I am looking for some input on surface grinder spindle design. I have an Abrasive that I threw a part last year, wasn’t a bad throw or crash, but since have had intermittent surface finish issues. Sometimes I get great finish, sometimes not, can’t tie any specifics, it really seems random.
This is my, or was my, nicest grinder, as far as accuracy, I need it for two potential jobs I am quoting.
Saturday I pulled the cartridge and took the spindle apart to see if I could find any direct issues. The rear most bearing is filthy and packed with black goo that may have been grease or oil once upon a time. Once I disassembled the motor, I noticed that the spindle shaft had about .008 movement front to back on the middle bearing. Problem found, or so I thought.
I have another Abrasive 1 1/2 that I am in process of doing a full rebuild. This has been great to have another to compare to. SURPRISE they are not identical!
Upon further study, there is apparently no “pre-load” as I was expecting the middle bearing to have. This bearing merely sits in its location with no clamping force to it. The front load on the spindle shaft (pushing towards the operator) is caused by 3 springs in a cup that sits in the back of the motor housing.
The spindle shaft then essentially floats, with forward pressure being applied by the springs. Checking my other spindle, the cartridge housing provides .130” clearance in front of the outer race of the middle bearing. My 3rd Abrasive, it you push on the wheel hub, the whole assembly will move about .008”.
Middle bearing is a 7206CG1DUJ74.
Does this sound correct? I don’t have a lot of grinder spindle experience?
This is my, or was my, nicest grinder, as far as accuracy, I need it for two potential jobs I am quoting.
Saturday I pulled the cartridge and took the spindle apart to see if I could find any direct issues. The rear most bearing is filthy and packed with black goo that may have been grease or oil once upon a time. Once I disassembled the motor, I noticed that the spindle shaft had about .008 movement front to back on the middle bearing. Problem found, or so I thought.
I have another Abrasive 1 1/2 that I am in process of doing a full rebuild. This has been great to have another to compare to. SURPRISE they are not identical!
Upon further study, there is apparently no “pre-load” as I was expecting the middle bearing to have. This bearing merely sits in its location with no clamping force to it. The front load on the spindle shaft (pushing towards the operator) is caused by 3 springs in a cup that sits in the back of the motor housing.
The spindle shaft then essentially floats, with forward pressure being applied by the springs. Checking my other spindle, the cartridge housing provides .130” clearance in front of the outer race of the middle bearing. My 3rd Abrasive, it you push on the wheel hub, the whole assembly will move about .008”.
Middle bearing is a 7206CG1DUJ74.
Does this sound correct? I don’t have a lot of grinder spindle experience?