Rebuild

Handwheel and handle

Things started off well...

I wanted to refurbish the main shaft which held the handwheel. The scoring was pretty bad and I wasn't convinced that the grub screw was going to hold, as it had obviously slipped off many times in the past. So I thought that I'd build up the damaged part of the shaft with welding, then turn it back down in the lathe.

I had trouble mounting it in the lathe because no part of the wheel casting was concentric with the shaft. Even when I could get the end centred in the chuck, I found it impossible to centre the free end, the whole thing would be tilted one way or another. I tried a number of approaches to no avail. I asked on the Practical Machinist forum and advice varied from "cut the shaft off and make a new one" to "weld it and file it off by hand" to "leave it alone". In the end I did something else:

I turned up an aluminium socket which was a close running fit to the shaft, and mounted that in the tailstock in a drill chuck. This then held the free end of the shaft centred, which prevented any tilt - much the same as a steady rest (which I don't have). Then I could centre the other end in the chuck (a bit of a battle but managed it eventually).

   The socket is holding the free (right-hand) end. The shaft has been welded up and I'm turning it down here

That went pretty well, I had a tiny ridge to clean up with a stone, but it was almost perfect. I then re-drilled the hole for the grub screw and it was as good as new:

  

So I was happy with that. Then I put the wheel down on the bench...I had been very aware that it might roll off, and had been so careful throughout to make sure that it wasn't going anywhere. But this time, I wasn't careful enough. It rolled, fell off the bench, and onto the floor with that hollow thunk that immediately told me it had broken.

And indeed it had. One of the spokes had cracked clean through. Cue a great deal of loud swearing (apologies to the missus, neighbours, cat etc).

It was quite badly displaced, but a quick couple of taps with a nylon hammer put it back into place. I was rather gutted.

I decided to try welding it back together. I'd welded cast iron once before, and knew that you needed to heat the piece to red heat first, otherwise it tends to crack on cooling. Mild steel in the Mig isn't really the best way, but it's what I've got (though I've since read that stainless might work better - mild tends to absorb carbon from the cast iron and turn very hard, and hence crack, whereas stainless won't).

So firstly I had to heat the casting up. To do this, I fashioned a diy forge using the barbeque, a load of coal, and a pump for blowing up airbeds. I attached this to some ordinary copper water pipe I had lying around, and ran the pipe into the bottom of the fire to give an airblast. Somewhat hard work but it did the job. Of course it was chucking it down so I had to do it all under the porch.

Then with the missus on standby at the vice, run into the garage, into the vice, then weld both sides while it was still hot. All a bit of a rush, but it seemed to work. I don't suppose it would be much cop for anything really critical, but seems to have held it all together. Here's how it looked after grinding:

  

Got quite a lot of cavities as various bits of rubbish came out of the casting, but it seems to have done the job ok - and when painted it's barely noticable. So I wouldn't say I was happy, but it's at least fixed enough to use.

Paint

I painted the main castings with hammerrite smooth, in a blue-grey colour. I just used a brush which gave a finish that seemed to fit the fairly rough castings.

Gears, Rust and Oil

I ran over all of the bare metal parts with a cup brush in the electric drill to remove any rust, then cleaned and oiled. There was only surface rust, nothing major. The main rod of the stand was well rusted, but stable, so rather than try to sand back to bare metal, I ran over lightly with oiled wire wool. This smooths the surface off and leaves a smooth oiled, "browned" finish, which will protect it just fine - and doesn't involve removing a large amount of metal.

Handwheel Reassembly

This was pretty straightforwards except that I'd drilled the hole for the grub screw a touch too close to the wheel end, with the result that everything bound a bit when it was tightened up. Easily fixed by filing a small amount from the casting which held it in, which was actually far from flat anyway (LH picture). Didn't take much until I had a nice, free-spinning handle. I locked the grubscrew with locktight to prevent any repeat of the scoring problem.

   Filed down the area arrowed to make it square

Fitting Main Shaft

This went together much easier than it came apart, now I knew how it all worked. Firstly I made a new keyed grubscrew to replace the one I'd drilled out. This was simply a job of grinding and filing down a new screw to form a retangular key on the end:

Then the shaft was inserted and repinned. The old pin fractured from all the bending, so I replaced it with a new one, simply made from a wire nail with the end filed smooth. It's important not to forget the chromed washer which sits on top of the shaft before you do this!

    

Another thing to note is that the pin hole which joins the lower part of the shaft to the upper is not drilled centrally or square. Rather than running straight through the centre of the shaft, it's on a chord. This means that it will fit two ways around, one is right, the other means that the two shafts are offset and will not run true. The offset is quite small and hard to see in the picture below, but getting it the wrong way around means that the drill bit has a considerable wobble.

Handle

I'd managed to save the old handle by glueing it where it had cracked. I sanded it down and revarnished and it should last another few decades yet. To fix it on and cure the fact that it was a very loose fit over its shaft, I turned up some bushings. One on the inside which runs loose on the shaft, then a longer one which is a press fit onto the shaft and is used to extend it. Onto this fits a third bushing which holds the outside end of the handle and runs on the extension. Then it's all held on by a simple bolt and washer. I used mild steel for this, rather than stainless, to match the rest of the machine.

  

Top Nut

Final job was to fit the top nut, spring and washers. I initially thought that this was designed to give some slip, and provide a sort of self acting mechanism. However after trying to get that to work, I decided that was wrong. I now think that the spring is simply to take up the slack, rather than having to machine everything to a very close tollerance. So I replaced the spring (which was flattened), put new washers on, and locktighted the top nut.

Edit: Actually, I've since decided that I was right the first time. The friction between the washers and spring does provide some self-acting, and actually works rather well. Most of the time I don't need to wind the top handle down at all, just turn the main handle and it does the rest itself.