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Edge routing a guitar body
Hi there, was hoping for some edge routing advice. I keep jacking up my bodies and am getting pretty frustrated. I had a mahogany DC jr style body that I was working on. I sanded the edges as close as possible to the template, and followed the pattern in the attached picture and still ended up with bad tearout at A to B. I can feel that even though I was routing “down the grain” in the area from A to B, I can feel that this is against the grain of the wood. I suppose my question is, how do I know which pattern to follow? Follow the curves of the wood, or follow the grain of the wood even though I may be routing in a direction that’s contraindicated by this image? Tired of always picking the wrong thing. Thanks!
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8 Replies
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Are you using a spiral bit or a straight ?
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Infinity Tools mega flush trim bit, 2″ height, 1.5″ diameter
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Can you also pop in a pic of the afflicted guitar.
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Unfortunately I already filled it, but I appreciate the reply
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Hi Joe! I feel for you! I’ve had some unhappy results doing these types of cuts as well.
The key to understanding this is to look at the rotation of the router bit in the same way you would look at how a chisel or plane cuts wood. If you are trying to plane or chisel into the grain (or against the runout) it has a tendancy to dig in, but going the opposite direction yields a smooth cut. Likewise, if the rotation of the bit is feeding into the grain it will tear out. The solution, as pictured in your drawing is to change the routing direction as the grain changes.
The direction is going to change depending on wether you are using a handheld router or router table. I definitely find I have more control when using a table. It will also be helpful if you have a setup that will allow you to take multiple partial depth cuts instead of one full depth cut.
Here are a couple of videos explaining grain direction considerations and routing direction,
https://www.youtube.com/watch?v=mrE4HyXiwqs
https://www.youtube.com/watch?v=aZ98Hj2RVo0
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Thanks so much for this info, I appreciate it!
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On my router table I have it marked with an arrow which way (in general) to feed, against the direction of the blade. It helps, the noise of the router and focusing on not cutting my fingers off, generally it’s not a super pleasant process and it’s helpful to have it marked in so I don’t have to think about it. It would not hurt to mark up your guitar body likewise with the way you want to make the cut.
Running some test pieces on scrap lumber might help get a feel for it.
You said you are trimming which is hugely important. The closer the better (obviously if you go over, you lose). When I started making guitars I didn’t get the trimming memo and would attempt to route off large quantities of material with disastrous results.
One thing I’m doing lately on my acoustics when I route the edge is touching into the problem areas first so that there’s less material there for the router to grab into when I do the full perimeter. I think this helps (?)
If you are doing everything right, the one thing I would say that’s more a feel thing is going very, very slowly, listening to the wood/machine (with hearing protection). If you’re going through the tough spots millimeter by millimeter I think it gives the bit more time to sever the fibers. I try to hold the body very firmly so that I’m in control.
Not sure any of this is helpful. Routers kinda suck, they are super useful but you can definitely destroy a lot of work very quickly in a few seconds. It’s a total attention kinda thing.
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HI. I have experienced this too, some with very dangerous results. I am glad I am not the only one. I no longer even try to use a trim router on a body. I user a spindle sander and then hand sand with a block. I wish I knew the secret, but I kind of gave up trying. I have the infinity bit too and spiral bits, but still decided I am not willing to risk it. I would love to see this as a topic the pros would walk through for us.
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