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I like the shear angled bits for flush trimming. They do seem to give a smoother cut and as mentioned they can be touched up with a diamond hone when they get a little dull. Spiral bits are good for CNC work and plunge cutting, but I'm not sure they are needed for free hand stuff.

I use a chisel to get as near flush as I can and then just use my regular binding bit which is nothing more then a rabbet. As mentioned I then just nip off a little bit around the whole edge before scraping the sides.

I use a 3/4" flush trimming bit in a router table and hold the guitar freehand while climb cutting. I'm not looking for a clean edge as I also cut in a 1/16" rabbit with the binding cutter prior to flattening the sides. I would suspect the 3/4" bit hogs away material easier and cleaner than would a smaller bit given its cutting angle is much lower. This has worked so well for me that I've never even given it a thought as to how to improve.




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Doug

Don't let fear or common sense stop you from trying to build something

Doug, when doing the back, do you just rest it on the center of it's belly with the edges floating to account for radius?

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Pat

Pat - Yes, correct. Keep in mind I'm not looking for a perfectly flush trim as I immediately move to my binding cutter to relieve the plates by a small amount. I use this step to simply hog away the bulk of excess material. I think I spend no more than 60 seconds to trim both plates on one guitar.

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Doug

Don't let fear or common sense stop you from trying to build something

Ok, so I'm now leaning towards a shear cut bit. I want a good one. Carbide. Thoughts?

Mike (and thanks for all the info)

The OLF'er formerly known as Todd Stock always recommended Whiteside, IIRC. I couldn't find any prices on the website though.

http://www.whitesiderouterbits.com/default.html

Then there's always the aforementioned MLCS.

http://www.mlcswoodworking.com/shopsite ... flush.html

I'm not sure you can go terribly wrong, assuming you use any of the reputable makers. I mean, we're talking about flush trimming prior to cutting a binding ledge, right? Get a shear cut or spiral cut and you'll be far better off than with any of the straight bits.

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sweat the small stuff.

I just use a Trend straight TCT 2 cutter bearing guided trim, which I clean build up off and "touch up" on a fine diamond card before every guitar.
Bearing off, equal number of light strokes each cutter face, (normally 1-3), bearing back.
I suppose it's done 5 boxes, plus other tasks like template cutting mold layers (18mm ply and MDF) and the odd D.I.Y. task.
Worked fine last time I used it, no real plans on throwing it yet.

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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.

I use a flush bit the I sand them flush and do binding. Don't need to over complicate it . Even without the sanding level the lip is no issue as the router guide is locating off the side and the lip would be trimmed out in the process.

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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

This is exactly what I do as well. The larger wood top attached to the router table is useful as a flat surface for all sorts of stuff. I have not routed the little ledge, just block sanded the sides but I like the idea.

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

+2, but I use a 1/2" bit, because that's what I have, and it's lasted a while. 3/4" may be my next step.

As mentioned already, Whiteside bits. Of course, I have a Woodcraft 20 miles away, and I wait for their sales, or my birthday month (10% off). For their price, they're hard to beat. Better than Freud, IMO. Then again, if Woodcraft still stocked CMT bits, I've not had any issues with their stuff and would spend the extra $$$. Got one of their table saw blades, and got rid of my cheapie red colored ones.

Once I started climb cutting (mentioned already) at the bouts where the tearout happens, then going around the "proper" way, I've had no issues. Of course, I'm only taking off >1/8".

Bigger bits are good. I try to use 1/2" shanks where possible, but the cost goes up considerably.

If I had a choice between a shear bit and a straight, I'd get the shear, but that wouldn't make or break a purchase. I have straight bits right now.

https://www.youtube.com/watch?v=NwFiWCUkk4M
the same advice on the binding will also work on flush bits.
Sharp bits are the key

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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

I have a carbide Amana. Amanda, Whiteside, quality brands... I don't think it's terribly crucial.

"minimizes tearout"
A bit, no matter what configuration or degree of sharpness, can only do so much
to minimize tearout. Speaking from experience, more often than not it is the opperator that causes the tearout. A fuzzy cut usually means a dull cutter. Also cutters need to be periodically cleaned. In the meantime I like a plain old flushcut bit with a shear cut, sharp, in my binding cutting rig.
ttfn
Ken

I'm with you on all that. Would some of you please post cartoons of your cut directions?

What it shows here on the Stew Mac site is the basic idea.
http://www.stewmac.com/How-To/Online_Re ... rings.html
They talk about climb cutting
but I look at it as if I were planing with a handplane ie, go downhill with grain so as not to go under,
digging in so to speak, causing tearout. The climb cutting they refer to has to do with the direction the bit is moving on the side that contacts the wood. The climb cut is used to maintain the downhill cut on the grain. What can make it confusing is the use of the words climb and downhill at the same time.
Hope this is of some help.
Ken

Hi mike

Just bought a 2 flute flush panel trim bit 1/4 " for £12 from wealden tool company..
Used it yesterday with no tearout at all..might be worth a go




Cheers

From the StewMac link that Ken posted, I do exactly the opposite of this image, only because i use a router table so its now "upside down".

I use a 1/4" down cut spiral bit with a bearing in a hand held trimmer. Works fine, quick.

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Rian Gitar og Mandolin

I use a 1/2" shaft, 3/4" shear cutter in a router table, climb cutting. I do it this way because it is quick and safe enough with my set up.

If you want slower and real safe, the binding jig solutions work really well with the guitar held in a cradle and using a column type router jig, again climb cutting. Normal cutting, you're pushing the job against the rotation of the cutter. Climb cutting, the job passes the cutter in the direction the cutter is rotating, so can tend to pull the job into the cutter, so you need the control to avoid that and keep it all safe. The reason this is done at all is to avoid the tear-out, but you must have good control of the feed.

Undercutting is important for those who use outside moulds. If you have any overhang left, even a very small amount, you can split pieces of panel out if you try to shove the part-complete box through the mould.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Before I got this from Trevor's book I would do the " this way on the top left hand section, that on the bottom right section and on and on routine". This was so freeing and is really appreciated.....!! Thanks Trev.......!!
Tom

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A person who has never made a mistake has never made anything!!!

Anybody had cedar top routing experience?

Yes. I treat all top and back woods the same with respect to flush trimming. See above.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au