A dividing head is a fixture mounted on a milling machine to divide a cylindrical workpiece accurately into equal parts. It is used to mill hexagons, splines and gear wheels.
In training and repair workshops, dividing heads often sit in cupboards for years, collecting dirt, swarf and oxidation, while their screws seize. Here is how to carry out a full service on a head showing clear signs of dirt and corrosion.
What you will need
Important: Lift the head off the machine with two people or a hoist: it is heavy. Always wear glasses when blowing out with compressed air, as swarf flies everywhere.
Step 1
Clean the outside
Place the dividing head on a workbench. Before dismantling, wash the painted body with a mild detergent so as not to damage the paint.
Treat bare metal surfaces with WD-40 Multi-Use: it dissolves old grease mixed with swarf and removes light oxidation. Wipe dry.
Step 2
Remove the external parts
Start with the crank, then remove the sector arms and the index plate. The slotted screws holding the plate often seize. Spray them with WD-40 Specialist Penetrant, wait a few minutes and undo them with a correctly sized screwdriver so the slots are not damaged.
Remove the self-centring chuck to give yourself more room. Then slacken the base screws and remove the half rings holding the swivel body. Pre-treat stubborn Allen screws with penetrant too.
Step 3
Dismantle the gearing
To remove the differential indexing unit, release the locking pin, separate its gear from the main body and undo the three screws.
Open the cover and inspect the worm and wheel. Even if they look clean, treat them with WD-40 Multi-Use: it displaces moisture that builds up in unheated workshops. Then blow dry with compressed air.
Step 4
Clean every part thoroughly
Wash the cover and refit it temporarily while cleaning the painted parts, so no cleaner gets into the gear mesh. The differential unit is usually coated with a film of grease and swarf, so clean it separately.
Put the base that houses the swivel body in a tray and clean it with WD-40 Multi-Use and a brush. Clean all screws and the index plate separately. The plate holes must be clean or the pin will not seat accurately.
Step 5
Lubricate and reassemble
Apply WD-40 Specialist White Lithium Grease to the worm gear, bearings and the sliding surfaces of the swivel body. Lithium grease clings to metal, does not run and protects against corrosion. Turn the mechanism by hand.
Reassemble in reverse order: swivel body into its seat, half rings, differential unit, plate with sector arms, crank. Check that the crank turns smoothly and the pin drops cleanly into the plate holes.
Tip: Between uses, keep the head under a cover and wipe exposed metal with
WD-40 Multi-Use every few weeks. The thin film prevents rust and is easily wiped off with a rag before work.
What next
Do a full service once a year or after a long idle period, and an external clean after each use. For workshops, WD-40 Multi-Use 5 l with sprayer is the practical choice.
These uses come from the experience of WD-40 users in many countries. Always follow the instructions and warnings on the product label.
More guides in «How to use».