Technical Standards

9. Burr on holes and shearing burrs

Normal view of drawings (upper side) is the punch entry side. Burr-side must be stated explicitly for non-symmetrical plates and for sheets that require ancillary work after perforating.

Shearing burrs are normally are placed on the same side as perforation burrs (see picture 10). Due to manufacturing considerations shearing burrs may also appear on the opposite side, unless otherwise specified.

In the flattening process it is possible that burrs could be pushed back into the holes.

The height of burr should be determined by measuring the thickness of the sheet close to a perforated hole. The first measurement should be taken between two holes, if possible, or alternatively at the unperforated edge, with a micrometer. Then the perimeter of the hole should also be measured with the micrometer. The height of burr will result from the difference between the two measurements.

Permitted burr heights for normal perforating conditions:

Thickness of sheet	Burr height*
up 0,6 mm	0,15 mm
from 0,7 to 1,5 mm	0,17 mm
from 1,6 to 3 mm	0,20 mm
from 3 to 6 mm	0,25 mm
from 6 to 12 mm	0,50 mm
12 mm and above	0,50 mm

* Special materials may have different values.

It should be noted that up to 10 % of the surfaces area, or 10 % of the number of holes, may be outside of the stated tolerances.

Tighter tolerance requirements, especially for plates used for decoration, must be agreed separately.