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Deburring aluminium parts: what the edge note means
Published 2026-09-10
The vaguest line on a drawing is often the most common one: deburr all edges. It reads like a requirement, but it specifies nothing — how much material may come off, which edges count as all, and how anyone judges the result when the parts land. With those three questions open, the shop does whatever is cheapest to do, the inspector judges by feel, and the disagreement surfaces at first article or, worse, on the first production shipment. This is about turning edge condition into something both sides can actually execute.
Where burrs come from, and why there will always be some
A burr is what you get when the last of the material is not cut cleanly but pushed over the edge by the departing tool. Aluminium is ductile, and the softer extrusion alloys — 6060 and 6063 especially — tend to roll a burr into a flap that stays attached rather than snapping off. That is not poor workmanship. It is what cutting a ductile metal does: every hole, every slot, every milled contour leaves something behind on the side the tool exits.
So the question a drawing has to answer is not whether there will be burrs. It is what condition the edge has to be in to ship. Write it as a state to be achieved, not as a reminder to be careful.
Hybrid extruded-and-machined parts carry an extra layer. The sawn ends of a cut extrusion and the features milled afterwards produce completely different burrs. A sawn end throws a burr around the entire profile outline, including the inner cavities of the section that no finger reaches; a milled feature concentrates its burr on the exit side of the cutter. When the drawing carries only one blanket instruction, those two places routinely receive two different levels of effort.
Three different things: deburring, an edge break, and a sharp edge you want kept
Deburring removes the raised material and leaves the edge clean, with the geometry essentially unchanged. An edge break or chamfer deliberately removes a band of material to create a transition surface that has a size and can be measured — it is a feature, and it belongs on the drawing like any other feature. The two are not synonyms, and they do not price the same: the first usually rides along inside normal processing, the second costs tool path and time.
The third case is the one that gets forgotten: some edges need to stay sharp. Round over the mouth of a seal groove and the O-ring gets squeezed somewhere it should never go. Break the entrance of a press-fit bore too generously and you have quietly shortened the engagement length. Round an edge that serves as a datum and every measurement referenced to it drifts. Those places need an explicit no edge break here on the drawing, or a conscientious operator will tidy them up for you.
The test is simple: if the shape of the edge affects function, it deserves its own call-out. If you only want the part safe to handle and free of anything hanging off it, what you want is deburring, not a chamfer. Saying which costs nothing on the drawing; not saying it can cost a batch.
There is a standard for exactly this: ISO 13715
Many engineers never learn that edge condition has a published standard behind it. ISO 13715 defines a set of edge symbols for edges of undefined shape — the ones you do not want to draw as a specific chamfer but still need to constrain. Its real power is that it lets you specify the outside and inside edges separately and state a direction: this edge may carry residue, this one must not, this one may transition toward a given side.
That is what a prose note cannot do. It pins down which side. Both mouths of a hole, the intersection of cross-drilled bores, the entry and exit ends of a slot — burr direction means something in all of them. A burr that folds into the inside of the part may be entirely harmless, while a burr on the other face of the same hole lifts the mating part off its seat. With a symbol, the inspector knows where to look. With a sentence, everyone interprets it privately.
If your drawing system has not adopted the symbols, a step down is perfectly workable: put one general edge requirement in the title block or notes, then pull out the few edges that genuinely matter and describe them individually. The point is not which notation you use. The point is that all edges stops being the only thing the drawing says.
Which edges are worth calling out on their own
Most edges really can be handled as a group — labelling every one of them would make the drawing unreadable. But the places below are the ones we end up asking about on almost every review. Say it once up front and you save a round trip.
| Edge location | Why it needs its own line |
|---|---|
| Mouth of a seal or O-ring groove | Rounding changes how the seal is compressed; usually the edge must stay sharp |
| Entry of a press-fit or interference bore | The entry shape drives both assembly force and effective engagement length |
| Inside intersection of cross-drilled holes | The burr sits where nobody can see or reach it, and often releases after assembly |
| Mouth of a tapped hole | A burr there stops the first thread engaging — the usual reason a screw will not start |
| Faces and edges used as datums | Once rounded, the first article and later batches are no longer measured from the same reference |
| Exposed edges that people will handle | This is a safety requirement and belongs in writing, not in the supplier's good judgement |
Surface treatment magnifies edge problems, it does not hide them
A common assumption is that anodizing or coating will cover the burrs anyway. The opposite is closer to the truth. Anodizing grows a conversion film on the base metal, following the geometry that is already there — the burr stays exactly where it was and merely changes colour. Worse, film growth and sealing conditions at a sharp edge are never as good as on a flat face, so those are the places that fail first.
Powder coating brings a different physical effect: as the film flows and cures it pulls back from sharp edges, and the sharper the edge the thinner the coating over it. For coated parts, giving the edge some transition is usually the right call — but it is a decision that belongs on the drawing rather than in the shop's hands, because the same part can easily carry both an exposed edge you want softened and a sealing edge that must stay crisp.
State the sequence too. Deburring is normal processing carried out before surface treatment. If a feature is machined after treatment — a bore left to be reamed last so the fit lands where you need it — then the edge requirement at that location needs its own note, along with whether exposed base metal is acceptable there.
Fix the acceptance criterion at first article, not at volume
Edge condition is one of the few characteristics where no amount of written detail beats comparing one physical part. The reliable route is to settle it at first article: we submit the part, you confirm the edge condition in the metal, and that approved piece becomes the reference for every batch after it. That works far better than piling adjectives onto a drawing, and it stops acceptable from meaning two different things to two people.
Agree the method of judgement at the same time — visual, by hand, or under a stated magnification. When the method is unstated, incoming inspection turns into a negotiation, and that negotiation always happens after the parts are already made.
If you are unsure how to specify it, send the drawing. Which edges can be handled as a group, which need constraining individually, and which requirement will collide with the finish you have chosen all come back together in the engineering review we run before pricing — with a suggested wording attached.
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