50s LP control cavity angle

[gtrmaker]

I would like to know on a late 50's LP what is the angle of the mahogany cavity wall that is routed flat as measured from the mahogany back surface of the guitar?

Also, what is the depth at that deepest point? from the mahogany to the maple?

[The Thruth]

Originally Posted by gtrmaker

I would like to know on a late 50's LP what is the angle of the mahogany cavity wall that is routed flat as measured from the mahogany back surface of the guitar?

Also, what is the depth at that deepest point? from the mahogany to the maple?

it is between 5° and 6°, depending on the belly contour

[rick13]

The sidewall of the cavity is also parallel with the centerline?
Rick

[gtrmaker]

I'm surprised that there would be that much variation in the angle since it was done on a routing machine and to vary the angle would mean that they would have to have an adjustable fixture that would allow them to adjust the angle based on the top carve. This would not have been done by hand holding the body so it would have required a variable clamping fixture to align the top curve relative to the cutter. Also, the top carve was done on a duplicating carver so other than the follow-up smoothing that they would have done on a stroke sander the top carve in the area of the controls shouldn't vary very much since at that point it's a shallow curvature that's easy to sand. The area of the belly on the other hand would have been more difficult because of the rapid changes in curvature and difficulty getting the sanding belt to conform to the complex curvature. I'm sure they did the minimal amount of sanding needed to clean up the router marks. This all sounds much too complex for a mass production factory. Is your angular data based on actual measurements taken from actual instruments?

[gtrmaker]

I'm surprised that nobody else wants to contribute to this thread! It's a topic that's not been beat to death like many others. I've read every thread regarding control cavities and not one discusses this angle other than to generalize that they made it to complement the top carve. You can generalize or you can measure. I'll believe data from a sampling of measurements over some statement anyday. Let's go guys!

[Ole'Lefty]

I really have only thought about monkey se-monkey do. How to make it look that way. Your point about a process out of step with even a 50's factory atmosphere is stirring my interest. BOTB just mentions the existence. there could have been a quicky jig that clamped on and a bushed router stirred around in there-the jig would have just accomodated a typical angle of the maple front carve.

I was loading pots into a metric LP-but US 3/8th" shaft. I played around a bit with a reamer-trying angles-it does not take much of an angle to get the pots to "harmonize" with the belly. I was working front to rear and the 5-7* seems like a range I crudely determined with the old eyeball. It was so easy, I started doubting someone's sanity-mine, or Gibson's. Tell me please; did Burst era LP's use long shank pots? On this EDEN, I could get eye worthy relationship with the long pots and reamer,working from the front. Short pots would require more precision. Ole'Lefty

[nuance97]

I too am kinda suprised at the lack of intrest in this thread. I think that it is a really good question. I have wondered the very same thing.

[alk-3]

I think if here is any varience at all between bursts it would be time related. For instance, if they made the jig to hold the guitar, then after a certain amount of use it becomes necessary to replace the jig, and when they make the new jig they make 'improvments' to it, and one of those improvements is to adjust the angle slightly.

Having said all of that, I do not belive the angle ever changed. I have seen no evedance that it did, but I could be wrong.

[nuance97]

Originally Posted by alk-3

I think if here is any varience at all between bursts it would be time related. For instance, if they made the jig to hold the guitar, then after a certain amount of use it becomes necessary to replace the jig, and when they make the new jig they make 'improvments' to it, and one of those improvements is to adjust the angle slightly.

Having said all of that, I do not belive the angle ever changed. I have seen no evedance that it did, but I could be wrong.

Lets rephrase the question then...alk-3 What was the angle you and ex-nihilo used when y'all did the control cavity on his build?

The cavity on this build looks spot on vintage specs!

[alk-3]

I'll measure it when I get home. Good memory!

[George "M"]

4,5 degrees on all 59's I inspected, and all were with long shaft pots.

www.master-guitars.com

[nuance97]

Originally Posted by alk-3

I'll measure it when I get home. Good memory!

Did you ever figure out what that angle was?

[xsouldriverx]

... i didnt even know the control cavity was done on an angle.

