Shoot Shoot Shoot --- Lathe died

[cfos00]

Hey guys-

Spoke with Ty McNeer on this, and didn't know if anyone else had any ideas on it. Lathe has up and stopped...and I mean stopped. The motor and gears are turning, but the headstock grinds to a complete halt and locks up. Meanwhile, the gears turn, and the the fly wheel and associated gears are freely moving. There seems to be friction building at the headstock right next to the body of the lathe and jaws. The headstock is driven purely by the gears and belt outside of the body.

In terms of fixes, I disassembled it as far as I could, which was everything up to the bearing at the back-end and everything off the shaft of the headstock. I could not, for my life, get the actual shaft to move. The gears and flywheel moved freely when I had it apart. Again, only friction seemed to be in the front bearings area near the front of the headstock.

Ty seems to think bearings. Any other things to try? And how in the world would I get the stupid shaft out to replace the bearings on this thing if that's what I need to do? The lathe is a harbor freight Central Machinery 9x20" gearhead metal lathe, which is a clone of the Grizzly G4000 bench lathe.

Any ideas?

[DocsMachine]

Lets see some pictures. Roller bearing or plain bearing?

Belay that. Missed the description. But let's see some pics of how far it was taken down.

Doc.

[cougar20th]

If everything else is good and you have isolated it to that one shaft it leaves bearings. Sounds like as it spins it heats up.and seizes.

As far as getting the shaft out it looks like from a quick search that it should come out to the Chuck end of the shaft. Issue is if the bearings have seized to the shaft and spinning in the housing it will be difficult to get out. I'm guessing it's a casting which means when pressing or hammering you want to support the casting so you lower the chance of cracking it. If you are hammering do not hammer directly on the shaft. Hit something else you have over the shaft.

[flyweightnate]

The Grizzly uses this size. It's important to get the right end play/ preload on these to prevent seizing. If there's no spring inside to keep the cups tight to the cones, you'll only want a couple thou preload so when it's hot and full of oil it doesn't jam up but isn't sliding and skewing from too much room.

TRBs are funny in that you have to turn them while tightening the nut, or they'll feel tight until you turn it on and hear them rattle.

I think, officially, 0.002" preload is about right for a small lathe.

https://www.skf.com/group/products/r...ctid-32007%20X

[flyweightnate]

Oh... and never buy bearings from Amazon. They're probably 80% counterfeit junk, that look real but trace as fraud (as I found out buying bearings for my table saw). Motion Industries or Applied will be good, reliable sources.

[cfos00]

I actually just ordered the part straight from Grizzly. Should be here soon, so I can try and get the new bearings in. I'm guessing they're the issue. The problem being that the shaft seems to be seized on there tight, so getting it out to put in the new bearings is going to suck. I also may need to pick up a new whacking stick for it.

[DocsMachine]

I also may need to pick up a new whacking stick for it.

-Don't whack. Press.

Pounding damages things- Even if the old bearings are, in fact, toast (and it sounds like they are) you can still damage the spindle, threads, spacers, the headstock casting, etc.

And, when putting new bearings in, pounding can "brinell" the surface, damaging the roller ways of the bearing.

The trick is to press the parts in and out. They're not going to be an interference fit, chances are they're a light press fit at best, so it shouldn't take a significant amount of force.

Use a chunk of all-thread, big as you can comfortably fit down the bore of the spindle. 5/8" or 3/4", most likely. (It's been a long time since I had one of those.) Get some good nuts, thick washers, and some pipe or tubing. Here's an old thread from Practical Machinist on what I'm talking about.

You want a thick disc or stack of washers to pull on just the spindle from the back, and some tube or wood frame or something like shown in that thread, so the pulling force from the chuck end is on the casting, not the spindle.

Should come right out.

Then, if possible, use a puller or hydraulic press to remove the old bearings, and install the new. Again, shouldn't take a lot of force, but still, you don't want to pound on them.

And get pics.

Doc.

[cfos00]

-Don't whack. Press.

Pounding damages things- Even if the old bearings are, in fact, toast (and it sounds like they are) you can still damage the spindle, threads, spacers, the headstock casting, etc.

And, when putting new bearings in, pounding can "brinell" the surface, damaging the roller ways of the bearing.

The trick is to press the parts in and out. They're not going to be an interference fit, chances are they're a light press fit at best, so it shouldn't take a significant amount of force.

