Official Luthiers Forum!

Howdy,

I recently made a short video tutorial that explains how I flip my electric guitar bodies over, so that I can CNC both sides.

Here's the link:



Let me know if you have any questions, or recommendations!

Thanks,

JeffKos

KOZM Guitars

Kudos, Jeff!
Very well presented!
Nelson

Very cool man. My necks & scrolls will have 4 sided machining so you've given me some food for thought.

One question though, it looks like you're eyeballing x,y zero on side one at the start of the video but then you mention the dowel pins in your table for the flip. I assume that side one is also indexed off of the pins in your table yes?

_________________
http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

Jeff, Nice job, that was a very professional video. I have a couple of questions for you. (Bear with me as I've never machined anything as large and detailed as one of your electrics.) Have you ever had problems with stability when carving the back? The reason I ask is that I would have assumed that larger mounting blocks were required to hold the body stable enough for machining - especially the amount of machining required for your bodies. If not, that certainly makes life easier and open up a new world of possibilities for jigging fixtures. Also, just out of curiosity, how long does it take to machine one of your bodies? Lastly, care to tell us about your machine and software?

Thanks again for putting together such a nice video.

Bob

Excellent. Very well thought-out too. What kind of machine is that? Looks like servo driven, correct?

Not really. I DO use pins, but this is only to get me in the ball park, so that I can use the same clamping holes (and T-nuts) on my CNC table. Once I'm in the ol' ballpark, I then make small adjustments in the block position so that the planks are running in the true X direction (I check this by traversing the spindle back and forth in X, with a shaft with a conical tip in the collet). Once I know the block is "true", then I just use the crude "x marks the spot" that I drew on the top of the block. This mark is basically at the center of the face...plus or minus.

If I didn't have any internal chambering, I could get away with quite a bit of inaccuracy with where I define zero. As it is now, I leave myself enough wall and margin for error, so that I can tolerate a little slop.

Regarding the pins though, on the very first guitar body I made, I calculated my X and Y zeros off the pins. The bummer was that my planks were all a little thicker than the theoretical 13/16", and the center of the guitar didn't line up with the center of the plank. As you can see from the photo below, the center of the neck didn't line up with the center of the mahogany spine. Oh well - live and learn. So now, I use the actual center of the block.





Hope this makes sense.
Thanks for asking .....
Jeff

Bob,
1) If you're referring to the piece flexing, I've never noticed it. That's one of the side-benefits of doing non-flat, non-orthogonal designs. If there IS a little distortion, there's nothing to guage it against.
2) Pure machining time only, including making my planks, 5 hours, plus or minus. (Don't tell anyone )
3) Machine: ShopSabre 3636, with 8" of vertical clearance. CAM software: VisualMill. CAD software: Pro/E and Solidworks.

Thanks for asking!
Jeff

It's a ShopSabre 3636. It uses steppers in all 3 directions.

After I thought about it a bit, I got what you're doing even before you posted but I didn't think about the centering thing. I'm of course assuming you used the machine to drill the holes.

As to the pins for side one, it seems to me that at minimum, the pins should get you lined up parallel to your axis and then you can eyeball the center point.

I've been pondering my indexing scheme for a few weeks now and will be posting on it shortly to get feedback before I start making permanent holes in my Al table! Stay tuned....

_________________
http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

Jeff,

Just wanted to post a special thanks to you for sharing this technique. This post and video is what got me thinking about how to do my 4 sided necks and I think without it, I would have gone down a different path that would have been even more difficult.

thanks man!

_________________
http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

Thanks for the video.

I'm awaiting delivery on my machine for my high school guitar building class (which I've been teaching for 12 years). As we step into the CNC world, I'm reading and watching everything I can on CNC because I not only have to learn the programming etc.... i have to teach high school kids to do it as well.

we won't be doing such elaborate carving (well, I might:-) but thinking about jigging up for our guitars and necks (as well as using it for my acoustic guitar building class) it's nice to be able to check out well thought out and presented videos on the subject.

Karl Hoyt

Watch all the Taylor and PRS factory videos, and steal their tooling and fixturing ideas

Kevin Ryan told me when I got started that you should start with the Taylor way and try to figure out a better way if you can.

_________________
Bob Garrish
Saint Lutherie CNC : http://www.saintlutherie.com