50s LP control cavity angle

[Sgt.Pepper]

Originally Posted by GooCart

Here are some photos of the '53 GT. I didn't have anything to measure the angle at home but you get the point, the marker stood on the cavity floor. It's angled in X and Y, the angle is settled by the top carve. The GT has a pretty flat top carve, therefor the angle is low.

I don't know the angle and don't even know how to start measuring it accurately, but I can tell you how it was done. Plugs that fitted in the switch cavity and the output jack cavity were used to hold the body with the top carve yet to be done. The body was angled from these two points and the cavity was routed.
What we really need is Singlecut54 to offer some help. He not only knows all about these guitars through repairing many of them, but he has a fantastic collection. Haven't seen him here for a while, so he must either be really busy or just annoyed that nobody ever takes notice of what he offers - pearls before swine?

[expo]

Originally Posted by GooCart

I've understood that the holes are drilled parallel to the table and reamed up to right size and angle.

So the first holes were maybe drilled before the topcarve?


What is with George Ms comment about longshaft pots? That was a Norlin?




I like this thread

Jo

[Greco]

Originally Posted by Sgt.Pepper

What we really need is Singlecut54 to offer some help. He not only knows all about these guitars through repairing many of them, but he has a fantastic collection. Haven't seen him here for a while, so he must either be really busy or just annoyed that nobody ever takes notice of what he offers - pearls before swine?

I heard a rumour that his health isn't that great and/or that he's concentrating on pickups and rings. Who knows? I always find his posts amazingly useful and generous though.

[Standard_59]

Originally Posted by Sgt.Pepper

What we really need is Singlecut54 to offer some help. He not only knows all about these guitars through repairing many of them, but he has a fantastic collection. Haven't seen him here for a while, so he must either be really busy or just annoyed that nobody ever takes notice of what he offers - pearls before swine?

I'd hope that is not the case, Sarg - he knows his onions.



Oh, and I love a Bacon Sandwich Inlaid with sauce.

[GooCart]

Originally Posted by nuance97

You guys really lost me with all of this inverted v business.

I really liked the way the control cavity came out on Ex-nihilo's 2nd build, and when I get around to building a Lester I intend on replicating that method. Is it dead on exactly identical to a '59? I don't know. Nor do I care. I know it was functional, and the jig looks simple to make and use so that is why I would like to know a little more about it.

alk-3, I don't know if you even have the thing any more, but if you do please take a look at my crude illistration below of the jig that you and ex used (I don't have all of this fancy cad stuff so a pencil and paper had to do), and if you would be so kind, answer a simple question.

If you took the jig, and mark a line (dotted line in the drawing) square to the straight edge of the jig then measure the angle that is created between the jig along that line and the flat surface of the guitar back what would that angle be?

Would that be 8 degrees?

I just checked in Rhino and if you give the template an angle of 13,95 degrees from the centerline and angle it up 8, 24 degrees you'll have the same result as with the 92/98 deg in the screen dump posted by Tom. That cavity bottom angle did I use on my build that's use the same 3d file as the Eastern Maple Carved Tops, I cant say that it would work with any other carve. It gave me a pretty equal hole length, it differs about I mm as worse.

[nuance97]

Originally Posted by GooCart

I just checked in Rhino and if you give the template an angle of 13,95 degrees from the centerline and angle it up 8, 24 degrees you'll have the same result as with the 92/98 deg in the screen dump posted by Tom. That cavity bottom angle did I use on my build that's use the same 3d file as the Eastern Maple Carved Tops, I cant say that it would work with any other carve. It gave me a pretty equal hole length, it differs about I mm as worse.

So I wasn't too far off. I had come up with 12 and 8 degrees, and that was totally by eyeballing the photos to come up with an educated guess! Thank you so much GooCart. You and alk-3's contributuions to this forum are immense!!

[MRJ5]

Here are a couple of pictures taken at the Custom shop. Although it is from modern times, I believe it may give some insight to the discussion. You can clearly see the hole in which the reference peg is sitting, is 90 degress to the back.

In the CNC the body (on the left) is being held at an angle. It very well could be referenced to the hole(s), seen in the other picture, creating at least one of the angles of the cavity. This may be evidence as well, the holes for the pots are drilled before the control cavity is routed.

[gtrmaker]

Originally Posted by Sgt.Pepper

I don't know the angle and don't even know how to start measuring it accurately, but I can tell you how it was done. Plugs that fitted in the switch cavity and the output jack cavity were used to hold the body with the top carve yet to be done. The body was angled from these two points and the cavity was routed.

That would make sense since the top arch was still uncarved. So, the pot & switch holes were done then the body flipped over onto an angled fixture with locating pins in the switch hole and one pot hole. Then, the angled secondary cavity route was done on the overhead pin router.

[theodoropoulos]

in my opinion it's not the angle of the pot the big problem.It can be possibly be drilled vertical to the bottom of the guitar with smaller hole and then reamed.The problem is the area around the hole in which the pot is screwed (inside the cavity).It must be routed at the same angle with the top surface at this point of drilling.
my question is this.Do all the 4 pots have the same angle?I dont own a LP so i cannot distinguish it from the photos..

