TechArt

Doh! forgot about epoxy....Good comments fryovanni. Epoxy is also good stuff for gluing oily woods like rosewood. Just a note; CA is not a strong gap filling glue(as a joining glue). Epoxy would be a good choice if you have gap to fill(in most situations). It is cool for spot filling(surface), and in situations where you have material that are very smooth(non porous) where Titebond will not work well. It is able to wick into fine cracks well. I would never use it to say set a neck as I have found it has limited strength in wood to wood joining applications.

Here's a few things I've picked up: Gorilla Glue - this is a polyurethane glue. The main feature of this of interest to guitar builders is that you can sand it and it won't build up on the sandpaper like traditional aliphatic glues will (see below). It's a pain in the butt to deal with gorilla glue and is generally not worth the time. Aliphatic glues - These include elmers wood glues and the tite bonds. When used properly, both brands have acceptable strengths. Elmers is generally not water resistant to any great degree. If I remember right, the main difference between the Titebond 1, 2, and 3, are in their environmental resistances. There are different ratings for resistance...Type 1, Type 2, etc....they basically indicate how permanent the bond is. Glues need to pass a series of tests in order to attain these classifications. The tests usually consist of boiling, heating, etc. and seeing if the joints delaminate. Titebond 2 has a type 2 water resistance. Titebond 3 has a type 3 (which means it is more resistant to delamination) but I believe that it also has slightly lower initial strength. Titebonds also have the added advantage of being RF ready (google "Radio Frequency Glue" for more info) CA (aka super glue) - these come in a few different viscosities of interest to the guitar builder. "Gap filling" varieties are good for inlay & other applications where you might want to fill a gap. The thinner varieties result in less glue lines. CA is good stuff, but has limited application to guitar building because of it's short open time. Works good for flooding inlays...but most other tasks are generally left to aliphatics. Good glue joints are dependent on flat surfaces, adequate pressure, set times and cure times. As for the concerns about tone, there are many many things that matter much more to tone than your choice of glue. Choose the glue that allows you to perfect these things and that will affect your tone much more than the .001" layer of glue!

Assuming that your brass inlay is made from fairly thin stock, it sounds like letting the dremel ride on the rounded fingerboard surface might be the way to go. How thick is the brass stock that the inlay is cut from? If you are interested in having the fingerboard CNC cut, let me know; I can do a cavity that follows the radius of the fingerboard without too much trouble. Trev

Here's the latest bit of work off my CNC - it's a brook trout/fly design done with recon stone in an ebony fingerboard. The recon stone is a bit more crumbly than I would prefer...but inlaying something that is 1/8" thick makes other things easier. I designed everything using hand sketches and then drew it up using Rhino. There are 16 parts in total.. Here's the whole fingerboard.. ..a closer view of the brookie ..and a closer view of the fly - Trev

If anyone is interested in having any boards radiused/slotted/cut for inlay, please let me know. I've got a CNC & would be happy to work something out. Thanks, Trev

I also enjoy doing some things by hand. I guess the main reason that I got into it for guitar making is that I do CAD & CAM all day long at work...so for me, they are better tools. I don't think there is any "handcraft" per se in CNC work. It's more "design craft" i.e., the art is in the 3D CAD work.

'Best' in this case only means 'most cost effective in a mass production setting'. And frankly, taking Taylor as an example, CNC is not the best way to go about it. 'Simple' carving setups (which are not CNC, they're single function, mechanical devices. Load up necks, machine moves the only way it can; no copy carving, which is how gibson did/does its tops) are much faster. Most of us aren't in this to mass produce, and since I've yet to make two necks that are identical, and don't feel like spending many, many hours fine-tuning and proofing neck carve code (ie, time in which I could likely easily carve 100 necks), it seems like a massive waste of energy unless you're mass producing. I know of a few smaller builders who use CNC for a lot of things, including necks, but most use it to get a 'rough', basic neck shape, and then further refine it by hand to fine-tune the profile to the customer's wishes. CNC is then just another way to get rid of the bulk of the shaping process. I believe Taylor uses the rotoshaper you are talking about as a preliminary neck roughing step (I'm guessing you saw this on the factory friday video?). If you check out episode 13 of Factory Fridays you'll see that the heel & final carve is done using CNC. CNC can definitely be an effective tool for quick turnaround as well as mass production...it all depends on how good you are with CAD/CAM.

