janicholson...preload bearing torque??

[glennster]

hey jim, need yer opinion. working on my older prime-mover skid steer. rt front axle bearings. am replacing both bearings, races and seal. has 2 ntn 4t-33895 tapered roller bearings. bearings are 2 1/8 inch wide inner id by 1 1/4. they ride on a 2 1/8 inch axle. has a drive sprocket, thrust washer and castle nut on the inner to hold it all together. no torque specs in the manual for this. any idea what to set the castle nut at? the drive chains and bearings are lubed with 30 wt oil from the chain case. thanks, glenn
 

[glennster]

heres a few pictures of what it all looks like.






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[the tractor vet]

I'll give ya may 2 and a 1/2 cents worth , Take all all the slop and give a light pre load where they turn free with out drag .
 

[Janicholson]

In that size range the bearing should be tightened carefully while tapping on the hub with a brass hammer to settle all races against the shoulders. they should be tight enough to feel strong resistance to turning by hand, and rolled several turns. Then back off the nut and tighten them till a spring scale will turn the hub at the sprocket at about 10 oz of force pulling tangentially to the sprocket tooth. Again rotate and tap on it to assure seating, and test the rotational force again. Jim
 

[glennster]

should the bearings be dry or oiled???
 

[Janicholson]

Installed and packed if they get grease or oiled with the axle oil if not. They stay assembled from that point. Jim
 

[glennster]

Ok, thanks for your help jim,
 

[Janicholson]

You are welcome. I have had experiences engineering those bearing sets on equipment for industry, and as a mechanic working on them for 45 years. Tapered roller bearings must have preload in proportion to their size, and because they have continuous line contact as they operate. If allowed to be loose (at all) they loose the line contact, and become rapidly worn and brinelled from point like contact at even tiny angels. Jim