Machinist help and/or information, please

Trying to help my father out with a part for his four post lift. He's had it since the mid 80s and the name brand and any identifying marks are long gone and he doesn't recall any details. Doing this over the phone has made things a bit more difficult, because quarantine. He called around to a bunch of car lift retailers he could fine online and everyone was either unable or not interested in helping out.

Anyway, so the "nut" that rides on the worm drive on the active post has stripped out after 30+ years of use. It's brass, I'm guessing to not wear out the worm drive. He was raising a car up and it got a few inches up and skipped and dropped. He lifted it up with a few floor jacks and has the "nut" removed. And I'm trying to help him with a solution.

I've attached a few pictures. Possible solutions are have a new piece machined or have a tapered insert with threads machined and pressed in and use the existing shell with the supports the lift rides on, which appear to be fine. Or find the original piece and simply buy a new one. However, it would appear as though everything is hydraulic or chain driven now and that might be why the places he called weren't helpful. Any solutions I'm not thinking of or other options are welcome.

The "problem" is that I spoke to two machinists locally that I've worked with before and neither of them were set up to machine a buttress thread. The "nut" is a 2" 3TPI buttress thread.

He held up a tape for rough scale in the pictures. I can get exact measurements from him, if needed.

 

Or maybe even a source for an actual nut (or two?) that's got the right threads and he can weld on the posts the lift rides on? Would the material be an issue if it was a stainless nut, for example, instead of brass? My Googling hasn't turned anything up.

 

Iv never done a buttress thread before, so my concern would be getting a correct thread fit, as having the threaded rod on hand for fitment obviously isn't a possibility. Buying the tooling(internal threading tool big enough for that size/pitch) is going to add a big chunk to the cost. Personally, I'd exhaust every option of buying a replacement part before looking at making one(or two if I was him), unless he finds just the right guy that has done this type of thread before.

 

Is that whole pictured assembly one machined piece of brass, or is there an "insert" for the buttress-threaded portion that is removable/replaceable?

 

Not the exact part but a couple of searches for that image and Car Lift Load Nut bring up various pages on this site -- https://awt-shop.de/en/search?page=search&page_action=query&desc=on&sdesc=on&keywords=lift+nut

They may have that part or something compatible. It looks like they have parts for every type of lift ever made.

 

It's a single piece of brass. However, one of our thoughts was to just machine the threads and use it like an insert. He has the ability to turn down the inside to accept a press fit.

 

Wow, that's surprising. Seems poorly designed for one of the only true potential wear items on the lift........

Unless you can narrow down the manufacturer/exact part, I think that would be your only option save for replacing the lift. However, if he got almost 40 years out of the thing......

 

I suppose they made the wear item the nut instead of the worm drive.

If he didn't re-do his garage and build this lift into the floor recently, he'd just get another lift. Trying to save him from some concrete work as well and exhaust all options before doing that.

 

Thanks. I forwarded that link to him and he said he went through that site for hours and even called them yesterday before we spoke. No dice.

 

Not that I have a solution, but more likely bronze. Brass would be way too soft for that. Pretty sure you'd have to have a tool custom ground to cut anything, if you could figure a way to safely combine the new and old part as you were describing. Seems like a risky proposition, given the end use.

 

Do the other three posts have the exact same piece?

Seems to me the “nut” could be built in two pieces and bolted together to get the inside thread cut properly.

I’d think building it from a harder material and making Teflon sliders to ride against the stainless screw would be a better way to design a replacement. Same with the lift pins (I’m assuming that’s what the nipples sticking out the sides are).

But I ain’t a machinist nor do I stay at Holiday Inn Expresses.

 

Look up Adam Booth on Facebook. He is one of the best machinists in the world and lives/works like two min from me. Motorcycle guy also.
Check out his Youtube also. I know he can do it. But not sure his timeframe.

 

i'd check with manufacturers like vsgdover, if they have a matching spare.

 

You may be right. It's a 10,000 lb lift I believe. If anything, we were discussing a harder metal, given the end use, like you were saying.

Edit: You're right. It's bronze. I was taking notes last night when I was talking to him on the phone and didn't write down the material. My mind must've turned bronze into brass when I saw the pictures he sent this morning.

 

If you don't have any machinist buddies you can call a favour in that is going to be a tough fix. Looks like a one piece casting, and given the application I wouldn't even think about sleeving it. Cast parts are usually already designed to minimum wall thickness and sleeves aren't a good idea for a structural part in a lifting device. The guys who said they weren't' setup to cut a buttress thread were telling you in a nice they didn't want the job IMO. Nothing special about a buttress thread other than some time to grind a proper toolbit. The material cost on the other hand $$$, it's gonna sting. Unless you want to re engineer it to be 2 pieces, but that's another can of worms altogether.

If you can't find an original part which is probably the best case scenario, then looking into a new lift might be a more cost effective option. I hate saying buy new, and will always try to fix something, but in this case it might be the best solution. On the other hand, there might be a lot of shops out there struggling for work right now, looking to keep some good guys busy and you may luck out and find somebody who wants to take it on. My boss does that sometimes and I've got to make some interesting stuff for some walk in guys who unknowingly got great deals.

 

Tell him to stop the cookout videos and make a video about making this part

 

No. Only one post is active. The other three have pulleys and cables linking them. This post does all the work, the rest just balance out and ride on the tracks. Only this post has the worm drive. So this nut takes the entire weight that's on the lift.

Not sure what you mean regarding a two-piece solution or if sliders would work. I would think the more threads, the more they're sharing the work.

 

Fair enough. Neither of them owed me anything and I wasn't asking for a favor. In the past, they've done jobs for me and I gave them money. I've worked with machinists, but it's not my gig. If it's a pain the the ass from their perspective, I can get why they nicely told me to f off.

Duly noted on the sleeving idea. I definitely don't want this part failing on my dad. Literally.

Adding the posts the lift rides on isn't an issue, at least I don't think. My dad is a pretty capable welder. The primary issue is just getting something that threads on to that drive.

 

Is it possibly made out of oil-impregnated bronze (Oilite)?

 

I sent him that link. Thanks.