Break All Sharp Edges: How to Write the Note

"Break all sharp edges" shows up on nearly every machined-part drawing. Most of the time it works fine. It stops working the moment someone needs to inspect it.

What Size Chamfer Do You Need If You Just Want the Edges Broken?

You often don't need a size at all. If the edges just shouldn't cut anyone, a general note is enough, and it lets the machinist file it or program a small chamfer, whichever's quicker.

That's what an r/Machinists user asked while drawing a part where "all the edges and corners" should be broken. One engineer replied that they put "All burrs removed and sharp edges broken" on nearly every drawing and leave the method to the shop. They've never had a machinist put a massive chamfer on a small feature. Another would write a maximum edge break of .010-.020" right into the note. A third warned that parts nesting into corners need real chamfers called out, so the outside corner of one part clears the inside radius of the other.

When "break all sharp edges" gets you in trouble

A different r/Machinists thread shows the catch. A machinist had a print with ±.0001" bores and only the bare note in the title block. Could a .015" chamfer on those IDs still meet the print? One reply said that without a tolerance the note just means deburr for safe handling, and "typically less is better." Another pointed out that it doesn't apply where a wall meets a floor, like a pocket bottom or a shoulder where the ID steps.

So the bare note leaves size and shape to whoever makes and inspects the part. Two good shops can ship different edges and both call it compliant.

Making it checkable

Add a maximum when size matters, something like "break sharp edges .005-.020". If an edge must stay sharp, say so on that edge.

If you want a standard, the Saola guide to edge breaks points to ISO 13715. It gives a symbol with a signed size: a plus value allows material past the sharp corner, a minus value means material comes off. You can put one general indication near the title block and list the exceptions next to it. The 2017 edition dropped its recommended sizes, though, so the number still has to come from your design.

Deburring is its own job, and these posts cover it: deburring aluminum without hand filing and deburring M5 holes from one side. If an edge deserves a real dimension, chamfer vs fillet on machined edges covers which one costs less.

At DigiForge

Our CNC capability page lists "ISO 2768-m standard, down to ±0.01 mm". ISO 2768-1 has a table for the chamfer heights and radii you dimension, but it won't pick a size for a bare note. If your edge break needs a limit, write it on the drawing. Not sure how a bare note will be read on your part? Ask us when you quote.