I bought a Dore Westbury Mk1 mill a little while ago but she's in need of some TLC before I can use her to make any chips.
Still working on her but thought I'd share something I came up with after getting stuck with a small project for it. The mill itself, while well made, was missing a locking lever for the quill. Instead, a large allan bolt had been used for the job, though I'm not sure how as the bolt was way too long and the quill fine feed has to be lifted out of the way in order to tighten the bolt down, which partially engages the fine feed gears:
My first thought was to make a nice new threaded bolt and lever on the lathe, but it transpired I didn't have a big enough thread guage so had no way of knowing what pitch the bolt was. With my first idea out straight out the window, I settled for making a spacer, so if the bolt was in use, it wasn't going to touch the disengaged fine feed:
Didn't take long before I was reminded why I wanted a locking lever in the first place though as I promptly lost the corresponding allan key. My second idea hit moments after finding the missing it again a couple hours later; make a chunky cover I can stick a lever into, and use the spacer to capture the bolt in the cover....bingo!
On it's own, this idea is doomed to failure, the key is..well..the key to making this idea work, twisting forces will simply make the bolt slip inside the cover without involving the allan key. To.get the ball rolling, I grabbed a short length of 1.1/4" stainless to make the cover with:
First I faced one side and cut a taper as close to the same angle as the other levers on the mill to match:
Then I flipped it round, faced and drilled a pilot hole all the way through, and bored out a seat to an easy slip fit for the allan head, and made a shoulder for the spacer to a press fit. The shoulder sits about .5mm lower than the base of the allan head so when the spacer is pressed home, it's pressing against it:
I then chopped a piece off of the key from the long half and took measurements from flat to flat, and point to point in order to find a suitable hole size to press the piece of key into:
In the end chose a hole .5mm smaller than the distance from point to point as I only have access to a 2 ton press and didn't want to give myself an impossible goal in that department, I also figured that the forces involved with locking the quill in place wouldn't be great enough to dislodge it:
After drilling the pilot out to the desired dimention, I measured the depth of the key hole in the allan head, and the length of the freshly drilled hole from the tapered end of the cover to the base of the allan head seat and added the two sets of numbers.
I then ground the piece of key down to the correct length so that when it was pressed all the way home, part of it protruded inside to fit all the way in the allan head, but not so much that it prevented the spacer from pressing all the way home.
To make things easy I turned a drift to a slide fit for the bores in the cover and drilled a recess to hold the short length of key straight, which also doubles as a dummy allan head to leave the correct amount of key protruding inside once driven home:
Unfortunately the key had other ideas about my plans for it and it made me look a total goon for fifteen minutes in front of my work colleagues (it was literally like sword in the stone, only in reverse), but I managed to gently persuade it to go all the way in with a lump hammer once I got home from work.
With that done I chucked it up in my lathe and turned down the excess key shaft sticking outside the end of the cover, and gave the tapered end a nice finish. I then put it back in the mill, screwed it home and chose the spot I wanted the lever to be when in the locked position. With the mark made, I took it out and drilled/tapped an M8 hole for a random lever I had kicking around from something or other to complete it:
Here it is fitted to my mill:
I'm quite happy with how it turned out for something so "off the cuff", I can see me doing this again with a few refinements and a more powerful press, or rotabroach....