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I was watching an episode of the Wood Whisperer on YouTube, and he was making a frame for a mirror. At one point in the video he was going to put a round-over on the frame and was using an electric router for it. He said that the rule is "on the outside of the frame, go counter clockwise; on the inside go clockwise". He didn't give a reason.

Now, I am a hand tool guy and my idea of a router is a good old Record 71.

Record 71
Image courtesy Record Planes

I understand grain direction and wanting to work with it; not against it. From what I have been told you generally don't have to worry about it when using power tools. Why would the direction you are going around a frame matter as stated in the video?

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  • As of this moment, this question has 3 views and 4 answers. From 4 different people! How does that work?
    – FreeMan
    Apr 20 '15 at 17:46
  • 2
    @FreeMan your answer is here
    – Matt
    Apr 20 '15 at 18:06
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    Please, remember, this becomes reversed if you're using a router table
    – Raystafarian
    Apr 22 '15 at 12:44
  • I was looking for the name of this traditional tool, having found yours on Google Images after watching a Youtube video: "router plane" for anyone interested.
    – Engineer
    Dec 1 '19 at 14:07
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It has to do with the rotation of the bit. In a normal cut, the work piece is fed against the rotation.

A normal cut works like this (shown for freehand):

Normal cut diagram

The cutting action will pull the work piece into the bit.

The other cut, is known as a climbing cut. It pushes the work piece away from the bit. Climbing Cut diagram

A climbing cut will have less tear out, but requires more control of the router to keep it from pulling away and injuring the operator or damaging the work piece.

A normal cut is safer in all instances. The tear out that can happen can be eliminated by using a backer board to support the wood at the end of the cut.

See this link at Lee-Valley tools for a complete description (images are from Lee-Valley)

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  • Much better response than mine. :)
    – TX Turner
    Apr 20 '15 at 17:41
  • Nice pictures! I was hoping someone would add that in...
    – FreeMan
    Apr 20 '15 at 17:45
  • I typically make a climbing cut on my first and second passes. Yes it is a handful to control, there must be much respect given to the router for what is being done with it. I give the last past the normal way to clean up the cut. This has solved the problem I have had of the router, going the normal way, grabbing the grain in a number types of wood and ripping out the grain well ahead of my cut, essentially ruining the work
    – Jack
    Apr 21 '15 at 7:09
  • @LeeG If I make a plunging cut, the same width as the bit, it doesn't make any difference does it?
    – Andyz Smith
    Apr 28 '15 at 12:22
  • It does. If you are making a normal cut, you are pushing the router into the stock, and the bit is pushing the router back into your hands. If you are doing a climbing cut, the bit will be pulling the router forward, so you have to both push it forward and hold it back at the same time. You can do it, but it requires a lot more control on the router.
    – LeeG
    Apr 28 '15 at 13:21
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It has to do with the rotation direction of the bit. You want to go 'against' the rotation with your pass, rather than 'with' the rotation (called a climb cut). This pulls the material toward the bit, but can splinter the last section of cut since the bit will be pushing out of the material.

There are times when you want to make a climb cut- if you have especially frangible material, you might make a climb cut for the last 1-2", then go back to the other end and start a regular cut- less tear-out at the end.

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When you are hand cutting, you push the sharp edge of the cutting tool into the wood so that it makes a cut, you don't drag it along the wood backwards waiting for it to wear down the wood via friction.

The same holds true with a power tool. When looked at from the top of the router, the bit will spin clockwise. In order to push the cutter into the wood when moving around the outside of the picture frame, you would move the tool counter-clockwise.

Once you jump to the inside of the frame, in order to keep the cutting edge of the bit pushing into the wood, you want to use the 'other' side of the bit and go clockwise.

If you're going the wrong direction, the bit will want to 'run' along the surface, and not cut cleanly into the wood, leaving you with an uneven cut.

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When using a router, the bit spins at up to 30,000 RPM in one direction (usually clockwise when holding it bit down).

Then if you run the bit in the same direction it is spinning, it will try and 'run away' and can totally mess up your work piece. The reason why you go one way on the outside and the reverse on the inside is you are basically flipping which direction the bit will try to 'run'.

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    Right- the bit will 'climb' out of the groove it's making-- hence a 'climb' cut.
    – TX Turner
    Apr 20 '15 at 17:34
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    @TXTurner I learn something new everyday! Didn't know it had a name, just the trouble when I've gone the 'wrong' direction.
    – bowlturner ♦
    Apr 20 '15 at 17:35
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There are times when a conventional cut has the potential for less tear out. If you are routing around the perimeter of an irregular outside shape like a guitar body, both cut directions will need to be used to avoid tear out and the conventional cut being the direction with less potential for tear out in some of the areas. Routing down hill with irregular outside shapes and a final conventional pass works very nicely to avoid tear out.

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