut can still press against the bearing race. The trick here is to allow enough clearance between the retainer ring so that you can still slide the leadscrew around for adjustment. You can also see the 6-32 set screw that I drill and tap into the ACME nut to keep it from backing out once tightened up against the bearing race.

 

This is what the thrust nut looks like when assembled. The ACME nut pushes against the bearing race on this end of the bearing and on the other side, there is a 1/8" roll pin that pushes against the back side bearing race.

 

Here you can see the roll pin and the amount of clearance that is left between the leadscrew and the aluminum bearing housing. There is plenty of adjustment here before the rollpin comes in contact with the aluminum.

 

I haven't settled on a spindle for this machine yet, but I have the ER-16 Sherline headstock in mind if I can justify the $120 for it. I've got one other idea that I'd like to pursue first to see if I can make a collet spindle though before I fork out the dough for the Sherline. With this in mind, I made the Y axis bearing plate adjustable so I can move the whole Z axis up or down. This plate is the only part that I'm not totally happy with on the machine and this is because I drilled so many holes in it trying to get the design right that it is just about beat up. For the next mill, I'll draw up the plate in SW and then cut it out on the CNC mill so that it is perfect. The Z plate that you see here was cut on the CNC Mill and is just about perfect. I added several bolt patterns to the plate to make spindle mounting a bit easier when that time comes.

 

View down the Z axis.

 

View up the Z axis.

 

This is the Z plate that was drilled on the CNC Mill. I messed up the edges a bit trying to clean them up, but it only affect is cosmetic. The holes are the most important part of this plate. You can also catch a glimpse of the fancy new joystick box that I built for this mill. Cool stuff!