Used to its fullest potential, CNC is one of the best ways to carve a neck. I believe The large manufacturers (Taylor, Martin, Gibson, Fender, PRS, and others) use one or both of the following two methods: CNC or copy carvers (i.e. large duplicarvers). On a run of the mill Fadal (a CNC used by many guitar makers) you can carve a neck in under 5 minutes. Accuracy will be within about .002" of what the machine code says that it should be. The copy carvers used by some companies such as Fender are also very effective tools, albeit less flexible (Fender uses a german made copy carver...zehnheiser? or something like that). They typically carve a large number of necks all at once. Of course with CNC & copy carving, your end result is only as good as your code. If it's great code, you'll get great parts...if it's not...it's the old crap in, crap out....!

I've heard that Guild did something similar but I have never played one of them. I'd like to see what shape they made the body. Also, you have to admit that it's cooler to have a solid piece of carved wood than something that's been thru a curved plywood press....!

I got this idea to do a carved back for the acoustic I'm working on...and I did the CNC work today. I'm really happy with the outcome, this back shape is really ergonomic - way more comfortable than the average 15' radius...! The wood is black walnut. This is carved out similar to the way you'd do an archtop - it is carved on the back as well as the front. It is about 1/4" thick at the peak and about 3/8" thick at the bottom of the carve. The bottom is milled flat so that I can glue it right to the kerfing/end blocks. As with the bridge I made the other day, I did all design work using Rhino.. I am going to assemble this one without bracing...I'm very interested to see what kind of sound I get out of this in the end. Here's a side view (sorry about the poor lighting) Here's a skew view of the back right off the CNC Here's a frontal view of the back right off the CNC Here's the frontal view sanded (it didn't take too long to knock the tool lines off) Fun stuff...I have a few ideas regarding inlay for this one but I haven't decided which design to go with. Let me know what you think of a flat top, carved back acoustic! Trev

I have something special in mind for the back of this acoustic. I have the box built right now...but I'm going to tear it down a little in order to get something better. I don't want to say anymore right now...but I'll post pics when I get it together. It should be killer....it's all I could think about today at work! Jer - I use a similar machine & software at work - we run Fadal's with SolidWorks, Rhino, and MasterCAM. I've never done much surfacing work with MasterCAM..but I can say that Rhino and Solidworks are both capable packages. Your LP surface looks cool - well done!! Surfacing is no easy task...!

The stepover for the carve is .050 and I carved it with a 3/4" ball mill. I chose the toolpath I did because with wood it is easier and better to cut with the grain than to quarter across it or go against it. The peak heights are so small that they will be easy to sand out regardless of the toolpath orientation. I definitely don't want to see toolpath lines as part of the finished part! It may look like a poorly programmed part to those with metalworking CNC experience...for those of us in woodworking, this is what you shoot for. You can use a smaller stepover and eliminate those lines...but it's a part that will need to be sanded in the end and you would just end up wasting machine time using such a small step. As for tolerances on wood - with woodworking I've found that you really only need to hold a few thousandths. The parts may measure more consistently right off the machine, but give it a day of fluctuating humidity & temperature and they'll be off by that much anyway! Now something like a neck pocket obviously requires a great fit..and this is best done by hand fitting it once you are ready to glue the neck in..

Cool - what type of machine do you have? What do you use for CAD/CAM?

I've got a K2 3925G with 8" Z and servo motors...I'm running Mach III as the controller & I'm using Rhino CAD & Rhino CAM for surfacing, drawing, & CAM stuff.

I just completed my first part on my new CNC machine..an ebony bridge of my own design for an OM that I am building: The box is sitka spruce, with black walnut back & sides and ebony binding. I was doing everything by hand on the box - including planing...but now that I have the CNC I'll do the neck carving & inlaying with that! So far I'm very happy with the machine...looking forward to seeing how this can help me build a better guitar!