Altering an Old Toy Wood Lathe

Way back in the day, I picked up an old, tiny wood lathe when I was picking up some other tools (the guy threw it into the lot).

Well, it's been sitting around for a few years, doing nothing (no bearings or prep on the bearings, fairly loose spindle, basically not really usable).  I finally decided to turn it into a pen-turning micro lathe.  I picked up a few bearings, measured, and started to work.

I used a boring head to bore out for the radial needle bearings, and the thrust bearings just fit in like expected.

I'm using a 4" router ER16 collet, and put the headstock onto the mill as my spindle, because an ER16 collet will hold the 7mm pen mandrel perfectly.

Yes, I don't have the pulley installed there.  It's marked and the set screw divot has been bored on the spindle, but I still need to drill it out length-wise (so I can easily shorten the pen mandrel without adding spacers), and thread the back end (left handed m12x1.0 - the whole spindle is metric, I might as well do metric).

The lengthwise-drilling was where the puckering came in.  I had to drill 4" on a stainless steel 1/2", ground and hardened rod shaft, with a drill bit diameter of 1/4".  [shudder].

So, I started drilling.  About 1.5" in, everything ground to a halt (no pun intended because of the next paragraph, seriously).

I knew I needed a better drill bit as well, and a longer one, too, (that meant special degree points, and it needed to be an "aircraft" length).  I went through this whole project of setting up a drill bit sharpener (which wasn't long enough to accommodate an "aircraft" drill bit needed to get the length of the spindle, so I had to modify the device with a longer rod so the shoulder could support it), then ground the drill bit with a 118 degree point instead of the 135 degree point it came with.

I then took everything in to the lathe and started drilling again, and got a little further before it ground to a halt again (seriously, no pun intended).  I re-ground the drill bit and drilled again.  I repeated grinding a few times with drilling until I had punched all the way through.

Now, it was next ready for threading on the end of the spindle so I could lock that spindle in place in the headstock.  Back to the lathe, I set up for a 32 pitch, left hand thread (I didn't want deep in the spindle with such thin walls) and cut the thread.

Time to figure out how big to drill the hole for the nut that will lock it in place, I pulled out the machinery handbook, and started doing math.  I needed wire diameters, micrometers, outside diameter of the spindle, and some mathy skills.  Then I just got sick of trying to think, and pulled up a thread wire measuring calculator in order to get the root diameter.

 

I put the stainless plate into the four jaw, and dialed it in.  I drilled to a 27/64's drill bit to open the hole to 0.421" (surprise! the hole was slightly smaller than I thought it would be, and that's just fine for this).

Next I can start the interior threading operation and continue until it fits, then pull it out and use the spindle as the arbor to make the nut round, and potentially put a knurl on it.  Essentially, I have a few operations before I can assemble the headstock.

1. Thread until it fits the spindle (not snug)
   
2. Face outside
3. Mill an inset for a screw to lock it
4. Drill tap size and loose fit size horizontally through the nut
5. Cut a narrow slot through one side using a slitting saw
6. Tap the nut
   
7. Install the spindle to the collet back in the lathe
8. Install the nut to the spindle/temporary-arbor while I face the opposite side
9. Turn the outside down to an appropriate diameter
10. Knurl the outside surface
    

So, off to awkward threading (a metric outer diameter using an American standard thread pitch).  I have this nagging worry that the motor/tension assembly is going to be a pain (need to figure it out before the headstock is installed back to the bed).