Dissolving (automotive) grease - Page 1
Forum section: electronics / general

author: John B
author_rank: Frequent Contributor
timestamp: October 02, 2025, 10:29:11 am
content: I'm refurbishing a lathe/drilling machine, and the gearbox has been greased with some type of automotive grease where I think a gear oil would be better.I would like to dissolve the grease over time, but I would like to avoid using a heavy solvent or degreaser that would strip out the existing lubrication and probably do more damage than good.I was hoping that an oil with a high detergent content, like diesel engine oil or maybe even a mix of auto trans fluid might loosen and dissolve the grease over time while also keeping the surfaces lubricated, and hopefully work it's way into areas that might be sealed by old grease. However I can't find this type of info, people generally want to strip away grease altogether.

author: indeterminate
author_rank: Regular Contributor
timestamp: October 02, 2025, 12:02:25 pm
content: Kerosene or Diesel will do what you wontDiesel being a bit slower but a better lubricant.

author: nctnico
author_rank: Super Contributor
timestamp: October 02, 2025, 02:05:12 pm
content: Doesn't sound like a good plan to me. I'd take the machine apart, clean each part and re-lubricate with the correct oil. That way you are sure that every part is lubricated correctly instead of hoping (that is also the reason people want to strip all the grease). Maybe this is a good time to replace some ball bearings (if any) as well. Problem with using red ATF is that it may attack seals so I wouldn't use that.

author: jpanhalt
author_rank: Super Contributor
timestamp: October 02, 2025, 02:25:00 pm
content: After 30 years of storage, the gear drive for the spindle Z-axis on my Bridgeport-type mill was very stiff. Removing it would have required a lot of time. I scooped out the gelled grease and replaced it with the appropriate grease (#2). A little working with it freed everything up, and it has worked fine.My question is whether it is an open or sealed gearbox? The mill was sealed, so contamination was not considered an issue. With an open gearbox, as the QC on my lathe has, I would consider a more thorough cleaning, but not complete disassembly. Scoop out what you can get (fingers and forceps with lots of towels work great),flush with a light solvent (Stoddard or kerosine), let drain and blow out, then add whatever the recommended lubricant is. My lathe that had been stored for the same period loosened up nicely. It just uses a 20 weight or so non-detergent oil.

author: Analog Kid
author_rank: Super Contributor
timestamp: October 02, 2025, 06:50:23 pm
content: Yes, Stoddard solvent or equivalent.I keep a couple containers of charcoal lighter fluid for this purpose. They're all some form of naphtha, which is an extremely clean, fast-evaporating solvent. Won't harm any machinery. (But watch out for dirt!)

author: thm_w
author_rank: Super Contributor
timestamp: October 02, 2025, 07:09:04 pm
content: You'll have difficulty with anything other than a strong solvent. D-limonene/zep citrus degreaser will have some slow effect but not close to naptha/acetone/etc.You shouldn't be worried about stripping out the existing lubrication if you are replacing it? Unless you are talking about it getting into sealed bearings, etc.https://www.eevblog.com/forum/mechanical-engineering/

author: Analog Kid
author_rank: Super Contributor
timestamp: October 02, 2025, 07:21:12 pm
content: Quote from: thm_w on October 02, 2025, 07:09:04 pmRight.If the equipment has any ball or roller bearings, sealed or not, I'd think twice or thrice before pouring any kind of solvent into the works. If you strip out or dilute the lubricant in sealed bearings, that is definitely not a good thing.

author: John B
author_rank: Frequent Contributor
timestamp: October 02, 2025, 09:56:55 pm
content: Quote from: jpanhalt on October 02, 2025, 02:25:00 pmIt's an enclosed gearbox, with an inspection plate. The manual was written by Chinese factory workers in the 1980's, so the wording is a bit light on in some sections.It generally calls for motor oil when it comes to lubrication points, but doesn't go into depth about the gearbox. It generally mentions "greasing" bearings (which could include spindles, adjustment handles etc). The gearbox has both unsealed tapered roller bearings and bevel gears in the same housing, the concern being that the bevel gears especially are not being adequately lubricated.I saw a video of a guy with the same model, and he fills the gearbox with 30 weight oil, though I'd probably use some gear oil. The advantage would seem to be that the roller bearings and bevel gear stays partially submerged in oil and ensures everything gets continually coated.At the moment, disassembly is probably a bit more work than I can undertake, plus all the rotating surfaces do feel quite smooth, so I am being careful not to make the situation worse. I might work my way up to the diesel solution. I'm already preoccupied with rebuilding/replacing the motor and electrics on it, I should get it spinning a bit before doing any major disassembly.

