Replacing G0709 spindle bearings

[mcdanlj]

A few years ago, I bought a used G0709. I've occasionally been concerned about noise from the spindle, and today I was justified. Under nearly no load (slowly drilling a 7/64" hole) it suddenly sounded loaded, and when I turned off power, it stopped quickly and the chuck was hard to rotate even in neutral. Clearly a bad spindle bearing.

Looks like I have the exciting opportunity to learn spindle bearing replacement.

• Would you buy the $120 set of NSK bearings from Griz, or is there a reason to consider anything else? [Edit: I have already ordered them...]
• Has anyone who has been through this before willing to help out if I get stuck?
• If you've done this before, is there anything that I should know ahead of time? Consumables that should be ordered with the bearings? Tools that I'll need?

Griz appear to be completely out of all gaskets; at least all gaskets associated with the headstock spindle, but I can make my own if these tear.


Edit: TL;DR of thread:

• Grizzly is shipping regular-precision bearings in boxes marked as precision bearings, and it shows. They are almost certainly legitimate NSK bearings, but regular precision and fabricated at NSK's plant in mainland China.
• Motion Industries can source precision bearings, @Cadillac reports about $400
• There are lots of pictures in the thread that might help you if you are trying to do the same replacement
• If you haven't already done this, 6x3mm neodymium magnets fit nicely in the oil drip channel that feeds oil to the bearings, which may help keep chips out.
• The internet is full of videos of changing spindle bearings in various lathes. After I watched those recommended in this thread, The Algorithm kept throwing more at me.
• You need large ratcheting snap ring pliers both for disassembly and reassembly.
• Comment #23 has a summary of the official Grizzly preload-setting procedure from the manual
• Comment #35 has a detailed textual description of the steps I used to put the lathe back together.
• Ultimately: The Grizzly replacement bearings are not as high quality as what was included in the lathe, so if you are doing this, buy quality actual P5 bearings through a reputable distributor such as Motion Industries. This is one of the more expensive components of the lathe, so don't be surprised when you pay for them.

 

[Ischgl99]

There was a thread a couple months ago by @Cadillac where he bought the bearings I believe go in your machine. The ones he got were not P5 precision bearings even though they say so on the packaging. He ended up returning them and I think he found something from a local bearing distributor, but they cost considerably more. If it doesn’t say P5 on the bearing, then you need to assume they are not unless proven otherwise. Here is that thread: https://www.hobby-machinist.com/threads/14x40-spindle-bearing-replacement.97976/

I would be curious to see what grade bearings are installed in your machine. Since they are selling standard precision, I would guess standards came from the factory. I wouldn’t recommend standard precision bearings in a machine tool, but some people do that and are very happy with it. Higher precision bearings will give you better service, but at a significantly higher cost.

As an FYI, Grizzly prices for standard precision bearings are higher than from a local bearing distributor. It might be cost effective to return them and buy them locally if you decide to replace with standard precision.

 

[mcdanlj]

Thank you very much!

I guess I can use the NSK app to check the barcode on the bearings that are sold as 30212 P5 and 30210 P6 NSK bearings when they arrive, but it sounds from that thread like they probably aren't legit. About three months later they are still definitely listed on their web site as NSK and that's what's on the email I got for the order, so if they aren't legit I can follow up if I have the energy... [Edit: Oh, it's specifically only for NSK N-series bearings made in Japan. "The app works with all Japanese-manufactured NSK bearings featuring an ‘N’ symbol in the lower right corner of the 2D code on the packing label of the box – the print run for which commenced in 2018." And they did open a facility in China; it looks like they announced in 2011 and started production in 2013 so my lathe probably already has those bearings in it.]

Griz sold my lathe to the original purchaser missing the faceplate, and Griz had ghosted him on replacing it. When I contacted them at the time, they quoted me rather a high price for the replacement, shipped. I added the replacement to my cart while I was ordering anyway, and the total for bearings and faceplate I think is similar to what they quoted me for only the faceplate a few years ago. (This is weird, hasn't the price of everything gone way up recently?)

