Hi there, all,
The latest stage in this project is 'Lead-Screw Modification - Part 1'.
I started with a bit of a set back, the spare lead-screw that I thought was the right length for the gear-box turned out to be standard length. So, whichever lead-screw I use, I'd have to shorten it.
I'd like to finish the shortened end in the lathe but the bore through my head-stock is 19/32" and the lead-screw diameter is 5/8". Hmmm.
And, of course, the lead-screw is too long to work on with one end on the chuck and the outer end in the fixed steady, the lathe carriage would be in mid-air!
The 'spare' lead-screw is of the two-piece type, connected by a collar and a couple of roll-pins.
If I use that one, maybe I can detach the short head-stock end section and mount that in chuck & fixed steady and finish the cut end in the lathe.
Here are the two lead-screws, the original one above and the 'spare' one below:
So, lets's start and see how we get on. First, remove the left-hand (head-stock end) lead-screw bearing bracket. This revealed something that forced the which lead-screw decision - the original lead-screw doesn't have the woodruff key slot required by the gearbox output gear (see below).
Here are the head-stock ends of both the lead-screws, the original one above and the 'spare' one below:
OK, now we know which lead-screw we're going to use. But to get the measure of the amount to be removed, I need to fit the 'spare' screw in place of the original one. So, up to the tail-stock end to remove the lead-screw hand-wheel, cross-pin (a parallel dowel) and thrust collar.
That area of the lathe has been undisturbed since about 1971 and those parts have got used to being together. Still, with a little bit of gentle persuasion, I got them all apart and swapped lead-screws. However, I couldn't refit the cross-pin, it just didn't want to go into the cross-hole in the lead-screw end. (The hole for the cross-pin is in the shadow to the right of the lead-screw bearing bracket.) Eventually, I proceeded without fitting it, I'll give it serious attention when I get to the final assembly stage. So, back to the head-stock end.
The Beeston Myford instructions say 'feed the gearbox onto the leadscrew and secure it in position with the three screws', that's two 1/4" BSF by 3/4" cap-heads in the two holes I drilled & tapped last time and a lower screw that goes into one of the holes previously occupied by the lead-screw bearing bracket fixings. Well, the top two are a bit fiddly but manageable. The lower one, described in the instructions as 'captive', escaped into the bowels of the gearbox!
It's got a slotted mushroom head so you can't hold it on the end of an Allen key and the gear-box innards conceal it from view!
So, again, I pressed on without doing that one up. I fitted the woodruff key, then the gear-wheel, spaced off the end of the gear-box casing by with a 15 thou feeler gauge (the shed gremlins had surrendered the feeler gauge set without too much of a fight
). That got me to this stage:
The Beeston Myford instructions say that I've got to shorten back that left-hand shaft so that not more than 31 thou is left protruding from the face of the gear hub.
So I've measured the total protrusion. Now I've got to take it all apart again and shorten the lead-screw, i.e. actually cut metal, where's the chewing finger-nails smiley?
So, once I've done that, I anticipate three issues:
1. If I drive out one of the roll-pins and just work on the short section of lead-screw, will it all go back together without prejudicing my measurement?
2. How do I get the cross-pin back into the tail-stock end of the lead-screw without damaging anything?
3. Shall I go crazy trying to get that lower gear-box fixing screw into position?
Here endeth 'Lead-Screw Modification, Part 1'.