The restoration or repair of almost anything like old machine tools, old engine, old motorcycles, old vehicles... requires making parts or service tools. Having worked overseas where we had to work with what we had, I can say I can really appreciate this sort of thing.
Overseas, on job where I'd field design a small powerplant around a used medium speed diesel engine and generator (O-P Fairbanks) or around a Skinner Unaflow steam engine and boilers was where I cut my teeth in this sort of thing. I'd arrive on site not knowing what I was going to find other than the basic engine, generator and switchgear. I had no idea what sort of shop and construction equipment would be on hand and what the level of skills and expertise the local people on site would have. I also had no idea as to materials and much else we take for granted.
I learned a lot in a hurry. First off, nothing was scrap. Second off was often the building of a forge (fired on charcoal made by local "charcoal burners" from branches and tree trunks cut localls). With the forge built, we could make tools. This meant forging chisels out of rebar (which hardens nicely) as well as hot bending rebar (slow cooling in dry sand) and similar work. We usually had a beat up lathe and maybe a wobbly old drill press. On one job, the previous users of the lathes had crashed the carriages into the headstocks. Some of the quadrant gears had stripped teeth. We needed a lathe to cut threads on the anchor bolts to hold the engine and generator on the foundation. fortunately, we had an oxyacetylene outfit. I built up the busted teeth with brazing, then I ground a form tool bit as best I could freehand. I set the gears up on an ancient G & E shaper which sounded like a rock crusher when it ran. Using the shaper, with the gears clamped to the end of the table with angle iron and all thread, I was able to rough cut the teeth in the brazed repair. I then "ran them in", letting the bronze cold work to form. With the lathe running, we cut threads on the anchor bolts and did other jobs.
On another jobsite, we were about 100 miles off any paved road. By day, we ran a diesel power unit (a Brazilian copy of a German 4 cylinder water cooled diesel on a skid with lever operated clutch & radiator) which was belted up to a 25 Kw generator. The generator had a brush type exciter cantilevered off the end of the generator rotor shaft. The slapping of the vee belts as the generator came on and off load played hell with the exciter brushes and commutator. We had to turn the commutator, but needed that generator to make power to run the lathe (a new "Romi" lathe made in Brazil, set on wood skids in a dirt-floor barn where we stored parts and tools). The nameplate on the generator said the exciter used 110 volts DC. We had a Lincoln SA series welder with magneto ignition. It produced, in addition to DC welding current, 110 volt DC power to run a few lights and tools with "universal motors" such as angle grinders. We moved the welder to the generator shack, and disassembled the exciter, removing its armature. I then took a long extension cord and cut off the female end. I stripped the wires and connected them to the terminals in the wall-mounted control box where the exciter leads had connected.
We then started the diesel engine and clutched in the generator. Once it was rolling, we crank-started the Lincoln welder. We had excitation and got voltage. We took the armature to the barn and set it up in the Romi lathe. We then cut the commutator, and I undercut the mica using a hacksaw blade with the set ground off the teeth, one slot at a time. Once we had the generator back together, another fellow took some angle iron and steel and built a better bedplate with jacking screws to square the generator and hold belt tension.
On almost any of these jobs, we used to go to junkyards and buy anything that looked remotely useable. Using old axles that we softened in a fire was commonplace for getting "good steel". I learned to make-do with what was at hand and not look back at what I might have had been on a job in the USA. It was one of the most valuable lessons I ever learned in my life and I apply it continually to all aspects of my life. In plain English, bitching and moaning about what you do not have will not solve anything and just wastes time. If the name of the game is to get machine tools running, then use any means available. Ask an old farmer about this sort of thing. One old farmer was telling me a story about how they broke a splined shaft in a hay baler when it was needed most, during haying. The dealer said a new shaft, aside from the cost, would take a few days to get. He approached a local machine shop who gave him some answer like they they really did not want to take the job on. The old farmer had a lathe in his barn. It was not quite long enough to turn a new shaft, but his son did it with the tailstock half off the end of the bed. He used any likely chuck of round stock he could find in their iron pile. The splines were cut in with an angle grinder, and the shaft worked well enough to get them thru putting in their hay.
