Cutting tube is more difficult than sawing solid bars. The bandsaw blade is performing two types of cut, sawing solid as it enters the material then entering the hollow tube. The blade is now cutting two thin solids with a space in between — an interrupted cut.
To achieve the best result in cutting tube, blade variables and bandsaw settings have to be carefully selected. Tooth pitch (TPI) is an important variable as well. The number of teeth engaged with the material determines both blade performance and durability.
A few teeth in contact with the material can lead to stripped teeth, bending, or premature dulling. Too many teeth engaged and the gullet will soon fill, resulting in a crooked cut if the blades doesn’t break first.
Remaining within the industry standard of 3 teeth minimum and 24 teeth maximum in contact with the material is best. Within this range, penetration of material is assured based on the amount of pressure each tooth applies. Shock levels are now tolerable and with enough capacity in the gullets to carry away chips.
Pitch can be either constant or variable (multiple configuration). Blades with multiple tooth configurations and spacing are recognized two ways: the coarsest single-pitch equivalent, and the finest single-pitch equivalent. A bandsaw blade with a 5-8 pitch has a tooth space that varies between 5 and 8 teeth per inch.
Varying tooth spacing between fine and coarse will reduce vibration and break up sawing rhythms. Ex: for a 5.25″ wall thickness, the minimum effective sawing pitch would be 8, so a multi-pitch blade around 6 to 10 pitch is the most effective.
Tube and structural materials cut recommendations are as follows:
Thin wall structural (0° rake angle), Wall thickness Diam. of structural (D) in mm, (S) in mm 20, 40, 60, 80, 100, 120, 150
2 14 14 14 14 14 14 10/14
3 14 14 14 14 10/14 10/14 8/12
4 14 14 10/14 10/14 8/12 8/12 6/10
5 14 10/14 10/14 8/12 8/12 6/10 6/10
6 14 10/14 8/12 8/12 6/10 6/10 5/8
8 14 8/12 6/10 5/8 5/8 5/8 –
10 – 6/10 6/10 5/8 5/8 5/8 –
Heavy wall structural (positive rake angle), Wall thickness Diam. of structural (D) in mm, (S) in mm 80, 100, 120, 150, 200, 300, 500, and 750
10 – – – 4/6 4/6 4/6 3/4 3/4
15 4/6 4/6 4/6 4/6 3/4 3/4 2/3 2/3
20 4/6 3/4 3/4 3/4 3/4 2/3 2/3 2/3
30 3/4 3/4 3/4 3/4 2/3 2/3 2/3 1/2
50 – 3/4 3/4 2/3 2/3 2/3 1/2 1/2
80 – – – – 2/3 1/2 1/2 1/2
100 – – – – – 1/2 0.75/1.25 0.75/1.25
Variable is the most effective tooth form. Tooth pitch selection depends on the tube wall thickness and outer dimensions. The above recommendations refer to single cuts. If cutting bundles, two or more tubes, or square pipes cut at once, then double the wall thickness to achieve the correct tooth pitch.
