That expanding bearing thing is the same as the nose bearing on my Town Woodhouse - I never knew they existed..Spindle install. The spindle obviously drives the horizontal tooling but also carries a gear that drives any vertical tooling that needs it, like the vertical milling head and slotting head. I got it out of the box it went in nearly 2 years ago. The gear on the left drives this spindle though the splines. The spline drive allows the slide to move whilst the spindle is held in place by a fork (the gear is on backwards in this pic).
The gear on the right is the one that drives the vertical head/slotting head.
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I cleaned and polished the spindle to aid assembly then made a jig so it could sit on my bench to allow bearing fitment etc without rolling about in the dirt.
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Now, the spindle has a radial bearing at the front and a pair of thrust bearings. the radial bearing is very clever (and probably horrendously expensive) because it's adjustable for radial play. The spindle and bearing bore are both tapered and the bearing fits onto this taper with threaded adjusters to push it onto or off the taper. This slightly expands the bearing inner race to adjust the backlash.
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The orange nut pushes the bearing (yellow) onto the taper whilst the green nut is threaded onto the blue collar to push it down the taper by jacking off the rear face of the spindle nose. You can just make out the blue/green jack screw assembly here:
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I started out by pre-setting the jack screw by popping the bearing firmly onto the taper then adjusting the screw up to nearly touching. Then after assembling the thrust bearing assembly onto the front housing I slid the spindle through, feeding all the bits on in their correct order. The big castle nut on the right is for adjusting the thrust bearings and the smaller one on the left for clamping the assembly together AND adjusting radial play.
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I fitted the key and bolted the stack all together then set about adjusting the spindle clearances. Here is the front adjuster (the green nut in the drawing above). Turning this anti-clockwise jacks the radial bearing down the taper increasing radial play.
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I have no info on what radial play value to shoot for (unless it's buried in the czech manual) so I shot for 0.0002". I set up a dial gauge and simply used my hand to put a good lift under the nose. It was initially lifting 1 thou so I used a c spanner to tighten the castle nut as tight as I dare, the radial play was now half a thou soI slackened it off and used an ally drift to tap the front adjuster round slightly then re-tightened the castle nut. I repeated this until I got 2 tenths of a thou radial play. The spinld still turned easily so I was happy with that.
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Afterwards I set the DTI on the end and tightened the thrust bearing castle nut until I could generate 2 tenths of axial play too.
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The spindle was still turning smoothly with no extra force so I finished assembling the spindle by installing the fork for the sliding gear.
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One job I do have to do is make some kind of bearing shield for the rear bearing. When I got the machine it was just open like this:
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