# Mahogany guitar routing



## drose21 (May 3, 2009)

Hi, im wonder what type of router bit i should use... I need to route out the cavity of into a mahogany, i dont want it to chip or blemish as little as possible, hopefully not at all, what kind of bit should i use? and what speed should i cut at? Thanks!


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## Mike Wingate (Apr 26, 2009)

I build a few guitars and basses each year. I make templates from 1/4" polycarbonate, for pickups, neck cavity, control cavities and other bits and pieces. I cut these with a 1/4" bit and a 3/8" template guide which gives me a perfect fit even allowing for the finish on the wood. I have developed these over the years. I now draw the jigs in CAD , print out onto paper which I stick to the polycarbonate. The waste is removed with drills, scroll saw, dremel and files. I did CAD CAM a handle template only for the machine to track back to the home position , mid route.


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## AlanZ (Aug 21, 2008)

I don't understand what you're trying to do when you mention routing out the cavity.

Are you asking about the router setup to cut channels for edge binding and/or purfling?


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## xplorx4 (Dec 1, 2008)

Greetings (your name here) and welcome to the forum, you Alan and Mike speak some strange language for sure but welcome anyway!!


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## Carl762 (Dec 31, 2007)

He's talking about routing cavities for pickups and sometimes bridges, the neck pocket, etc. Typically a bearing bit is used with a template. That's what I use.


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## westend (Mar 31, 2009)

Mahogany should machine pretty good, especially if you have a species that is known for it's consistent grain. There is an article in the "wood species" section of the forum discussing the different species that make up the generic "Mahogany" name.
I'm thinking an upcut spiral bit, 1/4" sounds about right. Most of the cavities in an electric guitar are relatively small. Don't try to hog out all of the cut in one or just a couple of passes. Slow your speed down a bit and barely cut on the first pass. That will prevent the most chances of tear out. Good luck on the guitar. if you have some pics of the guitar, I'd sure be interested to see them.


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## Eoin (Jun 6, 2009)

Hi. When Westend says 'slow your speed down a bit', he means the speed at which you move the router, not the rotational speed of the bit. With a small diameter bit, keep that high. Absolutely right about taking it a little bit at a time depthwise, especially the first pass. Remember that when you're routing out a cavity, you need to move the router clockwise as you look down on the workpiece (or you'll be doing a 'climb cut'). Start with little clockwise spiral motions in the middle of the cavity until you get near to the template but make sure you don't rout up to the template until you're deep enough for the bearing to run on the template. I typically take three or four passes to reach the full cavity depth, using a bigger diameter bit to hog out most of the waste in the middle of the cavity first and leaving a sixteenth or so around the edge. First pass (at the edge), the bearing rides on the template, and then for successive passes, the bearing will ride on the wood itself. Use double faced carpet tape to adhere your template to the work piece, and use a bearing-guided straight cut pattern bit with the bearing at the shaft end of the bit, not the tip The cutting length of the bit need only be 3/8 or 1/2 inch. Better to use a half inch shank (if you have the collet capacity) straight cut 3/8 or 1/4 inch diameter pattern bit (depending on the cavity corner dimensions you need - I use 1/4) . Although the books will suggest using a spiral bit, I wouldn't bother - they're very expensive, don't last, are difficult to sharpen (you should really send them out) and I've never seen one with a bearing. As for routing beading/binding, well, that's a different matter entirely. You really should be using a Dremel or similar for that. Are you aware of the Musical Instrument Makers' Forum (MIMF)? It will change you life...
All the best,
Eoin


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## Mike Wingate (Apr 26, 2009)

The MIMF site is really useful.


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## Check twice! (Feb 11, 2008)

Maybe these photos may help you on your build. This was taken from our build.

Have a fine day, and hope these may be helpful.


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## pinkwedd (Jun 17, 2009)

this is great stuff!!! Liking it..


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## Mike (Nov 22, 2004)

Eoin, when you are routing with wood on both sides of the bit such as making a cavity you will not automaticly be making a climb cut. A counter clockwise direction of cut will leave a good finished edge on the inside piece. A clockwise direction of cut will leave the good finished edge on the outside piece. This applies to solid material only where there is material on both sides of the bit. Cutting out a table top with a circle cutting jig is an example where the counter clockwise direction is used.


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## jakeelee (Apr 13, 2010)

Eoin said:


> First pass (at the edge), the bearing rides on the template, and then for successive passes, the bearing will ride on the wood itself.


When you start routing, do you drill a hole first?


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## Dr.Zook (Sep 10, 2004)

Hello Jake. Welcome to the RouterForums community. Glad to have you as part of our forums.


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## allthunbs (Jun 22, 2008)

Dave:

I just noticed your "router-skis." Cute!


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## Check twice! (Feb 11, 2008)

jakeelee said:


> When you start routing, do you drill a hole first?


