RF45 mill Gearbox photos

The oil seal on the spline drive shaft had perished (probably due to the sand floating around in the oil and overheating, makes rubber hard and brittle) note the wear marks on the shaft.



Text Box: High/Med / Low selector
Text Box: High/Low
Text Box: Wear marks from oil seal

The oil was leaking down through the damaged shaft seal, into the spindle and all over the mill table.


The oil that was leaking down through the damaged shaft seal, into the spindle had washed the grease out of the lower spindle bearings. Look at the scoring marks. I replaced all of the bearings in the gearbox and spindle, cost me approx $160 for good quality NSK bearings.


Text Box: Double lip  seal

The next step was removing the bearings with a bearing puller, and replacing with new ones.

Here is a list of the radial bearings required


35 ID x 62OD  x 14mm


17 ID x 35OD  x 10mm

Text Box: 6202ZZ 
15 ID x 35OD  x 11mm
Text Box: 6202ZZ 
15 ID x 35OD  x 11mm
Text Box: 6003ZZ 
15 ID x 35OD  x 10mm
Text Box: 6003ZZ 
15 ID x 35OD  x 10mm
Text Box: Two of 6007ZZ 
35 ID x 62OD  x 14mm

There are two more bearings in the spindle, Taper Roller bearings. 30206, for the top and 30207 for the bottom of the spindle where most of the force will be. I think that these are made for car axles? Spec is for 45000N of force, so I don’t think that they will ever be overloaded!


I cleaned all of the casting sand off with a wire brush and a pressure washer. It looks like the unit failed because not all of the casting sand was removed at the foundry. It had just been painted over loose by the lazy Chinese man who put the mill together knowing it would stuff up later.!!! If he had have spent five minutes at the factory cleaning and preparing the gearbox casting before machining and painting, it would have saved me two days!!!


When putting the head back together, make sure that there is plenty of silicone on the lip seal cover.


The first time I put the head back together I pushed one of the shaft oil seals out of place, make sure you are really careful not to move the oil seals as you slide the spline drive back into place or the oil seals will leak. 


Also, take note of the little brass pieces on the gear change levers, they fall off really easy, and then you will have to disassemble your gearbox again to get them out!!! I tied them in place with cotton thread, and then undid the knot as I closed the gearbox and pulled the cotton out.


I refilled the gearbox with a good quality 5W30 Synthetic

Oil and added some Teflon “slippery stuff” additive. After

Replacing all of the bearings and reassembling the head,

Installing spindle, gear change levers, return spring….

I turned the spindle by hand selecting each gear to make

Sure that gear changes were working, and every gear was

engaging. With a sigh of relief, I turned on the electric

motor and it roared into life once more!


After replacing the bearings I ran the unit for an hour in every gear to run the bearings in. During the first 8 or so hours, the spindle bearings got really hot. I did the “hand test” and placed my hand on the spindle bearing case, it was just a little hotter than I could bear to leave my hand on, so I assume it was approximately 60 degrees.


After the new spindle bearings had run in, it never got that hot again.


There is a lot to be said about good quality bearings. The gearbox is now so much more quiet when it is running,  there is the same noise level when running at 1600 RPM compared to what it used to sound like at 95 RPM with  the old bearings!!!