# router bits and usage



## cueball2 (Nov 10, 2008)

The differance between and up-cut and a down-cut sprial bit. When to use each bit.


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## bobj3 (Jan 17, 2006)

Hi cueball2

Spiral Upcut and Downcut Router Bits

2 flute flat bottom cutters. Top quality micrograin solid carbide. 
Will cut faster, smoother and stays sharper longer. Produces a very clean, 
fast and accurate cut with minimal chatter. 

Upcut spiral helps remove material. 
Ideal for making mortise and tenon joints.

Downcut spirals help hold the material in place while using handheld routers.
Will plunge cut and plane edges.

Eliminates chipping at the top of the cut. 
Ideal for soft & hard woods, plywoods & composites, laminates, 
plastics and some non-ferrous metals. Item #5155 will cut grooves for #20 biscuits. Item #7468 can be used with the Leigh Jig. Item #5161 can be used for inlay routing. item #5150/#5170 can be used for shelf pin router jigs.

Compression Up/Down Spiral Router Bit
This 2 flute solid carbide bit is needed to get clean, chip-free and splinter-free cuts in composite sheet goods such as Melamine or 2-sided Formica/Laminates and veneered plywood. The Up-shear/Down-shear design of the bit cuts toward the center of the sheet from both sides at once, saving time and eliminating waste.

http://www.mlcswoodworking.com/shop...s/bt_solid_sets.html#super_starter_set_anchor

http://www.mlcswoodworking.com/shop...rthtml/pages/bt_solid.html#spiral_down_anchor

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## Mike (Nov 22, 2004)

This comes up on a regular basis. Remember this: an upcut pulls chips out of solid wood, a downcut pushes chips back into the plywood or laminate, and a compression cutter is for making through cuts in plywood or material that has veneer or laminates on both sides. It does not matter if the router is hand held or table mounted, the cut direction does not change.


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## john heff (Sep 7, 2008)

Mike said:


> It does not matter if the router is hand held or table mounted, the cut direction does not change.


It seems like a up-cut bit in a handheld router would become inverted and become a down-cut when the router is mounted in a table. What am I missing? - John


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## dovetail_65 (Jan 22, 2008)

john heff said:


> It seems like a up-cut bit in a hand held router would become inverted and become a down-cut when the router is mounted in a table. What am I missing? - John


Think of it this way. When an up cut bit is in a hand held the piece and dust are pulled up toward the top of the router. When inverted in a table the dust is still pulled toward the top of the router and is still cutting the wood the same way.

It is true that when the up cut is in a hand held the piece can tend to lift so in an inverted position an up cut pulls the piece down toward the table, which is where your confusion probably comes in. But the cutting action and material getting cut is still pulled to the top of the router with the upcut bit, albeit the router is upside down.

Does this make sense to you.

Another way to think of it:

Forget about the orientation of the router and think where the dust flows. Up cut bit the dust goes toward the top of the router, turning the router upside down does not change that. A down cut pushes the dust and chips away from the top of the router and turning the router upside down does not change that either. Changing the router orientation does effect how the router bit pulls or pushes the work piece in relation to the router "table top", but not the orientation of the the dust or chip flow. So the cutting action remains the same as indicated by the dust flow no matter how you turn the router.


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## john heff (Sep 7, 2008)

Thanks for the explanation Nick. 

This subject interests me because I don't know whether to buy an up-spiral or down-spiral bit for use in a table mounted router when making box cuts (and I guess I still don't know). I understand the benefits of a spiral-cut-bit is the 'clean' surface-finish and the extraction of wood chips, therefore it seems that a up-cut-spiral bit mounted in a table would put the 'clean surface' on the bottom of the workpiece and the chips would be extracted towards the bottom of the table....which doesn't fit the common definition of 'up'. 

The following (partial) description is from Mark's old glossary. Spiral Bit: .....Up spiral bits extract wood toward the shank while down spiral bits push chips away from the shank. 

I'm willing to accept that explanation of up/down as it pertains to spiral-cut-bits. However, I still have this question, when making box cuts with a table-mounted router, which spiral-cut-bit is preferred? Thanks for your help. - John


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## Hamlin (Dec 25, 2005)

Hi John,

Many use an "upshear" or upcut spiral bit.


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## Gary696 (Jan 28, 2006)

cueball2 said:


> The differance between and up-cut and a down-cut sprial bit. When to use each bit.


Up-cut always pulls toward the router, down-cut always pushes away from the router.

Gary B


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## dovetail_65 (Jan 22, 2008)

That is personal preference they are both going to work. In my experince down cut leaves a better surface edge finish. Since most of my work is inlay and only 1/4" to 1/2" deep I always use the down cut for the clean surface edge it gives, especially for letters.

If you are making deep cuts up cut bits helps get the material out. 

You need both,. If you can afford them get them and test which is better for you. 

I think the down cut will give a better edge for your application.

The experienced guys here may have some other ideas...


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## Mike (Nov 22, 2004)

An upcut pulls chips out of *solid wood*, a downcut pushes chips back into the *plywood or laminate*, and a compression cutter is for making _through cuts _in *plywood or material that has veneer or laminates on both sides*.
Read this again and notice the accented words. This statement tells you what materials the bits work best on.


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## john heff (Sep 7, 2008)

As I shall be making the box cuts in *solid *wood I will purchase the up-cut bit. Thanks to everyone for your help. - John


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