Bi-Metal Oscillating Blades

Bi-Metal Oscillating Blades

Bi-metal oscillating blades offer great value for general purpose cutting.

Oscillating (or multi) tools are becoming increasingly popular, in large part because there are many more brands to choose from. Since the end of Fein’s patent in 2008 most of the major tool manufacturers have released their own versions of this tool. Prices have also dropped dramatically – several models can be had for around $100.

The popularity of these tools is well justified. An oscillating tool is unmatched in the degree of control it provides for a range of precise cutting, sanding, grinding, scraping and polishing tasks. Unlike other power tools, it operates by high-speed oscillation rather than rotating or reciprocating motion. Rotating motion follows a circular path, reciprocating motion moves forwards and backwards or up and down, while oscillating motion moves in a side-to-side, arced motion, like a clock pendulum. It’s this narrow and fast angle of movement that provides you with an unmatched degree of control.

One of the most common uses of an oscillating tool is flush cutting. Renovators, finish carpenters, flooring and cabinet installers, and furniture makers use them for undercutting door casings and jambs; making plunge or pocket cuts into drywall, paneling or flooring without risk of damaging anything behind the cutout; cutting out sections of molding or trimwork without having to remove the entire piece; cutting nails so that trim work can be quickly removed; and, flush trimming copper or plastic piping, screws, and nails.

While there are a range of different saw blades for oscillating tools, the most popular type of cutting blade is the bi-metal blade. These general purpose blades are designed to cut through just about any material, including wood, drywall, plastics, fibreglass, non-ferrous metals, and thin gauge metal.

The Blades

There are just over a dozen different brands of bi-metal blades on the market. I looked at seven of the most popular brands – Bite, Bosch, Exchange-A-Blade, Fein, Fitzall, Imperial, and Oshlun.

All these blades, except the Fein, have universal arbors – in general they will fit on most of the major brands of oscillating tools. The Fein blade will only fit on Fein tools. There are only a few oscillating tools (including the Rockwell, Porter Cable, and the Fein Supercut) for which you’ll have to purchase an adapter to use the blades. The Bosch blade is the only one in this group that required an adapter for use on the Fein AFMM14.

In general, universal blades are made by laser welding a high speed steel cutting edge to a flexible alloy steel holder that houses the arbor. This design helps to keep the blade from breaking. The exception to this is the Bite double-ended blade, which is made from a single piece of high-speed steel. In use I didn’t notice the Bite blade flexing any more than the welded blades.

All blades are rectangular except for the Fein and Imperial, which have angled sides, making them somewhat more maneuverable, particularly in tight, restricted places. At 1-3/4″ they are also the widest blades, with the Bosch blade being the narrowest, at 1-1/8″. Most of these companies also make narrower universal blades – Bosch has the narrowest, at 3/8″ wide, which is particularly useful for cutting nails in trim work. For trimming nails I didn’t find any advantage with a wider blade.

All the blades are 1/32″ thick, except for the Bosch (1/64″ thick) and the Bite (3/64″ thick). Even though it’s thinner, I didn’t experience any more flexing with the Bosch blade than with the other blades.

Depth of cut is more important than blade width. The Fein and Imperial blades provide 2-1/8″ of cutting depth, while the Oshlun only reaches 1-3/8″. Which means you’ll still need your recip saw to cut nails that are set further back than about 2″.

All blades have 18 teeth per inch, and tooth height is 1/32″. The Imperial blade is somewhat unique in that it has titanium coated teeth, which serves to enhance wear resistance. Some of the blades (Bosch, Exchange-A-Blade and Oshlun) have measurement scales laser etched on the blade. This can be useful when you want to cut to a predetermined distance into material.

All blades have a wavy tooth setting that is specifically designed to provide faster, cleaner cuts in metal. The teeth have a set of 3/64″, except for the Bite (1/16″) and the Bosch (1/32″).

If you use an oscillating tool on a regular basis, you know how expensive these blades can be. Generally you can realize big savings by purchasing blades in bulk. Most companies offer at least a three blade pack – a few offer ten and thirty blade packs.

Blade Test

I tested these seven blades using a Fein MultiMaster AFMM14. All the blades fit the Fein perfectly except for the Bosch blade, which required the use of an adapter. I began by sinking 2-1/2″ galvanized framing nails (which have a 1/8″ diameter) into 2 by 6s, and then cut as many nails as I could with each blade. I stopped cutting when it took more than 10 seconds to cut three successive nails. While this is a somewhat arbitrary cut-off point, it’s about when I would look to switch blades on a job site. I ran the test with two blades from each brand, and then averaged the results.

Your results might be somewhat different than mine. The pressure you exert on nails as they are cut, the angle at which they are cut, and how effective you are at removing swarf from the kerf will affect your results. As with any kind of cutting, it’s important to prevent the blade from over-heating, which can reduce blade life. This is especially crucial with an oscillating tool, as it uses a very short stroke, and coupled with the finer teeth on these bi-metal blades, isn’t overly effective at removing debris from the kerf. I let the Fein do the work, but kept moving the blade from side to side, to help dislodge metal filings from the cut.

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