Milling Rite

If you can deal with bores/counter bores and spacers to get them aligned, diameter doesn't mean much- just the ratio if you want the knee hand crank scale's grad marks to remain meaningful. I suppose you could even go helical for that baby bottom smooth feel. Match up the driven gear as best you can, then fanagle the driving gear to fit. That's why getting a close-enough gear pair is better than sourcing a perfect fit single replacement.
 
I would replace both while you are in there, whatever damaged the big gear might have cracked teeth on the small gear that might not be easily visible. I would think all the gear companies would make custom gears, but it won’t be cheap. I was looking for a particular metric gear for a project I will be doing and a local gear manufacturer was willing to do it, but I could have bought 10 of the closest stock gear for one of the custom ones.

Since this is an American machine, I think the chances are pretty good that you will find something close enough to fit. You might need to modify a bore or the length as Pontiac mentioned, but that should be easy enough.

If you can find something that would work, it might be worth trying to repair the old gears first, and if you screw it up, at least you know you can get something, so the pressure would be off.
 
I can deal with modifying things, as long as I can eventually get to a point of proper function. I'm not too concerned about the scales being accurate, to be honest; I think it makes more sense to set up a DRO and go from that.

I kind of wondered why this wasn't a helical gear set; I guess it's a matter of expense...or availability in 1966. It would be a fun modification to make, as long as I'm in this far.

I think my first step will be further cleaning and getting these screws and shafts out of the way; once I have everything in better condition I can assess anything else that needs attention, and in the meantime I can take some measurements on the gears and start looking for replacements. My touch and regulators arrived intact, so if I can locate a set of bottles I could actually get myself going pretty quickly with some brazing practice. Either way, there's a plan...and if I get totally stalled out, I guess it can start getting some body filler on the bad spots on the base.
 
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I skipped adding a scale on the knee, I figured using the dial for that axis was good enough, but if you plan on adding that, then whatever works for the gears is a good plan.

I never thought about using spiral gears for this instead of straight bevel. If you can find something that fits, might be a worthwhile upgrade.
 
Well, the good news is that I've slowed myself down and not jumped off a bridge. The bad news is that I've done so because I can't figure out how to get the retaining nut off the top of the elevator screw. I don't really have a way to keep the screw from turning and I don't see an obvious way to create that, and the retainer nut on the top is seriously tightened down. I might be able to get it loose if I could get an impact wrench on it, but there's no access/provision for that...so, I'm a bit stuck. Again.

So, question: what are the chances that a strap wrench is going to find enough surface area on that screw to allow removal of the retaining nut?
 
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jwmelvin said:
What about a block of soft wood, drilled then split?
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That could possibly work; I have some wood scraps laying around that might work. I don't think I have a 1.375-ish" bit, but I could probably use a 1.25" spade, let it cut roughly and then just crush the wood into the threads by clamping it together with a few bolts. That might hold up.
 
Strap wrench can be hit or miss. The Ridgid ones grip like hell if you rub a little beeswax into the strap. A little heat on the nut might do the trick. You can also wedge something (a fob of leather, a shoelace, a rag?) into the gears to chock the mesh enough to get a feist on the wrench. Ozzy said to never say die. I think it was for times like this.
 
Pictured: Friday afternoon, 4:47 PM.

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Like, I know this the location of this bore doesn't exactly matter so long as it's providing support to the elevator screw nut, but damn.

I've putzed around with a lot of machinery over the years, but I've not often torn something down to the base/frame...and that makes me wonder how often things like this are done. I suspect it's far more often than I suspect...and that was a very Austin Powers-esque sentence, but I'm leaving it as-is because it's funny and accurate, unlike the aforementioned bore.

Also, I thought I had a 1.25" bit...but I don't, so evidently it's time to add another bit to the "Stuff I'll Never Use Again" drawer. And I don't even have that drawer, yet, but I'm starting to need it.
 
Dave Bonzo said:
Yeah, that's solid advice; jumping off bridges is the only thing I'm good at, so I tend to gravitate - ha - towards it.

I do notice that they'll cut custom gears, so I guess that's always an option...at least, it's an option if I should need 24 backup sets. Hopefully they'll have a replacement that can be made to work; that's probably the fastest, simplest solution. If not, I can always email them the measurements on this gear and see if they know what could be done...and maybe work on a repair solution on my own, in the meantime. And I guess I can disassemble the rest of the knee and clean it up while I'm here; might as well work on some paint and finish restoration as well, at this rate.
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Custom gear cutting will be $$$.


I’ve done a similar repair in the past by making an insert and a profile cutter.
 
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