Technical Guide: Blade Basics
1. GAGE - The thickness of the blade.
2. BLADE WIDTH - The distance from the tip of the tooth to the back edge of the blade.
3. SET - The bending of teeth right or left to allow clearance of the back through the cut.
4. TOOTH BACK - The surface of the tooth opposite the tooth face.
5. TOOTH TIP - The cutting edge of the tooth.
6. TOOTH FACE - The surface of the tooth on which the chip is formed.
7. TOOTH - The cutting portion of the saw blade.
8. TOOTH RAKE ANGLE - The angle of the tooth face measured to a line perpendicular to the cutting direction of the saw.
9. T.P.I. - The number of teeth per inch.
10. GULLET - The curved area at the base of the tooth.
11. GULLET DEPTH - The distance from the tooth tip to the bottom of the gullet.
12. BLADE BACK - The body of the blade not including the tooth portion.
13. TOOTH PITCH - The distance from the tip of one tooth to the tip of the next tooth.
CORRECT TOOTH SELECTION
When the time comes to select the right number of teeth, try the following rule of thumb:
3 - 6 - 9 - 20
You should have a minimum of 3 teeth in the work at all times; having 6 to 9 teeth in the work is the optimum number; but more than 20 is too many teeth in the work.
There have been advances in blade design and manufacture, plus some testing results which tell us the following:
A) When cutting mild materials on a bandsaw you should use the 3 - 6 - 9 - 20 formula.
B) When cutting hard materials on a bandsaw, a few more teeth in the work piece will produce better blade life. This will not reduce the cutting time appreciably, but will increase blade life.
C) When cutting tough materials (alloys containing nickel and space-age materials), a positive tooth should be used.
The constant pitch tooth design is widely used for both cutoff and contour work and may be used for ferrous and non-ferrous materials. All constant pitch tooth configurations have a fixed number of teeth per inch. Available in both raker or wavy set, depending on tooth pitch selected.
The skip tooth design has greater gullet capacity for better chip clearance on softer metals, woods, plastics or compostiton materials. As the name implies, every other tooth is removed or skipped, without weakening the overall blade.
The hook tooth is similar to the skip tooth except the tooth face has a 10° rake angle which "hooks" or bites into the material more efficently, and penetrates the material better, even at reduced feed pressures.
The broach tooth was the original "varied pitch" developed by Diamond Saw Works, Inc. as early as 1937. Its generating cutting action is accomplished by varying the tooth pitch and set angles, giving marked improvement in a blade's cutting speed and life, smoothness of cut and greatly reduces noise and vibration in the cutting application. An exceptional tooth design for the tougher cutting jobs. Broach tooth blades have a special set.
The posi tooth is an improved variety of the broach tooth blade when a positive rake angle is desired. The hook tooth design has been applied to the proven principle of the broach tooth, giving additional value and performance. All posi tooth blades have a special set.
PROPER SET SELECTION
Widely used on all types of blades and teeth. Its pattern is one tooth set left, one tooth set right with the third tooth straight or unset. This pattern allows for fast, efficient cutting and uniform saw kerf. Generally used on solids and thicker sections.
Groupings of teeth are alternately set to the left and to the right, forming a wave pattern. Used for cutting thin or interrupted sections where tooth breakage or stripping is experienced. Because a group of teeth are set left, then right, the strain on each individual tooth is reduced.
E.T.S. (EVERY TOOTH SET)
Each tooth is set alternately left, then right. Used generally in woodworking or for nonferrous metals. Also known as alternate set.
NOTE: Broach tooth and posi tooth blades are specially set to suit each tooth design. Their sets do not necessarily conform to any of the above descriptions.