Hi!
I had just replaced both the stock bearings of my SIEG X2 Mill (MT3) to angular contact ones (rubber shielded), FAG 7206-B-2RS, using some guides, like Little Machine shop guide: https://littlemachineshop.com/images...ndle%20Kit.pdf and some guides with pictures like this one: https://www.arceurotrade.co.uk/revie...58_X2_Mill.pdf.
It all went well, I also trammed the spindle head to the back part of the head for left/right and tilt adustments.
I think the spindle, although having no play at all, and no runout apparently, seems a little bit stiffer than before.
I don't even need to adjust the left hand nut on the top of the spidle, as the method for inserting the two bearings already left it with no play at all.
I have a belt drive conversion kit installed also, and removed all the gears inside, even the spindle one.
I had the belt drive conversion kit modded (added two more pulleys in motor and spindle's original kit's pulleys) to allow also 10.000 RPM, just for engraving. It will be hardly used.
I think the spindle wiith new bearings, although perfectly aligned, seems stiffer, although not much more than before, and the spindle case gets hotter than before, the higher the speed it runs. At 4600 RPM in 10 minutes it gets to 60 degrees celsius, both the spindle housing, and even the pulleys attached to the spindle.
I connected a multimeter directly to measure the motor output draw (its rated for 220V - 2.2A)
With the 600 RPM pulley the motor draws IN IDLE (not endmills attached) at max speed, close to 0.6A
With the 4600 RPM pulley it draws in idle also almost at max speed too, close to 1.3A
But with the 10000 RPM pulley it draws almost 2.8A, at 7000RPM, in dle. If I go higher than this the controller stops the motor, for protection. With this high speed pulley the speed has to be reaaaaaaly slowly increased to the point of being useless practically.
Also it's only being tested in idle, not endmills attached. If I try to turn on the spindle and increase the speed a little bit faster, the current draw increases and the controller stops the motor.
So I have some doubts:
Are this Angular Contact bearings really stiffer than the Chinese stock ones, to the point of making the motor work harder than before (draw more current and heat more), when it had the original bearings?
Will the new bearings (bearings/spindle assembly I mean) , with use, become less stiffer than now, as they're new? Is there a procedure to make it happen, to make it... soften... like run at some speed for some minutes, let it cool down, do it again?
When I installed the bearings following the instructions on the LMS kit, could I have put too much preload when seating the bearings/spindle? If so, is there a way to undo it a little bit, without damaging the bearings? I'm not even using the top nut over the spindle top.
Will it be possible/practical to use the higher speed pulleys - 10000RPM - just for engraving, or these bearings aren't meant, or can't handle this speed?
Thanks for reading!
Regards, Rodrigo