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Hey,

I was making doors for a TV stand and my 1/4" straight bit broke and went flying. I normally use a straight bit to make a groove for doors.

Anyway, I had a 1/4" up spiral bit for my router and finished using that. It seemed to go throught the wood much easier than the straight bit.

BTW: I was routing Red Oak.

What do you guys use for slotting? Spiral or straight bit.

Here is a pic of what I was doing when the straight bit broke:
Photo 6.jpg
 

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where's my table saw?
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spiral up for slot and dados

It removes the chips instead of driving them back down into the work. If possible I'd use a dado head or at the least a saw kerf for relief, but not necessary. I also think you were trying too deep a pass, and for a 1/4" bit there is really only 3/16" of metal remaining right above the carbide ... not enough.
 

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If the slot is straight through for the end of a piece if the depth can be done with a slot cutter, this is my preference. For a through slot in the face I will use the table saw and maybe use a dado blade, otherwise multiple passes with the normal blade.

If the slot is stopped at one or both ends, I like to use a spiral cutter. As you observed, smoother cut, so less vibration, and a better edge at the surface.
 

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An up spiral will do OK, but it will leave fibers sticking up and maybe a little tearing/splintering along the edge of the cut. Here's what I do to make, for example, a 1/2 inch wide by 1/2 inch deep groove:

Start with a 1/4 up spiral and make a 5/8 or 9/16 inch deep cut along the center line of the groove using several passes. Then make your 1/2" x 1/2" groove using a DOWN spiral carbide router bit. The down spiral will ensure you have no tearout, splinters or fuzzies on the edges of the groove since the cutting action is down into the groove. The extra 1/4 x 1/8 channel centered in the bottom will allow the chips and sawdust from the down spiral bit to escape. The extra channel in the bottom also provides a place for glue squeeze out to accumulate, making glue up a little easier.

Kevin H.
 
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