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I have seen posts recommending to climb cut binding channels, to reduce chance of tear out. I have also seen diagrams showing routing some areas climb cut and others not, but I lost the diagram. Anyway, please educate me. Also, is climb cut just moving the router clockwise around the perimeter of the guitar?

Think about the grain lines as a hill. When routing for bindings I always "go downhill". Basically the guitar's outline has 4 zones. From upper and lower bout width to the waist and same starting point to the center lines top and bottom. Router bits are meant to cut from left to right. Right to left is a climb cut and only safe to do with a very light cut.
Starting at the bass side lower bout we'd make a conventional cut down to the center. Going from same spot we'd make a climb cut to the waist. Think about having the bit cutting "downhill" and climb cut vs conventional will become second nature.

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Same substance as Tom, but slightly different way of remembering what to do:

Always cut from the wide part to the narrow part. Never from the narrow part to the wide part. So, from the widest part of the lower bout to the waist, and from that same widest part of the lower bout to the tail. Then from the widest part of the upper bout to the waist, and from the widest part of the upper bout to the head block. Do the same thing, in the same order, on the other side. After the bulk is done, a continuous cut all the way around, in either direction (or both), is fine.

I climb cut all the way, which is clockwise around the perimeter.
Not all at once, but 0.5-1.0 mm per cut.

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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.

You may find the diagram on Stewmac’s website in their trade secrets section…

The direction you should cut changes whether you are cutting an inside (closest to soundhole) or outside edge of the rosette and it changes on which quadrant you are in. Going clockwise on an outer rosette edge (with a clockwise cutting bit rotation, of course) will have the grain lines from 12 to 3 o'clock pushed against the material behind it. Going from 3 o'clock to 6 will have the grain lines being potentially torn if your bit isn't sharp. Ideally, you would climb cut from 6 to 3 to eliminate that chance. I've always had better luck with smaller diameter bits on rosettes and just climb cutting around 0.005" of material for my finished edge . I'm not sure how circle cutters perform but I imagine they do quite well.

The basic idea is less about climb cut which is not so important with easy to cut woods like spruce that won't grab the router away from you. The main thing is to cut so that the grain lines are pushed against more material rather than pulled away into empty space. IF you think about it that way -- you will always know which direction will yield the cleanest cut and which ones have a possibility of tearing. Sometimes climb cut is best and sometimes not.

Anyway, I used to worry about grain direction in Spruce until I realized we were all using the wrong router bits. You should be using a single flute router bit in spruce. It has a much steeper rake angle and will slice the wood cleanly and never tear. I probably should make a separate post about this but I was always told to you spiral bits and whatnot -- but they are massively inferior to a single flute. I get mine at PreciseBits and they call them 0-flute. Buy one and never worry about grain direction again (use them for the binding channel on the top as well). I started using one about a year ago and it is game changing in terms of the quality of cut you get in spruce.

EDIT: Not sure why I thought this was about rosette channels. As mentioned by others, StewMac is correct about climb cutting. If your binding setup allows it, arrange so that you do a final climb cut that takes a very small depth of cut. And for your top purfling, try out that router bit I suggest (many binding setups don't allow for choosing the type of bit you want to use).

When I started building it was a StewMac kit that came with great instructions AND a diagram and explanation of why we do climb cuts and how to do it.

So I just went to our friends at StewMac's site and sure as shootin the instructions for their dread kit still contain the following pic and a written narrative as well explaining all of this.

The instructions for their dread kit(s) are free to down load and have lots of good tips in them.

I always did my climb cuts as per this pic and I would tape the pic on the wall in front of my William's jig and use it as my guide to cutting the binding channels. 55 guitars later I never had any drama from cutting the binding channels.

Thanks to StewMac as well.

Yup, what everyone says. Here is the diagram on the subject from my book Building the Steel String Acoustic Guitar. With the body oriented like this, it is easy to visualize the concept of routing "downhill".

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I did the same thing. I downloaded the pic from SM's site here: https://www.stewmac.com/video-and-ideas ... -bearings/

And it's taped to my router jig.

I never thought of it that way but that is a great way to remember it Don, always start at the wide parts.