When we did ours we used a large forstner bit and drilled out the cavity. The depth was just shy of the finished depth, and used the small bit shown in my pictures to finish the job. It did take several depth cuts, but we are always cautious,,, what a waste of good material if we make a mistake.

Hope this is of some help.


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## bobj3 (Jan 17, 2006)

Well John, it's about time you dropped the hammer, glad to see you on the forum....

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Check twice! said:


> When we did ours we used a large forstner bit and drilled out the cavity. The depth was just shy of the finished depth, and used the small bit shown in my pictures to finish the job. It did take several depth cuts, but we are always cautious,,, what a waste of good material if we make a mistake.
> 
> Hope this is of some help.


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## Check twice! (Feb 11, 2008)

bobj3 said:


> Well John, it's about time you dropped the hammer, glad to see you on the forum....
> 
> ==========


I popped in every so often, and answered any PM but my job did take my time. Starting to slow down now and spend a little more time on the computer and shop. We have our CNC router hopping along,,,,,, i should post an update to the green machine, even have a short video. 

Thanks Bj


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## Dr.Zook (Sep 10, 2004)

*Skis*



allthunbs said:


> Dave:
> 
> I just noticed your "router-skis." Cute!


Thanks Ron. I got tired of Harry always bragging on his skis, so I made my own set!:haha::dance3:


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## Eoin (Jun 6, 2009)

Jakeelee, 
No, I don't drill a hole first, although you could as long as it was bigger than the diameter of your bit. I simply start with very light clockwise circles, getting ever deeper and wider until I reach my first cut depth. My second cut depth will start in the same way, in the middle of the first cut cavity, so I'll end up with a step-sided cavity before I do the clean-up cut.

Mike, 
Re: your message #11, above, and just for the record, the OP was asking about routing pickup and bridge cavities, which is always done freehand with a plunge router - you can't restrain the router with a jig in the way you're talking about with circular cuts. Such pickup cavities are always wider than the width of a single bit, but still only 0.75 to 1.5 inches wide, so you have to be extremely careful and climb cutting in that circumstance is asking for it. The bit is never captured entirely by the wood other than at the very first instance of the cut as you're beginning to hog out. If you try to climb cut as you begin to hog out, it'll all go horribly wrong in a second. What you're suggesting (correctly) is that if you're routing a bit-width channel (e.g. a mortise), you always must cut from left to right as you hold the router with the guide fence on your side of the piece (unless you're using a circle jig). Cutting a pickup cavity is different; you have to be extra careful as the shoulder of the cavity will often be visible in the finished piece. You have to finish the edge with a regular (not 'climb') cut. Better still, (although I generally don't use them), come up to the line with a downward spiral bit through a collar to preserve your edge - you have to size your template according to whether you chose to use collars or bearing guided bits. The spiral bit will give you the best chance of not chipping the edge if your bits aren't perfectly sharp. There is no margin for error at all. Honduran or Cuban mahogany splinters easily here, if you're not careful (these are the optimal species for mahogany guitar bodies and six or eight quarter straight grained Honduran is horrible expensive). 

Cutting the outer edge of a guitar body is much more complex than cleaning the edge of a straight or curved edge table top - you're obviously aware that the edge contours of a guitar body are complex, and cut across the grain at wildly differing angles. To achieve a precise cut all the way around actually requires a mix of climb and regular cuts depending on the grain direction at any given point on the edge of the body. You just have to consider how the bit rotation relates to the grain direction. 

Anyway, the key point with cutting cavities with a router is to use templates and to cut small amounts at a time. The Forstner bit approach is acceptable if you don't have a plunge router, but then, so is a firmer chisel...life's too short - why wouldn't you use the router???

Apologies to the OP if all the above responses have gone a bit off message.

E


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## Mike Wingate (Apr 26, 2009)

I have made plenty of guitar cavity templates. I now design them using CAD and stick them to mdf sheet, cut and test, then use the mdf template to cut a keeper in Lexan. I have started to glue and piece together mdf templates as a quick solution, prior to copying them in Lexan.


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## Eoin (Jun 6, 2009)

Mike,
That's exactly what I do, too. If it's a template that I'll use many times, Lexan (polycarbonate) is the way to go. As the cut will be exactly the same as the template, I spend what seems like excessive amounts of time polishing the bearing edges of the template with micro-grit paper until it's as clear and smooth as glass. I think this is time well spent, especially for one that will see a lot of use. 

You can get by with Plexiglass/Perspex/Acrylic as an alternative, which is cheaper, but it's much more brittle, scratches easily and can shatter when you're cutting it if you're not careful. If you can run to it, polycarbonate is definitely the way to go.

Jakelee, this may be obvious to you, but you need to use a bit whose radius is less than the smallest radius you're trying to cut. However, only slightly less. Try and use the largest radius bit you can get away with - the smaller you go, the more vibration you'll have. As Mike says, make practice cuts first until you're comfortable with what you're doing.


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