If you are production sawing you probably know that getting the right blade takes some time. Often times trial and error is the "method" of choice. Selecting the right blade doesn't have to be painful though and we are always here to help.
Feel free to comment below or contact us with your particular application, we would be happy to help. Below we have compiled some basic information on bandsaw blades.
Let's start with some basic terminology:
- Blade Width: The dimension of the band saw blade from tooth tip to blade back.
- When looking at the blade form the side you might think this is height, but height is not used when defining a band saw blade.
- Thickness: The dimension from one side to the other (i.e. .045")
- Blade Back: The body of the blade not including tooth portion.
- Tooth Form: The shape of the tooth, which includes spacing, rake angle, and gullet capacity.
- Industry terms include variable, variable positive, standard, skip, and hook.
- Tooth Pitch: The distance (in inches) between tooth tips. (i.e. 4 TPI)
- Variable Pitch blades will often be expressed as 4/6, 10/14, etc.
- Tooth Set: The pattern in which teeth are offset from the blade. Industry terms include raker, vari-raker, alternate, and wavy.
- Width of Cut: The distance the saw tooth travels continuously “across the work.” The point where a tooth enters the work to the point where that same tooth exits the work.
Material and Width of Cut are two factors that determine most of the bandsaw blade requirements. Machine horsepower, age, lubrication, and other factors also play a part.
Blade Material
Several blade materials are available including: Carbon, Bi-Metal, and Carbide tooth. Blades come in a one piece design such as a carbon blades or two piece design such as carbide tooth (alloy steel backing with carbide teeth).
Carbide Blades
These products will cut faster and last longer than any other bandsaw blade in a wide variety of sawing applications. The blades are designed and produced for high efficiency cutting of difficult and abrasive materials as well as high performance cutting of large and difficult to cut work pieces.
Bi-metal Blades
High-speed steel tooth tips, combined with flexible alloy-steel backing material results in the most cost effective bandsaw blades for most metal sawing applications.
Bi-metal bandsaw blades cover most market requirements, including multi-purpose blades and contour cutting, cutting tubes and profiles, foundry cutting and production cutting.
Types of Set
The set is the tilt, or angle, given to the teeth of the saw blade to provide clearance for the blade body and the tooth edges. Below are different types of set:
Raker Set
In the raker set, one tooth is set to the left, one tooth is set to the right, and one tooth (raker) is unset. This set type is used on most evenly pitched blades such as regular and hook. It is also used for contour and friction cutting blades on vertical bandsaw machines.
Combo Set
In the combo set, used on combo toothed blades, a raker (unset) tooth is followed by teeth in a left, right, left, right sequence. This pattern is repeated with each series of teeth starting and ending with the largest tooth in the pattern.
Other Types of Set are available including: Vari-Raker, Alternate, Wavy, Vari-set, and more. Different blade manufacturers will use different terminology.
Tooth Form
The shape of the tooth’s cutting edge affects how efficiently the blade can cut through a piece of material while considering such factors as blade life, noise level, smoothness of cut and chip carrying
capacity.
Variable Positive: Variable tooth spacing and gullet capacity of this design reduces noise and vibration, while allowing faster cutting rates, long blade life and smooth cuts.
Variable: A design with benefits similar to the variable positive form for use at slower cutting rates.
Standard: A good general purpose blade design for a wide range of applications.
Skip: The wide gullet design makes this blade suited for non-metallic applications such as wood, cork, plastics and composition materials.
Hook: Similar in design to the Skip form, this high raker blade can be used for materials which produce a discontinuous chip (such as cast iron), as well as for non-metallic materials.
Tooth Selection Guide (teeth per inch)
Band saw tooth size (Teeth Per Inch) is determined by the size and type of material to be cut and the desired finish. To select T.P.I. using this chart, find the colored chart for the type of material you wish to cut. Move up to the correct material size next to the chart. Follow across to the chart for the appropriate T.P.I. for your blade.
The chart to the left is a good rule-of-thumb for selecting the correct TPI for the size and shape of your material.
Credit:
Morse Cutting Tools
The number of teeth per inch (TPI) defines the pitch of the blade and can vary from less than 1 to 24.
Thin-walled work pieces like tubes, pipes and sheet require fine teeth, otherwise there is a risk of tooth damage or breakage.
Large cross sections should be cut with a coarse-pitched saw, i.e. fewer teeth per inch. The fewer teeth engaged in the workpiece the higher the cutting capacity. This is because the penetration capacity of each individual tooth is greater if the saw's feed pressure is distributed over a lower number of teeth. A coarse pitch (few TPI) therefore increases productivity and provides a desirable, large chip space.
Soft materials, such as aluminium and bronze require a large chip space. A coarse pitch prevents the chips from building up and packing together in the gullets, which can impair sawing and damage the blade.
Band Width
The band width is measured from the tip of the teeth to the back edge of the blade.
On horizontal machines, the band width is dependent upon the bandsaw machine being used. There is, however, some variation possible on vertical machines.
For contour sawing, the blade should be as wide as the machine permits, but still narrow enough so that it can cut the desired shape.
Feed Rate
It is important that each tooth of the bandsaw blade cuts a chip with the right thickness. This is determined by the selection of tooth pitch, band speed and feed rate. You can now set the correct feed rate by studying the chips which the bandsaw blade produces when cutting.
1. Thin or pulverised chips - increase feed rate or lower band speed
2. Loosely rolled chips - correct cutting data
3. Thick, heavy or blue chips - too high feed, lower feed rate or increase band speed
Credits:
Bahco (A Snap-On Industrial Tools Company)
Lenox Tools
Morse (the M.K. Morse Company)