Bergman I would suggest however that you 'think' about it too rather then just rely on advice and diagrams. Turn your router on then off and watch which way it is spinning. Then look at the edge of your guitar and note the vertical grain (annular ring) lines. Then picture the router on a macroscopic level as it starts to cut wood fibers and cross over those grain lines.

If you start at the waist and move up to the upperbout then you can imagine that the router will be grabbing the front edge of each grain line and ripping it out. Think of the blinds on your window. When they are closed if you run your finger from the bottom to the top you will feel the edge of each individual blind and bump along it. If you start from the top then each blind is 'stacked' so your finger runs smoothly. Your finger is the router bit

Like Colin, I do a continuous climb cut clockwise around the guitar body. The idea behind the climb cut is that the wood is removed behind the cut so there is nothing for the router bit to grab onto. Taking smaller bites and holding the router firmly against the work when climb cutting often gives the best result. Like Don, I do a clean up pass in the conventional manner after climb cutting.
A single flute bit is more aggressive and will cut faster. A sharp bit does give a smoother cut than a dull one. My understanding behind using a spiral fluted bit is to reduce the possibility of blowouts on the sides of the guitar when routing binding channels.Personally, I prefer a two flute shear angle bit with a bearing rather than a spiral bit, because it can be touched up with a diamond hone and kept sharp.
Router bits and routing techniques are a personal choice and what works for one person may not work for another. Testing on scrap to find what works for you before risking the work is recommended.

sharp router bit!

when doing binding channels you are routing into 3 different woods....top/sides/linings...the top is most likely a soft wood and with a sharp bit there is little worry of blowouts more likely fuzzy edges...the sides are another issue though...worst case you blow something apart and tiny pieces of wood go flying and it's a FUBAR situation (I guess you might also just partially mess it up and think yourself lucky for finding a bad spot in the wood and being able to glue it back together and fix a future crack)...point being IMO a climb cut for most everything if you want to pretty much eliminate blowing wood up

did I mention a sharp bit?

really, it is worth the money to have a sharp bit when compared to the cost of woods these days

Always cut downhill has been my method. Pretty much what everybody else has said. It works.

Dave

Not to be argumentative -- but choice of router bit is not really a subjective matter. New advances continue to develop and improve knowledge and understanding of how to yield the best and most efficient cut in various materials. Feed speed, depth of cut, rake angle, etc ... do have an effect on which bits work best in certain materials.

2-flute Upcut spiral bits work well on the binding channel for removing the side material that is hardwood. They also work well on the back channel. Downcut work exceptionally well too - both big improvements over straight bits.

The reason the single flute works well on spruce is the same principle as a pairing chisel or a blunt (by comparison) bench chisel with a steeper bevel angle -- the cutter geometry helps to prevent tearing of the delicate wood fibers that can happen with a normal 2-flute router bit. Not all end mills are created equal -- the O-flute product by Precise Bits works astonishingly well in spruce. I learned about this from the owner (I personally no nothing about cutter geometry) and he strongly recommended that I try this bit for softwoods. As I said above, game-changing IMO. However, without question -- a sharp bit is king and many different bits (even if not optimal) can still yield flawless results.

I've been building guitars for a while now and occasionally I find something that really impresses me. These particular bits on guitar tops work really nicely. I'm curious to see whether you all feel the same way -- try one and see if you like it. Again, only use this for softwoods -- I think it will dull quickly in hardwood and isn't really designed for cutting them.

https://www.precisebits.com/products/ca ... r-O_1F.asp

Alas, they will only work with certain binding systems. Nevertheless, I can't help but like their name...

Ron gave me an over the phone masterclass in cutters and calculating runout when I was getting started with CNC. Great guy and great products. Their precision collets are great.


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Thank you for the link to the bits you are using. When someone mentions a single flute bit I think of the single flute straight bits that are commonly seen and used. The "O" flute cutter in a spiral bit is something I haven't seen before. It does look like it would work well for routing rosette channels and CNC work.

If I search on the name for Precisebits, I then locate a 1/4" bit for a router. If I search the second post with the link included, I get small bits for Dremels. I am assuming that the advice is the same, regardless of whether I use a router or a Dremel???

a Dremel is a real iffy tool...that being said, to use a 1/8" shank bit in a router you need a !/8" precision collet made to work on your router...

