Bullnosing, Cranking and Curving Sheets

Clotan Steel's IBR, Corrugated and Widespan sheets can be bullnosed, cranked, curved, smooth curved and sprung on site to customer requirements.

Bullnoses and Centre Cranks

Bullnosing and centre cranking of a profiled sheet incorporates lateral rib indentations pressed in at an uniform distance of 25 mm. Standard bullnoses are made with the narrow flute uppermost and the bend away from the angular inclination. Reverse bullnoses are made with the bend into the narrow flute. Bullnoses and cranks can be at the end of a sheet or at any position along the length.

Bullnoses and centre cranks can be manufactured in radii ranging from 350 mm to 800 mm for bullnoses which are bent through 0 - 135 degrees, larger radii will be classified as a curve.

The maximum sheet length which can be bullnosed is 15 m, with a maximum height of 2 m. The minimum runout from the bullnose is 30 mm on one side with a minimum of 500 mm on the other side of the sheet. It is important to clearly identify the critical end of the bullnose in order to ensure that consistent lengths are supplied to the customer.

The maximum height of centre and off-centre cranks which can be manufactured is 2 m with a limitation of 10 m total sheet length. These limitations are due to handling and transport limitations. High tensile material can only be bullnosed and cranked to a minimum radius of 450 mm.

Crank Curving

IBR, Widespan and Corrugated material can be crank curved with the same process used for bullnosing but with manual handling and with an increased distance between indentations in order to achieve the larger radius. In the case of pre-painted sheeting the colour can be specified on either side of the sheet.

Due to the manual process involved, bullnoses will be priced as curves when the radius exceeds 800 mm. The maximum height of curves which can be handled is 2 metres with a maximum sheet length of 10 metres.

Smooth Curving

In addition to the other processes described above, Corrugated sheets can be curved using a rolling process to achieve a smooth rolling finish on the sheet.

High tensile material (550 MPA) is not suitable for curving due to the hardness of the material. It is therefore essential to only use 0.58 and 0.80 mm material for smooth curving.

The minimum radius for curving on 0.58 mm ISQ300 material is 900 mm and on 0.80 mm ISQ230 material 600 mm. When tight bend radii are specified edge ripple on the roof sheets might prevail. When only a part of the sheet is curved or bullnosed slight crease marks on the sheets can be expected. Sheet length is limited to 10 metre with a maximum height of 2 metres.

Springing of Profiled Sheets

For roofs gently curved on elevation, sheets may be sprung on site. However, extreme caution should be used when attempting this procedure, to prevent buckling or canning. The following table indicates the minimum radii for on site springing of profiled sheets.

	Minimum Radius
IBR	40 meter
Gorrugated	30 meter
Widespan	35 meter

Bullnosing, Cranking and Curving of Profiled Sheets