Every sheared edge has a burr, and the burr is on one side or the other depending on which way the punch entered the material. Most drawings say nothing about it, which is how a part that looks correct on a bench fails in assembly.
How do you specify burr direction on a stamped part?
Burr direction is specified by naming which face must be burr-free, not by giving a burr height alone. The burr forms on the side the punch exits, so the direction is set by which way the tool is built - it cannot be adjusted at inspection. Write it as a note on the drawing, for example burr toward the inside of the housing, or burr away from the sealing face, and add a maximum burr height for the faces that matter. Where the part has a functional face - a seal, a bearing seat, a sliding contact - the burr-free side should be that face. If the burr cannot be avoided on a functional face, the process changes: a shave, a coining pass or a flip in the tool, and that is a tool cost rather than a deburring cost.
Why it is a process decision
The burr direction is fixed when the die is built, because it follows the direction of punch travel through the material. That means it has to be decided before the tool is cut, not discovered at first article. It also means a part cannot be turned over to hide the problem: flipping the part puts the burr on the other face of the same edge.
What to write
- Which face must be burr-free, named in words rather than by a symbol the shop has to interpret.
- A maximum burr height for that face, since 'no burr' is not a manufacturable requirement.
- Whether a minor burr is acceptable on the opposite face if it is inside the assembly.
- The deburring process if one is expected - tumbling, brushing or hand work - and who owns it.
Key point
Name the face that must be burr-free and give a maximum height. It costs a line of text before the tool is cut, and it prevents an argument after first article about a burr that was always going to be on that side.
Frequently asked questions
Which side does the burr form on?
The side the punch exits. Because the burr follows punch travel, its direction is set by how the die is built and cannot be changed at inspection - it has to be decided before the tool is cut.
Can a burr be removed by turning the part over?
No. Flipping the part only puts the burr on the other face of the same edge. If a functional face must be burr-free, the process has to change - a shave, a coining pass or a different tool orientation.
How should burr be specified on a drawing?
Name the face that must be burr-free in words, give a maximum burr height for that face, say whether a minor burr is acceptable elsewhere, and state which deburring process is expected if any.
Is 'no burr' an acceptable requirement?
No, because every sheared edge produces some burr. A maximum height on a named face is manufacturable and inspectable; a blanket 'no burr' is not, and it usually gets resolved late at a cost.