author: DavidAlfa
author_rank: Super Contributor
timestamp: October 02, 2025, 10:04:07 pm
content: As long as you don't run it with load or crazy speeds, wd40, kerosene, white spirits... will dissolve it pretty quickly without damaging anything, these still provide some lubrication (+ the grease it will take apart), solvent doesn't!Just like an engine flush.just keep it at enough speed to cause some sloshing so it improves the cleaning.Probably few 5-minute rounds will be enough, draining and refilling with new fluid until fully clean.

author: jpanhalt
author_rank: Super Contributor
timestamp: October 03, 2025, 06:48:07 am
content: @John BThere is no place on my lathe (1966 British toolroom type) that requires grease. I would not disassemble the gear box or for that matter anything needing precision alignment. Get it up and running. If it needs alignment, do that then. 30 weight in a gearbox is probably adequate. BTW, way lube per se is getting hard to find in my area. A good substitute is quality bar and chain oil for chainsaws.

author: coppercone2
author_rank: Super Contributor
timestamp: October 04, 2025, 02:10:52 am
content: I think its a flawed theory. If there is grease in a bearing and you get another oil in there its already compromised. Plus you are liable to wash very small dust into the bearing and possibly make it worse if something was emitting more material then the bearing. All that old stuff is probobly pretty dirty with stuff that might damage a bearing. I suspect things like gears make alot more dust then bearings because their just inherently much less precise and have much more wear and shock forces and stuff that goes through them that leads to wearI think that if you want to be sure, you need to take the whole thing apart and deal with everything on a case by case basis. Big job though, I watched people do it on youtube. But I guess there is no free lunch to get value out of a clapped out machine. For those lathes it looks like you can only get your 'deal' if you happen to have a giant assortment of disassembly tools like special bearing pullers and whatnot for every single part. I suspect that alot of 'reassembly' problems people have is because the disassembly tools that are used are bootleg and damage the parts. Plus you need to be ready to replace some thing that just seized beyond reasonable....Gears are easy to damage, you might need to weld up and then 'fit' some pretty precise geometries to make that process work right, but I suspect there are reasonable solutions if you bother to do research. It is frustrating because you know basically you can remove it in short order by putting the work on it with a pipe wrench and vise grips .The worst is if you don't know if there is some severely flawed part that makes it uneconomical (like damaged motor windings) that can lead to purchase or manufacture of special tools. If I could go back in time I would tell myself to 'start by running a megger test on it'.And probobly seating tools would help too. Not many people own these. I assume hammer and wood is eventually gonna catch up with you.I guess its the mechanical engineers equivalent of wearing or not wearing a ESD strap when working with fets.And the nice thing for disassembly is, you can wipe and scrape ALOT of crap off. Then you use much less chemicals. Less bath replacements etc.

author: bdunham7
author_rank: Super Contributor
timestamp: October 04, 2025, 03:35:47 am
content: Quote from: John B on October 02, 2025, 10:29:11 amDoes the gearbox have a drainplug? Is the gearbox sealed well enough to keep the oil in when the machine runs? If so and you think it really should use oil, it probably should have something lighter than typical automotive gear oils or even diesel engine oils. You don't need a detergent as the grease will slowly dissolve and you can drain the machine a few times over some period of usage. Assuming this is a smaller machine that runs 1000-2000RPM or so, an ISO 32 machine oil like Grizzly T26685 or even just plain ISO 32 hydraulic fluid is probably a better choice.

author: John B
author_rank: Frequent Contributor
timestamp: October 06, 2025, 12:02:55 am
content: I'll fill it up today with oil and see how it cleans up over time.There's no drain plug, but the gearbox housing could easily be drained with a large syringe (maybe a few hundred ml of oil).BTW I forgot this AI gem the other day. Have you guys washed your hands in fresh engine oil today?Quote from: AI

author: coppercone2
author_rank: Super Contributor
timestamp: October 06, 2025, 12:07:58 am
content: thats the slums of pakistan edition of google AIMay be coming to America, for mechanics that happened to think of grocery prices while ordering more gojo

author: Analog Kid
author_rank: Super Contributor
timestamp: October 06, 2025, 12:17:20 am
content: Quote from: John B on October 06, 2025, 12:02:55 amNo, but I use something even better: vegetable oil.I have a bottle of safflower oil that's probably 25 years old. Quite rancid, would never want to use it for cooking.Works wonderfully well for removing anything oil-based from your hands, and nothing toxic in it. (It doesn't even smell bad.) And leaves skin nice and soft.

author: John B
author_rank: Frequent Contributor
timestamp: October 06, 2025, 08:41:26 am
content: Quote from: John B on October 06, 2025, 12:02:55 amWell that was an epic failTurns out the oil seals are no good, so the 30 weight oil leaked out through the spindle and pulley. I've got the manual, and can only see an oil seal on the spindle side, which is odd.While the chassis was free, I've had to purchase a motor and electrics. Not too much outlay, but I'm wary of the sunk cost fallacy at the moment.

