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Reciprocating factors

From material type to teeth per inch, choosing the right reciprocating saw blade involves many factors

Reciprocating saw blades, also known as “recips,” offer many advantages for efficient cutting. Recips are less labor intensive to use, provide ease of access in many applications,

Using the right reciprocating saw blade can help prevent fires by reducing the amount of sparks produced.

cut faster and more accurately than hand saws, and can offer a greater cutting capacity compared to abrasive cutoff wheels. When compared with cutoff wheels, recips also have higher levels of safety due to reduced vibration and noise and the production of minimal to no sparks. There is less risk of operator injury in a spark-free process as well as less risk of fire.

Designed to cut all types of materials, including metal, wood and plastics in solid and profile form, Starrett’s new 3X Power bi-metal reciprocating saw blades are for use in numerous industries and applications. These include metal fabrication, construction and engineering, and for dismantling metal and wood structures and frameworks. They can also be used in the reclamation industry; for pallet dismantling and vehicle repair and dismantling; for fire and rescue for emergency extrication; as well as for DIY projects.

Choosing the right recip for the application can be summed up in five steps.

Step one: Identify materials

Understandably, the material that is being cut has the most influence on which type of recip blade to use. This is especially true when cutting metals, such as aluminum, steel and stainless steel.

For aluminum, it is generally recommended to use a blade with less teeth per inch (TPI) to increase gullet size, increase strokes per minute (SPM) and turn the orbital function on. (This function is explained later.) Aluminum is a “different animal” in that it requires plenty of space in the gullet for swarf and chips to be evacuated and remain cool enough to fuse with the teeth.

For steel and stainless, the TPI should abide by the recommendations per material thickness. The general rule of thumb is the thicker the material, the lower the TPI. Also, use a medium SPM and medium feed pressure with the orbital function turned on for improved cutting rates.

For stainless steel, set to low SPM and light feed pressure with the orbital function turned off.

For example, when cutting 2-in. steel tube with a wall thickness of 0.16 in., choose a cutting blade with a blue shank, which is available on the 3X Power recip blades. The same blade type and shank is suitable on an SAE 1020 1/8-in. sheet of metal.

No matter the material type, it is always a good idea to consult with the blade supplier for recommendations. It can also be helpful to reference the TPI chart for useful guidelines based on the material being cut.

Step two: Calculate length 

The type of metal and its thickness determines which recip blade is the right fit. This chart provides the information needed to choose wisely.

To calculate recip blade length, first measure the dimension/thickness of the cut section in the material to be cut. For example, use this calculation for cutting a 2-in. steel tube:

Add 2 in. for blade tip clearance plus 1 in. for the machine stroke to the cut section. (This additional 3 in. is standard and needs to be added to any cut section.)

When added together, the result is a 5-in. minimum blade length: 2-in. cut section + 2-in. blade tip clearance + 1-in. machine stroke = a minimum of 5 in. And because most recip blades are available in 4-in., 6-in., 8-in., 9-in. or 12-in. lengths, the choice is the 6-in. blade.

Another example involves an SAE 1020 1/8-in. sheet. Following the same formula, add 2 in. for the machine stroke and 1 in. for blade tip clearance to the cross-section of 1/8 in. The length for this application is a 4-in. blade.

Step three: Select TPI 

Equally important is selecting the correct TPI, which is also referred to as pitch. To do so, use the easy-to-follow chart as a reference.

For example, the chart shows that a material wall thickness of a tube measuring 1/8 in. to 1/4 in. calls for a TPI of 18. To make a cut that delivers a fine finish with minimal burrs on material measuring 1/8-in. thick, use a 24-TPI recip blade.

Step four: Identify the blade

Once the correct blade length and TPI have been determined, it’s simply a matter of identifying which product fits the application best.

Starrett’s 3X Power line of recip blades includes color-coded shanks for easy identification.

Some recip blades, such as those in the 3X Power range, have shanks that are color-coded to enable easy identification of the blades’ cutting capability. The 3X Power blades also feature a universal shank that is designed to fit any corded or cordless machine.

The color code on each shank indicates the blade’s intended use:

  • Blue – metal cutting
  • Red – multi-use for cutting metal, wood and other types of materials
  • Yellow – wood cutting, including hard and soft woods
  • Black – heavy-duty multi-use for cutting metal, wood and other types of materials
  • Grey – unpainted for pallet dismantling, cutting through wood-and-nail combinations

Step five: Identify the shape

Depending on the application at hand, the recip blade shape should also be considered. Starrett offers two recip blade shapes: Parallel and tapered. A parallel blade is

recommended for harder cuts, especially when the tip needs to be forced. For straight cuts, a tapered blade is recommended, which can more easily get into hard-to-reach places. A longer tapered blade is more flexible and may be the best choice when making a cut flush to a flat surface.

Looking at the metal product range for Starrett 3X Power recips, for the 2-in. steel tube with a wall thickness of 0.16 in., select a blade that is at least 6-in. long, with 18 TPI. The first choice is B618 and the B818 is second. For the SAE 1020 1/8-in. sheet, because this is steel, select the 3X Power – Metal series with a material number of B424 for best results.

Orbital action

This chart helps users zero in on the right teeth per inch for their material.

While not influenced by the blade, another important feature to consider while cutting with a reciprocating saw is the correct use of the orbital function. Even with the correct blade for the application, challenges arise with misuse of the orbital function. This function adds a circular motion to the stroke, changing the contact area and allowing for chip removal throughout the stroke rather than just when the blade has exited the material.

This is especially helpful for soft materials where loading can be an issue. The orbital action feature also improves speed of cut. It should be noted, however, that improving the speed of cut can have a negative impact on blade longevity, so users need to be mindful of this as they determine which variable is more important to improve on the operation.

The L.S. Starrett Co.