[xsouldriverx]

+1

[gtrmaker]

I started this thread because I think this is an important constuction detail. Unfortunately, the owners of these guitars don't seem to want to share this info with us under-priveledged members. I wish there were more measurements being done and the results shared with everyone. I don't believe that the angle varied "depending on the top carve". On page 74 of Robb Lawrence's book The Les Paul Legacy he states that before the top was pattern carved that "A large angled cut into the maple of the control cavity was done to slightly tilt the rhythm pickup controls for the curved face of the instrument." This I believe because the body at this point would be in a rectangular form which makes it easier to template route this angle. Given this, then the angle would not vary hardly at all from guitar to guitar.

I'd still like to see some actual measurement data from actual 50's guitars. Anybody have access to someone who owns an actual late 50's Les Paul that they could measure? The more instruments that can be measured the more conclusive the results will be.

[alk-3]

Originally Posted by gtrmaker

I started this thread because I think this is an important constuction detail. Unfortunately, the owners of these guitars don't seem to want to share this info with us under-priveledged members. I wish there were more measurements being done and the results shared with everyone. I don't believe that the angle varied "depending on the top carve". On page 74 of Robb Lawrence's book The Les Paul Legacy he states that before the top was pattern carved that "A large angled cut into the maple of the control cavity was done to slightly tilt the rhythm pickup controls for the curved face of the instrument." This I believe because the body at this point would be in a rectangular form which makes it easier to template route this angle. Given this, then the angle would not vary hardly at all from guitar to guitar.

I'd still like to see some actual measurement data from actual 50's guitars. Anybody have access to someone who owns an actual late 50's Les Paul that they could measure? The more instruments that can be measured the more conclusive the results will be.

Sorry I forgot to post the angles on here. After working it out on our plans (with some difficulty) here is what Magnus came up with. It's hard to describe the relationship between the angles and the top, as there is no real flat surface to measure from, and it's a compound angle. Hopefully this screen dump shows it with some clarity.

[gtrmaker]

Thanks for sharing what you came up with for the cavity angle. Magnus is certainly the master of all things 3d! And his build came out great too. I've already placed an order for the plans and really look forward to seeing them as I'm sure they will be the best ones available from now on.

The angular data is very intriguing because I did not know that about the 2 degree angle parallel to the cross body centerline making the cavity deeper at the neck end when compared to the tailpiece end of the body. And the 8 degree angle parallel to the body centerline is more than I expected and what was being discussed (4.5-7). Do you know if Magnus' numbers were taken from at least 1 actual vintage 50's Les Paul?

[gtrmaker]

Originally Posted by George "M"

4,5 degrees on all 59's I inspected, and all were with long shaft pots.]

George, thanks for your input. Were the measurements you got taken from original '59 LP's or reissue '59 LP's?

[alk-3]

Originally Posted by gtrmaker

Thanks for sharing what you came up with for the cavity angle. Magnus is certainly the master of all things 3d! And his build came out great too. I've already placed an order for the plans and really look forward to seeing them as I'm sure they will be the best ones available from now on.

The angular data is very intriguing because I did not know that about the 2 degree angle parallel to the cross body centerline making the cavity deeper at the neck end when compared to the tailpiece end of the body. And the 8 degree angle parallel to the body centerline is more than I expected and what was being discussed (4.5-7). Do you know if Magnus' numbers were taken from at least 1 actual vintage 50's Les Paul?

I don't think Magnus has measured a burst for this, but I'm sure he has, or at least can measure the '54 he has for the angle.
The real clincher is that in order for the shafts to poke through enough to get the pointer and the nut screwed onto them, this is the angle that is required, so I would be VERY surprised to find that an actual burst angles differ.
As you know, the purpose of the angle is to allow all 4 pots to stick out the top equally, and this is the only angle that allows that.
Also, when figuring out this angle we looked at the nibble marks caused by the pin router that does the job. Based on those nibble marks, and knowing where the pot centres are, this can only be made possible with the above angles.
Hope all this makes sense.

[landsharkey]

Hope all this makes sense.

