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A Guide to the Bi Metal Hole Saw

A Guide to the Bi Metal Hole Saw

So let us start with the basics: What is a Bi Metal Hole Saw anyway? A Bi Metal Hole Saw is made up of three key parts, the Arbor, a drill bit and the saw itself. Without any one of these three components you cannot operate a Bi Metal Hole Saw.

The arbor is the central part of a Bi Metal Hole Saw; it has a hex drive shaft on one end that allows the power of a drill to spin the Bi Metal Hole Saw. On the other end is a slotted hole that allows for a special drill bit to be inserted. The center of the arbor has large threads to allow for the Bi Metal Hole Saw to thread into place and has a larger thumb set to lock it into place by pushing two posts into the saw.

The drill bit or pilot bit is slightly different than a standard drill bit. It has a flat spot on the shank of the bit to allow it to chuck into the arbor. The arbor has a small inset bolt to allow the bit to be held tightly in place.

The Bi Metal Hole Saw is a cylinder with one side capped and the other an edge of sharp teeth able to cut through wood and other softer materials. The saw comes in a variety of sizes from 9/16” (14mm) to 8-17/64” (210mm).  The solid end usually has three holes that allow for it to be hooked onto the arbor.

Depending on the diameter of the saw you do not need to tighten it all the way down. Turn the saw onto the arbor all the way down and then slowly turn it back until you can see the two smaller holes lining up with the arbors posts.  Now turn the set screw until the posts are securely inserted into the saw cap. You now have a complete Bi Metal Hole Saw and are ready to chuck it up to a drill.

What does Bi Metal mean?

Bi Metal refers to the saw itself, but we need to back up a bit in history first. Blacksmiths used to make all of the modern world’s tools. They handmade drill bits, files, axes, nails and even saw blades. They knew that you needed two separate hardness’s in the steel to make a good saw blade, but the tricky part was how do you do that with such a thin piece of metal? Well they figured out that you could make two separate hardness metals and then weld them together. This produces the hardened edge that could hold an edge and cut and the softer metal that would withstand the stresses inflicted on the blade of the saw. Now enters metallurgy, or the science of metal, Bi Metal is the combination of two separate metals to make a superior metal. This newly made and hardened metal makes up the teeth of the saw that it is then welded to.

Photo courtesy of ThreadedThoughts.

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