Introduction: Modified Drill Powered Lathe
Sometime around the sixties or seventies, the hand-operated power
drill became cheap enough to be owned by the Common Man, and so began a new era for the handyman. On the back of this new phenomenon came a whole raft of accessories that utilised the electric drill as a source of powered rotary motion. And of course, one of these was a lathe.
I came across one of these on a tool-buying excursion in the middle of an Essex field at silly o’clock on a Sunday morning. For a fiver I thought it was worth a punt, being as all my other attempts to acquire a lathe had all come to nought. That was probably the sleep-deprivation talking, actually.
Obviously I had bigger plans than just using a power drill as nature had
intended. That would have been far too simple! What was needed was a new headstock….
Step 1: Starting the Headstock
The plan was to machine up some form of headstock to hold a new dedicated spindle with a pulley, and then find a donor motor from somewhere. The headstock would be formed from three lengths of steel bar arranged in a “U” shape and screwed together. The bottom of the “U” will mount to the bed of the lathe. The two uprights of the “U” will hold either end of the spindle. I started by milling three pieces of steel bar using on my ML4:
Next I drilled pilot holes in the bottom part of the headstock. These holes will be opened up to 10mm. These holes are for the mounting bolts that hold the headstock to the bed. I could have drilled these holes on the bench drill (my only other metal-butchery machine apart from the ML4), but it struggles a bit with holes this size:
Step 2: Boring the Holes
While the bottom was set up like this on the milling slide, I also
drilled the screw holes that secure the headstock uprights. The holes were drilled to clear M6 screws, then counterbored with an 11mm slot drill. It was only after taking this set-up apart that I realised the 10mm holes weren’t going to big enough. I was going to need some wiggle room for aligning the headstock. To open up the holes a bit more I mounted the bottom on a faceplate and drilled them out to 1/2″:
The T-bolts that secure the headstock to the
bed were simple enough; I just loctite’d some short lengths of M10 studding into some suitably sized aluminium bar that I had to hand.
Next I wanted to bore out the uprights to take some ball bearing races. The easiest way to do this was to drill and bore them nearly to size on the faceplate:
Step 3: Final Boring
With the holes bored in both the uprights, I could screw the “U” shape
together. Both the uprights could then be bored together to final size, ensuring that the two bores are aligned. The “U” was mounted on the milling slide and the holes were bored with a between-centres boring bar:
In hindsight using the milling slide wasn’t a great idea. The size of
the assembly I was machining meant that the crosslide was hanging out a lot further than I would have liked. I should have made a fixture to mount the headstock better.
Step 4: Bearings and Spindle
Once the bearing holes were to size, I drilled and tapped a hole and sawed a slot up to the bearing holes. This allowed for a pinch bolt to close the bore up around the bearings and clamp them in place.
Now I needed a spindle. This was turned down for most of its length to suit the bearings with a shoulder on one end. I had a spare Jacobs chuck handy that was threaded 1/2″ UNF, so I screwcut a matching thread onto the end of the spindle. Later on I also drilled and tapped the spindle to M6; this would give me a few more options for work-holding.
Step 5: The Pulley
Rather fortunately, while I was making this I came across a pillar drill for spares or repair. The motor and cone pulleys would be ideal for the little lathe. In order for the pulley to fit my spindle I had to make up a bush:
Step 6: Tensioning Bar
The aluminium bar between the headstock and the motor is there to keep tension on the belt. This was an offcut of aluminium that I had (the same offcut that made the T-bolts). The slot was milled on the ML4:
Step 7: Mounting the Switch
The switchgear and start/stop buttons came off the donor pillar drill with the motor. In fact, I didn’t have to make any wiring changes at all. But what I did need was a suitable housing to mount the buttons in…
The tin was perfect! The fact that it was also full of cookies was just a bonus…
Step 8: Assembling
Finally the whole thing could be assembled. I had an oak board that was just the right size, it just needed planing smooth.