Apron Rebuild
November 2014
So, on to the scary apron. The casting was all painted up and ready, the bench was clean, so off we go.
Actually, it wasn't scary at all, and was mostly a pretty pleasant thing to reassemble. That said, again you really do want the book to hand, as several bits would probably have you scratching your head for hours otherwise, particularly putting the new felts in. It took a few evenings to do, what with cleaning every shaft (I polished each up with fine emery paper to make sure there were no burrs, wire brushed all of the gear teeth etc).
I won't give a full commentary on the rebuild as the book does a great job, I'll just show some of the stages and point out any particular issues I had.
First steps - in goes the lockout plunger. This prevents the clutch and the half nuts being engaged at the same time.
Pressing the shaft into the clutch:
My trusty vice handled this without difficulty. Getting the circlip on was a million times easier than getting it off! As per the book, I'd kept the various clutch plates threaded onto a wire so it was easy to refit them in the same order and orientation as they came off.
The clutch was a bit fiddly to get back in, because of that damn oil distribution ring again. The ring was a bit warped so I hammered it back flat first; you just have to make sure it seats properly above the shaft as you push it in. One of those "magnet on a stick" tools is quite useful here. Shown below in its proper position:
At the same time as this, plus holding the clutch cover on so that all of the plates don't fall out, you need to keep the lubrication felt in place. 5 or 6 hands would probably do it! Keeping the felt aligned was probably the hardest bit, it's easy to trap it. I finally got it where I think is correct, but it took a good few attempts! This is the view from underneath:
There are lots of felts to run through the apron. The book suggests this slip knot which works well, for tying them off to the various pins in the sumps. A set of long forceps is very useful for doing these.
Routing is important so that they don't get caught in any of the gears...
Mostly, the felts are put into their groves, then the shaft pushed through. However some, like the one on the RH side of the worm gear, have to be pulled through the hole after the parts are in place - these are the bits which would take hours and hours to work out if you didn't have the rebuild guide. Make a hole in the felt with a fat needle, and thread a bit of stainless wire through(I'm using some lockwire I had lying around), this can then be used to pull the felt through.
Once the worm gear was in place, I set about making a new key. This key fits into the keyway on the leadscrew, and transmits drive to the worm gear, which powers the cross and longitudinal feeds. As mentioned >previously, the old one was very worn.
The keyway is 3/16". I could find ordinary square keystock in this size, but this key isn't square - it has "ears" at the end which stick downwards and prevent it sliding back and forth. (shown in the first picture below). I couldn't find any 3/16 steel plate either, so I had to resort to 5mm, which is 0.24mm oversized.
Cutting the basic shape was easy enough - saw, flap wheel on the angle grinder, then finished off with a hand file.
To get the width down to 3/16, I used a heavy flat steel plate with a sheet of emery paper on top, and simply sanded the sides of the key on that until it fit into the keyway. I wouldn't want to have to take off much more than a quater of a millimetre like this, but it was ok. The whole thing took about an hour and a half, so not too bad. Shown below with the old one underneath.
And in place...old on the left, new on the right:
Then more felts and gears....
This gear runs very close to the one below it, and you need to set the clearance between them with a feeler gauge. It's then locked in position using a set screw as shown.
In general, all of the various shafts and gears seemed to be in very good condition. A couple of marks on some of the shafts, a couple of small chips out of a couple of teeth, but surprisingly little. However the main winding shaft which takes the big winding handle for moving the carriage back and forth did show quite a bit of wear towards the front.
The book mentions this; there is no specific lubrication system for this shaft, instead relying on splashes and drips from elsewhere - odd since it is the most used part of the apron! The book suggests making a modification to the apron, which consists of drilling a hole in the top of the boss which supports this shaft, and fitting a new oil cup into it, so that the shaft can be lubricated directly. Sounded pretty good to me, so I thought I'd do the same. The shaft itself, although visibly worn, seems ok to reuse - it runs in a very long hole so the slop at the front doesn't really affect it noticably. Wouldn't be too hard to make up a new one if needed though.
Nice and easy, a new 1/4 "gits" type cup only costs a couple of pounds (I bought mine from Myford), the whole process only takes a half hour if that. Hopefully should improve things a bit
Here's a shot of the completed apron from the rear - well almost completed, this is before fitting the sump cover, as that obscures most of the gubbins.
I particularly like the hi-tech oiling system for the half nuts. It just kind of drips down on top of everything and eventually works its way down to the edges of the nuts and from there onto the leadscrew.
It was easy enough to fit onto the saddle - but make sure you fit the gib strip to the rear of the saddle first! Wasn't sure about adsjuting this, the book is a bit vague, I just screwed it up until it stared to drag, then backed it off a bit. So that's the apron almost complete, I'm just missing the handles. It's all a bit of a mess still as I'm still stripping and painting various parts on the floor and there isn't much room to work in.
Handles
Half of the apron handles are away at the rechromers, but I could do something with the rest. I'd painted them before, and polished up the metal knobs on the end, but they rusted up again over time. The reason was that I'd just polished them, I hadn't removed the pitting which was there. The pits collect moisture, rust up again, and the whole thing looks tatty.This is a good example - it's the halfnut shifter handle, I've stripped all of the paint from the main part, with a closeup to show the pitting on the knob
For the new scheme, I thought I'd leave the main part in bare metal, just burnished off with a cup brush, then laquered so that it wouldn't rust. I'm basically leaving all of the fixings and shaft ends as metal, rather than painting over them, to give a contrast against the paint.
Then for the knob, I wanted to take it right back smooth, remove all of the pitting, then polish up. A smooth surface with a smear of oil will hopefully keep the rust at bay on those handles which are heavily used. For the ones which are rarely used, I'll laquer the knobs too.
To do the knobs, I've started with a couple of flap wheels in the electric drill (not the angle grinder type, they are too fierce, and the wrong shape), touching up here and there with a hand file, then emery paper from 120 grit down to about 400-600, then using a 3-mop polishing kit (sisal, stiched cotton, loose cotton). This has worked pretty well:
Takes about an hour to an hour and a half for each one. Below is the tensioner handle - you can see the damage I mentioned before, this has been snapped off and brazed back together at some point.
...and the gear shifter handle from the top of the gearbox, shown after rough filing, sanding, and final polishing
So far (and I'm talking about a month after I did these), they seem completely resistant to rust, which is nice. Providing, that is, you get all of the pits out - in a couple of cases, although it looked smooth and polished, I'd missed a couple of small pits, and they very quickly show themselves as rust spots, so I had to redo those areas. Below is the gear shifter handle, a couple of weeks after the polishing shown above:
Since redoing it, it has been fine - just a point to watch.