How accurate are custom metal cuts? Saw tolerances explained

How accurate are custom metal cuts?

Every cut we ship lands within ±1/8″ of the length you ordered, and the cut itself is free. Order a 36″ bar and the piece on your bench measures between 35-7/8″ and 36-1/8″. Most cuts land closer than that. The ±1/8″ is the worst case we'll let out the door, not the average day.

That window is the standard class for sawn metal. Metal service centres across North America typically promise between ±1/16″ and ±1/8″ on cut-to-length stock; tighter numbers come from different machines at different prices. The window doesn't grow with length, either. A 96″ stick of carbon steel carries the same ±1/8″ as a 12″ offcut. We've been cutting metal since 1997, and this is the number our saws hold all day.

Why do bandsaws cut to ±1/8″ and not ±0.005″?

Because the cutting tool is a long, flexible steel band, not a rigid blade. Our saws run bands 1″ to 1-1/4″ wide and roughly 15 to 17 ft around, held straight by wheel tension and a pair of guides. Feed too hard, set the guides too far apart, or let a blade dull, and the band drifts in the cut. Saw operators call it blade wander.

The stock adds its own wiggle. Mill bar arrives with bow and twist inside its own tolerances, so a stick can sit a hair off in the vise even when it's clamped hard. And on a production saw, the face left by the last cut becomes the reference for the next one, so any lean gets a chance to stack. None of this matters at ±1/8″. All of it matters at ±0.005″.

We cut on Hyd-Mech horizontal bandsaws: an S-20A and an S-23A running automatic feed for production work, plus a manual S-23 for one-offs and awkward setups. The biggest takes rounds up to 16″ across. On a fresh blade and clean bar, these saws hold well inside the promise. We still quote ±1/8″ because the number has to cover the last cut of a long afternoon, not just the first cut of the morning.

How square is a saw cut?

Square enough to weld against, not square enough to machine against. The trade yardstick says a band saw cut counts as straight when it leans no more than about 0.002″ per inch of depth. Across a 4″ round, that allows roughly 0.008″ of lean, about the thickness of two sheets of paper.

On a gate frame or a set of railing posts, that disappears into the fit-up gap before you ever notice it. Where it bites is precision work: don't use a sawn end as a datum face, a bearing seat, or a shoulder another part registers against. If one face has to be dead square, face it on a lathe or mill and let the sawn end stay the rough end.

What will the cut ends look like when they arrive?

Expect a saw finish: a flat, clean face with fine tooth marks and a light burr on the corner where the blade left the metal. That's a normal sawn edge, not damage. Budget a few seconds per piece with a file or a flap wheel before parts go to paint, assembly, or anyone's bare hands.

Materials burr differently. Aluminum throws a soft burr that clings to the edge. Stainless burrs come off sharp, so keep gloves on when you unpack fresh 304 or 316 ends. If your pieces go straight into a finished product with no shop time in between, say so on a quote request and we'll talk through what the edges need before anything ships.

How accurate are sheet cuts on the shear?

Sheet never meets the bandsaw. It runs on hydraulic shears: an 8 ft Barcorp rated to 1/4″ and a 10 ft Ermaksan rated to 1/2″. A shear drops one blade through the full width against a back-gauge stop, so it repeats length very well, and your sheet still ships under the same ±1/8″ promise as bar stock.

A sheared edge has its own character. The top corner rolls in slightly where the blade entered, the face shows a smooth band and then a break, and the bottom corner carries the burr. On a properly gapped shear, that burr stays under about a tenth of the sheet's thickness. Thin sheet comes out crisp; closer to 1/2″, the break zone grows and the edge looks rougher. If an edge ends up visible on the finished piece, plan a quick dress with a file, same as a sawn end.

How do you design around saw tolerance?

Send the tolerance somewhere harmless. Most projects have an end that gets welded, buried, or trimmed anyway; let the saw cut live there. When a length truly matters, order long and face to length: buy 37″ to finish at exactly 36″, and your lathe removes what the saw left.

The per-inch model makes that insurance cheap. On 1″ 1018 cold finished round bar, a 36″ piece runs $30.64 and a 37″ piece runs $31.39 as of June 2026, so the spare inch costs 75 cents. You type your length in inches on the product page and the price shows up; here's how ordering by the inch works if you haven't bought metal this way before.

Two more habits worth stealing. Order matched parts in one order, so four table legs cut together on the same saw and blade; pieces from one run track each other more closely than the absolute window suggests. And dimension your drawing so the critical face is one you machine, not one we saw.

When should you ask for machining instead of a saw cut?

The moment your drawing says ±0.005″ or tighter. That's the standard tolerance class for lathe and mill work, 25 times tighter than a saw promise, and not a number to ask of a bandsaw. Faced ends, exact shoulder-to-shoulder lengths, bearing-quality surfaces: that's machining, and we'd rather tell you so at the quote stage than ship you a problem.

Send the drawing through a quote request and we'll tell you straight which side of the line your part sits on. The same form covers traceable material; if your job needs certs with the metal, our guide to mill test reports on small orders explains what to ask for. Need 20 blanks cut a half inch long for your own lathe? That's the everyday move, and those cuts are free.