author: jpanhalt
author_rank: Super Contributor
timestamp: October 06, 2025, 10:32:14 am
content: Quote from: John B on October 06, 2025, 08:41:26 amAt least the dried grease is gone. I wouldn't worry about a seal on the spindle right now. Unless the seal is split, it will require disassembly. What type are the spindle bearings?In the meantime, I think #2 or #1 EP grease will give protection and is soft enough not to interfere with how it works. My rotary tiller chain drive uses EP00 (aka cotton picker grease). That is way to fluid and will leak without a seal. #2 EP is found everywhere.My lathe does does have a 3-speed gearbox, which is not the gear box I referred to earlier.* It's sealed and just uses oil. I assumed the gearbox you were describing was a QC for feeds and threading. Is it for spindle speed instead?I hope the motor you got was 3-phase so you can easily add a VFD. I added one to my lathe and rarely use the 3-speed gear box anymore.*From the factory it had a total to 6 speeds -- 3 from the gearbox and 2 with the flat belt on the spindle.

author: John B
author_rank: Frequent Contributor
timestamp: October 06, 2025, 08:44:15 pm
content: It's this type of arrangement, where the lathe chuck is powered straight through from the pulley, while the drilling/milling head is powered through a bevel gear off that main shaft. Either is (dis)engaged through a dog-tooth mechanism. It uses unsealed tapered roller bearings. At least they got some fresh oil shooting straight through themI did mull over a VFD setup, but again, scope creep and sunk cost fallacy. Moving the belt manually between pulley grooves selects the speed. Currently I can get it all working for $200 USD of parts. That will probably be good enough for me to get whatever remaining life out of the bearings.

author: jpanhalt
author_rank: Super Contributor
timestamp: October 06, 2025, 09:12:37 pm
content: I have never been much of an advocate for such mill/lathe combinations. That said, I would focus on getting it running, then fix, rather the restore to some idealistic level of performance.To a machinist, a couple of thousands is huge, but for what you need, that may be OK. Forgetting the really crappy home built lathe I had in High School, my next real lathe was a Southbend light 9" scavenged from a local HS that was about to put it in the trash. It had no change gears, and the back gear was missing teeth from students trying to make it stop instantly, or something. I took a community ed course in machine shop (almost no $$$), brazed in the missing teeth, and re-machined them with the horizontal mill so they worked, I used that lathe for years and even made landing gear bushings a high performance GA airplane with it.Your measuring tools are at least as important as the machinery.My advice is and has been, get it running and have fun. Then, fix what doesn't work for your needs (if possible). I doubt the latter will happen. It is often said that CNC is faster, but not more accurate than a good machinist.

author: tautech
author_rank: Super Contributor
timestamp: October 07, 2025, 10:32:54 am
content: FWIW some results from oil research for my 1970 Harrison 12.Shell Tellus 68 is a commonly specified lube for many of the Harrison range of lathes.Tellus is a range of high lubricity hydraulic oils, 68, 46 and 32 are the common flavours where these also double as slideway lubricants.While 68 will give the best protection its higher viscosity adds additional drag to the motor in the higher gears until it warms up some and bear in mind some of this equipment was designed for all-day operation but the heavier viscosity oils fight against us hobbyist turners spinning stuff at high speed doing odd jobbing.You can cross the Tellus range to your favorite lubricant brand but IMO you should lower the viscosity rating unless always doing heavy cuts/work.32 weight hydraulic oils are available most everywhere and considering the use it is put to these days, the modern lubricants with their numerous additives are more than adequate to keep an old lathe lubricated.Oh and one more thing, my Harrison 12 is bristling with lubrication (grease) nipples however the manual clearly specifies NOT to use grease in them, only oil !!With luck a buddy that collects blowlamps scored a US made 1 pint oiler with a needle point that we traded for a blow lamp he didn't have so is now mine and reserved for Harrison 12 oiling duties.And another....White Spirts/Coleman fuel and a rag and some elbow grease is magic for making old grimey lathes look good again.

author: jpanhalt
author_rank: Super Contributor
timestamp: October 07, 2025, 11:27:50 am
content: @tautechMy Smart and Brown (British) lathe also has lots of nipples and a few ball valves for oiling. At the time, I bought Eagle pump oilers for a decent price. I liked the design and fortunately got several. Here's a picture from a recent eBay listing. Mine are in much better shape than that one. That tip and the pump design work great for servicing those nipples and ball valves. The prices today are outrageous. Unfortunately, I have not seen anything comparable.

author: tautech
author_rank: Super Contributor
timestamp: October 07, 2025, 11:33:35 pm
content: Quote from: jpanhalt on October 07, 2025, 11:27:50 amYup.First I tried a push type oiler ....much like a chainsaw clutch drum and bar roller nose greaser but keeping oil in it was a losing battle although I could get oil into the nipples in this unknown to me lathe with unknown maintenance history.When this oiler came up it was the obvious fix and being DeVilbiss it was always going to be good quality.