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Lathe Maintenance

It’s time for some maintenance on my lathe.  Everything is working, but over the last ten years the slop in the cross-slide has been progressively increasing and now exceeds 0.5 mm which is a bother.



Figure 1.  HQ800 Lathe Mill


A lathe is one of the few machines that can make another lathe.  This is really handy for maintenance provided that the machine is not critically crippled.  The key here is to find stuff that is on its way out and make a replacement before the part actually fails.  Maintenance should precede and preclude repair.

All of the jibs have plenty of adjustment and I tweak these from time to time to ensure an easy action with no perceivable play in the carriage and the cross slide.  I will define ‘slop’ as axial movement in the line of the feed and ‘play’ as lateral movement or rotation perpendicular to the feed (but note that there are other terms such as back-lash that are also applicable).

Almost every machine has some slop and play.  The standard method for dealing with slop it is to ensure that the feed is always positively engaged.  Play is addressed by adjusting the jibs.  For non-active drives both can be addressed by simply locking the moving component to its respective bed.

To machine in the presence of slop if we’re right hand turning (tool moving from the right to the left towards the chuck) and have just completed a cut, then we back off the cross-slide somewhat more than the slop, return the carriage for the next cut, feed in the cross slide, and take the next cut.  For a roughing cut some folk won’t back off at all and will simply return the carriage with the chuck drive still engaged.  While this is very time efficient it risks a poor surface finish (hopeless for accurate measurements) and blunting  or chipping the tool because most right hand turning tools are not ground to cut to the right.



Figure 2.  Right Hand Turning with Slop
(Proceed Left to Right, Top to Bottom)



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