Shenwai SW-900B (Asian 12x36) Spindle Bearings

[ChandlerJPerry]

I've had this machine for awhile now as a refurb project, and found the spindle bearings are toast. There was no oil in the reservoirs and a nice pile of metal shavings behind the sight glasses. The part numbers are 30212 and 30210. The ones I pulled out of it are standard precision tapered roller bearings. The replacements that Grizzly sells also appear to be standard precision.

My question is if it's worth pursuing higher precision? Perhaps ISO P5. The whole lathe isn't a high class precision machine in the first place, and has some way wear, so I can't see anything more precise than P5 being worth it. I was also looking at SKF Explorer bearings, which I believe are all P6 rated. It seems in general tapered roller bearings don't tend to come in precision ratings.

I'm not trying to split tenths with this machine, and honestly it may run perfectly accurately with standard precision bearings. I've just never had it operating so have no frame of reference for it. Any thoughts?

 

[Ulma Doctor]

I wouldn’t try too hard to increase the precision or lose any sleep over it.
If you can get better bearings at a reasonable price, no foul , but i don’t think that they would turn the machine into something more than it is.
I have 2 VFD converted Shenwai SW900B’s,
They are very useful machines, luckily they have been well maintained

 

[Ischgl99]

Precision bearings are more than just about radial runout, the higher precision allows for better control of preload. The amount of preload you can put on the bearings determines how rigid the spindle is. The higher precision bearings will help there over a standard bearing, but if the rest of the lathe is not that rigid, then you are not really gaining anything. P5 might give you an improvement over P6 on that lathe, but going up to P4 would be a waste of money. I'm not even sure if they make P4 tapered roller bearings.
There was a post here a few years ago about the Grizzly, bearings, they had a sticker on the box claiming to be P5, but they were not marked that on the bearing or the factory box and a colleague of mine at NSK verified they would have been marked if actually P5, so I don't trust anything coming from Grizzly.
SKF Explorer bearings and FAG X-Life are different internal designs that are an improvement over the standard bearings, better quality steel, and are also made to higher precision and surface roughness than standard bearings, but what tolerances they meet depends on the size. I would always use an Explorer or X-Life bearing wherever possible. I couldn't find the info on tapered roller bearings, but SKF Explorer ball bearings only meet P6 tolerances up to an OD of 110mm, over that they are standard tolerances. Since SKF is not saying the TRBs meet P6 tolerances in any of the literature I have found, they may have the other improvements of the Explorer class, but not able to meet P6 tolerances. This is what is said on the website:

• Consistency of roller profiles and sizes
  The rollers incorporated in SKF tapered roller bearings are manufactured to such close dimensional and geometrical tolerances that they are practically identical. This provides optimal load distribution, reduces noise and vibration, and enables preload to be set more accurately.

 

[Liljoebrshooter]

I went through the same situation awhile back with my lathe. Mine is a different brand but they are virtually the same.
I ended up finding one P5 bearing and one standard. They are much smoother than the ones that were in there originally and had less runout.
I remember reading somewhere that said, new standard ones are going to be better than worn or damaged precision ones.
I would have to bet if you bought a set of nice new SKF bearing and put them in, you would be very happy with the outcome and they are probably better than what was in there from the factory. Because they most likely used the cheapest ones they could get to reduce costs.
Joe

 

[Downwindtracker2]

I did the bearings and belts on my BusyBee version of the Taiwanese generic,. First off they bondo'ed over a shaft end . The bearing were simple Timken style , much like you would find on your utility trailer . The nuts are on the back side. Hook spanners are required. Before I took mine out I checked the bearing clearance, a very very important step. I can't stress the importance of bearing clearance enough. I bought a new 1/10 th Mituyoyo dial indicator, you don't go cheap here. I found 2 tenths. So that's what I aimed for. One of the methods for measuring bearing clearance on big industrial machinery is to put portapower under the shaft and dial indicator on top. Here I used a 2x4 as a lever. Wood just crushes.

I went with genuine Timkens, but any quality brand like SKF, NSK, or FAG are good. Avoid like a very contagious plaque Chinese or Korean bearings. A poster mentioned that their tested precision bearing were the same the regular bearings except they were tested. My headstock casting wasn't overly robust so I wouldn't expect 1/10th splitting levels. The bed is broad and solid though.