Rigging a temporary drive to get a machine tool running to make parts for another old machine tool is commonplace. It may mean cobbing up a bracket from 2 x 4's or scrap steel and hanging a motor and jackshaft off it. Another lesson I learned very early in my life is "there is no single right way to do very nearly anything". As long as it works safely and does the job, this is what matters. How many old flat belt driven lathes and mills are setup with drives using old automotive transmissions rather than countershafts with correct flat belt pulleys or gearboxes with proper ratios for machine tool drives ? How many old flat belt driven machine tools are setup with "turned in place" wooden pulleys rather than cast iron pulleys ? In short, if a person needs a machine tool to run to make parts for itself or another machine tool, getting it rigged up to run by any reasonable and imaginative means is what it's about.
I lost track of how many parts and service tools I've made for old "Airhead" BMW motorcycles. I can speak from experience, and say there is a special feeling or satisfaction that comes when I am riding a motorcycle with parts I made running in it, and having had work done using tools I made for the jobs. At 70 + mph, taking a nice curve, going with the bike nice and easy, it is quite a feeling. In 2008, the slip rings on the generator in my own old Lincoln welder failed. Lincoln had discontinued that machine and told me that the slip rings were from a "bad batch"- i.e.- brass tubing with a seam weld. They said I had gotten one of the "bad machines", but it was then about 25 years old. The local welding supply said it did not pay to repair my welder. I knew I could make a new insulating bushing and slip rings in my shop. A local "armature shop" who works on anything and everything said they'd work with me on repairing my welder. I machined a new insulating bushing from Micarta, and new slip rings from bronze- both scrap from the powerplant shop. I had to make a mandrel to turn the OD of the insulating bushing, and figure some interference fits. I got the bushing and slip rings in place on the rotor and silver-brazed the pigtails to the slip rings. The rewind shop did the rest, connecting the pigtails to the right windings, then dipping and baking the rotor and dynamically balancing it. I've used the welder many times since. Usually, I do not think about the slip ring repair, but when Hurricane Irene came thru, we were without power for ten days. We ran the welder a couple of hours at a time x 3 times a day to keep the refrigerator and freezer contents from spoiling and to run the well pump and boiler burner. We had hot showers and three squares a day thanks to that old welder. This past winter, we had a five day outage, and again, the old welder came through. When that snow storm outage ended, I gave that old welder a kiss on the generator sheet metal, and my wife gave it an affectionate pat. This is what having old machine tools and imagination are about. I machined the parts for the welder on an old South Bend heavy 10" lathe with a ridge worn on the front bedway and some backlash in the cross feed screw, and did it accurately enough to make the interference fits. I ground my own HSS tool bits. The next person might look at my lathe and turn up their nose. Knowing how to get the work out on old machine tools is part of the challenge.
In the real world, old machine tools are pretty much a non-starter, incapable of meeting today's requirements for production and accuracy. I am realistic. An old friend, a master toolmaker (since deceased, the guy who made the stainless steel case for my railroad pocket watch) once asked me if CNC could do the work he did. He had no DRO on his machine tools, and was into his 90's when he asked the question. He was machining jigs and fixtures for the grinding of prisms for medical lasers or something on that order. It was very fine work, and he was still being contracted to do it, despite being in the age of CNC machine tools. The oldtimer knew about CNC, and he asked me that question. I did not have the heart to tell him that CNC could do the work he was doing, aside from generating geometries that no human could manually machine. I told him CNC could not do the work he was doing (thinking in terms of the shop math he did on paper- waking me with phone calls at 2 AM or so to check his numbers- and in terms of his use of sine bars, rotary tables and similar on machine tools he'd scraped in to get the accuracy he required).
Machine tools are great teachers and for a home shop or occasional use on one or two special jobs in "working shops", the old machine tools have their place. I liken working on old machine tools to how two different people see a busted spring leaf or old axle: one sees junk to be disposed of, the next is already seeing what can be made from them or at least thinks in terms of ratholing them for future projects.