Spare Parts & MRO Store

What this tool does

CM8-277 is a register for a maintenance store: the spares, consumables and MRO items you hold so a machine can be put back into service. Each part is recorded against the machine it fits, classified by criticality, and given a minimum stock level, a lead time, a supplier and an honest note on whether it is still made. The tool works out the value on the shelf, the months of cover held, which vital parts have nothing behind them and which have not moved in a year.

Everything runs inside this single file — no account, no upload, no network request of any kind.

Why MRO spares are not the same as stock

A general stock register — the free Stock Inventory Register covers that job — is built around turnover: stock that sits still is a problem, and every instinct in that world says a part with no movement in twelve months should not be there.

A maintenance store is the opposite in the one respect that matters. You hold a critical spare hoping never to use it. Its value is not the margin when it sells; it is the downtime avoided on the day it is needed. A servo drive untouched for four years that gets a machining centre running again the same afternoon has earned its shelf space many times over. Judge it on turnover and you throw it out the week before you need it.

So the arithmetic here never treats stillness as failure on its own. It asks two questions instead: what happens if this part is not here, and how long would it take to get one. Those answers make a spare worth holding — or, where they are "not much" and "next day", not worth holding.

Vital, essential, desirable — classified by consequence

Criticality is a statement about consequence, not price — and that is the commonest mistake in spares management: expensive parts get called critical because they are expensive, cheap ones ignored because they are cheap.

• Vital — the machine stops without it and there is no workaround. A low-cost proximity sensor interlocking the guard on your bottleneck machine is vital. So is a drive belt.
• Essential — the machine runs degraded, or there is a workaround that costs time. A coolant pump on a lathe that can cut dry on soft material for a shift; a compressor air filter.
• Desirable — convenience, planned work, or a part you could get before it hurt. Contactors that arrive next day from three suppliers.

Two tests keep it honest. The cheap sensor test: if a part costing very little stops the line it is vital, and its low price makes holding six an easy decision. The redundant pump test: an expensive spare motor for a duty-standby pair is desirable, because the automatic standby already does the spare's job. If those tests move parts around your list, the list was priced rather than classified.

Classify with production in the room: maintenance knows what fails, production knows what stopping costs, neither knows both.

Setting the minimum, and reading cover months

The minimum stock level is your reorder trigger. It comes from two things — how fast you get through the part, and how long a replacement takes.

Cover months answers "at the rate we have actually consumed this, how long does the shelf last?" Where nothing has been consumed the tool prints a dash rather than a confident infinity — and for a vital insurance spare a dash is exactly what you expect.

For consumables the minimum is a lead-time calculation: twenty-four filters a year on a two-week lead means roughly one consumed in that window, so a minimum of six buffers a supplier hiccup and a bad month. For vital insurance spares it collapses to a judgement — one, or two if the failure mode can take out a pair, or the lead time makes a second failure during the replacement window plausible.

The tool will not accept a vital part with a minimum of zero: if a part genuinely stops the machine, "how many should we always have?" cannot answer none — and if it can, the part is not vital.

Single source and obsolescence

Single source means there is no alternative supplier you have actually qualified — not that you never looked. Minimum stock protects you against consumption; nothing protects you against your only supplier going quiet. Qualifying a second source is cheap and almost always deferred, because it is never urgent until the week it is impossible. Hence the tile: a short list you can work through in an afternoon of phone calls, and every name you remove is a real reduction in exposure.

Obsolescence comes in two stages and the difference matters. Watch means end of life is announced but the part can still be bought — the only moment a last-time buy is possible. Decide how many years of the machine's remaining life you are covering, buy that many, record the decision. Obsolete means the window has closed: what is left is a specialist repair house, a compatible part from another maker, reverse engineering the item, or replacing the machine. All four are slow and none certain, which is why an obsolete part at or below its minimum is flagged as an exposure. Obsolescence is rarely a maintenance decision on its own — it is a capital planning conversation maintenance must start early.

Dead spares — machines leave, spares stay

Every long-lived store accumulates parts for machines that are no longer there. A saw is sold, a line is re-laid out — and the spares stay, because nobody's job is to find them. Years later they are a shelf nobody recognises, with a value that would surprise the finance director.

The dead-stock list is the answer: parts with nothing consumed in twelve months, holding more cover than your threshold (24 months by default, adjustable in Settings), or no longer manufactured. Each row carries a suggested disposition; the foot totals the money.

Vital insurance spares appear here too, deliberately — by design they never move. The list marks them "keep while the machine runs, confirm it still does": the failure mode for an insurance spare is not that it is unused, it is that the machine it protects left three years ago and nobody told the store.

Maintenance resists the annual purge, rationally: whoever scrapped a part needed six months later remembers it for a career, and nobody is thanked for shelf space. So make it a decision, not a clear-out. Take the list to production and ask one question of each row — is the machine still here, and would we buy this today? Two noes is a disposal; one no is a transfer or a sale. Anything undecided stays, dated, and comes back next year.

The long-lead vital chart

The chart of vital parts bucketed by lead time is the one to take to a management meeting. It converts the store into the only currency the rest of the business cares about: how long the machine would be down.

A vital part with a one-week lead is a nuisance. A vital part with a sixteen-week lead is a quarter of the year's output riding on one item on one shelf — and if that item is also single-source, no longer made, or below its minimum, you are one failure away from a problem no amount of overtime will fix. Read it alongside the critical-gaps tile, which names the longest-lead gap rather than merely counting them.

Linking it to maintenance

A spares register works best beside a maintenance plan. Planned work tells you what you will consume and when — the filters, belts, seals and elements that come off the schedule rather than off a breakdown. The Preventive Maintenance Schedule tool is the natural companion: add up a year of the parts each planned task consumes and you have the 12-month usage figure, without guessing.

The habit is a short loop. When a job consumes a part, update the quantity and the last-used date. Once a quarter, read the critical-gaps figure and the dead list. Once a year, review the classifications with production — the bottleneck moves, and the vital list should move with it.

FAQ

Should consumables sit in the same register as insurance spares? Yes — they compete for the same shelf, budget and attention. The charts split by criticality so the filters do not drown the servo drive.

What if I do not know the 12-month usage? Leave it blank. The tool prints a dash for cover months rather than inventing a number — the honest position until you have a year of records.

Is unit cost the purchase or the replacement price? What it would cost to buy one today. For an obsolete part the difference can be large.

Does this replace a stock count? No. Quantities here are what somebody typed. Count the critical shelf at least annually and correct the register from the count, not the other way round.

Saving your work

Parts, settings and the report header are written to this browser's local storage as you type, and the toolbar shows the last save. That storage belongs to one browser on one computer: another browser, a private window, a second machine or a clean-up tool that clears site data will not have it.

Treat Export .json as the real save — one file containing everything, which Import .json restores anywhere. Export CSV gives you the register for spreadsheet work. Reset asks twice, then erases everything this tool has stored. There is no undo.

Accuracy & disclaimer

The tool calculates faithfully from what you enter; everything that matters sits underneath the arithmetic. Cover months divide the quantity you typed by the consumption you recorded — they describe the past and predict nothing. Criticality is a judgement, and a register classified by price produces confident charts about the wrong things. Lead times are what the supplier said last time, not a commitment.

Above all: a spares register cannot tell you what will fail. It can tell you what you could not replace quickly if it did — a different question, a more useful one, and the only one a list on a shelf was ever able to answer. This is a prioritisation aid, not maintenance engineering advice, not a reliability analysis, and not a substitute for counting the store.