Cut-piece pricing: kerf, facing allowance and the saw maths behind an honest price

A customer rings for twenty pieces of 50mm bright round, 300mm long. The quick answer is length times weight per metre times price per kilo. It is also the wrong answer, because a 300mm piece does not consume 300mm of bar.

The saw takes some. The ends need cleaning up. Whatever is left at the end of the bar may or may not be sellable. Every stockholder with a saw knows this. The question is whether the price on the quote knows it too.

This article sets out the arithmetic behind an honest cut-piece price, works through an example, and shows where the money leaks when the sums are done in someone's head.

What a cut piece actually consumes

Three things sit between the length the customer ordered and the length you have used up:

• Kerf. The width of material the blade removes in each cut. It leaves the building as swarf, and you paid for it by the kilo.
• Facing allowance. Extra length added so the ends can be faced or cleaned up. The customer receives a clean 300mm piece; you cut something longer to get there.
• What is left over. The end of the bar after the last cut, plus any end trim taken off the bar before the first one.

The first two belong in the price of every piece. The third belongs in the price of the job, and whether it costs you anything depends on what you can do with it.

Kerf depends on the saw

Kerf is not one number for the business. It depends on the machine. A bandsaw blade is thin. A circular cold saw blade is thicker. If you run more than one type of saw, the same cut length consumes different amounts of bar depending on where the job is sent.

That matters for two reasons. First, a fixed allowance set for one saw is wrong for the others. Second, the person quoting often does not know which saw the job will go on. If the allowance is built into a mental rule of thumb, it is built for whichever saw the estimator had in mind on the day.

The honest approach is to hold the kerf against each saw type and let the price follow the machine.

Facing allowance: the ends nobody ordered

Most customers ordering cut-to-length bar want the stated length, with ends that are square and clean. Getting there means cutting slightly long and facing each end. So the facing allowance applies twice per piece, once at each end.

It is a small figure. It is also on every piece, which is why it matters.

A worked example

Take the order above. 50mm bright round weighs about 15.41kg per metre. For illustration, assume a bandsaw kerf of 2mm, a facing allowance of 1.5mm at each end, and a selling price of £2.10 per kilo.

The chargeable length of each piece is the cut length plus the kerf plus the facing allowance at both ends:

300mm + 2mm + (2 × 1.5mm) = 305mm

The difference is £3.24 on this job, about 1.7%. Small on one quote. Not small across a year of cut-to-length work, and it is margin you have already spent on material.

Now run the same order at 50mm long. The chargeable length is 55mm, so kerf and facing add 10% to the material in every piece. Short pieces are where the saw maths hurts most. A quote priced on cut length alone gets less honest the shorter the pieces get, and the estimator rarely notices because the job looks small.

Minimum usable length: the offcut that cannot exist

Carry on with the 300mm order. Say the bar comes in 3m lengths and you trim 10mm off the end before the first cut. That leaves 2,990mm. At 305mm a piece you get nine pieces from a bar, with 245mm left over.

Is 245mm a remnant or scrap? That depends on your minimum usable length for that size and grade. If your rule is that anything under 300mm is not worth putting back on the rack, those 245mm ends are scrap, and the job needs three bars, not two and a bit.

This is where quotes go wrong in the other direction. Someone promises an offcut back to stock, or prices the job assuming the leftover will sell, and the leftover is too short to be anything. A price that ignores minimum usable length is quietly assuming a remnant that cannot exist.

The useful rule is simple. Below the minimum, the leftover is scrap and its cost belongs to the job. At or above it, it goes back into stock as a remnant, with its own value.

Pricing the piece versus pricing the job

Kerf and facing are per-piece costs. They go into the chargeable length of every piece, every time.

End trim and the final leftover are job costs. How much they cost you depends on the cutting plan: how many pieces you get from each bar, what is left, and whether that leftover clears your minimum length. Two orders for the same total length can produce very different scrap depending on the cut lengths.

So there are really two questions:

1. What is the honest price per piece, allowing for kerf and facing?
2. What does this job do to the bar, and is the leftover stock or scrap?

Most pricing mistakes in cut-to-length work come from answering the first and forgetting the second, or from answering neither and pricing on cut length.

Why this lives in spreadsheets

General-purpose systems price a line as quantity times rate. They have no concept of a saw, a kerf or a facing allowance. So stockholders do the saw maths elsewhere: a spreadsheet beside the quoting screen, a laminated card by the phone, or one experienced estimator who just knows.

Each of those works until it does not. The spreadsheet has the old kerf figure for a saw you replaced. The card does not cover the new size range. The estimator is on holiday, and the person covering prices on cut length because that is what the screen shows.

How MetlSys handles it

MetlSys does the saw maths at the point the order is priced, as part of sales order entry:

• Chargeable length is the cut length plus kerf plus a facing allowance at each end.
• Kerf is set per saw type, so the allowance follows the machine.
• Minimum usable length flags stop anyone promising an offcut that cannot exist.

The same thinking carries through to the shop floor. Works orders show the theoretical yield, with kerf and end trim allowed for, before anyone touches a saw, and 1D cutting lists handle kerf, end trim and minimum offcut. When the works order runs, it creates one batch per cut length, remnant batches at or above your minimum length and scrap below it, and records the actual yield along with the input, product, remnant and scrap weights. Cut pieces carry the parent's full unit cost and its heat number and certificate, so margin and traceability both survive the saw.

Cut pricing and production are on the Professional and Corporate tiers, not Lite.

The short version

An honest cut-piece price is the cut length plus kerf plus facing at both ends, with kerf taken from the saw that will do the job. A cutting plan that respects minimum usable length tells you whether the leftover is stock or scrap. Do both where the order is priced and the margin you quoted is the margin you make.

If you want to see your own awkward cut-to-length job priced and planned end to end, request a demo.