# are spiral compression bits useful without a CNC???



## Mike_C (Jul 11, 2020)

I have several up and down cut router bits.

I use the upcuts when mortising or grooving mostly on "real" wood and use the downcut for doing the same on plywood or veneered sheet goods.

I am planning to buy a up/down flush trim bit - which makes sense for trimming or template work on sheetgoods or veneer

but i wonder - are compression bits without bearings useful if i dont have a CNC???

i realize that with a CNC these types of bits are essential for sizing any veneered or sheet goods....

but for non CNC use - when would they be uesful?

Mike


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## Biagio (Mar 2, 2013)

Hi Mike,
very useful for "jointing" the edge of sheet goods cut approximately to size with a saw. If you use a straight-edge to guide a handheld router, you will land up with a true edge, at 90 degrees to the face on which the router rests. No fuzzy edges top or bottom, if you are using mdf, for example. Limit the amount to be routed to 2 or 3 mm, mostly to minimise dust.


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## Mike_C (Jul 11, 2020)

@Biagio 
You do that with a handheld router and not you tablesaw?? Or jointer?

That seems strange
What is the rational?

M


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## Biagio (Mar 2, 2013)

Cutting up large sheet goods, too big to fit into my small workshop, and difficult to handle on a tablesaw. Admittedly, I used the method more before I bought a table saw - previously only had a radial arm saw. Do not have a jointer, could do edges on my planer (up to a certain width of board), but a finicky setup, and then there is the risk of snipe.
I also do not have a good-quality track saw, which could probably also assure a good cut.
Years ago I made a set of guides, which have a central straight-edge of square tubing, mounted on a board of laminated chipboard. The width of the board on either side of the straight-edge is the same as the width from the edge of the router base to the bit (in fact, trimmed to size with the bit). The guide was used first with a circular saw, then without changing position, the router was used to trim and joint the edge. A useful feature was that, if the straight-edge was not 100% straight, it did not matter: if the mating board was cut on the other side of the straight-edge, the imperfections would be complementary, and cancel each other out.


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## Mike_C (Jul 11, 2020)

@Biagio 

since i work in a full size workshop with eurostyle full size sliding table saw - cutting sheet goods is not an issue

M


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## Biagio (Mar 2, 2013)

Then you probably do not have a use case. Mostly for us make-doers, when a better solution is not at hand.


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## Bits&Bits (Sep 18, 2020)

They're handy when using a guide bushing and a template, I cut out box joints on 2x10 rough cedar for a garden box. Rough cut with a jigsaw, then cleaned up with a 1/2 compression.


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