Use a chunk of all-thread, big as you can comfortably fit down the bore of the spindle. 5/8" or 3/4", most likely. (It's been a long time since I had one of those.) Get some good nuts, thick washers, and some pipe or tubing. Here's an old thread from Practical Machinist on what I'm talking about.

You want a thick disc or stack of washers to pull on just the spindle from the back, and some tube or wood frame or something like shown in that thread, so the pulling force from the chuck end is on the casting, not the spindle.

Should come right out.

Then, if possible, use a puller or hydraulic press to remove the old bearings, and install the new. Again, shouldn't take a lot of force, but still, you don't want to pound on them.

And get pics.

Doc.

Yeah, this was the issue that I was having when trying to disassemble---the spindle was not moving out. At all. I really, really do not want to hurt it in removing. I got the rest moving, but it really doesn't seem to want to, and I wonder if I am missing something in the disassembly.

[DocsMachine]

Yeah, this was the issue that I was having when trying to disassemble---the spindle was not moving out. At all. I really, really do not want to hurt it in removing. I got the rest moving, but it really doesn't seem to want to, and I wonder if I am missing something in the disassembly.

Okay, the spindle is going to be 'constrained', meaning something at the back will keep I from going forward, and something at the front will keep it from going backward.

Look for something that might 'retain' the front bearing. The manufacturer may have assembled the headstock, and then painted it, so seams or screws may be hidden.

At the back, look for a snap ring, locknut, tight washer, or anything else on the spindle, that might prevent it from passing through the bearing.

Doc.

[BrickHaus]

Here is a page from the grizzly 4000 manual.
en-e7cc9aee1b7d9af2c715e5bb2b2fb622.pdf

Docs puller suggestion is likely to be your best bet. Make sure the rear spanner nut and the key stock are off of the shaft.

The " 3 jaw chuck mounting plate" may also have to come off, but it should pull out of the way side of the headstock so if anything that is a spot you can pull from.

Id say make sure the rear spanner nut is gone and find a way to pull it with a jig

Once you get it to move it'll keep coming. The bad bearing may have heated things up a few times so its stuck.

You could also back the 3 jaw chuck mounting plate onto it with shims undwr it, and see if you can draw the spindle out.

Edited to finish sentence.

[cfos00]

Victory!! Got the spindle out. It DID NOT want to cooperate, but I got it out. The front bearings nearest the chuck had definitely turned cherry red from overheating. I also wonder if any of the lubrication I had tried to put in ever got there, and it definitely didn't have any from the guy who owned it previously.

My lathe did not come with easy to access lubrication holes like the grizzly version. I was thinking of drilling a couple into holes in order to allow for easier adding of lubrication. Good idea? The grizzly has them but the harbor freight doesn't.

[BrickHaus]

It depends on the bearings. Pumping grease into a solid outer race isnt going to do much, typically a greasable bearing will have a hole in the outer race to allow grease into the moving bits. Furthermore spindle bearings are typically greased for life in a cnc or lathe application. I doubt the specs on your spindle are as stringent, but if you really use that bad boy a lot you may as well do your best to prolong the life of them.

I used to use klubber nbu20 on large bore lathe spindles when rebuilding them. The bearing manufacturer typically called out a specific CC capacity of the bearings to work into them. Then wear rubber gloves and work the bearing back and forth as you work grease into the races.

here is a link to some similar grease from the same brand. It seems to be a lighter viscosity and highly rated. 50 bucks for a syringe is no joke, but its one of those cry now or cry later situations.



https://www.amazon.com/Kluber-Isofle.../dp/B07NQPXNP7

I have no personal affiliation with klubber and or knowledge of nbu15 listed here, but I know they make a top notch grease for a spindle application.

ive also had good success with skf bearings in general.

[cfos00]

The Grizzly manual mentioned using ISO 32 Oil on them, but nothing else. I was thinking that I would be putting that in when rebuilding, and then adding that regularly.

[flyweightnate]

Kluber makes some incredible grease (I was a big fan of the Kulberquiet line for high speed) but roller bearings can be more picky than ball. TRBs will "pump" it, so an oil (non- detergent) has a much better cudgel of going the distance.

