Shifts, attendance and cover in CNC and precision machining shops: rules that hold on a busy day

It is the fortnight before Diwali, with Dussehra just gone. Five operators want leave for one week, and two of them alone can run the horizontal machining centre with its pallet changer. A customer has asked for early delivery. The second shift is already one short. The supervisor grants leave to whoever asked first, then spends the festival ringing people to come back. Every rule the shop has lives in the owner's head, and the owner is travelling.

Thin cover appears again and again on the CNC machining group hub. Most shops already know who should cover what. What is missing is a short set of written rules that survive pressure.

Unwritten rules depend on the person applying them. On a calm day the supervisor is fair and careful. On a frantic one he says yes to the loudest voice, or to the friend who asks nicely. The night in-charge, alone with a turn-mill alarm and a half-loaded tombstone, improvises his own version. Payroll then receives a muster that does not match who stood at which machine, and the month closes in quarrels.

Shift times: first, second and night, each with a paid handover overlap spent at the machine.
Absence: phone the shift in-charge before a fixed hour; a message alone does not count.
Planned leave: request on the leave sheet with the notice printed on it; two operators cleared on one machine are never away together.
Festival weeks: the leave calendar opens early, and Diwali, Pongal, Onam or Eid leave rotates year on year instead of going to the quickest asker.
Swaps: allowed only between people cleared on the same machine, entered in the swap register and signed by both.
Overtime: requested by the in-charge and written on an overtime slip before it begins, with a cap on consecutive long days.
Late arrival and missed punch: regularised on the form before the following shift closes and approved by the in-charge.
Night rotation: published a month ahead on the rotation chart; any change follows the swap rule.
Setter call-out: who may ring the setter, for what, and how the call-out is paid or given back.
Weekly off and compensatory off: how a worked off-day is returned, and by when.

Who turns up matters. So does what they do in the first and last minutes. A machine shop has its own routine, and writing it into the shift rules stops each operator inventing one.

• At start. Run the spindle warm-up cycle before cutting close-tolerance parts, so thermal growth does not show up as a drifting bore. Check coolant concentration with the refractometer, way-lube level and air pressure.
• At handover. Name the job and the count released so far. List tools close to worn out by magazine pocket, offsets changed and why, parts on hold with their tags, and any alarm or odd noise, even one that cleared.
• Before a long overnight run. Load enough bar stock in the feeder or castings on the pallets, check wire spool, filters and deionised water on the EDM, and empty the chip conveyor bin.
• At close. Back up any program edits to the shop's master copy, park the spindle, clear swarf from the vice or chuck, and leave the shift note on the machine.

One rule sheet serves the whole shop, but a few lines need adding per machine family. Night cover fails at exactly these points.

• Horizontal machining centres with pallet changers. Whoever loads pallets for the night must be cleared on pallet offsets, fixture clamping and the tombstone loading sequence.
• Bar-fed lathes and sliding-head machines. Long night runs depend on bar stock, remnant ejection and collet or guide bush wear. The night operator must be able to change a guide bush, or the call-out rule must say who does.
• Wire EDM. Threading, flushing nozzles, resin and filter changes and water conductivity decide whether an overnight cut finishes. Name who checks them before the in-charge leaves.
• Grinders. Wheel balancing and dressing happen at shift start, never in a hurry mid-run, and nobody leaves a grinder cutting unattended.
• Five-axis cells. Nights run proven programs only. Prove-outs and first cuts on costly billets are saved for the day setter.

• Ask before, record before. The slip is filled before the extra hours start, not pieced together at month end.
• Spread it. Keep an overtime rota so the same three people are not asked every time.
• Cap the long runs. Limit consecutive long days, and give a rest day after a stretch of them.
• Read it monthly. Overtime per person and per machine shows exactly where cover is thin.

1. 1

   Draft with the shift in-charges

   They know where today's habits bend. Write down what they already do well.

2. 2

   Test against a bad day

   Take last month's worst day and walk it through the draft. Fix any rule that would have failed.

3. 3

   Read it out at each shift start

   In the language the floor speaks, with time for questions from operators and helpers.

4. 4

   Pin it near the timekeeper's punching machine and in each bay

   One sheet, signed by the owner, carrying the date it took effect.

5. 5

   Apply it identically on days and nights

   The night in-charge gives the answers the day in-charge would. Exceptions are written down with a reason.

6. 6

   Review after a quarter

   Count swaps, missed punches, overtime and idle spindles. Change any rule that is not working.

These rules sit inside a wider process for attendance and leave, including how records reach payroll. Job-work units with sudden peaks and raw helpers are covered on the VMC shift page. Overnight unattended cutting needs its own rules, and the wire EDM attendance notes lists them. A ready attendance regularisation request form handles missed punches. If one absence still idles a machine, read our piece on thin night cover.