I have a batch of screw jacks used for lifting houses. A couple of them are newer, most are old. What is the right lubricant to use on the threads? They are all Acme threads as far as I know, screws are mostly 2″ diameter, and a lot of them need a good cleaning and relubricating. These threads are put under very heavy loads (2″ threads are rated at 20 tons as far as I know).
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I would think any kind of grease would suffice. Crisco? Bacon fat?
A tub of wheel bearing grease ought to work well. It's thick enough to use as rust preventative in between uses as well.
If you are never going to turn the jack under load (we all wish), anything will work.
Under load, use a high pressure grease, or even better, 120 wt hypoid gear oil (car rear end oil)
They are definitely used under a lot of load. Currently using a bunch of them to deform a house that has settled. Probably need to exert more force doing that than if I just lifted the house entirely.
Sounds like I oughta stop by Napa and see if they have 120wt hypoid gear oil.
Next question, I guess, is there any smart way to clean the female threads on these things? Small wire brush and paint thinner?
clean the female threads
Since they are big (2"), I'd try a pressure washer with angle nozzle.
Beleive it or not, I do not have any big screw jacks. Pop had a bunch, too heavy to ship out here after he died, so brother has them. Pop had some mil surplus EP grease (extra pressure) that the railroad called out for use on screw jacks.
Kinda got spoiled with hydraulic jacks.
Recall the MD80 (think it was) that crashed off LAX due to horiz stabilizer jack screw being improperly lubricated? If you are turning your jacks under heavy load some type of high pressure lube is needed, and hypoid gear oil is about the highest pressure stuff there is IIRC.
I have and sometimes use hydraulic jacks but in this case, where the jacks are in place for a long period, screws are easier. They can sit on the piers right next to the (now too short) posts and I can raise them a little each week. It would be awkward to lug a large hydraulic around under the house to each location. Noticed some big Simplex ratchet jacks on eBay, they look very cool but weigh so much that shipping is ridiculous.
I have both hydraulic and screw jacks. The screws are better to leave a load on. Anytime we go home for the night or weekend, we block up next to any loaded hydraulics. They can blow of bleed down.Always used 90 weight for the screws,mostly because I have it handy and it is easy to use, but wheel bearing grease is probably the more right thing for them
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Cleaning the female threads: For a solvent I use 10w-30 thinned with kero.
Male end of a battery post brush for getting into the threads, or one of the wire brushes used to clean out drilled holes in concrete.
Edited 6/3/2009 7:19 pm by dovetail97128
Kerosene or heating oil. Thats what my grandpop told me to use on the ones i got off off him. It lubes em and cleans em. Grease tends to collect too much dirt for my taste, especially when dragging around under houses.
A grease containing molybdenum disulfide. The MoS2 is an additive for very high pressure, low speed sliding surfaces, which is what you have with a jack screw. "Regular" grease is better for bearings with rolling elements such as ball bearings or roller bearings.
As far as the female threads, I presume you can dismantle the jack. Yes, a small wire brush or even a toothbrush with a suitable solvent. I like electrical contact cleaner myself, but thinner should work fine.
Edited 6/3/2009 7:07 pm ET by WayneL5
I second the reply of using kero or diesel. A little messy, but it makes them turn really easily. I have found that heavier grease in cold weather makes the screws a bear to turn. I have also used Wd-40, but you have to keep re-applying it during the job.
As for cleaning the threads, I scrape as much junk off with a metal scraper, then I use any degreaser solvent that I can find. I then add a light layer of grease and use the spraying of wd-40 to thin it out. Basicly, a little of this and a little of that.
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Any weight motor oil slopped on with a brush.
mike