[cfos00]

My concern is actually the way that the bearings are mounted. There's literally nothing to keep the oil from just immediately draining straight out of the spaces that are cut for the bearings. There's a press in cover, but it's far from oil or water tight. I just worry that it would just drain straight out.

[BrickHaus]

Iso 32 is essentially hydraulic fluid. But is commonly used in gearbox applications. I could see that being a viable way to run it if the headstock held oil, and the bearings basically splash lubricated themselves. But Id say oil it before every use if it doesn't hold a small capacity of oil in the headstock. Iso 32 is too thin to stick to bearing races for a long duration of time especially when it warms up. The same rules apply though, simply adding a spot to drip onto the bearings isn't going to do a lot unless you can wet the inner races. The bearing required seems to be a typical tapered roller bearing so it shouldn't need anything super fancy, but I would personally grease them if its a dry type spindle. If it does hold oil, add a sight glass, filler cap, and drain plug for ease of oil changes.

[cfos00]

I actually changed my mind---going with the grease that you mentioned!

[cfos00]

Here's what's weird on the manual for my actual model's manual----no mention of ever oiling the bearings, or access to them. They have a small well behind the bearings, and it did have a grease there that felt and honestly looked like vasoline. The bearings seemed like they may have a had either a really like grease or oil----but mostly seemed like the only thing lubricating them was that small amount of vasoline-like grease.

[DocsMachine]

My lathe did not come with easy to access lubrication holes like the grizzly version. I was thinking of drilling a couple into holes in order to allow for easier adding of lubrication. Good idea? The grizzly has them but the harbor freight doesn't.

-The PDF you linked showed "open" bearings. You'd need to either periodically grease these, or have a way to regularly oil them.

If your machine doesn't have some sort of oil passage, well, that can be a problem. One fix however, is to get sealed bearings- and if it were my machine, that's probably the route I'd go. Those are not going to be Grizzly-specific "lathe" bearings- they're off the shelf bearings that happen to fit the application. It should be possible- and fairly easy- to find bearings the same size (OD, ID and thickness) and application (preferably angular contact) that come already greased and sealed out of the box.

Not shielded, make sure they're sealed.

I would be very surprised if there's not a half dozen YouTube videos and other articles that detail that exact mod.

Doc.

[cfos00]

-The PDF you linked showed "open" bearings. You'd need to either periodically grease these, or have a way to regularly oil them.

If your machine doesn't have some sort of oil passage, well, that can be a problem. One fix however, is to get sealed bearings- and if it were my machine, that's probably the route I'd go. Those are not going to be Grizzly-specific "lathe" bearings- they're off the shelf bearings that happen to fit the application. It should be possible- and fairly easy- to find bearings the same size (OD, ID and thickness) and application (preferably angular contact) that come already greased and sealed out of the box.

Not shielded, make sure they're sealed.

I would be very surprised if there's not a half dozen YouTube videos and other articles that detail that exact mod.

Doc.

I've been trying to google this exact thing (similar situations mentioned on posts/groups/videos/anything), and had almost no luck at all trying to find anything of use. It's been a pain and honestly shocking to me. The Grizzly version has the ports for oil. Nothing on this version of the machine (HF/Central Machinery). It seems kinda of ludicrous that there isn't a way of oiling the things without complete disassembly, but I really don't see one as-is. Sealed bearings really do seem like the way to go.

[DocsMachine]

Keep in mind those machines are generally all made in the same factory- Jet, Harbor Freight, Busy Bee, Grizzly, Little Machine Shop, etc.- but built to different price points. One of the makers will say "I'll pay $XXX for each one, can you do that?" The factory will see what corners they can cut, and know what slightly-out-of-spec parts they can get use, and will say "sure".

Skipping drilling the oil-feed holes makes the machine cheaper, and since the bulk of these machines are bought by people who might use them very little, often doesn't matter.

That's why there's so many 'upgrade your import lathe' articles and videos- the factory could make a mini-lathe as clean, tight and accurate as a Levin watchmaker's lathe, but no home-shop guy is going to buy one at $10,000 or $12,000 each. So they make sloppy crap- no offense - that in order for us to get decent use out of, we have to tweak and fit and repair.

The bearings will have a number on them- you might have to wire brush to find it on the burned one. Use that number to search (which you probably already know) but if that doesn't work, try searching by measurements. (And bearings are almost always measured in metric- IE, 50mm x 20mm x 12mm, etc.)

Doc.