Draining the oil to prepare for disassembly (and/or rocking the gears moving them around) seems to have dislodged a chip or something in the bearing and the lathe started turning freely. I'm confident that catching a chip would have done surface damage to the race and/or rollers (how could it not?) so I'll still want to replace the bearings, but I can now use the lathe in the mean time. (I'm just a home gamer, no one is paying me for precision work...)

 

[fitterman1]

Timken, FAG, SKF, are the brands i look for.
Your bearings are tapered roller brgs. Good for trailers and car axles. They will do the job in your lathe if correctly adjusted.
And they are robust which is why they are used. You could get angular contact brgs, but you'll pay through the nose for that size.
How are they mounted? Is it a geared head or simple spindle arrangement?
Either way one or both bearings are contaminated and they need to be removed, washed out and inspected before purchasing replacements. No good replacing both if one is shot. Thats false economy. Rip out the spindle and inspect them. If you're creating mission critical parts buy the highest specced brgs you can afford. If not just use normal brgs, they'll be fine for sub thou work.

 

[fitterman1]

If you have a geared head lathe is there an oil circulating pump?
Or is it just splash?
Check out the sump for metal particles and run a telescopic magnet through there and see what you find.

 

[Ischgl99]

Yes, NSK has a factory in China so those bearings likely would come up as genuine. I’ve used the counterfeiting app to check some bearings that I know are 100% genuine and it came up suspicious, so it’s not perfect. If you look at the box in the previous thread, the sticker put on by Grizzly is the only place it says P5, so the bearings were likely genuine standard precision bearings that someone decided to call high precision and made that sticker. It’s also possible they measured the bearings and determined they meet P5 standards, but I find that unlikely.

Since you are draining the oil, you might want to look into adding a magnet to the drain plug to capture metal particles in the oil. I bought a small magnet from McMaster-Carr and will be adding it to mine at my next change. I will drill the plug to accept the magnet and epoxy it in place. Since it looks like there might have been a good size metal particle causing the problem, I would inspect all the gears and make sure there is not any damage to them, it would be a shame to put expensive bearings in there and then have them damaged because a gear is spalling and sending more metal into it.

 

[mcdanlj]

How are they mounted? Is it a geared head or simple spindle arrangement?

Geared.

If you have a geared head lathe is there an oil circulating pump?
Or is it just splash?

This is why these lathes specify ISO 32 oil; they are splash lubricated. The oil splashes on the cover, and some of it drips into a channel that feeds to the bearings to cycle oil through the bearings. There is no pump.

Either way one or both bearings are contaminated and they need to be removed, washed out and inspected before purchasing replacements.

I already purchased replacements. I didn't think to put my endoscope or inspection mirror down to try to see whether I could identify any surface damage until I'd already filled it back up with fresh oil.

Since you are draining the oil, you might want to look into adding a magnet to the drain plug to capture metal particles in the oil.

One of the first things I did when I got the lathe was put some neodymium magnets into the headstock where I could see and reach them. They definitely collected ferrous metal. It sticks fine to the case and won't bounce into the gears; I didn't need to bond it to the drain plug. I plan to always keep a magnet in the headstock oil.

It's quite possible that some damage had already been done before I ever got the lathe. But that's a reason for me to seriously consider replacing both bearings.

Since it looks like there might have been a good size metal particle causing the problem, I would inspect all the gears and make sure there is not any damage to them, it would be a shame to put expensive bearings in there and then have them damaged because a gear is spalling and sending more metal into it.

I didn't see any obvious damage on the spur gears when I spun them around. I don't think it would take a large chip to have caused bearing drag.

This lathe is such a weird mix of imperial and metric. I'd like to replace the drain plug with a drain cock to make oil changes easier, so I'm more likely to get around to doing them on a smart schedule. Of course, with the lathe broken down I couldn't cut a new drain plug, so I just measured and wrote down what I found so that I could make one later. I wrote down 5/8-16 as the thread spec for the plug, and now I am doubting myself after re-filling the headstock with fresh ISO 32, because that thread spec is a "special". Did I read an "18" as a "16"? Or was it really a metric thread and I just accidentally skipped a blade on the thread gage when I started guessing metric? Maybe I'll check at next oil change!


