Two suppliers receive the same drawing with the same note on it — "deburr all edges" — and send back two completely different parts. One knocked the worst burrs off with a hand grinder in ninety seconds. The other ran every part through a double-sided machine to a uniform radius and priced it accordingly. Both claim compliance, and both are right, because the note does not contain a number. Sheet metal deburring is one of the few specification items where the drawing note is routinely written in adjectives, and it is the one where the gap between what the buyer meant and what the supplier did is widest. This guide sets out the ISO 13715 symbol system in plain English, how much burr is actually acceptable, what each removal method costs you, and the exact lines to put on a drawing and a purchase order.
Key Takeaways: Sheet Metal Deburring and Edge Condition
- "Deburr all edges" is not a specification. Neither is "burr free" without a number and an inspection method.
- ISO 13715 gives you a signed edge value:
+permits excess material,−requires removal,±permits either and is only valid with a size. - A single symbol element does not specify burr direction or size — those are separate indications, and direction is the one almost nobody uses.
- Burr direction matters because the burr sits on the exit side. On a bend, a burr on the outside is a crack starter; on a sealing face, it is a leak path.
- Every removal method changes the part. Mass finishing is all-or-nothing per part and can shift dimensions by roughly ±0.1 mm.
- ISO 2768 does not cover burrs. Writing a general tolerance and assuming it controls edge condition is a common and expensive mistake.
Why "Deburr All Edges" Is Not a Specification
The note survives because it is short and it has always been on the drawing. It fails for three reasons: it does not say how much material may remain, it does not say where, and it does not say how anyone would check.
That last point is the one that decides disputes. A requirement without an inspection method is a preference. If the buyer's QA checks tactically and the supplier's operator checks visually, they are running two different specifications against the same note, and they will disagree on the same part.
There is also a cost reason to be specific. Uniform deburring of every edge on a part is a real process step with a real cycle time. If only four edges on the part actually matter, you are paying to finish forty. The fix is not a better note — it is a general indication plus local callouts on the edges that carry a function.
What a Burr Actually Is, and Which Process Made It
A burr is plastically deformed material that was pushed out of the cut rather than removed by it. Which process made it determines what it looks like and what it takes to get rid of it, and one part routinely carries three different burr types at once.
Laser dross vs punch rollover vs shear feather
Punching and blanking produce rollover at the entry side and a breakout burr at the exit side. The burr height tracks die clearance and wear, which means the height on the last part of a long run is not the height on the first.
Laser cutting produces dross or recast on the underside, an adherent layer rather than a folded flap. It comes off differently — usually by mechanical means, sometimes only with aggressive media — and cutting parameters move it a long way.
Shearing produces a feather edge, thin and ragged, most often at the intersection of two cuts.
This is why one removal process rarely suits every edge on a part. A method that takes the punch burr off cleanly may not touch laser dross, and a method aggressive enough for the dross may round an edge that needed to stay sharp. The process choice behind the burr type is covered in our laser cutting vs stamping comparison, and the tooling side in the precision metal stamping service guide.
ISO 13715 in Plain English: The +, − and ± Edge Symbol
ISO 13715 (current edition ISO 13715:2017, adopted in Europe as EN ISO 13715:2019) defines how to indicate the condition of an edge on a technical drawing. The symbol is a small triangle that points at the edge, and it carries a signed value.
+(positive value) — excess material is permitted at the edge. In plain terms: a burr may remain, up to the stated size.−(negative value) — material must be removed: an edge break, a chamfer or a radius of the stated size.±— either is acceptable, and this indication is only valid when a size is given. A bare±with no number says nothing.
The standard provides a ladder of preferred edge sizes. In practice most drawings need only two or three of them; +0.1, −0.1 and −0.3 mm cover the overwhelming majority of sheet metal work we see.
Reading a positive and a negative edge value
Two things catch people out.
First, a single symbol element does not specify burr direction or burr size. Those are separate, additional indications. If you write an edge value and nothing else, you have specified the edge geometry and left the burr direction uncontrolled.
