3 Axis Foam Cutting Mill

3 - Axis Foam Cutting Mill - Part 11

Lead Screw & Couplers

These parts are all slated to be melted down the next time the "Fat-Boy" is fired-up. They all started out as potential lead screw couplers, but somehow lost their way.

How hard can it be to drill a 1/4" hole half way, and then a perfectly centered 5/16ths" hole from the other side. Tap it to 3/8th" and expect that it turn a 21" rod true.

Obviously this is a skill yet to be developed. I can't really blame the drill press, though I did make a simple fixture to hold the pieces in a vise, and it had an inherent problem, in that it was not perfectly square.

Ultimately I cut a length of 3/4" mild steel, drilled a single 1/4" hole through, and drilled and tapped a pair of holes for the set screws.

So as it turns out I never did need to build a lathe to make the lead screw couplers, perhaps it will be handy down the road.

After deciding on a single 1/4" hole for the coupler I had to run down the ends of the Lead screw from 3/8 to 1/4".

I chucked it into an electric hand drill, placed a nut and a threaded coupler to protect the start of the thread and used a file to slowly remove an 1/8th" of it's diameter.

This is a variable speed drill and my foot runs it like an accelerator.

This is what the finished end looks like that will mate to the stepper motor.

Initially I tried filing the rod with the threaded coupler clamped in a vise, but it wasn't coming out round

The other end was turned down to loosely fit into the ball bearing guide and 3 more inches for a hand crank to fit onto out the front.

The zinc coating on the threaded rod, must make it slightly over sized, as the driving nut seemed to be very tight or stiff when I first tried it.

Here I'm running the rod through the appropriate 3/8ths #16 die with a liberal dose of goose grease.

The rod is still in the drill and 2 complete passes are quickly run the full length.

Here I'm running the driving nut numerous times the length of the screw to see how it will wear, and because it is rather relaxing.

The drill is perfect for this application, as I was previously turning by hand and it seemed to take forever to get from one end to the other.

Finally the first of the 3 lead screws is ready for test assembly and mounting.

As much as I want to just slap the motor into place, I'm taking my time to ensure that I get the best possible fit and performance.

The rod does still have a minor amount of deflection as it rotates, but how that will effect the movement of the table has yet to be determined.

And here is the drive nut ready to be bolted to the drive plate under the table.

I've made no provision for Backlash on the nut yet, as I have to determine how it will effect the way that the system moves.

Of the numerous CAM applications I've looked at, all have Backlash compensation that makes allowances. Until I can determine how strong the motors are, I don't want to load them unnecessarily.

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