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Tomorrow I’ll flush cut my first cedar top. I’m concerned about chip out from the router on the cedar. Is this more common than w Spruce it am I over thinking it?
If it is... are there ways to minimize the potential?
Here is the body glued up today


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1) do it in stages, that a lot of overlap. Don't try to get it flush on the first pass.

2) follow the climb cut pattern for on the StewMac trade secrets section in on of the binding tuts. This should be followed for all binding routs.

3) some folks like to add a few layers of shellac to harden the wood

4) sharp bit

Just finished a WRC guitar. Used a sharp new bit for the cuttoff and binding channels, put a coat of shellac on the top, paid attention to the direction of the cuts, all went fine.



Looks like we have similar thoughts about rosettes.....

Red arrows first, second full pass in opposite direction...

Do it with a chisel. Cedar cuts like butter.

That’s what scares me haha




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I like to have my tops, and backs for that matter, with a lot less overhang before putting the router to it. When you have a big overhang,
as you have there, it stands to reason that there's a lot of wood in contact with the cutter, more wood for the cutter to grab. By having a
smaller overhang there'a less wood in contact and a better chance for a successful route with no tearout. A sharp cutter is a must.
Ken

I’ll definitely cut some of that down before cutting
And I’d never whack that at once.


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Of course you have to mind the direction when using a chisel too.

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Pat

cuchillo spanish luthiers knife, or vlnmakers long knife , and traditionally in europe they used knives to cut down the backs and tops,, Works very quickly with a very sharp clean knife . You have to pay attention to the grain direction !!!

Top woods are so easily carved that we use a shop knife to trim to within 1/2 of the diameter of the bit to be used to flush trim - and usually closer to 1/8"-1/16". Using a razor saw to make a relief cut down into the waist as well as any other location where the blade may follow the grain and raise the potential for a split reduces the tendency of split-prone woods to misbehave. Our preferred shop knife is the Pfeil Brienz large carving knife, which works well for the task (http://www.chippingaway.com; $23 + P&H)

If your top or back is fitted and ready to glue to the rim, an angled pencil (i.e. 3/8" stub of carpenter pencil CA'd to popsicle stick at 90 degrees) can be used to update the outline and permit a closer trimming of the top before closing the box.

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For the times they are a changin'

- Bob Dylan

I use a chisel too. Just pay attention to the orientation of the annular rings. When they are straight like in the apex of the curves of the upper and lower bout you have to be real careful. Work it to a point from both directions then just lop the point off. I usually get it close enough that way then just do the bindings.

At the tail and head block when you have to cut across the grain just angle the chisel so you make the cedar top a knife edge then remove that. If you go for it all at once you can get tear out even with a sharp chisel.

I use my belt sander, very carefully, holding tightly, to take excessive overhang down to where I feel more comfortable with router and flush bit.

I've used my bandsaw to trim back the overhang. After a bunch of masking tape on the sides and the plate being trimmed. A very high tpi count I suspect would be a good idea. Worked for me, but one side at a time after gluing it on. Or I guess that the guitar body could be tilted out of the way if both top and bottom are on, doing one with a tilt and the other flat to the surface. I think no harm would occur if some familiarization cuts were made first, before trimming close to the body.

For trimming right up to the body, Ken Cierpolowski (KMG Guitars) suggested using a flap sander in an electric drill held at an angle, after masking the body so no random whacks with the flap wheel will get to the surface.

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Peter Havriluk

grain "awareness" is critical no matter what method you use. FWIW, I use a chisel.

a 60 to 80 grit sanding drum about 2~2-1/2" diameter mounted to a drill press or mill is also a pretty safe choice. move down and along the grain not up against it. put the body face down and position the drum roughly in its center.

Although we usually knife-trim plates for trimming with the router, it's a good place in the order of build to emphasize that the technique called out in the guide is just one of the many approaches. The boss did a very funny demo on trimming plates which I saw the last time our Wednesday PM student did a weekend work session...think frenetic hamster scrambling around a room-sized cage.

1. Draw knife/scraper (mounted in the trojy)
2. Knife/scraper
3. Chisel/scraper
4. Spokeshave (round bottom)/spokeshave (flat bottom)/scraper
5. Block plane/shave/scraper
6. Oscillating spindle sander and disk sander with tables angled 10 degrees/flush trim router
7. 6x48 stationary belt sander/router
8. Rotozip in trim router (leave the plate oversized)

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For the times they are a changin'

- Bob Dylan

I climb cut (figure A above) all the way around. It tends to push the router away and takes smaller bites. If there is a lot of overhang I will take light passes (still climb cutting) to get closer to the side. On Cedar I will often skip the "B" rout and just use a block sander to knock off fuzzies and smooth up the edge.
It doesn't hurt to run a strip of tape around the sides where the bearing will run - sometimes the bearing will spin and leave a mark if you don't hold it firmly against the side. And always check the tightness of the bearing screw.

I’ve had the problem w the bearing leaving a mark. Would the tape thickness be an issue? Or I guess... just account for it in the bearing size when you cut the channel for binding


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Good tips above. I use a chisel to trim plates close, then go with the router as described in the Stew-Mac diagram. For binding channels, I score with a gramil before routing. Scratches or indentations from tools can be a problem with cedar. Leaving the top slightly thick can allow for minor imperfections to be removed during final sanding.

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George :-)

+1 for "A" all the way. Do the same for binding and purfling ledges. Never a lot of overhang as I chisel/spokeshave excess making a saw cut into the waist first.
Very sharp cutter should go without saying but is essential.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Made small cuts all the way. No issues



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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

That's the way to go. Well done.

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George :-)

That’s great.

What I have been doing the last few years is putting the guitar upside down on a good sized wood platform clamped to my router table and use a top bearing bit. I think you are pretty safe doing climb cuts all the way taking off small amounts each pass.

Finish up with a block sander. So far so good. With cedar I’d protect the top with some paper taped on. I have had no problems with Spruce. You can hold the guitar slightly off the table as you rout.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

Use a good flush trim bit
climb cut the bout areas and rout the rest
watch your chips

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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