Ran a long pocketing job yesterday. The 8HP liquid-cooled spindle hit 190F halfway through and tripped the alarm. Lost the blank.
Flow and preload are both cleared. Coolant flow is steady and the preload was set last month, so I am not chasing either of those.
What I want is a test I can run without pulling the spindle apart. My money is on heat not getting out of the bearing rather than going in, but I would rather measure than guess. If you have diagnosed one of these on the machine, what did you check?
A cooling fault with flow and preload both cleared usually means the heat is not getting out of the bearing, and a tired seal is the usual reason. Coolant slips past it, so you make friction heat faster than the chiller can pull it back.
Shut it down and let it cool first. Run the coolant pump for ten minutes with no rotation, and feel the outer seal ring — the one nearest the collet — with the back of your hand. Warm like the collet, the seal is passing. Cold, look elsewhere.
That tells you direction, not severity. Measure before you pull anything apart.
Mike, I’m probably being thick here, but where exactly is the outer seal ring? Is it the round plastic thing right where the collet screws in, or the metal ring further up the spindle body? I don’t wanna poke the wrong part and wreck my ShopSabre’s spindle. I’ll try the hand test tomorrow and report back.
Work the coolant side before you touch the spindle.
Temperature delta across the coolant, inlet to outlet, is the first number. Flow can look healthy and the delta still be way over spec — that is usually blocked internal passages, and the cause is often a seal that let go and pushed material through.
Pull the inlet filter and look. If it is loaded, blow the passages out with shop air and recheck the delta.
You came in with flow and preload already cleared, so this is the next thing worth your time. Get the delta number and it will point you at the seal or the chiller.
Heard that router noise? Wait, no—heard that overheating spindel story.
I’ve had a similar issue with an old liquid-cooled unit, no exact match but close.
First, try the temp delta test Brian mentioned. That’s fast and no disassembly.
If delta’s off, pull the inlet filter. I’ve seen fine aluminum swarf get past worn seals and clog those tiny internal passages.
If delta’s normal, run the coolant pump for 10 minutes with no rotation like Mike said. Feel the outer seal ring near the collet with the back of your hand.
Warm means the seal is failing and letting coolant slip, so friction’s spiking.
Give it a test run first.