Official Luthiers Forum!

Hey guys, I came up with a better way for me to cnc my electric bodies so I thought I would post it here.

I had been using double stick tape to stick my body and neck blanks down. This works out ok, but I had one neck blank tear loose and it destroyed itself and I had another body blank move a little...so it was time to come up with something more positive.

Another thing I was taking into consideration was the fact that my cnc machine is actually a metal cutting machine. This means 2 things for me: 1.) the machine is always a mess. 2.) there are 2 vises mounted to the machine at all times. All this means its a giant pain to get the machine ready to cut guitar stuff if I don't use the vises for my work holding ( at least 1 hour of cleaning before I can even start to set things up).

So my jig started with a 2' long piece of 1 1/2" X 4" steel. I drilled and tapped 2, 1/2"-13 holes on the center line of this piece of steel. Next my partner in crime, PRSguy, hooked me up with a chunk of plywood. The plywood is about 2'x2' and is a double thickness of 3/4" glued together for a 1 1/2" thickness. I transferred the 2 tapped holes from the steel onto the plywood centerline.

The 3rd part of my jig is a template that I use to prep my body blank for machining. Here is a picture of this template attached to a body blank.



As you can see the template has a tab at each end of the guitar and each tab has a 1/2" hole in it that corresponds to the 2 holes in the rest of the jig. I attach the template to my body blank with a couple of screws then I use the holes in the template to transfer the holes to my body blank. Then I trace around the template. Then I remove the template and cut out the body on the bandsaw leaving about 1/8" outside of the traced line. The blank is now ready to go to the mill

The steel part of the jig gets clamped in the 2 vices on the mill. Next is the 2'x2' piece of plywood...this acts like a table to fully support the body blank. Then we add the body blank. The steel is held tight in the vice and the plywood and the blank are attached to steel with 2, 1/2" bolts. I start out the guitar face down and from here I machine the control cavity.



Since the bolts are on the center line of the guitar all I have to do is unbolt the blank, flip it over and I'm ready to start cutting the other side. Here are a couple of pics of machining the top side.

http://i202.photobucket.com/albums/aa201/jer7440/P1010039.jpg
http://i202.photobucket.com/albums/aa201/jer7440/P1010040.jpg

Once the carving is complete it is time to finish the outside boundary of the guitar. The entire outside contour of the guitar is machined...even cutting through the mounting tabs. We finished almost the whole outside contour leaving only 1/8" at the bottom to hold the guitar to the mounting tabs.



At this point it was back to the bandsaw to trim off the mounting tabs.

http://i202.photobucket.com/albums/aa201/jer7440/P1010043.jpg

Here is a close up of whats left after the tabs are sawed off.

http://i202.photobucket.com/albums/aa201/jer7440/P1010045.jpg

A quick trip to the router table and the flush trim bit and everything is clean and ready for finish sanding. Anyway, this is what I came up with and it really worked out great. I was much safer than double stick tape...probably more accurate too. Next up: a neck jig that uses a similar type setup.

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Jeremy Vonk

That is very good.

That is very similar to the method I use, but I just cut the 1/2 inch holes directly on my guitar blank (usually square piece of wood), and then line-up the machine (index it) to one of those points (as my 0,0 point). I do not bother to cut the blank first on a band saw, since I create contour paths to do that at the CNC machine.

As you probably know, you can also create a contour path to cut out "most" of the body, leaving just about 2 inches or so to the left and right of the tabs.

Do you know that a program like Mastercam will actually let you machine tabs? So basically, you can tell the program that you want tabs (specify how many) and how thick you want them. It will then place these tabs around the contour. Think of it like cutting out a plastic part from one of those model cars/airplanes (as a means of me explaining the feature). This way, the body still stays secure, and you do not have much cutting to do after wards at the bandsaw/router table.

Great job machining the guitar! Looks awesome!

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-CyborgCNC
http://www.cncguitar.com
https://www.facebook.com/CncGuitar

I actually use Mastercam Mill level 3. I think the tab feature is part of Mastercam router. I bandsaw the blank first to leave less material just like you would if you are using a hand held router. With the limited RPMs in my mill I find that I get a better surface finish that way.

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Jeremy Vonk

looks good jeremy!

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http://www.PeakeGuitars.com

Thanks!

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Jeremy Vonk

Two passes, problem solved!

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

What machine are you using? What size bit and how many RPMs? Thanks.

