Martin Panev

Lathe Milling Spindle Build

Status: Almost complete!

10/02/2025

One of my overarching goals in the workshop for ages now has been a clock or a geared mechanism of some kind. Not having fancy machinery and tooling, or frankly the money to buy it, I have been limited to making my own, and after making an electronic dividing head, the last piece of the puzzle is a way to actually cut the teeth. For this, I would like a cross-slide mounted lathe milling spindle. I was inspired by some of the spindles you see on small clockmakers and watchmakers lathes used for this very task, and with some scrap materials available, I decided to get to work making one. For reference, this is Chronova Engineering's lovely attachment.

For starters, on the Burke mill, I squared up an aluminum block (which I believe I found in a lot at a flea market), and after doing a slight overhaul on the mill, I can now take much more rigid cuts, and this gave a really clean surface finish. I believe this is a machining alloy.

Next, I needed to make a hole lengthwise along the stock, and to make bearing seats on either end. To do this, I did a somewhat sketchy, although fun operation on the Dalton lathe. I held onto the stock between two of the jaws on the three jaw chuck (as I do not currently have a four jaw for this lathe), and the third jaw served as "indexing" to let the stock seat in the same place every time. Doing this relies solely on the grip of two jaws, which meant I needed to run the lathe significantly slower than standard. Lastly, with a small boring bar, I turned the bearing seats for the flanged bearings (intentionally left deep as the flange stops the bearing). Achieving a good fit on the bearing was imperative, so great care was taken to make sure they were in tolerance. Here was the process:

Cutting bearing seats and drilling main hole

I fitted the spindle that I bought off of ebay (search 10mm er11 spindle on eBay if you would like to buy one) to get a general idea of fit and tolerance. Everything was good!

Next, I wanted to make some aesthetic facets on the front corners of the body. I layed out some guidelines on dykem and threw it on the mill to quickly take the corners down. The end result was quite pretty!

Next, I needed a way to preload the bearings, and decided on a thread on the spindle. I chucked the spindle (quite hard steel, but not fully hardened) in the lathe, and began turning. The thread portion was turned to 9.8mm to accept an M10 die, and the pulley portion was turned to 8.5mm. Next, using an M10 fine thread (1mm pitch) die, I threaded the spindle. It turned out reasonably well.

Next, I needed a preload nut. Unfortunately, slim profile M10x1 nuts are not extremely common and quite expensive on McMaster, so I took a flange nut left over from rebuilding my Puch clutch, and made it into what I needed. I decided to use a setscrew to lock the nut from moving, so I ground a flat onto one side of the flange, drilled through, promptly broke a tap in the hole, and then retapped the hole with a new tap, and ta-daa! Nut. Also, later, I had to turn the serrated bottom flat to seat on the bearings.

Next, just for added security, I decided to drill and tap some retaining holes that hold the bearings in. The tolerances are good enough that this does not throw anything out of alignment. I quickly drilled and tapped the holes, and cut some small flathead screws to length instead of setscrews. You can see my new M4 tap here ;). I think this turned out quite nice aesthetically!

Next up, I had to mount the motor which will drive the whole system. I decided on a small DC motor, mostly because I already had it, and speed control on DC motors is quite simple (MOSFETS yay!). I used some scrap aluminum bar to mount the motor. This involved cutting relief for the motor's boss on the mill, and drilling a bunch of holes. I decided to mount the bracket at an angle to give clearance for future mounting. I also matched the contours of the motor onto the bracket for no other reason besides the fact it looks good.

The bracket is great, but not really useful alone. Because of this, I had to drill into the spindle body for mounting. I transferred the holes, and again, you can see my angled mounting solution. I drilled and tapped for M4, and moved on. Next, for cutter clearance, I needed some standoffs for mounting, so I used some aluminum on the lathe to make them:

To pretty up the whole assembly, I spent some quality time with Scotch-Brite (the best abrasive on the planet), and cleaned off all of the invincible, indestructable Dkyem with acetone. The spindle came out very good looking, indeed.

The last of the mechanical bits are the pulleys which connect the motor to the spindle. For conciseness, I only took pictures of the making of one of the two pulleys, but they were both the same with the exception of the hole diameter. I use 4mm PU belting, which is probably one of the most useful things to keep around in the shop, especially for clockmaking tools. Here is the process of that:

Here is the final product! It turned out better than I ever could have asked for, no friction, no play, strong motor, and a very universal collet system of ER11. Now all that is left is mounting. I have left myself a free canvas on the back of the spindle, but this will probably wait until the Hjorth lathe is fully rebuilt. For now, take a look!