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SG project - The T.N.T


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Agreed. There are a number of pressures surrounding this build, some of which I created and those that simply are. As @ScottR pointed out, SGs have a significant weakness which the long tenon will easily solve. A neck pickup might just blow that, hence why this headed down the Jr route in the first place. The fibreboard is on-hand right now, and these things accumulate into relaxing the financial constraints.

Obviously, I like to use as much work as possible as the basis for longer-form educational articles. Certainly, the pantograph for making a pearl headstock inlay from a laser-cut template is a big one here. It'll be another under the "Lumi" (snow) name, however I might leverage the logo to be a little Gibson-esque. I'm not a fanboy of the marque, however there are certain stylistic elements which we want to maintain here. This project will definitely play no faster than the pantograph. As soon as the headplate comes into the workflow, everything will have to hang fire.

Sometimes I am a little reticent in letting my internal decision-making out into the wild. I contradict myself a lot, which can be interpreted incorrectly by some. Mostly it's because I rarely have a single defined vision from the outset....everything develops of itself. Unfortunately, I have to do what I can with the pressures I don't have a choice about and hope they don't affect the ones I do!

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12 hours ago, verhoevenc said:

I can't take the credit, first person I ever saw do the radial purfling was my friend Todd at Greenridge guitars. I'm even talking years before you started to see it pop up in custom builds and even mini-factories. He's one creative, and geniusly-inclined, dude!

Chris

 

Ah, I meant the credit for inspiring me to try it rather than you having invented it. I do think you went some way as to popularising it though.

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I did a little measuring of what we have on the table right now, and it seems that there will be more than a fret of adjustment; more like three. I can either leave it as is with nineteen frets that place the end of the fingerboard more or less in line with the cutaways, or I can consider shortening the scale length as a partial compensation. It places the bridge further back than I had originally expected.

I also need to check as to whether the neck mating end of the mortice is square. I'll shave about half a mm off there to make sure.

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11 hours ago, Prostheta said:

Sometimes I am a little reticent in letting my internal decision-making out into the wild. I contradict myself a lot, which can be interpreted incorrectly by some. Mostly it's because I rarely have a single defined vision from the outset....everything develops of itself. 

I think this approach is what triggers inspired creativity.

Some years ago I did a fair bit of writing (never huge amounts published but I did get start to get a much better class of rejection) and not only practised writing but read widely about the process.  The truly inspirational writers maybe had a broad plan, but often let the characters take over events.  WHAM! Out of nowhere a character does something that no one - especially the writer - expected!  The kind of event that could never be planned, but is so, so RIGHT.  It even happened to me once or twice (which is why I can, with only half a tongue in cheek, say that I wrote a cameo scene that James Caan played in a 1980's film).

I really believe that the most creative design features come from this 'flexible' mental approach - allowing the subconscious to now and again pop in a suggestion of 'what if I put the pickup there......????  Because....because....wow...well.....heck...actually, why not????'   And usually it becomes the defining 'wow' factor within a great guitar build. 

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I can't say that all of the compromises aren't bothering me, you know? I mean, Nina is more used to playing acoustic than electric so from a rhythm instrument standpoint, the slightly shorter fingerboard and body join location could be construed as no big deal. I guess they aren't a big deal really. It bothers me mostly because I don't like having to "fix things in the mix". Measurements are best being worked out at the design stage, which is my personal forté.

If I happened to have some more Khaya/Sapele (I think it's Khaya....) on hand, I'd just make a new neck. That is the one thing that is off-spec here, and happens to be driving all of the other design decisions other than perhaps neck pickup.

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Okay, so I did some basic rejigging of the plan in CAD by incorporating specific component dimensions and altering the underlying design from my original EB-0 plan to suit.

The neck is further into the body than an actual SG Jr. by about one fret. This alters the way the pickguard meets it; either it meets at both corners and messes up the line corresponding to the lower cutaway or (like here) it meets below the fingerboard and look a bit weird. I'm playing around with the slanted diamonds idea that I mentioned a while back to you, @Andyjr1515; simple slotted diamonds angle to make one edge perpendicular to the frets. Simply and attractive.

