This Old Lathe

This Old Lathe - Part 2

Milling & casting some simple fixtures...

I did get a few responses from the the first posting on this lathe, and the consensus seems to be that it is most likely a pre 1928 Atlas Utility Lathe.

Since I've done some of these items before (free-hand with the drill press) I thought I might try to do things a bit differently since I now have the CNC mill.

All pieces were drafted with an 1/8" endmill as the cutter, and oversized to allow for 21thou per inch shrinkage off the foam to Alum.

It was interesting to try this on some simple objects, and the compensating factors were fairly easy to work out once I had some constants on paper.

Since the mill plots the center of the toolpath, a couple of test pieces were cut just to ensure that 0.062" made enough allowance for the 1/8" cutter.

It seemed to behave well once I deducted the Shrinkage factor off the actual measurements.

The drive plate is quite snug as it gets threaded onto the spindle.

The spindle is a 1" by 12 TPI thread, and I want to see about casting a "Starter Thread" right into the plate.

Here is an attempt at the Back-Plate for the 3 jaw chuck.

The holes and raised center were all misaligned as this was an early attempt at the "Shrinkage Compensation" factoring.

The mill does produce fantastic pieces, as they are so dimensionally precise and square (even when their wrong - but so precisely wrong...)

This part is a 2-Step Pulley that will drive the spindle.

Notice the 1/8" flange that hopefully will cast out.

These were milled as 2 separate pieces from the 1" foam, but were hot glued together on the 1/2" rod to ensure that they were well aligned prior to casting.

Although I only need one Back-Plate for the chuck I did keep the flawed foam part as a back-up incase the proper one didn't turn-out.

The flawed unit once cast, could be machined down to work, but I'd lose close to 1/4 " off the plate in the process.

Once I get some experience with Brass, I'll upgrade the Back-Plate, but this will have to do for now...

This is a key that I knocked together while the mill was cutting the pieces out in foam.

It is 7/16ths mild Steel... The square end was just filed down, while the other end was punched, drilled, tapped and a groove was filed that holds the handle.

The cross bar is drilled and the endcap bolt is counter sunk sort-of...

In the past I would have just fired-up the furnace and cast these pieces "raw" in the sand... But things are improving, and I've had enough successes with refractory type coatings to know that their worth the effort.

One of the places I've had grief in the past are holes that don't fill completely or at all in the sand, a light plaster of paris skin is rubbed over the pieces, while the centers are well lined to preserve any threads that are cut into the foam.

The image on the right are all the pieces right our of the sand. These pieces are featured in LFMC #12 with more detail on the casting process... but for our purposes on this page they came-out near flawless.

This is a tight shot of the thread that was cast into the Back-Plate for the chuck.

The next step will be to find a 3 to 4" length of 1" 12tpi rod or a bolt, taper at least 3 threads, cut a series of grooves the length of the piece. And Case-Harden the finished piece to clean-out the "Starter Threads".

I've priced a tap @ over $90.00 US (too much...) but can't find a local source of the threaded rod or a bolt.

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