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Improve Longevity of Worm Gears?

the gear lube ......which must never be an EP oil.....EP oils kill worm drives.
john.k, I think you are thinking about the EP additives which have activated sulfur and are not safe for red metals. There are lubes marketed explicitly for use in worm gear drives, with EP additives that are safe for red metals. These are, in fact, the most commonly recommended lubes for worm gear drives, by the drive makers.
So "must never be an EP oil...EP oils kill worm drives" is too broad a statement. "EP additives that are not safe for red metals will eat bronze worm wheels" is absolutely true. But there are EP additives that are safe for red metals, and some of them are used in lubes explicitly intended for use in worm gear drives.
 
1800 worm RPM is concerning. Research pitch line velocity and recess action. My precision gear hobbers are treated to Mobil SHO 634 synthetic, worm drive oil. It's an amazing product having notable difference in temperature. On machinery we build, carburized and ground worms are enhanced with DLC coating. Properly setup, it's "almost" frictionless.
 
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If you want it to last, use better materials, ensure proper contact and optimal lubrication. Most of this has already been covered here. I would go for a hardened worm (8620 cased is great) and an aluminum bronze worm gear in an oil bath if you want the best longevity. I'll defer to EG or 10fingers on the gear cutting.
 
I have a worm gear box on a band saw that always got quite warm after 30 minutes of use. Drained the oil and replaced it with Mobil SHO 634. Still ran seemingly too warm. Then I added a couple ounces of this (below).....and it runs just barely warm to the touch. It's the lowest cost PTFE additive I've found. Huge improvement, witnessed the results in person.
A bit of it on lathe ways, and it feels like the gibs have been backed off. NAPA does or did carry it. YMMV

GL addative.jpg
 
You can blue up the teeth to check contact. Phosphor Bronze or Aluminum Bronze with a hardened steel worm works. Cast iron gear and soft steel for worm also work. Mobil 634 Synthetic works well for worm gears.
 
The worm and wheel in my grinder's workhead is only a tad over $9000 now.
Mobil SHC-630 made a huge improvement in life over the factory recommended gear oil.
Easily four to six times the life by just switching oils.
 
Its hard to tell but the tooth form on the wheel looks a bit thin to me, you have 2.5” dia available to use so try a lower dp, the finish on the worm is important as it rubs on the wheel, so make that as well as you can from steel and the wheel from bronze, run them in hp gear oil as used in car diffs, in the uk it’s SAE 90 hp or similar
 
I really appreciate all the replies, guys. Sounds like I need to connect with a specialty gear maker to get optimal thread geometry and use a proper lubricant before I rule out a worm gear setup. I forgot one important detail: The end product must use a food-grade lubricant. Any recommendations?
Thanks again, everyone.
 
For food grade lubes, do some searches for that, then get samples for testing on your product. If this is used in pharmaceuticals or food preparation, you'll want to do some careful studies of particle generation and how to minimize it, including whether seals on the exterior are themselves "food safe" if any bits are shed.
 
Blew up your photo big to see what you were doing, that's not a great picture there, hippy :(

It's also not very nice machine work, ahem. And it appears (from the not-good photo) that the throat on your gear doesn't match the diameter of the worm very closely which is not so good.

I thought you were running a helical against the worm from your description - actually you could try that and use carburized parts, it might actually work better, but the traditional solution for this was hypoids. Sewing machines used them a lot. Just offset the shafts a tad. If you can rearrange things a little, ground hardened spiral bevels are available off the shelf. (But maybe not this small ?) And there's people (Fanuc robots for one) using spiroids, under a new glitzy-sounding name. I've never done it but you are supposed to be able to cut those on a conventional hobber. All of those methods will keep your single-reduction, right-angle setup the same but should have longer life.

Better materials, finish and lube will help but I don't see you getting eight times better results that way :(

Since there's so little load, I'd probably try the carburized or nitrided helical first ... it's easy and cheap to give it a shot. You can do the worm, too. Stainless nitrides nicely.
 
The compact mechanical actuator mechanisms have a very interesting combination of a worm and a hypoid system........the hypoid pinion is so far offset ,that it has a single spiral groove cut on a conical form which meshes with what appears to be a hypoid crown wheel ,IE a worm wheel that is driven on the face ,not the periphery.......verry interresting!
 
The compact mechanical actuator mechanisms have a very interesting combination of a worm and a hypoid system........the hypoid pinion is so far offset ,that it has a single spiral groove cut on a conical form which meshes with what appears to be a hypoid crown wheel ,IE a worm wheel that is driven on the face ,not the periphery.......verry interresting!

Those are spiroids, invented by Illinois Tool Works in about the fifties or so ? Nowadays they have different names for them and they don't credit who invented them but that's where they came from. ITW had a few different varieties which they gave different names to - spiroid and planoid I think and some others but basically, "spiroid" covers the family.

You can cut them on normal hobbers, that was intended to be the advantage over conventional bevel gears. Also you can get pretty high reductions with them, which might interest the OP.
 
I have bought worms and gears from Boston gear in the past. Seems that they were very reasonable. You might see if they have any thing for you and price it.
Just remembered that your size Stock Drive Products might be a better source, they specialise in small gear drives.
 
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