[gtrmaker]

Originally Posted by MRJ5

In the CNC the body (on the left) is being held at an angle.

The body on the left does appear to be clamped into onto a compound angle fixture ready for CNC routing the secondary control cavity angle. Thanks for the photo. Now I just need a CNC....

[Metamatic]

Originally Posted by gtrmaker

The body on the left does appear to be clamped into onto a compound angle fixture ready for CNC routing the secondary control cavity angle. Thanks for the photo. Now I just need a CNC....

I am wondering what's going on to the body on the right. The angle seems to be the opposite when routing the neck pocket.

[theodoropoulos]

is there any skilled luthier to enlighten us?

[expo]

There is nothing to wonder about.

The neck pocket is routed parallel to the neck plane, the neck tenon is straight. That shows the 4,5 degrees needed for the neckangle.

The angle you see under the jig on the right side puts the bottom of the mortise / the neck plane parallel to the table.

Maybe it is needed for the CNC with such a long router bit, even if the head can move.
Same direction as a router on a template laying on the neckplane. Where do you see the opposite?

[theodoropoulos]

some skilled luthiers as EX-Nihilo do not refer the issue of angled cavity(if i am correct) and that's what i ask...How do they angle it?a photo would be very appreciated...

[Metamatic]

Originally Posted by expo

There is nothing to wonder about.

The neck pocket is routed parallel to the neck plane, the neck tenon is straight. That shows the 4,5 degrees needed for the neckangle.

The angle you see under the jig on the right side puts the bottom of the mortise / the neck plane parallel to the table.

Maybe it is needed for the CNC with such a long router bit, even if the head can move.
Same direction as a router on a template laying on the neckplane. Where do you see the opposite?

Got it.

Strange, the first view was obviously an illusion. I took for granted that the table was plane and the jig was lifted. Now I see that it's the opposite of what I was thinking. I am not good explaining it in words so here's a picture instead. Look at the skull.... what skull?

[alk-3]

Originally Posted by theodoropoulos

some skilled luthiers as EX-Nihilo do not refer the issue of angled cavity(if i am correct) and that's what i ask...How do they angle it?a photo would be very appreciated...

I'm not sure what you mean. The neck mortise is angled to accommodate the neck angle.

[alk-3]

Okay, so I got some time this morning to get some photos in the shop. This first one shows the fixture for routing the flat bottomed cavity. The little wedges are to keep the body from moving around in the jig because the top is attached at this point.



This one shows the body in the jig. This is straight forward, and by no means is a pin router required to do this job.



These next photos show the jig for routing the angled rout.






And here, with the body in the jig.







and here we have the resulting "v" caused by the first and second routs intersecting. This allows the pots to stick out the top at their appropriate angles.
It's a bit hard to see, and does very in it's placement depending on the height the router bit is set at. Just a mm or two of router height adjustment will move the "v" around in the cavity a fair bit, thus accounting for the seeming randomness of this feature's location on original bursts.



I dont have a good way to measure this angle , but Magnus and I are working on a 'mathematically correct' angle based on the resulting measurements.

I did look for the original Jig we used for Scotts guitar, but I couldn't find it.
I think if one were to try to make one of them, it's best to do it with trial and error based on your top carve. It's important that the angle match the top carve to give the proper results.
It's not hard to do, but just takes some time, and very careful planning so you don't make an irreparable error.

Hope this answers some questions.

[tulsah]

Tom,

Do the bottoms of these jigs have the patterns cut in them for the pin router to follow, or do you use another pattern along with the jig?

-tulsah

[theodoropoulos]

alk-3

do you create those angles at this scetch ?

[alk-3]

Originally Posted by tulsah

Tom,

Do the bottoms of these jigs have the patterns cut in them for the pin router to follow, or do you use another pattern along with the jig?

-tulsah

the jigs have patterns attached to the underside of them. like this:

[Fletch]

Here's the setup I used on my first replica. This one looks great from the top and very authentic, however it wasn't deep enough in the innermost pot and had to be relieved slightly with a forstner bit to get the nut on the pot.

This template was destroyed pretty much when I tried to modify it to get more angle, and then a second template was made that didn't work out so well either. The third one will be the one that will work if I ever get to it, I am going to make it hinge on the crown of the "V" that everyone is talking about and make the depth adjustable.

[alk-3]

Originally Posted by theodoropoulos

alk-3

do you create those angles at this scetch ?

That sketch was just to illustrate the idea. It is not accurate necessarily.

[The Thruth]

Originally Posted by alk-3

That sketch was just to illustrate the idea. It is not accurate necessarily.

Tom Thanx for this great details

[nuance97]

Originally Posted by alk-3

While I do really like this jig, and I am sure you get very accurate results using it I can't help but think how much more complicated it looks to build. Complicated in comparison to the one you and Ex used on his build that is.

