Cutting and Blades
Blade Break-In Procedure
All band saw blades, regardless of the manufacturer, need to be “broken in”. When new, the teeth are just too sharp. Cutting at full rate will cause fracturing of the feather edges which will lead to premature blade failure. Breaking in a saw blade wears off this ultra sharp edge and allows the blade to retain its cutting ability longer. Each manufacturer has their own preferred method for blade break-in. However, they all share the same principles:
- Maintain recommended band speed
- Reduce feed pressure to ½ normal rate
- Run at these settings for the first 50 square inches of material cut (150 square inches on mild and low carbon steel)
Note: If you are unsure what the normal feed pressure is, start light. Increase feed pressure until good, curly chips start to form. After cutting the recommended area, slowly increase the feed pressure until you reach your desired cutting rate.
Special consideration must be given while breaking in a saw blade on nickel-based alloys. (Stainless Steel, Inconel, Hastelloy, D2 Tool Steel, etc.) These alloys tend to harden very quickly; therefore, sufficient feed pressure must be applied during the break-in period to remove some material. As a general rule, alloys sawed at lower speeds need more pressure during break-in period.
Blade and Sawing Terminology
Beam Strength is the result of a combination of a blades hardness, thickness and width. A wider blade provides greater Beam Strength which usually produces straighter and smoother cuts. However, never use a blade wider than that specified by the saw builder.
Cutting Edge is the toothed edge of the blade from the points of the teeth to the base of the gullets. The rest of the blade is considered the back.
Gullet is the valley from the tip of one tooth to the tip of the next tooth. It is designed to carry the chip from the kerf.
Kerf is the cut in the material being sawed. The width of the kerf is determined by the thickness of the blade plus the set of the teeth.
Set that is given saw blades is actually the tilt or angle given to the teeth of the blade which provides clearance in the cut. The overall set to right and left is another factor in determining the width of the kerf.
Tooth Pitch is always measured in the number of teeth per inch—from tip of tooth to tip of tooth. Variable Tooth blades are indicated by two numbers since the tooth pitch and the gullet depth varies.
Tooth Types are determined by tooth shape. Examples are Regular, Hook, Skip, and Variable Tooth. Tooth types are designed to do different kinds of sawing. It is essential to match the blade to the job.
|Section Size (mm)||Constant Pitch (TPI)||Variable Pitch (TPI)|
|Up to 10||24 or 18||14/18 or 10/14|
|10 – 15||14||8 – 12|
|16 – 30||10||6 – 10|
|31 – 50||8||5 – 8|
|51 – 80||6||4 – 6|
|81 – 120||4||3 – 4|
|121 – 200||3||2 – 3|
|Over 200||1 or 1.3||0.8 – 1.3 to 1.4 – 2|