A manual lathe is a simple, stubbornly honest machine. It has no ball screws to compensate for wear and no control to smooth over a tired bed, so everything it turns reflects the condition of the iron underneath. The good news is that lathes rarely wear out through honest work. They fail slowly through neglect, and most of what keeps one accurate takes a few minutes a week. If your turning comes out tapered, your finish looks torn and your dial readings drift, the answer is almost always cleaning, lubrication and a bit of careful measurement.

Start with cleaning, not adjustment

Swarf is the enemy of accuracy. It works its way under the saddle, into the cross slide ways and behind the chuck register, and from there it grinds away at surfaces that were scraped flat at the factory.

Clear chips with a brush and a vacuum rather than an air line. Compressed air drives fine swarf deeper into the ways and into the headstock bearings, where it does real damage. Once the loose material is gone, wipe the bed ways with a clean lint-free rag and check the felt or rubber wipers at each end of the saddle. Those wipers are cheap and they are the single best protection your bed has, so replace them when they harden or fray.

Finish the job by clearing the chip tray, cleaning the T-slots on the cross slide and compound, and brushing the leadscrew with a stiff brush. Leave the machine with the saddle parked at the tailstock end so the ways and the leadscrew are covered.

Lubrication: the right oil in the right place

Different parts of a lathe need different oils, and using the wrong one is nearly as bad as using none.

• Bed ways and slides: a proper slideway oil, typically ISO 68, which is designed to cling to vertical and horizontal surfaces and resist being squeezed out under load. Engine oil runs off and leaves you with dry patches.
• Apron, half-nut, leadscrew thrust and tailstock barrel: oil every nipple and felt wick at the start of each session. If a nipple will not take oil, the passage is blocked and needs clearing.
• Change gears and open gearing: a light open-gear lubricant or chain oil, applied sparingly. Excess grease collects swarf.
• Headstock: check the sight glass before each use and top up to the line with whatever grade the manual specifies, usually a light spindle oil. Change it annually if the machine sees regular work.

Buy a decent oil can with a rigid spout and a small brush bottle. Keep both next to the lathe so lubrication becomes a reflex rather than a chore.

Levelling and bed alignment

A lathe bolted to an uneven floor will twist, and a twisted bed turns taper no matter how careful your technique is. Check with a precision level of around 0.02 mm per metre. Place it across the ways at the headstock end and again at the tailstock end, then along the bed on the flat and V ways. Adjust the levelling screws or shim the feet until both readings agree. Do this after moving the machine, and again a fortnight later once it has settled on the floor.

Twist is the main cause of taper, but a bed can also be worn low in the region where most work is done. A dial indicator on a magnetic base, run along the bed on a carriage-mounted arm, will show a dip in the middle of a well-used machine. If the bed is worn, keep long work near the chuck or spread the wear by using the whole bed for everyday jobs.

Chuck, spindle and tailstock checks

Take the chuck off periodically and clean the register and the spindle nose. Any burr or trapped chip here shows up as runout you cannot dial out. On a three-jaw, always tighten with the same key hole; if the jaws are bell-mouthed from years of gripping short parts, a light regrind with a tool post grinder restores them. A four-jaw deserves a dial indicator on every job.

Check spindle runout with a test bar and a dial indicator, and check tailstock alignment by turning a test bar between centres or by using a test bar in the tailstock taper. Slide the barrel fully out and check for play; a worn barrel will let the drill wander and will ruin a between-centres job.

Gibs, backlash and the feel of the machine

Adjust the cross slide and compound gibs so the slide moves freely with no detectable rock when you lift the tool post by hand. Tighten until drag appears, then back off a fraction. Check leadscrew backlash with the dial indicator against the saddle and the half-nuts engaged; a little backlash is normal, several millimetres is not. Clear backlash by always approaching a dimension from the same direction.

Finally, listen. Chatter, a clicking apron or a rumble in the headstock are messages. Deal with them in the quiet weeks and your lathe will keep turning straight, clean shoulders and fine finishes for another generation of work.