# Spiral bit help



## KenBee (Jan 1, 2011)

If using a spiral bit with my PC dovetail jig should I use a down cut or up cut? Up cut makes more sense to me because I would think the shavings would be pulled up and out of the cut with an up cut bit. Or maybe a regular 2 flute straight bit is the way to go. The price difference is minute so I can go either way. I am open to any and all suggestions.

Thanks,

Ken


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## dutchman 46 (May 23, 2007)

I think I would use the up-cut. I haven't ever used one yet, but I will be! Pulling out the chips would help to keep the cutting edge keener, and clear the bit by moving the chips up and out.


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## jlord (Nov 16, 2009)

While these bits do help remove material another purpose of theirs is to to help with tear-out. You want the cutter to apply downward force on the wood fibers on the show side as it cuts the material. They work great for plunge cuts. There are spiral bits that are a combination of both also. These work ok if you have two sides that need to look good. As long a you have a clean sharp bit dovetails are not much of a problem. Read this article it may help in deciding which bit you need.

Spiral Router Bits vs. Straight Router Bits


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## Mike (Nov 22, 2004)

Ken, read the sticky thread about spiral and straight bits for a good understanding of the bits functions.
James, the Woodcraft link does not not address the tear out problem that can occur when using a spiral bit. With some woods you are better off using a straight plunge bit for a clean tear out free cut.


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## KenBee (Jan 1, 2011)

jlord said:


> While these bits do help remove material another purpose of theirs is to to help with tear-out. You want the cutter to apply downward force on the wood fibers on the show side as it cuts the material. They work great for plunge cuts. There are spiral bits that are a combination of both also. These work ok if you have two sides that need to look good. As long a you have a clean sharp bit dovetails are not much of a problem. Read this article it may help in deciding which bit you need.
> 
> Spiral Router Bits vs. Straight Router Bits


Thanks for that article link. I think after reading it I may just stay with a high quality straight bit for my dovetails. I have several spiral bits but have only used them in my router table and I for one am a firm believer in Pat Warner's advice so that also helps with my decision. I have cut a few decent dovetails with the supplied Porter Cable bits but I need the ones for the 4215 mini dovetail and box joint template and at the same time order the full size bits for future use.


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## KenBee (Jan 1, 2011)

Mike said:


> Ken, read the sticky thread about spiral and straight bits for a good understanding of the bits functions.
> James, the Woodcraft link does not not address the tear out problem that can occur when using a spiral bit. With some woods you are better off using a straight plunge bit for a clean tear out free cut.


Thanks Mike...I can't believe at the number of times I have been in the forum I missed that sticky. Now after looking it over I am in a quandary as to which way to go. It would make sense for me to try both types of bit and decide for myself which best suits me. I am a firm believer in the old saying "an opinion is like an a$$, everybody has one".


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## jlord (Nov 16, 2009)

Mike said:


> Ken, read the sticky thread about spiral and straight bits for a good understanding of the bits functions.
> James, the Woodcraft link does not not address the tear out problem that can occur when using a spiral bit. With some woods you are better off using a straight plunge bit for a clean tear out free cut.


I believe it addresses this with the different types of spirals in the paragraph headlined "Spiral Bits leave a clean edge". It also talks bout a compression bit. Shows pictures as to the difference also.


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