Second, the collective versus local rule. A general indication — typically placed in or near the title block — applies to every edge not otherwise called out. A local indication on a specific edge overrides it. This is exactly the structure that saves money: a permissive general note, plus tight local callouts on the handful of edges that do something.
Edge Break vs Radius vs "Sharp": Four Different Callouts
Four conditions get used interchangeably in conversation and are not interchangeable on a drawing.
| Callout | What it is | What it is for | Watch out for |
|---|---|---|---|
| Sharp (as cut) | No removal | Sliding or wiping surfaces, some sealing faces, press-fit entry | Handling injuries; coating pulls back from a sharp edge |
| Edge break | Typically 0.1–0.3 mm removed | Handling safety, coating preparation, general de-sharp | "Break all sharp edges" is still not a number unless the size is stated |
| Defined radius R | A stated radius | Gasket lands, cable pass-through, fatigue-critical edges | Harder to hold consistently than a break |
| Defined chamfer × 45° | A stated chamfer | Weld preparation, assembly lead-in, cosmetic edges | Needs a second dimension to be complete |
The reason this table matters commercially: a radius and an edge break are different processes with different costs, and a supplier quoting "edge break" will not give you a radius. Our sheet metal surface finishing guide covers what each one does to coating adhesion downstream.
How Much Burr Is Actually Acceptable
When no limit is specified, the rule of thumb in common use is a maximum burr height of around 10% of the sheet thickness. It is a reasonable baseline and it is not a standard — label it as a rule of thumb if you use it, and expect your supplier to read it that way.
Then note the counter-example, which is the reason the rule is only a baseline. A burr comfortably inside 10% can still break a spot weld, hold a mating part off its seating face, or cause arcing at a terminal. Our own powder coating vs liquid painting guide specifies burr height below 0.05 mm on cut edges before coating, which is far tighter than the 10% rule, and it is tighter for a reason: coating pulls back from a sharp or burred edge and the corrosion starts there, on the edge, not on the flat face we measured.
The general principle: the limit follows the function, not the process. Our clearance and creepage guide takes the same approach from the electrical side, requiring edges broken to R0.5 within 20 mm of a busbar. Same edge, different function, different number — which is exactly why a single blanket note cannot do the job.
And one structural note on direction
A burr on the outside of a bend is a crack starter, because that surface is in tension and the burr root is a ready-made notch. Our hem, bend relief and corner joint guide makes the same point from the forming side. Since the burr always sits on the exit side of the tool, controlling direction is often just a matter of specifying which way the part is formed or which face is up at the punch — a free change at the design stage and an expensive one later.
Five Deburring Methods and What Each One Costs You
| Method | Best for | Edge outcome | Dimensional risk | Cost per part | Volume threshold |
|---|---|---|---|---|---|
| Manual (hand tool / flap wheel) | Prototypes, large parts, localised edges | Operator-dependent | Low on the part, high on consistency | High | Any |
| Vibratory tumbling | Small parts, high volume, all-round break | Uniform break or radius | In our experience up to roughly ±0.1 mm — confirm for your part and media; can curl thin sheet | Low | Hundreds |
| Rotary brush / belt | Flat parts, one-face requirement, laser dross | Directional finish | Low if fixtured | Low–medium | Tens |
| Abrasive belt / wide-belt | Flat blanks, consistent stock removal | Very uniform | Low | Medium, high set-up | Hundreds to thousands |
| Thermal or electrochemical | Complex geometry, internal cross-hole burrs | Uniform, reaches internal features | Process-specific, needs control | High set-up, low marginal | Thousands |
Three practical rules that come out of the table:
- Mass finishing is all-or-nothing per part. You cannot tumble one face. If two edges on the part need to stay sharp, tumbling is the wrong route and the process has to be a belt or a brush with fixturing.
- Thin sheet moves. Below about 1 mm, aggressive mass finishing can curl or dish a part. Check the flatness requirement before you choose the method.
