[InMesh]

Looking great I like your methods the bridge came out nice .I was thinking that I have so many sizes I would like to make on a number of Instruments ,maybe I could have a work offset for a one size work board . Say a 2 x 2 foot and work all the different sizes from that or something like it .

[Kosh]

so last night I decided to make a neck caul to help in clamping the fretboard onto the neck. I usually put it in the go-bar deck, but I need
a little pressure this to make sure it lays flat (long story, don't ask).

So I got onto F360 and modeled a caul with a concave surface perfectly matched to the neck model (just did a solid subtraction on the two parts),
and then CNC'd it last night. Came out with a perfect fit, and now I can use regular woodworking F-clamps on it.

Attachment 356112

Attachment 356114

Attachment 356116

Attachment 356118

[A_Camera]

Hi,

Do you mind me asking what sort of plastic you are using for the vacuum fixtures? Trying to guess, but it is difficult. The one in this post and others looks like something else than POM but I cant guess what it is. Like I said, it is a very interesting thread, I have never seen guitar making in such detail and never had an idea about how much work it is behind the I have in my house... even if you have not made that one.

[Kosh]

Hi,

Do you mind me asking what sort of plastic you are using for the vacuum fixtures? Trying to guess, but it is difficult. The one in this post and others looks like something else than POM but I cant guess what it is. Like I said, it is a very interesting thread, I have never seen guitar making in such detail and never had an idea about how much work it is behind the I have in my house... even if you have not made that one.

They are vhmw but as I mentioned a couple posts ago I'll be using corian now to avoid warping.

[A_Camera]

They are vhmw but as I mentioned a couple posts ago I'll be using corian now to avoid warping.

Thanks for the information.

[Kosh]

Hi,

Do you mind me asking what sort of plastic you are using for the vacuum fixtures? Trying to guess, but it is difficult. The one in this post and others looks like something else than POM but I cant guess what it is. Like I said, it is a very interesting thread, I have never seen guitar making in such detail and never had an idea about how much work it is behind the I have in my house... even if you have not made that one.

@a-camera

Hadn't thought about Pom (delrin). Have you used it? Is it stable ?(flat for large pieces)?

[A_Camera]

@a-camera

Hadn't thought about Pom (delrin). Have you used it? Is it stable ?(flat for large pieces)?

Yes, I use that for many things, but never actually made anything large so I don't know how flat it remains, but as far as I know the material is very stable. It is pretty heavy, solid and easy to machine. You can thread it and work with it as you would with aluminium but can mill it faster. No cooling necessary, very nice to work with, I like it. The material is very strong and temperature and humidity stable. If it is suitable as vacuum fixture, I don't know. Perhaps not because it is a "low friction material, when milled everything easily slides off, which is why it is suitable for backlash-free nut as well. No lubrication necessary for good, easy and even rotation. I made custom nuts for my first CNC using POM, it worked very well, almost as a ball nut.

[Kosh]

Ok, I didn't get good pictures, but today I installed my tail grafts. I say plural because due to the floating neck design I use, I have to graft both ends of the body.

So I have this tail graft jig from luthiertools.com (themselves a good source of CNC produced luthier jigs). It takes a template which can be used to route the tail graft and also route the inlay itself.

But what Ive done instead is make a custom template, and also modeled the inlay in CAD. So I CNC'd the template, then CNC'd the inlay, then used the template in the jig to route the pocket.

Perfect fit as you can see.

[A_Camera]

@a-camera

Hadn't thought about Pom (delrin). Have you used it? Is it stable ?(flat for large pieces)?

Hi,
Here is a second answer, since I just came in after doing some cutting up of POM. I have a large sheet (22 x 300 x 500 mm) and remembered your question about flatness and I measured it... Well, the sheet I have is not that flat, it is bent about 1.5mm across the longer side but flat on the short side, so that sheet would not be good for a fixture unless it is faced. I also have another sheet, which is only 5mm thick and that is even worse. Note that I bought these sheets fairly cheap, and I think I was not given the most accurate information about the quality, but for my needs this is not a problem. Never the less, maybe next time I will return to my considerably more expensive Swedish supplier who sold me much better quality, even if it was also for a much higher price. The cheaper POM behaves differently even during the cutting and milling, compared to the more expensive one. They are probably manufactured differently. I am far from expert in plastics, but my guess is that one is cast under pressure (the more expensive one) and the other is extruded. Anyway, since I am making mostly very small things (15 x 20 x 22mm) so for me this is not an issue at all, but for making a fixture it definitely needs facing.

Corian is nothing I have ever heard about. Googled and it seems some sort of new material. I don't know how it is when machined, seen that they make kitchen benches and similar things out of it. If I ever make a vacuum fixture I will definitely check it out, though I have no idea where to buy in reasonable size... but thanks for the material name, will definitely look into it when needed.

