Setting up 6202 bearings

[GKman]

Trying to rebuild a spindle for an old toolpost grinder and I don’t know how to set up the preload on the bearings. They are SKF 6202 2ZJEM shielded ball bearings for a 15mm shaft and a 35 mm bore. The bearings fit in each end of a tube about 8 inches long. I will turn shoulders on the new shaft for the inner races to stop against. For simplicity I’d like to use Belleville disk springs to take out the end play. McMaster’s sells them specifically for this bearing. Any information would be appreciated.

[CCWKen]

Don't know what kind of TPG it is but the 62xx series is probably the wrong bearing. These aren't meant to have an axial preload. If you do they'll probably self destruct in short order. You should use angular contact bearings. Off hand, I think they're the 72xx series but I'd have to check to be sure. Besides that, the spring washers are not for preload they're used to fill space. If you try to grind with an axial load, the spring will most likely move and cause grinding chatter--Just before the bearing blows apart.

[J Tiers]

Belleville springs are OFTEN used for preload. I have done it with perfect success. Logan 10" (later types) use them for preload, and that has been working for 50 years now.........

I don't think there is any problem with them chattering. The usual procedure is to preload with a significant pressure.

While angular contact are most common, it is also possible to use deep groove type with some anti-chatter preload. My Dumore 2" TPG uses a coil spring inside one pulley to provide preload on a pair of deep groove bearings to avoid chatter. The Dumore is not exactly a "farm-built" device.......

[wierdscience]

Here is what you need to calculate your preload.From the SKF website-

Specs for the bearing you have selected inculding static and dynamic loads in both axial and radial.

http://www.skf.com/skf/productcatalo...did=1050070202

Now the page with the formula and recomended factors from SKF-

http://www.skf.com/portal/skf/home/p...newlink=1_1_13


You should be able to figure your preload from that.

[lazlo]

My Dumore 2" TPG uses a coil spring inside one pulley to provide preload on a pair of deep groove bearings to avoid chatter. The Dumore is not exactly a "farm-built" device.......

I'm just seeing this thread.

Dumore spindles come with angular contact bearings!!!

Like Lakeside says, it's common for the bearings to wear out, then some moron replaces them with radial ball bearings. Then the spindle chatters like Hell, and it ends up on Ebay.

The Dumore 7x-250 spindle I posted in TexasTurnado's thread was an Ebay purchase. I spun it up, and it chattered badly and the grinding wheel was not stable. I popped the spindle and found a brand-new set of 6203 radial ball bearings:



A quick call to Dumore and the tech rep assured me that the spindle is supposed to have a matched pair of 7203 angular contact bearings, which just happen to have the same dimensions as the 6203's. So the Ebay seller swapped-out bad angular contacts with cheap radial ball bearings.

Like CCWKen says, for a high-speed spindle, you really need pre-loadeded angular contact bearings. Dumore recommends the Barden 203HDL's (light preload), which unfortunately run $300/set (which is why people swap them out with cheap ball bearings).

[GKman]

posted in TexasTurnado's thread was an Ebay purchase. I spun it up, and it chattered badly and the grinding wheel was not stable. I popped the spindle and found a brand-new set of 6203 radial ball bearings:
.

Are you saying it had two 6203's back to back in one end of the spindle? I think I can see how that would have a built in rattle problem but my sketch shows 1 bearing at each end of the spindle with the slack taken out with a Belleville spring and adjusting nut.

[lazlo]

Are you saying it had two 6203's back to back in one end of the spindle?

No, if you look at the picture I posted above, the Dumore spindles have two opposing angular contact bearings, one at each end, and they use the internal spindle cartridge as the preload spacer. It's very close to the picture you've drawn -- the Dumore's do have a Belville spring on the pulley side AC bearing.

So on my spindle, the Ebay seller replaced the two 7203 angular contact bearings with common ungraded 6203 deep groove radial ball bearings, which have the same dimensions. It runs really, really bad.

I've been looking for the correct Barden 203HDL or Fafnir 2MM203WI DUL's for months, but they're very expensive.

But last week, I found a set of SKF "Explorer" 7203B angular contact bearings for a really cheap price on Ebay. They're ABEC-5, and they're universal pre-loaded (not ground as a matched pair), but that should be a hell of a lot better than what I have right now.

The SKF Explorer angular contacts are marketed as a (relatively) low-cost alternative for precision spindle bearings, so they retail for around $25 each (as opposed to $300 for a matched set of Bardens or Fafnirs). So you might want to look for an SKF Explorer 7202, which would fit your spindle.

[tiptop]

Who was the tool post grinder made by? I have an old Tom Thumb #11, made by Dumore, it looks like new, and I believe a parts break down for it. Let me know if you want a copy and I will dig it out. Jay

[lakeside53]

I also doubt those are the correct bearings... Someone has put them in as replacements because they "fit".

If you want to continne down that path (with non-precision bearings), you can axially load them like you suggest, but... you would be better off with 2MM202WI DUL pairs (or something similar..) These are preground for the correct preload at flush mounting - just clamp them togther at each end of a precision ground shaft with equally precise spacer or shoulders.

[CCWKen]

Since when does a Logan spin at 36,000rpm?