I have had my X3 for around 18 months now and it gets a lot of use, currently around 1400 hours.
When it first arrived I spent a couple of weeks stripping and rebuilding it like most owners but steered clear of removing and rebuilding the
spindle. It looked far too difficult.
From new the machine has had a very noticable 'knocking' or even light 'hammering' sound from the head and spindle and this could be felt when
placing a hand on the head. Recently this got much louder and I decided to bite the bullet and rebuild the spindle.
This was much easier than expected.
Remove the top cover and belt.
Remove spindle return spring.
Remove 4 bolts and slid spindle feed shaft to the right until the internal gear clears the spindle - no need to dismantle or disconnect
tapping switch or completely remove the feed shaft.
Remove depth gauge.
Remove stop pin (behind depth gauge) and slide out the spindle.
After removing the locking nuts the spindle can be easily tapped out with a soft faced hammer.
After cleaning and greasing the bearings I refitted them but left out the top thrust bearing as it does not have a fixed centre and the upward
thrust from milling is handled by the lower taper roller bearing and the top bearing can easily handle the preload.
I may fit an angular contact type at some point.
I adjusted the preload (I had to reduce the spindle diameter slightly as it was too tight) and reassembled the machine.
I ran it up and hey presto it still knocked
I removed the spindle again and ran the motor/belt/front top bearing and the knocking was still there so I replaced the top front bearing.
After reassembling the machine I ran it up and the knocking was still there.
I Ran just the motor alone and it was almost silent at all speeds.
After a bit of investigation I found that the motor shaft could be moved laterally by around 0.3mm at certain points in its rotation.
After checking the price of a new motor I decided to attempt replacing the bearings in the old motor but when I stripped the motor I was
surprised to find that the bearings were fine.
The problem was a very badly worn rotor shaft where it passed through the top bearing. It had obviously be spinning inside the bearing and was
rocking as it spun so causing the knocking. This loose bearing had obviously be the problem from new.
I found a new bearing but one with a 16mm bore instead of the original 17mm
I ground the motor shaft down to 15.998mm (Using my old MG9).
The new bearing was a good tight push fit onto the shaft.
After rebuilding (again) the machine is transformed.
It runs almost slently with a very satisfying whirr sound and no trace of knocking or vibration at any speed.
Cutting is also greatly improved and finish quality is much better. Cutting marks that I thought were unavoidable are gone.
I hope this may be of help to others
Thanks for the information. You can do mine now. (hehe)