The placement of the battery box and preamp unit is also in place as is the side-mounted DPDT switched jack socket. It'll probably end up in a milled Tele cup if the size fits.

The bevels have been drawn in, however I'll discuss how they work in a separate post.

SG.thumb.jpg.ef8f4944ffdf07f8b4c9e898479

 

 

Normally I would make a permanent template for the bevelling and I still can. I didn't think there would be much advantage in it, so I simply printed the bevel plan 1:1 onto two sheets of A4. These were drawn on both sides since the bevelling will be the same in mirror image.

IMG_7657.thumb.JPG.0e6b2df0b1adf5cabd016

IMG_7658.thumb.JPG.13c1d361b6104dd5e491c

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Okay. Let's discuss a little on the bevelling of an SG, or in fact any instrument with constant-angle bevels.

Even though the SG has rarely been consistent in terms of bevelling, modern SGs are primarily because of Gibson's method of manufacture having become very consistent. The angle at which the bevels fall off the body is one angle across their length. I may be wrong on some level here, however for the most part this holds true.

The first two solutions to applying bevelling of this sort that occur to me are both template guided; a spindle moulder or a pin router. One guides directly off the body as a template and the other a sled or template attached to the body itself.

A spindle moulder generally has a far larger-diameter cutter and bearing set than a router, so this would not work within cutaways or very sharp waists. They can however support larger cutters of varying profiles and angles. The idea is to cut the body blank large from the outset, using an outline (red) which the spindle moulder can follow. It is also possible to mount a template. This outline is extended outwards from the bevels themselves and allows the cutter to "miss" the body where no bevelling is required, and "dip into it" where they are. The light blue path shows the areas of material removal in comparison to the final body outline in green.

bevel_path.jpg.8dd5efba224885832d3bab5b0

 

I've used this exact method before, however it is wasteful. If you're even considering this approach on a spindle moulder, consider whether your ability to manage this safely is sufficient, especially since it would ideally require two passes to eliminate uphill cuts against the grain. If in fact you are able to do this kind of work this way, you should already know that spindle moulders are the enormous evil cousins of router tables, and they eat hands for lunch not fingernails.

Anyway. I thought I would share this concept simply because it's pretty interesting and a little different to how we normally look at this kind of work.

The second option is almost exactly the same, however the template that a pin router would ride off would be on the underside of a sled. This would likely involve a somewhat non-standard chamfer cutter and a fair degree of geometry compensation for the template itself thanks to the pin and cutter design. The upside is that it is less wasteful on the body blank from the outset, however pin routers are one-way only requiring uphill cuts to be made, plus a lot of complex work going into the sled and templating for cuts both sides.

A final "true" outline pass brings the body back into shape. For the purposes of a one-off instrument, these are all very labour-intensive and have their own working implications for safety and effectiveness. Certainly, if I were considering how to make a large number of SG bodies then the spindle moulder would be my choice, albeit with a pair of auxiliary sleds; one for each direction of cut to eliminate climb cutting.

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The difficulty with dialling in these bevels manually is that the guitar body's outline is not straight. This leads to all kinds of weirdness in the width of the flat around the perimeter.

IMG_7695.thumb.jpg.c19e7f1911dff155ed05c

 

There's three ways I could approach this. One would be to wing it; simply draw in the width of the flat by hand, eyeballing it to make it "look right". For the most part, this is not too difficult. It's hard enough for the eye to consider planning this aspect of the bevelling, let alone the eye to tell if it's wrong! The most important thing to maintain is the symmetry. That alone sets alarms ringing.

The second is to figure out what bevel angle we want to use and work that out as a ratio. For example, a 30° angle drops 5,77mm for every 10mm the bevel sits perpendicular from the body outline, or about 1,7:1 as a ratio. This can also be done the opposite way of course. What's more important is how the bevel looks; the mathematical part of this is only a means to developing the process. If it looks like shit, all the maths in the world won't change that! Measuring what an acceptable "remaining width" at the deepest bevel point is should provide a good idea. Taking this and plotting points around the perimeter calculated as a ratio of the bevel depth, joined up and mirrored for both sides is a lot of work, but achievable with patience.

