3/8″ Short Flute Spiral Compression Bit – 1/2″ Shank *AstraHP Coated*
3/8″ Short Flute Spiral Compression Bit – 1/2″ Shank *AstraHP Coated*

3/8″ Short Flute Spiral Compression Bit – 1/2″ Shank *AstraHP Coated*

$77.39 $85.99
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Also called a Mortise Style compression bit, this bit has a short up cut flute. This allows for shallower cuts while taking advantage of the compression cut.

  • Astra Coated
  • Solid Carbide
  • Tip Diameter: 3/8″
  • Shank Diameter: 1/2″
  • Length of cut: 1-1/4″
  • Spiral Change: 0.22″
  • Overall length: 3-1/2”
  • Made In USA

These tools are coated with a proprietary high performance *Astra coating* that allows higher speed & feed rates as well as 2x the extended tool life & increased lubricity in abrasive material

Jonathan's Hot Take:

Compression bits have quickly become my absolute favorite type of spiral bit. The short flute allows a shorter first pass and it gives you super clean edges on both the top and bottom. This is really advantageous in plywood and on the CNC.

These bits provide the HIGHEST VALUE because the Astra Coating makes them last at least 2-4x longer than uncoated bits. This is one of those times that spending a little more upfront saves you a lot of money down the line.

Spiral bits perform 100x better and 100x longer than straight bits. I recommend staying away from straight bits in general, because they dull so much faster and their aggressive cutting profile can be much less safe.

Check out the video in additional resources for more info.

Solid Carbide Compression Router Bit with a cutting tip diameter of 1/4 and a 1 inch length of cut. Spiral change at 0.12″ allows for shallower cuts while taking advantage of the compression feature of the bit. Perfect for smaller CNC routers!

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.

Made in the USA by KM Tools

This data serves as a general guidance only.
  • Soft/Hard Woods/ Plywood – (Spindle Speed- RPM: 18K ) – (Feed Rate – IPM : 180-200″) – (Ramp Down: 90-100″) – (Chip Load per Tooth: 0.0056″)
  • MDF / Laminate / Melamine – (Spindle Speed- RPM: 18K) – (Feed Rate – IPM : 325-375″) – (Ramp Down: 150-200″) – (Chip Load per Tooth: 0.0111″)