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I haven't been using a plunge router long, but I'm having trouble making vertically straight cuts in alder.

I'm routing out holes in the back of a guitar - a piece of alder 1.75" thick. I using a collar and 5/16" bit, making passes about 1/4" - 3/8" at a time. When I remove the template there are ridges at each pass. Does this sound like something I'm doing wrong or a hardware issue? Is it the bit flexing perhaps?

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Music. And Stuff.

You're taking too much material at once. Try taking 1/8" or less per pass, and you should get a better result. You could take the bulk of the wood out with a forsner bit in a drill press as well.

Alex

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"Indecision is the key to flexibility" .... Bumper sticker

Are the ridges a problem?

Routing that way is not a really precision operation and there are several different things that could cause that. Vibration, plunge mechanism that isn't perfect, not keeping the router flat on the surface, surface that isn't flat, bit not square to base, bad bit.

If smooth sides are more important than overall size, Todd's method should work fine. If size is critical then you really have to dial in the whole operation.

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http://www.chassonguitars.com

Most likely your template guide on the router isn't centered. Either center it properly (using a centering bit), or keep the router orientation the same all the way around the cuts (i.e. rotate the router as you move around the template) so the offset is the same all the way around. Alternatively, you could put one or two layers of blue/masking tape around the outside of the template guide, route 1/4" depth at a time (IMO, this should be fine in Alder), and then take the tape off for the final pass, leaving a nice clean wall.

Cheers,
Dave F.

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Cambrian Guitars

"There goes Mister Tic-Tac out the back with some bric-brac from the knick-knack rack"

Is this a 1/4" collet router? If so, then ridges are to be expected. But a 1/2" collet router should give you a lot smoother results.

In most cases the ridge shouldn't be that big of a deal , are we talking just visible , I can catch a fingernail or it is a speed bump? You will often see a witness mark when making multiple passes but these shouldn't be significant, A few thousandths won't matter.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

OP is likely running the risk of disaster and injury-those flimsy 1/4 shank bits flex and sometimes as a result explode with tragic results. I regularly re-check my centering of the base or a bushing. The inherent vibrations often slowly move the assembly.

Great tips, thanks gentlemen. I like the idea of using masking tape for all but the last pass.
The steps aren't bad,per se, but I'm trying to do as clean a job as possible, and I see other peoples work that is much cleaner. I think most are using heavier duty routers. Mine has a 1/4" chuck, so perhaps that is the issue. I could live with some steps I guess, until I can afford a heavier duty router.

"OP"? You can call me Nicholas Thanks for the warning. I already snapped one bit, but I put that down to Canadian Tire's low quality. I use Lee Valley bits and they work much better.

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Music. And Stuff.

I didn't measure the steps, but they would be a round 1/64", maybe a little more.

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Music. And Stuff.

+1 for the masking tape. I leave mine on even on the final pass, and then take it off and do the final cleaning of the entire slot.

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Jim Kirby
kirby@udel.edu

Trying to cut deep mortises cleanly with a 1/4" router is not practical.

Bingo!
Also, why a 5/16" bit?

Sadly it's the only router I have so I'll have to make do until I can afford a 1/2" router.
The 5/16" bit fits the collar I have.

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Music. And Stuff.

Buy a one to one bit,
with a bearing on top.
You will need to buy a short one,
and a longer one.
Then you need a one to one template.
Once you use the template,
keep stepping the bit down into the cavity,
as it will eventually be riding on the sides of the cavity,
not the template.
Dig?