Jump to content

SG project - The T.N.T


Recommended Posts

Good for you! Carl is such a humble guy. He deserves far more credit than he gets, however that's never bothered him much. Carl seems disappointed in people that take credit for his work and ideas. Surprisingly, there are some VERY well-known names on that list of people....

Link to comment
Share on other sites

  • 3 months later...

Time to bring this one up to date a little, if only in terms of thought processes and plans. The next job for the body is of course the bevelling. I knew that would be a hugely important thing to get right since SGs are defined by that. The question has always been, "how to mark out the bevels?". As I understand it, their angle is constant or at least, has been over the various iterations of the SG.

Short of doing this work using a pin router or a spindle moulder. I figured that this should be an exercise in simplicity rather than manufacturing. I could do the latter, but it seems a bit daft given that I'm only making the one. Total overkill, and it isn't like I'd be learning anything new (I did this kind of work for a long time).

So, simplicity is the order of the day. A constant angle means that the distance that the top bevel markings are laid out as should simply be a ratio when transferred to the sides. If I work out the angle I want to use, I can work out that top/side (actually, "adjacent/opposite" in trig.) ratio and make myself a temporary right-angle rule in CAD. This can also be made specifically to take into account the body thickness so that I can mark out both sides at once for the symmetrical bevelling....

Link to comment
Share on other sites

My first thoughts go to identifying the deepest bevels, since we don't want the body ending up too thin/sharp at these points. These should serve as a reasonable way to figure out the angle. Applying that to the rest of the contour should produce a good result.

bevel_cad1.jpg

Link to comment
Share on other sites

The exact body thickness is 36,5mm so we can divide that up nicely. Using this reference photo of an Angus Young sig....

IMG_7696.jpg

 

....note how the approximate area identified correlates with the thinnest part of the outer edge. I'm happy to go with that. I see minor variation, however it'll be of nearly zero consequence.

Since Gibson never used a consistent approach to bevelling, I started from approximate round numbers to see which eyeballs well:

bevel_cad3.jpg

  • Like 1
Link to comment
Share on other sites

I've seen 30° quoted a couple times around the net and it certainly looks less severe than 35° and more effective than 25°. A lot of the differences can be modified in/out using the softening over the sharp edges. A slightly larger roundover makes a big visual difference.

Link to comment
Share on other sites

If you draw these things out in CAD, there's no real maths involved really. Just basic geometry.

bevel_cad4.jpg

 

....alternatively, you can work out a perpendicular distance from the top to the bottom of a bevel with a bit of trig. Assuming a distance of 1cm from the edge to the marked line on the top produces us a simple length ratio relationship from the top to the side....

SOHCAHTOA

tan (angle) = opposite/adjacent
opposite = adjacent * tan (angle)
opposite = 1 * tan (30)
= 0,577

 

So whatever the distance is from the edge to the marking on the top, multiply it by 0,577 to find the "drop" at the side. Simples.

Link to comment
Share on other sites

I have an entire box full of scrap pieces and sticks that I collect, which have been thicknessed, squared and cut straight at the ends. They come in useful for all kinds of things when you need precise yet quick jigs.

 

Chop a stick in two.

20160705_121115.jpg

 

Flip the small piece 180° so that the right-angled end is facing inwards and add a bit of glue (Titebond I in a small chilli sauce bottle I saved - very handy).

20160705_121205.jpg

 

Clamp it from the sides to keep it flat and inwards to make a good join.

20160705_121314.jpg

 

This makes me a perfect right angled ruler....I'll get back to this when its dried....

Link to comment
Share on other sites

A glue stick gets the scale pasted onto both sides....

20160705_123158.jpg

 

From hereonout, it's a case of transferring marks and "joining the dots". For the convex surfaces, this is no problem. In the waist however, the thickness of the rule means it is impossible to align it perpendicular to the outer edge. This is no huge problem since the bevel rate of change is fairly linear at this point. The outer dots line up satisfactorily. Most of the dots were placed fairly closely, however this wasn't that important. Interpolating them using a straight-edged piece of spring steel (my INCRA T-rule's scale) produces an excellent line to work towards with a rasp....

20160705_125339.jpg

Link to comment
Share on other sites

Okay, it's just far too warm today in the workshop. 25°C/53%. No thanks.

I left it at this for today. All shaped with my trusty Liogier rasp. Like I've always said about that tool, you can work right up to your lines without worrying. There are a couple of areas where I didn't get right up to the line, however that's far from being an issue of course. I'd estimate that as being about 20-25mins of work with the body chucked up in the leg vise. That worked out really nicely, however the rasp being stitched for right-handed use meant a few changes in work direction to get the most efficient cut.

20160705_143025.jpg

  • Like 2
Link to comment
Share on other sites

In some ways, I think that 30° is slightly much. If I ever repeat this project, I'd like to try something between 25-30°. It's certainly not super thin at the edges (unlike say, original 60s SGs) or making me regret going 30°, however I think slighter bevelling and softer roundovers are on my mind. Maybe a 40mm thick body would support 30° better.

Still, it's all going swimmingly. It was worthwhile spending time mulling over how to layout and implement the bevels. That rasp makes it a breeze. I need more of them.

Link to comment
Share on other sites

That bevel reminds me my last build, but I had a different angle all around the perimeter. It was the hell to get a fluid constant plane without hitting the contour limits. Also was specially hard to make a true flat bevel, so take it with calm, it looks easier than it is.

Link to comment
Share on other sites

I've actually not found it difficult. Like I mentioned, being able to work up to the lines without worrying about it blowing out or anything is useful. Khaya, Mahogany and other African "Mahoganies" tend to be cottony and soft, so aside from the end grain retaining scratches, it's easy to work with. Always a pleasure to go back to carving and shaping Mahogany. The trick is in knowing how to keep the tool moving in a way that helps to maintain straighter lines rather than rounding them out or taking it off course. I could do with a smaller half-round rasp I think. The cabinet maker's rasp is a little big for the cutaways....

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...