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mikem
11-09-2009, 11:45 PM
I bought an old router at an auction a while back and the bearings are shot. The oiled bronze top bearing is easy enough to figure out but the ball bearing in the bottom (where the bit mounts) is marked 7R8, which is a .5 inch by 1.125 inch bearing, about .310 thick. Looking in my MSC and Enco catalogs, I find bearings that size but they are only rated up to about 5K RPM and the router goes 23,000 rpm.

I might go to the local bearing house tomorrow but thought that a web supplier like Enco might be cheaper. Does the 7 mean high speed? Will a standard bearing work or will it burn up quickly?

The router isn't worth a whole lot even if I get it fixed, although it would be handy to have one with a round over bit ready to go w/o having to change bits all the time.

lakeside53
11-10-2009, 01:27 AM
Find a bearing with metal shields instead of rubber seals - the seals will be lower speed limited. Your bearing may have a thinner grease it it, but ...

The duty cycle of a router is generally low, so I doubt it will be an issue. If it gets hot the grease will tend to leak out, but it won't fail catastrophically without warning.

Oh... don't buy "cheap" bearings. Go for a major brand. (VxB isn't one...)

EVguru
11-10-2009, 09:01 AM
I think you've missread the spec. There's now way a bearing that small is going to have such a low rpm rating.

I had a quick look in ENCO since you mentioned them;

http://www.use-enco.com/CGI/INSRIT?PMAKA=327-7951&PMPXNO=22568870&PARTPG=INLMK32

LOAD capacity 5070

Maximum rpm 24,000

mikem
11-10-2009, 10:50 AM
Thanks for the info. That bearing looks like it will work. I'm not up on bearing limits. The catalog pages didn't always give the RPM max. thanks again.--Mike.

lazlo
11-10-2009, 11:31 AM
Thanks for the info. That bearing looks like it will work. I'm not up on bearing limits. The catalog pages didn't always give the RPM max. thanks again.--Mike.

You might want to double-check, but I thought the max rpm is with oil lubrication. If that's the case, that just means you should wash-out the grease pack and oil it.