1986 QT10 Motor Bearing Rumble

gmc1724 said:

This is worse when it's cold too but I'm suspecting a rear bearing based on when I run the spindle up to about 1500rpm, where the noise seems at it's worst, and then kill power to the lathe, the noise is still present as the spindle ramps down.

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gmc1724 said:

Thanks for all your replys. The shop has been quite warm today and the noise has been all but absent. I take it by killing power to the machine whilst the spindle is running and still getting the noise as the spindle ramps down should discount any sensor issue?

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Romefu12 said:

Yeah, that should tell you. I would be interested in how much those bearings run if you could purchase them yourself. I would also be interested in what they quote to rebuild the spindle as well. It does not look all that difficult to rebulid.

Regards
Romefu12

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cwtoyota said:

I rebuilt my spindle a year ago with help from this forum. If you're a competent/clever machinist with access to a grinder and some patience, you can pull it off.

Search this Mazak forum for threads started under my name and you'll probably find the lengthy thread where we detailed my QT-10N spindle rebuild process including some drawings, specs and lots of photos. It should at least give you an idea what you're getting into before you start.

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Romefu12 said:

cwtoyota
Why would I need access to a grinder? I don't plan on waiting till I wipe a bearing or destroy one before I rebuild. What would a grinder be necessary?

Kind Regards
Romefu12

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gmc1724 said:

I think we're at crossed purposes here, it's not the spindle that's making the noise, it's the rear bearing in the motor. I have replaced a front bearing before (pulley end), access to the rear bearing seems a lot more difficult, I think it'll be getting sent out to a rebuilding specialist.

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GuntisK said:

Replacing bearings in spindle motor is a simple task- done it on my QT-15 in one evening. Now motor is soo quiet even at high rpm's.

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gmc1724 said:

Care to elaborate, I'm not looking for hand-holding just a brief description of how you got to the rear bearing, plus did you have to disconnect the electrics or can it be done by just swinging the motor out of the machine and working on the deck?

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GuntisK said:

The motor in my inQT-15SP (year 1988) should be the same SJ type like on other QT's from that time. First of all You should disconnect motor phase wires and somehow mark them (phases U, W, V) to avoid any connection mistakes later, then disconnect connector from magnesensor board and fan wires. Remove motor out of the machine (engine crane or somewhat similar would be very useful)- I just slip it out on a wooden planks. Then carefully remove magnesensor and its disc (located underneath aluminium cover)- for that purpose there is two threaded holes in it (as far as I remember for M8 screws).Under that disc is located 4 screws that hold bearing in motor aluminium cover with round plate. I replaced both bearings in motor (this is a recommended practice in these cases)- in front side where pulley is mounted sits 6310N bearing. In rear where we removed that magnesensor disc is located 6308N bearing. Now here the most complex part is removing of pulley to get to 6310N bearing (both bearings and pulley are pressed on rotor shaft). You can use any suitable pulley remover to take these off or use a press. Replace bearings and assemble everything together. Only notable thing here is setting of magnesensor- it looks like aluminium cylinder that is fixed at a certain distance from magnesensor disc. Distance should be set at 0.25mm- for that just place a thickness gauge blade between sensor and disc- and fix sensor by two screws. Thats all. Reconnection of electrical wires is the easiest task here.

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