# Why different straight bits?



## darsev (Feb 3, 2012)

This is such an obvious question that there must already be an answer out there somewhere. Can someone point me to somewhere that describes how the different types of straight bits should be used. My starter kit has several straight bits that differ only in diameter and length, and apart from the obvious practice of not using a big bit to cut a small channel, I am a bit fuzzy on how to best use the different sizes. None of the bits I am talking about have bearings - I think I have a reasonable understanding of using trimmer and rebate bits. It is the straight bits that only vary in size that have me curious.

Photo attached.

thanks, 
Darryl


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## bobj3 (Jan 17, 2006)

Hi

The bits can be used in so many ways you could say it's like a set of screw drivers all the same but not used in the same way.  some are to big for the job and some are to small for the job...the right tool for the job thing.

=



darsev said:


> This is such an obvious question that there must already be an answer out there somewhere. Can someone point me to somewhere that describes how the different types of straight bits should be used. My starter kit has several straight bits that differ only in diameter and length, and apart from the obvious practice of not using a big bit to cut a small channel, I am a bit fuzzy on how to best use the different sizes. None of the bits I am talking about have bearings - I think I have a reasonable understanding of using trimmer and rebate bits. It is the straight bits that only vary in size that have me curious.
> 
> Photo attached.
> 
> ...


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## Cochese (Jan 12, 2010)

Have to think three dimensionally. While you shouldn't take out a deep or wide channel in one pass, you'll need to hit either the depth or the width eventually.


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## Gene Howe (Jul 10, 2007)

Depends, Darryl.
I have a few large diameter ones I use for edge jointing on the router table. 
Often, I'll need a mortise that can only be made in two passes with guides. That's where the smaller diameter one's are handy. I like the plunge type, where the cutters extend a bit beyond the end of the tool.
But, in all honesty, I think the variety of straight ones (especially without bearings) are often included to pad the number of bits offered in the set.
I've always bought bits singly for specific applications. The only exceptions being rail and style and raised panel sets.


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## Mike (Nov 22, 2004)

Darryl, beyond the obvious width for a dado or slot you can use your bits with guide bushings for following templates. The bit diameter will effect the corner radius on a square pattern or the curves possible. The larger the bit diameter, the bigger the bite it takes out of the wood and the faster it evacuates chips. This is important to understand for a couple reasons. Smaller diameter bits require a slower feed speed since they do not remove as much material and take longer to evacuate the chips. 
In the same way a thin kerf saw blade removes less material than a standard kerf it is like increasing the power with the same motor. A smaller diameter bit will reduce problems in wood prone to tear out. We remove wood in multiple passes, usually about 1/4"(6 mm) at a time for best results. That is how much of the bit will dull. Shorter bits cost less to sharpen or replace. The majority of dado cuts will be 3/8"(10 mm) so a 1/2"(12 mm) bit length is plenty. Edge work and mortises requires longer bits.


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## darsev (Feb 3, 2012)

Thanks all of you, particularly Mike. That gives me a better basis for selecting bits rather than gut feel.

Darryl


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