Small Wheel Attachment Bearings Running Hot

Bill Hubbell

Bill Hubbell

KNIFE MAKER
I built a small wheel attachment for my 2x72 grinder recently. I used some used bearings and shaft that I had around, so I wasn't too surprised when a bearing went out after about an hour of use. I ordered new bearings and installed them, but they seem to build heat after running only a little while. I know that with a wheel that small (I have a 5/8 and a 7/8), they must be spinning pretty fast, so should I limit my use to my low speed? I have four speeds to choose from. I was just wondering if I should expect significantly shorter bearing life with these small diameters? I did buy two extras to have on hand, but thought that would hold me 'forever'.
Thx,
Bill
Sm Wheel 1.jpg
 
Hi Bill. When I talked to the dealer when I bought my Burr King, he said that using the small wheel attachment, NEVER run the VFD over 30% of MAX speed or you'd burn the bearings out in short order. Just like what you're describing.

I can't imagine it'd be any different with any grinder so, yeah, probably running them too fast. At low speeds, like around 20% of my VFD capability, mine (two wheels only, different sizes) are still going strong 5 years later.
 
This is good to know. I never put much thought into it but I will from now on. They always did run a bit hot.

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I noticed my bearings getting warm on my small wheels when only going at 600 or 800 rpm on the drive motor. There are some pulley and gear calculators on the web, so for example, I put in a 4" drive wheel going 1800 rpm. If you used a 1/2" small wheel it would see 14,400 rpm at that speed. Even a 1.5" wheel would see 4800 rpm, which is actually quite a bit for run of the mill bearings.
 
Just a thought but, couldn't you install those small bearings into larger ones? You would have to machine or change the bracket.
 
The bearings I used are about 1 3/8 OS Diameter, so it would take a pretty big bearing to go outside them. But, might be an option... I just used what I had on hand- and will probably get by okay, no more than I do, by staying at slower grind speeds. But with 20/20 hindsight, I suppose if I were building it again, I would be a little more open to checking manufacturer specs to see which bearings might be more suited to higher speeds.
Bill
 
I don't know of any small bearings that could withstand those RPM's. I would turn some 6061 round stock to look like a mini dumb-bell then fit large bearings on the ends.BOOM DONE.
 
I actually did a little research on bearings a little while ago. Based on what I learned, go for a bearing with a high ABEC number (i believe 9 is the highest ). In what i was reading it was saying ABEC 9 ratings are intended for aplications up to 10,000 rpm. Easy and fairly cheap source is ebay/amazon if you can make skateboard size bearings work, just search 'abec 9 skateboard wheel' I think they're running in the range of 25-30 a set, and that would give you 8 bearings...
 
Hi guys
You should be using steel seal bearing instead of rubber seal bearing 2RS bearings run a lot hotter than ZZ as the rubber causes more friction
just my 2cents
Rerards
 
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