[danielcoyle]

Hello out there.
I have two JST JGD-125C 4.5 KW water cooled spindles on my JCUT Router. Both of them need new bearings. I am looking for anyone out there who has done this sort of work before on their spindles, ideally the same chinese ones that I have. There are some markings on the bearing pair that mark the bearings as different (though they look identical) and I just haven't ever pressed bearings on to a spindle before and want to make sure I am doing it all correctly. I can take the second spindle apart to make sure everything is correct on the first one but am a bit scared to make both spindles out of commission at the same time. I had wanted to source a non chinese bearing but could not find one (any help here would be great too as these bearings don't seem to be long lifers.)
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[ger21]

There are some markings on the bearing pair that mark the bearings as different (though they look identical)

Those are angular contact bearings and must be assembled in the correct orientation.

What size are they?

[mactec54]

danielcoyle

Are the Bearings you are holding, how they were assembled in the spindle???

If so this will tell you the orientation of the Bearing, different spindles have different bearing orientation, it just depends how the spindle was designed/ made

Holding the bearings in your hand as you are if this is how they were assembled, push in & out on the center of the bearing, holding the outside of the bearing tight together, if the center of the bearing does not move, in/out, then the bearings are either mounted Back/Back or front/front, so the are 3 ways they can be assembled, if there is no movement, they are most likely mounted Back /Back

How to know if they are Back/Back, look at the outer ring of the Bearing, one edge will be thicker than the other side of the Bearing, when they are mounted Back/Back the ( 2 ) thick edges will be facing each other & the ( 2 ) thinner edges will be facing outwards

Most of these spindles have the ( 2 ) Front Bearings facing the same way with the thin edge of the bearing facing outwards, towards the end of your Spindle, the preload is then adjusted at the top of the spindle

If you want a longer life for your spindle bearings, you will need to add rotor grounding, all VFD driven Spindle Bearings have a short life, the voltage build up in the rotor arcs out through the bearings, this causing a short Bearing life

[danielcoyle]

Well, I have misplaced my calipers but measured them with tape as 36mm ID by 61mm OD. Know what orientation they would be put in based on the arrows imprinted on them? Know where I might find a higher end bearing for this.

[mactec54]

Know where I might find a higher end bearing for this.

It won't matter what Bearing you put in there, they will last about the same, unless you can ground the Rotor, you will pay a lot of money for a sealed / matched pair $300 to $800 depending on the grade any Bearing supplier could supply you with what you need

The photo is just one type of Grounding ring, that will help to extend your Bearing life, this would have to be designed/modifided to fit in the top of your Spindle