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jer7440

My Cnc Body Jig

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Hey guys, I'm seeing more and more talk about cnc machines around here so I thought I would share the latest jig I came up with for cutting guitar bodies in my cnc.

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.

template

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.

bandsawed blank w/ control cavity machined

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.

pickup routes

neck pocket and starting to carve

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.

P1010042.jpg

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

sawing off tabs

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

whats left

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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Thanks for the pics Jon. Do you have any idea how they do the back of the neck? I gets a little trickier with an angled head stock.

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I can't seem to locate any pictures. I'm guessing they just adjust the work piece to the bolt holes in the CNC table. For the neck profile they just flip the neck over, bolt it down in the same position it was in, then CNC the profile out.

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