Lathe gearbox lubrication

[rficalora]

I'm reassembling the gearbox on my Samson (Tida) lathe.

I see four different types of areas to lubricate:
1. Shafts where they rotate on the gearbox case. These have oiling holes. The Tida manual calls for 160 SSU which I've not been able to correlate to a consumer designation. The Grizzly manual (for a later version of the same lathe) calls for ISO 68. And, I read another thread here arguing for ISO 32 which I was able to get locally. Should be OK or should I get ISO 68/something else?

2. The gears themselves. No sign of oiling holes/paths except one side of the shaft with the change gears which has a spiral oil galley. The others are smooth shafts. Like above, the TIda manual calls for SSU 160 for the gearbox generically. The Grizzly manual calls for ISO 68 for the gearbox generically but shows oil plugs which my lathe does not have. I read somewhere a recommendation for grease on the gears but can't find that reference now. I do not see how oil would get on the gears from the oil holes going to the shafts other than what works its way past the shafts. Any ideas how the gears should be lubricated? And with what? Once bolted to the lathe bed, access to the gears is limited.

3. Thrust bearings. Two sets on the outside of the case where there are couplers going to the lead screw and carriage drive. One set is inside the case on the lead screw shaft. ISO 68 oil?

4. Roller bearings - two roller bearings on the shaft with the gear selector handles. Should these be packed with grease? Or should I use the same ISO 68?

 

[pontiac428]

2. The gears themselves. No sign of oiling holes/paths except one side of the shaft with the change gears which has a spiral oil galley. The others are smooth shafts.

I see bronze bushings presed into those gears, which means there are indeed oil paths to the shaft- through the sinters and pores in the bronze. Splash oiling should be sufficient. Sometimes, wool wicks with wire cores are used to direct oil from (relatively) far away oilers to places like that.

3. Thrust bearings. Two sets on the outside of the case where there are couplers going to the lead screw and carriage drive. One set is inside the case on the lead screw shaft.

These look suspicious to me. What's with the worn thrust surface on the side of the gear on the opposite side of the cast shaft support boss? That tells me someone traded one friction point for another. I don't know Sebastian from Ganesh, but I'd assume there were bronze washers on BOTH sides of that boss when the lathe was new. There is no need to control THRUST on a straight cut gear in a radial-loading arrangement. My money says that's some Ozarks engineering there, or there is at least a thrust bushing missing.


ISO 32 is plain-jane HDO hydraulic oil. Depending on brand, it may or may not have extreme pressure additives. It is called out on many many gearbox applications all over the shop. EP additives are said to eat the zinc out of yellow metals, so those bronze bushings will require you to shop for non-additive oil (that is easier said than done, oil companies don't like sharing their "proprietary" formulations, even when the law requires it)

ISO 68 is circulation oil. It's a little bit stickier and has a little bit more viscosity than your HDO. There is enough overlap in the spec for some oils to receive both ratings. What is best for you will realistically come down to temperature. Canada outbuilding shop, use ISO 32. South Texas use ISO 68.

No matter what, consult the lubrication schedule in your manual and go with its advice before taking mine.

 

[Chipper5783]

I have a few machine tools - the gear boxes are all quite similar - straight cut spur gears, the gear sliding on splines for selection, motor input speed of 900 to 3600 rpm, the gear boxes are all quite similar. I have manuals for nearly everything, I try to follow the manufacture’s recommendations - most of the time the recommended lube is not something that the local lube dealer has ever heard of! The all recommend a mono-viscosity, or straight viscosity, non-detergent “circulating” type oil, with rust & oxidation inhibitors, ideally anti-wear additives. What drives me crazy is that the viscosity is different on every one: I now stock ISO 32, 46, 68 & 100. In terms of the mechanical function, the gear boxes all look about the same. My first lathe specified a 32 weight oil - I went with Gulf Harmony HVI 32, which is a hydraulic oil. Hydraulic oil likely has some other additives (such as additives to manage moisture), but I can’t imagine that such would cause a problem. These may also be referred to as gear oil, but I would avoid extreme pressure (EP) additives unless it has been specified. EP additives are generally only used on gears that have a wiping action (like hypoid gears).

All that said, you pictures look like the cluster gear in the threading/feed gear box - which looks like an open gear box on that particular machine. Indeed, they would probably specify a heavier lubricant (ISO 68 or 100). I have a Standard Modern lathe with that style threading/feed gear box, and a splash lubricated main gear box - the manual calls out ISO ~100 (near enough) for both applications. They specify same oil for everything on the lathe. I have a few other machines, I generally use a “way lube” on the slides (a 30 year old jug of Doall way lube that is nearly empty, or Mobil Vactra, which is also a way lube), the exception is if the machine has a one shot oiler, then I use what the manual specifies.