[Kosh]

Corian is nothing I have ever heard about. G

What country do you live in????

Corian (DuPont IIRC) came out in the 80s as the "new" (poor mans) granite.

It's cool because you work with carbide WW tools, and can get the stone look but cool things like integrated drain boards etc. another selling point was ability to sand out scratches. But at first only certified installers could get it since they did want amateur installations (glue ups) to give it a bad name.

Now you can get it along with scrap sizes at solidsurface.com

[A_Camera]

What country do you live in????

Corian (DuPont IIRC) came out in the 80s as the "new" (poor mans) granite.

It's cool because you work with carbide WW tools, and can get the stone look but cool things like integrated drain boards etc. another selling point was ability to sand out scratches. But at first only certified installers could get it since they did want amateur installations (glue ups) to give it a bad name.

Now you can get it along with scrap sizes at solidsurface.com

OK, it is not new but new to me. Anyway, good to know about it.

[InMesh]

I have been using the bone color for ukulele nuts and saddles works easy and polishes well and 300% cheaper than other products I have used Delrin for 30 odd years i have machined almost everything out of it so versatile .

[Kosh]

I have been using the bone color for ukulele nuts and saddles works easy and polishes well and 300% cheaper than other products I have used Delrin for 30 odd years i have machined almost everything out of it so versatile .

Good to know, was about to start doing that too. I want to CNC some fancy nut shapes, but difficult to get bone in sizes you could clamp in a fixture.

I have used corian nut and saddles (purchased) in last two and they seem fine.

[InMesh]

I did try some resin with very fine glass blasting beads in but although ok not the same as Tusk I have in the past used brass ,nickle silver ,and wood .I believe if you can work it and it is hard and also solid though out the transfer of sound/vibration will be the same as the smoke and mirror stuff.

[louieatienza]

Kosh great work! I tend to get a little lazy with fixturing and end up doing a lot by hand. Still have my router in a pile of pieces... But I do have my mini-mill up and running again!

[Kosh]

Time to catch up the posts with my progress. I got into a flurry of building and finishing, had to get the guitar in lacquer so it had time to cure. I have to start
level sanding it tomorrow and it must be ready and setup by Sunday when I drop it off with my in-laws to take up to Montanna (we're flying there and I don't trust the TSA to "inspect" this custom instrument!

First up, I decide to try some quick and dirty profiling of the lower back braces, without a jig, just to save myself some time. In a future post I'll show my ideas for brace profiling jigs (after I've done them!). But for now, this saved me a bit of time:

So I just wrote a simple program that let me profile them from the top, with simple clamping to the spoil board.

Attachment 360724

Roughing:

Attachment 360726

Small stepovers in a parrallel operation:

Attachment 360728

And then all I had to do was hand sand it on the radius dish.

Attachment 360730

[Kosh]

And time to make the rosette. I didn't have a piece big enough to make a full rosette in one pass (actually, I *did*, but that's another long story....).

So I decided to make a segmented rosette, and fit them together. Perfect for the CNC! I just segmented the rosette model in the computer, then located them in model space
over the top of a piece of leftover curly walnut from a previous guitar:

Attachment 360732

Attachment 360734

After the pockets were cut, I had it trace the contours of the 4 segments

Attachment 360736

Then I cut a test pocket in some scrap plywood to make sure I have the fit. I just adjust the "stock to leave" option for this pocket until it fits well. For this one, I'm actually
just fitting it tight, then running another program to cut the purfling slots, but I have also done it all in one with a perfect offset for the purfling to go in at the same time.

Attachment 360738

[Kosh]

And time to put out money where our mouth is, inlay the rosette and but the outline of the top. I also use this to cut an inlay pocket for the purling line that will define the beveled armrest. This way I have material (the soundboard) in place to file the 45 degree bevel the is made for the armrest veneer

Attachment 360740

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[Kosh]

In Cumpiano's book, he has you put a couple of VERY small (3/8" square) diamond patch on the soundboard between the lower tone braces. This is always a pain to shape them into pyramids without slipping and cutting the soundboard. So I thought I'd see if I could CNC them to shape before gluing on. worked pretty good.

But, after consulting with my mentor (Alan Dunwell of dunwellguitar.com), I think they aren't really necessary with modern WW glues. if I do use them, I may switch to some CNC'd carbon fiber patches.

[Kosh]

A few misc pictures of things fitting together. I CNC'd a bridge locator jig. I provides me with a drill guide for the two outermost bridge pins, , and those will be used
to locate the bridge in place when I glue it on with a vacuum jig.

Attachment 360756