The machine is a Haas VF-3. I used a 1/2" carbide cutter, 2 flute for most of the pockets and the outside contour and 1/2" carbide ball nose for the carve. I also used 3/8 endmill for the ears on the pickup routes. I run everything at 7500 rpm because thats all the machine has.

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Jeremy Vonk

Sweet...do you have that just for guitars or are you a machinist. I'm a machinist too, so I've got a full metal and wood shop. I don't have a metal CNC just a wood cnc but I'm thinking about getting one. Around where I live you can find decent VMC for $5000 and up, but I'm not sure I have the room.

I work in my families tool and die business...so the machine comes with the job. I do all the cnc and EDM work.

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Jeremy Vonk

Cool, not only is having the machines handy you have the knowledge of the intricacies of cutter configurations. How do you like the Haas?

I love the haas! The machine is about 10 yrs old, but it is as accurate as ever. I just need about twice as much in the RPM area...that would make inlays much easier.

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Jeremy Vonk

Cutting inlay with spindle RPM is for suckers

On a mill, the standard is to use air turbines: http://airturbinetools.com/hss.html

Helluva lot cheaper than getting a 15K spindle, though I'm eyeing up those new 30K spindles Haas is offering...

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Hey Bob,

What does an air turbine like that run? The kicker for me is I don't really need it for work...so it would have to be a personal expense. I can't really afford an expensive air turbine for my hobby right now.

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Jeremy Vonk

I forget what I paid for them, I get a bit of a discount through my channels. They're in the $500 range, IIRC, for the one you'd want for inlay work (the aluminum model, 65K as the bearings in the 90K ones don't last nearly as long). I do a good deal of micro-machining, so they come in useful in non-lutherie jobs as well...

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

You could just do it the easy way and crazy glue a router to the Haas, I'm sure it'll work fine.

Actually, building a router mount would be pretty easy. But most routers have too much run out for tiny inlay bits.

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Jeremy Vonk

You'd be surprised at how close the solutions certain guitar companies have come up with are to that...

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Nice way of solving your problem.

I am extremely interested in seeing how you hold down the neck while carving. I have found that the double sided tape can turn loose at unexpected moments and ruin a blank every once in a while, so this is most definitely something I am interested in solving.

Thanks for sharing!

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Reguards,

Ken H

I use vacuum, as you know, but I've used DST in the past for one-offs and I often use it in other production work. It's as reliable as vacuum is, but there are a couple things that need to be done. First is to find a high-quality brand of DST; the best stuff I've found has a clear plastic backing and is sold at a flooring supplier nearby here. The thickness is consistent and the hold is very good. The other thing is that DST is pressure sensitive, so you need to make sure the both surfaces being held together mate perfectly and that they're clean...and then beat the Hell out of the blank to seat it on the tape. If the surfaces are clean, they fit well, and you really put some pressure on the blank (not the kind you can exert with your hands!) then the problem will turn into getting them apart rather than keeping them together!

If you still want a 'manual hold-down' solution then just screw the blank to another, longer board, through the fretboard side and use 'real' clamps to hold down the 'fixture board'. It's a bit slower, but there's the nice guarantee you have with a real fastener.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Hey Ken,

I have the neck fixture in my head I just haven't had a chance to make it yet. I usually start with my neck blank scarfed and the truss rod slot cut. I locate everything off of the TR slot and the edge created by the headstock and the surface the fretboard will glue to. To start I clamp the HS in my vice, I locate off that edge and the TR slot...the HS is perpendicular to the spindle. I drill out the tuner holes with 1/4" bit. Then I have an aluminum fixture the has 2 of the tuner holes spotted in it and tapped for a 1/4-20 bolt. I bolt the HS down and the body size screw holes locate the HS. This fixture allows me to cut the outside contour of my HS.

From here I have another steel fixture that has a "key" cut into it that would fit into the TR slot. I used to put DS tape on either side of the key and that is how I would hold the neck for carving. I hated it...your heart would be in your throat the whole time worrying that the tape would let go. My new plan is to leave a tab on the heel of the neck and a tab or two on the headstock that I can bolt to. Just like I did with the guitar body. When I contour the outside of the neck I will cut through most of the tab and trim off the last little bit with my router.

My friend that works with me on some of this said he has a couple of neck blanks ready to go....so hopefully I will have some pics to post here before too long.

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Jeremy Vonk