 

[rficalora]

Thanks for that quick reply Pontiac428.

On #1 (the gears themselves), just clarifying two points:
- "Splash oiling should be sufficient." The bottom of the gearbox case is open, so there's no oil bath at the bottom. Does that change anything or are you saying splash oiling as the oil drips & gets flung off the shaft where the oiling holes lead?

- with respect to "wool wicks with wire cores" to direct oil from (relatively) far away oilers to places like that." I didnt find any wicks. Would it be advisable to add some in the oiling holes? There are 6 holes in the top of the gearbox case, each leading to one of the machined holes in the case where the shafts pass through. Each hole had a plastic plug on top.

On #2 (thrust bearings) - According to the exploded diagram, it's designed as I have it (to be fair, the diagram shows that gear flipped 180° but the cradle drive would never engage if it were flipped that way). The thrust bearing picture above is #3-10 in this diagram with #4 being the thrust washer and #8 being the gear.

And, thanks for your info on oils and the bronze bushings.

 

[pontiac428]

You might need to ask around about Sebastians and wicks, but wool wicks are pretty common. I bought a lifetime supply of wool wick cord from McMaster Carr for a few bucks. I bought oversized and whittled it to fit, and it doesn't go bad for a decade or three, so it's a minor expense but a major component if your system was intended for it. So this gearbox is a total loss oil system that depends on a daily lube schedule. That would mean those are definitely oilite bronze sinter bushings, which can hold oil all day.

With total loss systems, it doesn't matter if you use detergent oil or not. Splash systems should never use detergents, which keep particles in suspension to be caught by an inline filter. You want particles to fall out of a splash system and settle to the bottom where they won't be entrained into the bearings and gears. But total loss oiling washes it all into your chip tray, away from sensitive parts. It's actually an elegant system.

I might try to slip a thin bronze shim washer/thrust washer onto that #8 gear to keep it from running against the gearbox like that. You can also order needle bearing thrust bearings (not very expensive) that take up 1/2 the stack space, allowing them to be put into assemblies as a retrofit. Axial movement on your lead screw always has the backlash taken out by the feed, but any play will cause finish problems at minimum and dimensional problems at worst as you change feed directions. You want that part of the system to turn freely without resistance or play.

 

[Richard King 2]

Many of those designed machines are close in design. Grizzly Machine lets you download manuals for free on all of their machines. Here is one for a small Asian design. Look at the lathes on their site that is closest to yours. On page 49 show lubrication. I suspect all designs use the same lube..

https://cdn0.grizzly.com/manuals/g0765_m.pdf

 

[rficalora]

Thanks again! Excellent information!!

Seems like if needle bearing thrust bearings are 1/2 the thickness, I could retrofit two - one on the outside of the case and one on the inside. That, plus a bronze shim washer if/as needed to take up the slack sounds like the best answer.

I'm collecting my parts list as I disassemble the lathe. I've already found a drive gear missing its woodruff key, two missing bolts (both bolts that hold the block that retains the lead screw & the carriage drive shaft) and one taper pin missing.

 

[rficalora]

Many of those designed machines are close in design.

Thanks. Mine (Samson TD-5aa) is very similar to the Grizzly, Jet, and others and the Grizzly operation manual is very well done. But, the gearbox is notably different than the Grizzly version - functionally the same with one lever moved from the top to the front - but internally different. I also have a Tida 4aa manual & so far the exploded diagrams match. I think the 4aa is the same except smaller swing &/or bed length.

 

[matthewsx]

Thanks. Mine (Samson TD-5aa) is very similar to the Grizzly, Jet, and others and the Grizzly operation manual is very well done. But, the gearbox is notably different than the Grizzly version - functionally the same with one lever moved from the top to the front - but internally different. I also have a Tida 4aa manual & so far the exploded diagrams match. I think the 4aa is the same except smaller swing &/or bed length.

I have a Samson 5aa as well. I just use tractor supply hydraulic oil, it's IOS 68.

https://www.tractorsupply.com/tsc/product/vp-racing-lubricants-ultra-j20a-plus-utility-tractor-fluid-5-gal-vp2040114

These things are pretty low stressed in hobby applications, I'm sure you could wear them out if you really tried though. Don't use grease, chips will stick to it and not make you happy.

I have 6 little holes on the top of mine with rubber plugs.

Not much oil seems to go into them though before it comes back out the top but there may be some kind of wick in there distributing it, don't know. Since you have it apart you could get some small copper tubing and fashion a pressure lube system. Don't know if I'd bother to change out the thrust bearings but you could look into it, when you run it you'll see how slow it turns most of the time.

John

 

[rficalora]

Thanks John. Do the oiling holes in the top of the gearbox have felt wicks in them?