[alk-3]

This one took less time to build actually. This one also does a much better job. You just pop the body in and the machine does the rest. With the one we used on Scotts, you have to get it lined up perfectly, which takes ages. If it's not perfect it cuts into the body outside of the cavity cover.
This jig is also used on a different machine. They're both routers, but one is hand held, and the other is a monster overarm pin router.

[tulsah]

Originally Posted by nuance97

While I do really like this jig, and I am sure you get very accurate results using it I can't help but think how much more complicated it looks to build. Complicated in comparison to the one you and Ex used on his build that is.

These jigs look far more geared to a production environment as opposed to the previously used jig. Given the multiples that can be produced from this new jig and the apparent simplicity of going from body to body, I can understand why a jig like this would be required - even given its obvious complexity. At least that's the way I see it.

-tulsah

[alk-3]

Originally Posted by tulsah

These jigs look far more geared to a production environment as opposed to the previously used jig. Given the multiples that can be produced from this new jig and the apparent simplicity of going from body to body, I can understand why a jig like this would be required - even given its obvious complexity. At least that's the way I see it.

-tulsah

Absolutly. The first jig is certainly adequate for doing several guitars. I use the larger jig because I have the tool to use it with, and I use the tool for nearly all the routing I do in the shop.

[Texas07R8]

wow, what a head full of info on this thread. I've wondered about this but never pressed the questions as I'm not yet reaching critical mass here... I'm still fiddling with building a few Juniors before stepping up to a carved top Std.

Kudos to all who have shared there methods to the madness, we do appreciate your sharing your tricks, tips and ideas.

So, let me step off the dock here and ask perhaps an obvious question that seems to be either ignored as it's irrelevant to the topic or perhaps it's been overlooked or simply a non issue.

To me, the whole purpose of angling the control cavity bores are to make the control knobs on top be at right angles to the top carve where that particular pot shaft comes out through the top.

If that's the case, then wouldn't one want to make sure that the thickness of the maple cap or roof on the control cavity has a common thickness across all four pot holes?

If that is the case, say all the cavities are supposed to be 5/32" thick at the maple, then it really depends on how that particular top was carved to get it right?

If the guy running the slack belt back in the day was a little heavy handed he could waste away a good bit of maple around the control knob area of the top. Isn't it possible that a fixed common jig could cut too deep into a top that's been carved a little deep which may result in a dangerously thin cap over one or more control knob holes?

Now take that scenario and apply it to any home builder/luthier and you know the top carve isn't going to be the same from builder to builder and probably not the cavity either? Would it not be better to simply define what thickness the finished maple cap is where the 3/8" holes come through the top and just bore each individual cavity (the small round part where the pot sits) to be a consistent thickness relative to the top being made? Granted, that may not be the way the vintage ones are made but I think I'm just searching for simplicity here.

[Texas07R8]

double post, sorry.

[alk-3]

Originally Posted by Texas07R8

wow, what a head full of info on this thread. I've wondered about this but never pressed the questions as I'm not yet reaching critical mass here... I'm still fiddling with building a few Juniors before stepping up to a carved top Std.

Kudos to all who have shared there methods to the madness, we do appreciate your sharing your tricks, tips and ideas.

So, let me step off the dock here and ask perhaps an obvious question that seems to be either ignored as it's irrelevant to the topic or perhaps it's been overlooked or simply a non issue.

To me, the whole purpose of angling the control cavity bores are to make the control knobs on top be at right angles to the top carve where that particular pot shaft comes out through the top.

If that's the case, then wouldn't one want to make sure that the thickness of the maple cap or roof on the control cavity has a common thickness across all four pot holes?

If that is the case, say all the cavities are supposed to be 5/32" thick at the maple, then it really depends on how that particular top was carved to get it right?

If the guy running the slack belt back in the day was a little heavy handed he could waste away a good bit of maple around the control knob area of the top. Isn't it possible that a fixed common jig could cut too deep into a top that's been carved a little deep which may result in a dangerously thin cap over one or more control knob holes?

Now take that scenario and apply it to any home builder/luthier and you know the top carve isn't going to be the same from builder to builder and probably not the cavity either? Would it not be better to simply define what thickness the finished maple cap is where the 3/8" holes come through the top and just bore each individual cavity (the small round part where the pot sits) to be a consistent thickness relative to the top being made? Granted, that may not be the way the vintage ones are made but I think I'm just searching for simplicity here.

All very good points!


For the average home or garage guitar building just building one for themselves to play with, doing each pot with a forstner bit is probably the easiest way to make it all work for them, but in a production setting where the people doing the work are not necessarily skilled luthiers the pattern makers are charged with the task of making jigs that allow said unskilled worker to pop the body into the jig and rout it with no real concern of what they're doing.

Also, as a side note, when jigs like the one I made for the pin router are used there is no chance of going through the maple because the body rests maple side down on the jig, after the carve is complete. So the router indexes off the carved top. If the carved top is thinner, then the body sits lower in the jig, thus not allowing the router to cut through the top, and always guaranteeing the same top thickness under the pots.
I hope all this makes sense!