Incidentally, I did discover that the spider coupling thread is the same as an ER40 collet nut. That means I could turn an ER40 adapter to fit in the back of the spindle and use an ER40 collet on the back as a very precise spider that doesn't require me to clock in four screws.

 

[Ischgl99]

Incidentally, I did discover that the spider coupling thread is the same as an ER40 collet nut. That means I could turn an ER40 adapter to fit in the back of the spindle and use an ER40 collet on the back as a very precise spider that doesn't require me to clock in four screws.

That sounds like a really nice feature, I had to make a spider with the four screws for my lathe.

It wouldn’t take much of a chip in the right place to get lodged in between the rolling elements and the cage. Most metal particles are fairly small and get run over or pushed out of the way, but the bearing could be spalling and a chunk flaked off and caused the problem as well.

The drain plug could be BSPP or BSPT. PP is parallel pipe and PT tapered like NPT. Depending on the size, the tapered threads are close enough to NPT that they frequently fit close enough. Here is a chart with the dimensions. https://torqbolt.com/bspt-british-standard-pipe-taper-threads-dimensions-specifications. It could be a straight metric thread as well, you never know what gets put in some of these machines.

A magnet on the bottom will work fine too, I suggested installing one on the drain plug so that when you remove the plug, the metal particles comes with it. If you install a drain valve, then you won’t be able to do that and would need one in the bottom of the gear case.

 

[mcdanlj]

Yeah, the lathe came with the typical four-screw spider. And I've used it. I'm cool with using the 4-jaw, but it's hard to reach around to turn the spindle to indicate in the workpiece, so something that was self-centering would be awesome. I've been really pleased with my ER40 collet chuck and I doubt that my 5C will see very much more use now.

A spalling bearing would make a lot of sense. I did my initial knurling work before learning that I should buy a scissors knurling tool, so the straight knurling tool definitely put some pressure on the bearings. That's what happens when a tyro buys a set of tools and doesn't know right away that one of them is an abomination! ☺

The drain is at the side rather than the bottom, so it kind of fails to drain the dregs. I put the magnet aligned with a large gear on the spindle so I know it will circulate oil past the magnet. It's in the easiest, most open part of the gear box to reach into.

I had been saving up for a PM lathe when this one came up on craigslist locally. It's not a terrible lathe, but I'm pretty sure that if I'd waited and bought the PM1440GT I really wanted I would have had a far better lathe — but then maybe also made more expensive mistakes?

 

[Ischgl99]

Sometimes it’s better to get something and start working than to wait for the better one that may never come. Most of these lathes are probably better than our abilities anyways. I had a 9x20 lathe and wanted to upgrade 10 years ago to something like the G4003G, but things kept getting in the way, and prices kept rising. I decided in 2020 to stop putting it off and bought a PM1236T instead of the Grizzly, so I guess things worked out for the better anyways. I had good timing, that lathe is $2,000 more now than I paid for it in Nov 2020. I also didn’t need to wait 6 months, it was actually in stock! If you waited, it might have cost you a lot more to get what you wanted.

Sounds like the magnet in the bottom is better in your case. I’ll have to check mine, I think the drain is right at the bottom, but now that you mention it, I’m not sure. If you aren’t doing this already, when you clean the headstock, it would be a good idea to use a rag to remove all the remaining oil to take out and dirt or debris that has collected.

These aren’t the same lathe as you have, but these videos might give you some ideas on removing the spindle bearings. As was mentioned by someone earlier, it would be a good idea to change the other shaft bearings in there. They are mostly fairly cheap ball bearings, so the cost is not much and you will have everything basically new again. In the first video, I believe Max used standard precision bearings for the spindle. It might be worth it to send him a message and ask if he still thinks that was a good decision.