*AstraHP Coated* Bits&Bits 820-CM125 – 1/8″ Spiral Compression Bit – 1/8″ Shank

What is a Compression Bit?

A Compression bit is a spiral bit that combines up cut and down cut action into one bit. The cutting tip pulls the fibers and chips up towards the center of the workpiece. The rest of the bit is cutting and pushing wood fibers down, also towards the center of the workpiece. This up cut down cut action is what leaves a sharp, clean edge on both edges of your workpiece. The up cut flutes on a compression spiral bit is typically equal to the diameter of the bit, for example, a 1/2" diameter has a up cut flute of 1/2". The transition point is referred to as the 'Spiral Change'. We also offer several sizes of compression bit with a shorter up cut flute length which is referred to as a short flute compression (also called a mortise style compression bit). The slow-mo video clip below was shot by none other that Jonathan Katz-Moses and shows the cutting action of the compression bit. You can clearly see the difference between the up and down cut portions of the bit.

How do I use the Compression bit correctly?

In order to properly use a compression bit to get it's full benefit, your initial cut needs to be slightly deeper than the upcut flute length, which as mentioned above is usually equal to the diameter of the bit. When used correctly, you shouldn't see any tear out or chip out on the edges. In the video above, the bit on the left is seen cutting not deep enough to pass the up cut flutes. The bit on the right is set at the correct depth.

Can you use a Compression Bit in a router?

Yes, all of our compression and spiral bits can be used in a CNC, handheld router or a router table.

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