The third can be done within my CAD software; "unfolding" the perimeter curve into a straight line to make a printable template strip that can be laid around the workpiece to show the bevelling depth at any point. This will either be a lot of work....or not....mostly it is figuring out the geometric process to manipulate the drawings.

I am undecided as to which of these three methods I'll use. I'm going to mentally balance out the time and effort required for each method vs. the results. Sometimes that extra work doesn't generate better results. Sometimes I like solving problems elegantly just for the enjoyment of it.

So there; a problem for me to sleep on. Even though it's 9:39AM and I've only been up a couple of hours. It can wait.

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That's some interesting ponderings, @Prostheta  

When I did my tribute, I did it by eye and used rasps and scrapers but, at the time, realised that trying to machine such a thing was far from straightforward:

ZImEjB6l.jpg

 

I couldn't actually work out how you would in fact do it.  I think your diagram probably nails it.  But, as you say, doing that kind of stuff with general and small-scale guitar making machinery is surely challenge!  You've got me thinking again about the angle base on my little Bosch.  Maybe there IS a use for it....because I certainly haven't found one up to now :rolleyes:

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Same here about angled bases. They only make sense if you're doing a chamfer on a straight edge and have a straight fence for the base to ride against. The only guitar application I can immediately thing of here would be the decreasing bevels on a modern flying V.

It could be construed that I overthink things, however I disagree. Having more that one answer to a problem allows you the benefit of choice. You can solve it in as complex a manner as you're capable or willing to do. Like yourself, I could easily do the bevels by hand. Sometimes doing it by hand is the only option for some.

It is more about the accuracy and process of marking up than it is about geometric perfection. I too will be going down rasp/scraper route. It's a good opportunity to teach Nina how to use a hand-struck rasp too.

SGs do have a certain sculptural grace to the flow of the curves. I went through a good many photos of historic examples in order to decide on what I felt most appropriate. Norlin-era SGs we truly awful, and some transitional examples make you wonder how Gibson even made it to the 80s, never mind the 21st century. Recent news is appropriate to mention here....

Your own SG ticks a lot of the boxes, however it might not do so for the real history wa...purists. Part of its mystique is the svelte edges. It's a really important aspect that I want to spend time nailing to the wall. Doing it right will be very apparent in the finished instrument.

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I'd do by hand, although is not as easy as it looks at first sight... you're gonna sweat. :thumb:

Nice template concept, but I'm not sure if I could get a template totally parallel by hand... by that way, the top edge of the bevel would depend a lot on the curve in the template... I think I'd trust more in my eyes while carving myself.

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I completed it didn't I? Argh. Well, that one was always meant to be the prototype rather than a finished item. There's a few things I am not 100% happy with on it such as the side markers, plus I've never put time into installing the preamp permanently. I did epoxy in some cavity cover magnets though, and it's drilled for the controls....

I tell you what though....it's LOUD acoustically. Not having a big thick bulky body totally alters the instrument in that respect, and its a prominent aspect of the amplified sound also. Proof that the intrinsic properties of the body shape do effect the sound at the extremes.

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@Prostheta, I have been thinking about this a lot lately, as I have a plan for a build that needs such beveling. And I haven't had time to sit and read everything you just wrote, as I am running out the door from work, but this idea just occurred to me. It isn't perfect, but what if you built some kind of set-angle jig that worked with a spindle sander.

Please excuse the really crude drawing, but....

spindlejig.jpg

Where the dotted line represents the guitar body. The weakness is the waist and other inset areas, but I think there might be a solution to that.

I'll think about this more on my stupidly long sit in traffic on the way home.

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1 hour ago, Prostheta said:

That approach will work, yes. You can also do a similar thing with bandsaws to cut tummy tucks. I don't have a spindle sander handy, only an oscillating belt sander....even then the diameter of the end drum and table size make it impractical.

Tables sizes can always be increased with some MDF with a hole cut out of it.

But the spindle / sander height occurred to me last night while I was thinking about this.

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