- Tap after, not before. Threads finished in a tumbler lose their lead-in and arrive with media packed in them. Our material selection guide covers the material side of media choice — aluminium needs non-ferrous media or you will embed iron and get rust blooms under the paint weeks later.
How to Write the Edge Requirement on the Drawing and the PO
Here is the structure that works, in the order you would write it.
On the drawing:
- A general (collective) indication near the title block: "General edge condition per ISO 13715: edge break −0.1 unless otherwise indicated."
- Local indications on every functionally critical edge — gasket lands, sealing faces, user-touch edges, thread starts, cross-hole intersections, anything within 20 mm of live parts.
- Burr direction stated where it matters: "Burr direction: internal face" on a sealing ring, "no burr on outer bend radius" on a formed flange.
- The inspection method for each: visual at 4×, tactile (fingernail or glove), gauged (burr-height gauge or comparator), or borescope for internal cross-holes.
On the purchase order:
Edge condition per ISO 13715. General: edge break −0.1 mm. Local: item A gasket land −0.3 mm, no burr on sealing face; item B all user-touch edges R0.5. Burr height on cut edges < 0.05 mm prior to coating. Inspection: burr-height gauge at first article and 1 per 50 thereafter; visual 4× on 100% of user-touch edges.
One negative specification worth stating explicitly: general tolerancing to ISO 2768 does not control burrs. It covers dimensional context, not edge condition. Buyers write a general tolerance block, assume the edges are covered, and discover otherwise at goods-in. Our sheet metal tolerance guide sets out what ISO 2768 does and does not reach, and our quality control and inspection guide covers how to write the inspection clause so it gets applied.
And the closing principle: do not write "burr free". Zero burr is not measurable at zero cost. Write a number and a method, and you will get a part you can accept or reject on evidence.
Frequently Asked Questions
What does ISO 13715 actually specify?
ISO 13715 (ISO 13715:2017, EN ISO 13715:2019 in Europe) defines how to indicate the condition of an edge of a workpiece on a technical drawing. Its symbol carries a signed value: a positive value permits excess material at the edge, a negative value requires material removal such as an edge break, a chamfer or a radius, and a dual value permits either but is only valid when a size is given.
What does "burr free" mean on a purchase order?
On its own, nothing enforceable. Physically, zero burr is not measurable at zero cost, and suppliers interpret the phrase differently. Replace it with an edge value from ISO 13715, a burr-height limit in millimetres, the location it applies to, and the inspection method and sampling rate.
How much burr is acceptable on sheet metal?
Around 10% of sheet thickness is the usual rule of thumb when no customer limit is specified, and it is a rule of thumb rather than a standard requirement. Function drives the real number: edges to be coated are often held under 0.05 mm, because coating pulls back from a burred edge and corrosion starts there, and a burr well inside 10% can still break a spot weld or arc at a terminal.
Does ISO 2768 cover deburring?
No. ISO 2768 covers general dimensional tolerancing and does not address burrs or edge condition. If you rely on a general tolerance block and say nothing about edges, edge condition is unspecified regardless of how tight the tolerance is.
Which deburring method should I choose?
Match it to the geometry and the volume rather than to the burr. Flat parts with a one-face requirement suit a brush or wide belt; small parts at high volume suit vibratory tumbling; internal cross-hole burrs need a thermal or electrochemical route. Note that mass finishing treats the whole part, so if some edges must stay sharp, or the sheet is under about 1 mm, it may be the wrong choice.
Get the Edge Condition Into the Drawing
Send us the part drawing or model, the material and thickness, the volume and the function of each critical edge — sealing, coating, handling, electrical. We will return an edge specification with ISO 13715 values and burr direction, the removal method we would use and why, the dimensional effect you should expect, and a fixed-price quotation within 24 hours.
Edge condition is also one of the most common coating defect origins — our powder coating defects guide shows where edge pull and thin coverage come from.