Spiral cut router bits

[Mark J Bachler]

I have a production job coming up. I'll be cutting 5/8 plywood using an inverted pin router with the pattern above the workpiece. My question is if I go with a spiral router bit do I want an up cut or a down cut, seeing as the bit upside down?

[Grant Wilkinson]

I'd say that you want an up cut. Even with the router upside down, you still want the wood pulled into the router. It doesn't matter if the router is right side up or upside down, the up cut bit still pulls into the router.

[Peter Quinn]

Down shear will leave a better surface quality, up cut will give better chip removal, a compression bit will give you the best aspects of both, but possibly a slightly reduced feed rate? So it sort of depends on what you are making, the demands of the job, the thickness of the work. But the choices are the same as on a router table or free hand router, just have to imagine it upside down.

[Jerome Hanby]

Well, an up cut bit would pull the shavings toward the router (in this case away from the pattern) and leave the pattern side a little rough, the down cut just the opposite and would leave the router side of the cut a little rough. You may want a compression bit which would do a little of both but leave both sides pretty clean, looks like Whiteside makes one for pattern routing for about $126 at Woodcraft.

[Harvey Melvin Richards]

Why not use an up and down shear combo bit. They work great for plywood where you want a nice cut on both edges.

[Rick Fisher]

I like down for through cuts and up for cuts like mortises .. I have tried mortises with a down cut.. lol Gotta stop and clean out the hole because it gets so jammed with chips.

Down is good for straight cutting where your all the way through the thickness.. Just my 2cents.

[Jerome Stanek]

A compression bit is what I would use. It is an upcut and downcut I use them for cutting .75 oak ply on my CNC

[phil harold]

I have had good luck with their saw blades
search ebay for "60-138 Onsrud 12MM One Edge Solid Carbide Comp Router Bit"
for 10 bucks it worth a shot

[Stephen Cherry]

http://www.youtube.com/watch?v=pmad-5JIqBc

Up cut will hold the wood on the table, plus help with getting rid of the dust.