What type of blade should be used with a portable band saw?
When cutting metals with a Mirage portable band saw, an M42 Cobalt bi-metal blade is the way to go.
Blades if this type incorporate a high speed edge material that’s welded to a fatigue resistant spring backing. These tough blades are capable of cutting carbon steel, tool steel, structural steel, stainless steel, pipes, tubes and mixed metals. Blades supplied as standard with Mirage bandsaws are made from triple tempered M42 cobalt high speed steel with hardened teeth.
Blade material is just one of the things that influences the performance of a band saw. What also matters is the geometry of the teeth in the blade’s cutting edge.
Bandsaw blades used for cutting metal have ‘bent’ teeth. The bend in the teeth creates a cut wider than the thickness of the blade – this helps clear the chips and prevents the blade from getting stuck. The blade tooth pattern is critical - For most heavy section metal cutting work, the ‘raker’ pattern is the type to use.
A raker tooth set uses one tooth to the left, one to the right, followed by a straight unset, tooth (called a raker).
Tooth pitch is measured in tooth per inch (TPI). Using the correct tooth pitch will ensure optimum cutting performance and prolong the life of the blade.
As a guide you should aim to have at least 3 teeth in contact with the work piece at any time. Note that the coarser the pitch, the rougher and faster the cut will be.
Breaking in a new blade
Going full force from the start with your new blade isn’t advisable. Taking a little time to break-in the blade will reward you with an increased blade lifespan and more effective cutting.
A new bandsaw blade has razor sharp tooth tips, but for the teeth to withstand the normal band saw cutting pressures the tips should be worn slightly to form a micro-fine radius. Cutting with high pressure without performing this honing will cause tiny damage to the tips of the teeth, resulting in a much shorter blade life. (Think of a newly sharpened pencil and how it only starts to write properly under normal pressure after a small radius has been formed).
To break-in a new blade, it is recommended that its run at the normal speed - but at only 20 to 50% of normal feed rate for a few minutes. ‘Normal’ speed will be dependent on the material being cut and its thickness. (For metals it will be somewhere between 80 and 250 surface feet per minute).
Begin the first cut at the reduced rate and make sure that the teeth are forming chips. When the blade has fully entered the work piece, the feed rate can be slightly increased. Gradually increase in feed rate over several cuts until the normal cutting rate is established.
Know your chips
When using your band saw, you should monitor the chips being produced:
- If they are burnt heavy chips – reduce the speed and feed
- If fine or dusty chips – increase the feed
- Curled, shiny and warm chips – this shows you are using the optimum feed
Eventually, any band saw blade will get blunt from continued use. But by being careful you’ll get longer than normal wear on the blades. Two common causes of a blunt blade are; 1. using too rapid a speed for the metal being cut, and 2. The metal to be cut being too hard for the pitch of the blade. Your blade supplier will be happy to advise on the correct pitch to use.
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