# Upward - Downword and Compression bits



## EdC (Mar 3, 2020)

Can someone please tell me what a compression bit does?

Thanks - Ed


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## Semipro (Mar 22, 2013)

*What is a compression bit?*
A compression bit is the combination of both upcut and downcut spirals. Typically, a compression spiral has an upcut single, double or triple flute at the tip of the cutter, approximately one third of the cutting length. The remaining two thirds is ground to give a downcutting shear.
By combining both geometries, you achieve a win/win situation. The bottom of the material is pulled upwards while the top of the material is pushed downwards thus eliminating the risk of damaging the laminated surfaces. When run at full depth, the bit leaves a sharp, clean edge on both sides of your workpiece.
A compression bit can be a little more expensive than standard router bits, we recommend them as an essential tool when processing double laminate wood materials.


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## difalkner (Jan 3, 2012)

I would add to what John said in that it works really great on plywood. I cut 1/2" BB full depth with a 1/4" compression bit nearly every day for Longworth chucks and these bits are fantastic for that.

David


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## EdC (Mar 3, 2020)

Semipro said:


> *What is a compression bit?*
> A compression bit is the combination of both upcut and downcut spirals. Typically, a compression spiral has an upcut single, double or triple flute at the tip of the cutter, approximately one third of the cutting length. The remaining two thirds is ground to give a downcutting shear.
> By combining both geometries, you achieve a win/win situation. The bottom of the material is pulled upwards while the top of the material is pushed downwards thus eliminating the risk of damaging the laminated surfaces. When run at full depth, the bit leaves a sharp, clean edge on both sides of your workpiece.
> 
> ...


Thanks John - I have a possible special use for this kind of bit. I have an old skill planer that I cannot find a bit for and wondering if the bit would work in my router?


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## EdC (Mar 3, 2020)

difalkner said:


> I would add to what John said in that it works really great on plywood. I cut 1/2" BB full depth with a 1/4" compression bit nearly every day for Longworth chucks and these bits are fantastic for that.
> 
> David


Thank you David for your additional direction! - Ed


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## Bob Adams (Jul 5, 2014)

Here is an excellent video that compares down/up spiral and compression bits. Bits


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## EdC (Mar 3, 2020)

EdC said:


> Thank you David for your additional direction! - Ed





Bob Adams said:


> Here is an excellent video that compares down/up spiral and compression bits. Bits


Thank you Bob - Really informative!! - Ed


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