Agreed. For rosettes I use a Precise Bits 1/8" collet in a DeWalt 611 router. Huge improvement over my old Bosch Colt. Bosch Colt was a big improvement over my old Dremel.

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Again, I hope I didn't come across as argumentative -- I have no right to be as I know little about CNC stuff and cutter geometry. I believe this design was originally meant for plastics but it does work exceptionally well with tearout in spruce. It is also apparently more rigid than the 2-flute design (so better for the really small bits). I use a Dewalt 611 and have the aftermarket collet/nut from PreciseBits (1/4 & 1/8 collets). That idea makes a lot of sense to me when running very small diameter bits. Again, try one of these O-flute bits if you can. I really think you guys are going to like them. Because you only have 1 cutting edge, I imagine they will dull faster but for me, the results are worth it as I don't have to worry about taking really tiny cuts or paying attention to grain and router direction.

I've bought a number of other bits from PreciseBits and have always been pleased by the quality.

This is timely advice about the single flute bit, thanks, I’m just about to buy a slew of new bits for inlay, rosettes etc as my current ones are past their prime. I use the precision aftermarket collets in a 611 and also highly recommend the combo.

RE bits for binding channels, sharpness is definitely king. Even with best practices re feed direction, a blunt bit will happily rip a chunk out of your sides…



Rework really slows things down. The time spent invisibly fixing these issues ends up costing a lot more than any money saved trying to avoid buying a new bit. When in doubt, throw it out


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Charles Fox used the single flute bits years back when I went up to Earthworks. We used them for jointing tops and backs, rosettes, bindings... Not quite as sophisticated bits as the Precise bits, but same basic idea. Worked very well.

Dave

The climb cut is one of the most feared uses of the router when talking to furniture makers. I am firmly in that camp, as I have had the most dangerous and frightening experiences in my shop (over about 30 years of woodworking) when using a router "incorrectly".

That said, what makes a climb cut dangerous is the force created by the bit when interacting with too much wood. If you are taking a 0.10" x 0.10" corner off the corner of a mild wood with a sharp bit, you might not even feel much affect of the climb cut trying to pull your piece out of your grip. If you happen to have a 7/8" thick piece of hardwood that you are taking a 1/8"+ deep cut off of with a climb cut, you had better be ready for some excitement. Last time I did this, I almost had to go the the ER from the damage caused to my hand when the bit not only destroyed the workpiece, but threw it into my hand at a speed I don't remember and created multiple deep lacerations (from the wood, not the bit).

This can be particularly dangerous with smaller pieces of hardwood, like bridges. I pattern route all my bridge outlines after rough cutting them on the bandsaw... and even though I leave a VERY small amount of wood left to remove with the router, I still refuse to do a climb cut. Instead, I have a Whiteside 7/8" compression bit with bearing on top and bottom. I then use two brass pins inserted at pin 1 and pin 6 on the template and bridge to make the bridge a "two-sided" template. So, I do the safe cuts using the top bearing on the bit (avoiding climb cuts and grain issues) with template on top and bridge on bottom, and then put the bridge on the other side of the template, flip it over and do the remaining edges.... and yes, before doing this I had additional injuries and shattered bridges due to router bit force. FWIW, I use a 3HP router in a table for bridges.

So, all that said, how do I deal with bindings and perflings? First, I use a shop-made version of the "floating router tower" style jig where a trim router with an angled bearing bit (LMI) rides along the top of the guitar while the guitar slides on a sort of "sled". Anyhow, on the top, where it's critical to get a clean cut on the top plate edges, I start by wrapping a thin piece of painters tape around the bearing a few times to make the cut more shallow and cut only the perfling depth, and do a traditional cut all the way around, going slow-ish with a sharp bit to avoid burning or significant tear-out when going against the grain. Then, I remove the tape and do a full pass all the way around the guitar in the climb-cut direction. It's now removing so little material that the guitar body will not get pulled out of your grip whiled climbing, but leave the best possible cut behind safely.

I've found that the same strategy works well for the bindings on both top and bottom. Use the tape trick to get most of the material out of the way and do a final climb cut pass without the tape to get a clean final cut.

*whew!*