Millwaukee 5625 router bearing pre-load

--- >>> UPDATED <<< --- Still, might be worth to read...

Thanks to Gerald (meet Gerald at MechMate forum), I found what I was looking for to get rid of the end play I had with my new bearings. The part is a wave spring and Smalley Steel Ring Co. had just the kind of on line documentation and catalog I was looking for to find the specific part.



I ordered the part through my local bearing reseller. I was a little concerned at first about the work load since I estimate the compressed thickness to be too tight on the router motor. I did got very good specifications regarding the Smalley wave springs but I couldn't get any accurate reading on the router motor regarding the room above the upper bearing and the motor frame (black plastic) where the bearing sit.

Upon assembly, the spring didn't seem too compressed and the test I made after reveal no problem. In fact, the bearing seem to be cooler than before!? With the shield bearing, it was already more cooler than with the factory sealed one but even at 18 000 RPM, the shield bearing was not even that warm to the touch. Those tests were made with without tool load (not cutting). I did read, on Smalley Steel Ring Co. web site, that they were actually proposing the wave spring to reduce bearing wear.

The following picture show how the wave spring is install. When the motor cover screws are tighten back in place, the bearings are now pre-load; their is a downward push effect that sit the bearing's balls into both the inner and outer races which, in theory, keep them from being "loose" (bearing clearance) between the two races. Pre-loading the bearings do fix the end play problem too which add to cutting depth accuracy... which I was looking for at first.





If you decided to go this route, once the wave spring is installed, test the router at the very slower speed first for the first few minutes then gradually raise the RPM and monitor the lower bearing temperature. The SKF shield bearing I installed (the lower one) is rate to up to about 18 000 RPM; I don't think it is wise to run the motor above that speed even if it can. When I ran my tests up to 18 000, I promptly removed the cover to monitor the upper bearing and it was slightly warmer than the lower one and I assume it is because the electrical rotating "connection" on the armature get quite hot.

As I post this, the bearings have been running with the wave spring for a weeks (say some 30 hours) and still cool so far and no end play what so ever.