Upgrading the Mini Mill with Taper Roller Bearings

An article about Upgrading the Mini Mill with Taper Roller Bearings, giving part numbers and the impact of changing to taper bearings.

I bought an Amadeal XJ12-300 milling machine, sometimes called a Mini Mill, this is actually a Real Bull milling machine. I bought this as it was cheap, but since buying it I’ve spent a lot of time making upgrades.

The head of the mill had been dismantled into all of it′s parts…..this got me thinking about the bearings on the main spindle which are 62mm OD, 30mm ID and 16mm thick and are quite rough ball races. I found a close match with the SKF 30206 J2/Q on size, but these are taper roller bearings and are around £33 for a pair including delivery from Bearingboys.

Another image of the bearing showing the two parts.

Note: the original lower spindle bearing comes apart very easy and the balls spill out and go free – take care if you intend reassembling with the original bearings.

The taper roller bearings make a huge difference to the shaft, it runs smoother and have not measured it yet, but I can see that the chuck is running much truer than it did. Taper rollers are worth the effort of upgrading even if you do nothing else.

I have been using the milling machine for over a year since replacing the taper roller bearings and this is a must upgrade. There is just no play in the spindle and it runs absolutely true.

Upgrading the mini mill with taper roller bearings really worked on this machine, but would have a similar effect on most machines if they are running ball bearings now. What I haven’t tried is just changing a machine that is running cheap taper rollers to a proper set made by SKF.

7 thoughts on “Upgrading the Mini Mill with Taper Roller Bearings”

  1. That is odd. This is the first X2 mini mill that I have seen that has the same
    bearing ID at the top and the bottom of the spindle. The different versions of the spindle that I have seen all had 30mm ID bearing at top, and 35mm bearing ID at the bottom.

    • The difference being he is running the 3 MT spindle. As you an are running the R8 spindle. The R8 is the same spindle along with the 7/16 X 20 Draw Bar (different lengths ) as Bridgeport mills . One thing i have found owning both the Sieg mini mill (SX2) an mini lathe (as in the 7 X 10 thru the 7 X 16 ) is both have the same gear/spindle box, the lathe box has a triangle rail cut into it for alignment on the lathe box, but the 2 speed gears are interchangeable, along with the bearings for 3mt mills and factory Sieg lathes.

    • Hi Luciano, I didn’t actually have a problem replacing them and getting the spindle back together – I changed these bearings and at the same time changed to metal gears and all was fine. Best regards, Nigel


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