RakerSkip Hook
Figure 40. Raker, Skip & Hook tooth styles.
•RAKER — This style is considered to be the standard because the tooth size and shape are the same as the tooth gullet. The teeth on Raker blades usually are very numerous, have no angle, and produce cuts by scraping the material; these characteristics result in very smooth cuts, but at the same time do not cut fast and generate more heat while cutting.
•SKIP — This style is similar to a raker blade that is missing every other tooth. Because of the design, skip toothed blades have a much larger gullet than raker blades, and there- fore, cut faster and generate more heat. However, these blades also leave a rougher cut than raker blades.
•HOOK — The teeth on this style have a pos- itive angle (downward) which makes them dig into the material, and the gullets are usu- ally rounded for easier waste removal. These blades are excellent for the tough demands of resawing and ripping thick mate- rial.
Tooth Pitch
Usually measured as T.P.I. (teeth per inch), tooth pitch determines the size of the teeth. More teeth per inch (fine pitch) will cut slower, but smoother; while fewer teeth per inch (coarse pitch) will cut rougher, but faster. As a general rule, choose
blades that will have at least three teeth in the material at all times. Use fine pitched blades on harder woods and coarse pitched blades on soft- er woods.
Blade Care
A bandsaw blade is a delicate piece of steel that is subjected to tremendous strain. You can obtain longer use from a bandsaw blade if you give it fair treatment and always use the appropriate feed rate for your operation.
Be sure to select blades with the proper width, style, and pitch for each application. The wrong choice of blades will often produce unnecessary heat which will shorten the life of your blade.
A clean blade will perform much better than a dirty blade. Dirty blades pass through the cutting material with much more resistance than clean blades. This extra resistance also causes unnec- essary heat.
Blade Breakage
Many conditions may cause a bandsaw blade to break. Blade breakage is unavoidable, in some cases, since it is the natural result of the peculiar stresses that bandsaw blades are subjected to. Blade breakage is also due to avoidable circum- stances. Avoidable breakage is most often the result of poor care or judgement on the part of the operator when mounting or adjusting the blade or support guides.
The most common causes of blade breakage are:
(1)faulty alignment and adjustment of the guides,
(2)forcing or twisting a wide blade around a curve of short radius, (3) feeding too fast, (4) tooth dull- ness or absence of sufficient set, (5) excessive tension, (6) top blade guide assembly set too high above the work piece, (7) using a blade with a lumpy or improperly finished braze or weld and
(8)continuously running the bandsaw when not in use.
G1012 18" Bandsaw |