The best things since sliced bread

Getting to know the ins and outs of reciprocating saw blades

by Clair D. Urbain

A reciprocating saw is downright useless without a blade. Blade manufacturers have taken the basic recip saw blade and made it bigger, smaller, thinner and thicker, all in the quest to help users better match the blade to the job.

“Recip saws have been niche tools, but with the growing number of blades available, their use for other jobs is gaining momentum,” says Andrew Gongola, chief engineer for Milwaukee Electric Tool Corp. accessories. “Today’s recip blades are more than a piece of bandsaw blade with a tang on them.”

Research and development efforts have resulted in a plethora of blade styles that can help you be more productive in the types of recip saw cutting jobs you do. Conversely, there are some very good “jack-of-all-trades” blades that can adequately meet the variety of cutting jobs a maintenance worker may face.

A first look at recip saw blades shows there are distinct groupings of blade types, but close inspection reveals that the variety of blade types make a gradient from group to group.

“Manufacturers know this and most make blade selection easier by listing them by application,” says Lori Stigman, accessory product line manager at Porter-Cable.

Users generally know what a certain blade is best at cutting, but they usually don’t understand how the design and blade materials affect performance. Bi-metal blade construction is a good example.

“Many users do not understand the true meaning of bi-metal as it pertains to the blades they use,” says Brian Kagen, DeWalt’s senior product manager for linear-edge blades and rough-cut drilling. “It really refers to the blade’s construction, where a strip of high-speed steel is welded to a carbon steel back. The high-speed steel provides cutting edge durability and the carbon-steel backing provides flexibility users need in recip cutting applications. Almost all recip blades used by professionals have bi-metal construction.”

Blade characteristics affect performance
The number of teeth per inch (TPI), tooth design and the width, thickness and length of the blade affect blade performance.

“The blade’s pitch, or TPI, is the most important consideration for efficient cutting. If you have too few teeth in the cut, teeth will be stripped and the blade damaged,” says Sal Locascio of Primark Tool Group. “If there are too many teeth in the cut, cutting will be slow and inefficient. We recommend you have at least two teeth in contact with the work at all times.”

Other sources suggest three teeth in the work surface for best results.

Some blades have a variable pitch, which is a combination of tooth sizes on a blade. For example, a 5/8 variable-pitch blade has 5 TPI followed by 8 TPI.

“The configuration of the variable-pitch blades can cut a wider variety of materials than a constant-pitch blade,” says Michael Connor, hardware division manager at L.S. Starrett.

How the teeth are set on the blade also affects performance.

“A wavy set, where three teeth are set to the right followed by one tooth set to the center and followed by three teeth set to the left, makes the blade stronger, but also makes a rougher cut,” says Locascio. “A raker set, where the teeth are consecutively set right, left and center, offers a good, all-purpose cut.”

Further, manufacturers modify the tooth’s gullet size and angle to affect performance. A larger gullet helps remove more material in the cut, but can compromise life; a smaller gullet beefs up the tooth, but can affect performance, says Gongola.

“You’ll also see thicker blades for demolition or rescue work. These blades are .062 inches thick, so they are stiffer and last longer,” he says.

If you use a lower-powered or cordless recip saw, Gongola recommends using thinner blades.

“A thicker blade makes a wider kerf. That equates to the need for more energy to make a cut,” he says.

Generally, the blades fall into the following categories. They share similar characteristics across all manufacturers, but like power tools, they vary slightly, resulting in different performance characteristics. The blade experts supplied the information for each category.

Blade categories
Wood blades: Most are bi-metal, but some are also available in high-carbon steel, which are low in cost and acceptable if you are cutting wood. Low-cost blades often have ground-set teeth instead of mill-set teeth, which tend to stay sharp longer.

Bi-metal blades can take more bending and stay sharp longer. Most have 6 TPI, but are also available in up to 10 TPI for cutting thin wood or for a finer edge. Most are 3/4” wide and .050” thick and come in 6” to 12” lengths.

Wood with nail blades: These blades must be able to cut through nails users come across in wood. These bi-metal blades usually have 6 to 10 TPI with milled teeth for durability. Most have a tapered back for plunge cutting and are 3/4” wide and .050” thick. Available in 6”, 9” and 12” lengths, they can cut metal, but are not the best choice for these jobs.

Metal-cutting blades: These 3/4”-wide, straight-backed blades minimize wobble for accurate cuts. Generally, the blades are available in 14 to 24 TPI. The 14 TPI blades work well cutting pipe, structural steel and heavier stainless steel; the 24 TPI blades are better for sheet metal. If your metal-cutting jobs are varied, an 18 TPI blade is a good all-around blade. They often have 8 percent cobalt in the high-speed steel teeth area for greater heat resistance and durability. They come in 4” to 12” lengths.

General-purpose blades: These jack-of-all-trades blades can cut just about anything. They range from 8 to 14 TPI, although 10 TPI is the most common. Some have a variable-tooth pitch to reduce vibration and allow them to cut a greater variety of materials. Most are .050” thick and available in 6” to 12” lengths. While the straight-back design gives these blades strength, they can’t be used for plunge cuts.

Demolition and rescue blades: These are recip blades on steroids. They are built for fast cutting in demolition work or for fast, life-saving cuts to free accident victims. Thicker, wider and longer than other recip blades, you will find metal-cutting blades and aggressive tooth geometries with 10, 14, 18 or 10/14 TPIs that can take on 3/16” to 3/8” steel and sheet metal. They are .050” thick or slightly thinner and come in 6”, 9” and 12” lengths.

The wood-cutting blades usually feature 6 TPI for no-nonsense cutting in nail-embedded wood. However, a new 3 TPI blade offers aggressive, albeit rough cutting. Some blades have 9 TPI for more cutting versatility. The blades are 7/8” wide and .062” thick. They are available in 6”, 9” and 12” lengths.

Specialty blades: Some jobs are simply done better and faster with a specialty blade.

Use a scroll blade to cut tight angles. Depending on TPI, these blades can cut metal or wood.

To cut abrasive materials such as iron pipe, fiberglass, ceramic tile, reinforced plastics, stone, slate or brick, use a carbide grit blade.

They are available in 6”, 8”, 9” and 12” lengths.

Blade killers
Recip blades are truly consumable items, getting sacrificed as they tear through a variety of materials.

“Blades fail in one or more of the following ways: The teeth break off, they wear down, the blade snaps or it bends past the point where it can’t be bent back into shape,” says Kagen.

Proper blade selection will help you get longer life from your blades.

Improper blade speed is the leading killer of metal-cutting recip blades, says Gongola.

“Users tend to run metal-cutting blades too fast,” he says. “In general, the tool should run at half-speed to cut metal. Otherwise, it creates heat that will quickly ruin the blade. If you manage speed, you may get double or even greater life from a metal-cutting blade.”

In wood, Gongola recommends top speed once you get into the cut. If you are cutting a section that is much thicker than the stroke length of the saw, rock the saw up and down to aid in sawdust removal.

To reduce the risk of injury, make sure that the blade extends beyond the shoe and work throughout the stroke. Blades can shatter or break if they impact the shoe or work.

Clair D. Urbain is the editor and associate publisher of Contractor Tools and Supplies magazine, a sister publication of MRO Today. Contact him at curbain@milomediapub.com.

This article appeared in the February/March 2003 issue of MRO Today magazine. Copyright 2003.

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