Metal Cutting
When cutting metal on a bandsaw the two important factors are the cutting speed and the tooth pitch.
A lot of wood cutting bandsaws come with 2 speeds and the slower speed is sometimes listed as being for metal cutting - this is sort of true as the slower speed can be used for non ferrous metals (brass, aluminium etc) but is no good for ferrous metal (mild, stainless steel etc).
If the cutting speed is too fast then this will put too much heat into the teeth of the blade and will either cause them to go blunt really fast or the teeth will strip off the blade completely.
Generally the harder the steel, the slower the cutting speed and the following speeds are a rough guide:
Aluminium: 150 – 1000m/min
Mild Steel: 50 – 120m/min
Stainless Steel: 20 – 75m/min
There can be a wide range with the speeds as the quality and thickness of the steel, whether it’s solid or tubed will all make a difference.
When cutting metal with a new blade, it’s important to run the blade in – when a blade is new, the teeth are very sharp but for best results when metal cutting the tip of the tooth needs to be slightly rounded. This is achieved by using a slow feed rate for the first 5 – 10 minutes of cutting, by doing this you will improve blade life and cutting performance.
Another way to improve blade life and cutting performance when cutting metal is to use a cutting fluid, although not all bandsaws have the facility to use cutting fluid and you can cut metal dry, but you will always get better results from using a cutting fluid.
A cutting wax can also be used and can be especially good on non-ferrous metal.
Carbon and M42 are the most popular blades for metal cutting with the M42 being the better option. They are more expensive but will last around 5 – 10 times longer and will work out a lot cheaper in the long term. Another advantage of the M42 is that they are available in a vari-tooth format where it has 2 different tooth pitches. The vari-tooth format improves cutting performance and will also help in coping with different thicknesses etc.
Similar to wood cutting, the thicker the material being cut, the coarser the tooth pitch required and the thinner the material, the finer the tooth pitch. With metal cutting, the tooth pitch can also vary depending on whether the material being cut is solid, tubed and the wall thickness if tubed.
For general cutting either the 10/14 or 9/11 from the M42 range or 14tpi from the Carbon range are ideal – these blades will cope with the widest variety of thicknesses and types of metal but here is a chart to help pick the best tooth pitch:
Vari- Tooth | Solid Material | Pipes/Profiles |
2/3 Vari-Tooth | 120 to 400mm | Over 20mm |
3/4 Vari-Tooth | 80 to 150m | 12 to 20mm |
4/6 Vari-Tooth | 25 to 80mm | 6 to 12mm |
5/8 Vari-Tooth | 35mm to 80mm | 4 to10mm |
6/10 Vari-Tooth | 25mm to 60mm | 3 to 6mm |
8/12 Vari-Tooth | 20 to 50mm | 1.5 to 3mm |
9/11 Vari-Tooth | 0.5mm to 30mm | 0.5mm to 5mm |
10/14 Vari-Tooth | 0.5mm to 30mm | 0.5mm to 5mm |
14/18 Vari-Tooth | Up to 15mm | Below 0.5mm |
Straight TPI | Solid Material | Pipes/Profiles |
3tpi | 120 to 250mm | Over 20mm |
4tpi | 80 to 120m | 10 to 20mm |
6tpi | 50 to 80mm | 5 to 10mm |
8tpi | 30mm to 50mm | 4 to 6mm |
10tpi | 15mm to 30mm | 1.5mm to 3mm |
14tpi | Up to 30mm | Up to 8mm |
18tpi | Up to 20mm | Up to 3mm |
24tpi | Up to 8mm | Up to 1mm |
32tpi | Up to 6mm | Below 0.5mm |
Again this is only a guide and it’s not to say that you can’t use a blade for cutting outside of the ranges above. The above ranges will give the best performance for that tooth pitch but if for example you’ve got a 10/14 Vari-Tooth on your bandsaw and you wanted to cut 50mm solid, the blade will do it, just at a slower cut than an 8/12.