Just to be clear - The view above is looking at the underside of the cap on a right-handed guitar, correct? As if the top was sliced off and turned over. Tempting to route this cavity before the top is glued on and use it as guide with a bottom bearing bit to match the shape in the mahogany.

[gtrmaker]

Others can correct me if I'm wrong, but I'm sure if Magnus measured off of his '54 then I doubt it changed for the 'bursts.

I'm going to open up a new can of worms and hope that the experts will chime in on this one. In the most recent issue of Guitar Aficionado magazine, Chris Gill makes the following statement in his article:

"The portion of the maple top that the potentiometers are mounted should be a shallow 'V' shape, with the point located between the volume and tone controls." He then goes on to say that "The pots should be angled away from each other but at a 90 degree angle to the curved top. If the posts are parallel to each other, the cavity is flat and the guitar is not original."

[alk-3]

Originally Posted by landsharkey

Just to be clear - The view above is looking at the underside of the cap on a right-handed guitar, correct? As if the top was sliced off and turned over. Tempting to route this cavity before the top is glued on and use it as guide with a bottom bearing bit to match the shape in the mahogany.

You are correct in the perspective of the drawing. You can't rout the top first though as the routing does not got all the way into the mahogany.

[gtrmaker]

Originally Posted by landsharkey

Just to be clear - The view above is looking at the underside of the cap on a right-handed guitar, correct? As if the top was sliced off and turned over. Tempting to route this cavity before the top is glued on and use it as guide with a bottom bearing bit to match the shape in the mahogany.

As alk-3 says, you are correct on the viewing perspective.

However, you are wrong on routing this before the top is glued on because this compound angle route also removes material from 2 sides of the mahogany cavity walls. So, in order for it to look and function correctly it has to be done after the top is glued.

[alk-3]

Originally Posted by gtrmaker

Others can correct me if I'm wrong, but I'm sure if Magnus measured off of his '54 then I doubt it changed for the 'bursts.

I'm going to open up a new can of worms and hope that the experts will chime in on this one. In the most recent issue of Guitar Aficionado magazine, Chris Gill makes the following statement in his article:

"The portion of the maple top that the potentiometers are mounted should be a shallow 'V' shape, with the point located between the volume and tone controls." He then goes on to say that "The pots should be angle away from each other but at a 90 degree angle to the curved top. If the posts are parallel to each other, the cavity is flat and the guitar is not original."

This is certainly a new can of worms. I'm in no position to say that chris is incorrect, but if what he says is true than the "v" is VERY subtle and undetectible in photographs, and to the naked eye in real life. Also that would require a fair amount of added work for the factory for no gain whatsoever. The pots are angled to follow the curve of the top, and easily follow the curve without any "v" carved into the cavity, so why bother?

[gtrmaker]

Originally Posted by alk-3

This is certainly a new can of worms. I'm in no position to say that chris is incorrect, but if what he says is true than the "v" is VERY subtle and undetectible in photographs, and to the naked eye in real life. Also that would require a fair amount of added work for the factory for no gain whatsoever. The pots are angled to follow the curve of the top, and easily follow the curve without any "v" carved into the cavity, so why bother?

Yes, Chris does also state that "This can be hard to see or even feel with your fingers, so I recommend examining the alignment of the potentiometer posts by removing the knobs."

I believe what he says is correct because I've also read somewhere on a forum a post that one of the top "experts" on 'burst authentication alludes to this same feature as one of the tells of a fake and that he does the inspection by feel.

I've pondered this quite a bit to envision the fixture that they would use to perform this operation and I have not quite figured it out.

[landsharkey]

You can't rout the top first though as the routing does not got all the way into the mahogany.

Ok, I was just thinking routing cavitiy on the back side of the maple top before gluing. It would be a similar setup to the photo below - just without the mahogany. The cavity edges in the maple would probably not be deep enough to a bearing though.

[alk-3]

Originally Posted by landsharkey

Ok, I was just thinking routing cavitiy on the back side of the maple top before gluing. It would be a similar setup to the photo below - just without the mahogany. The cavity edges in the maple would probably not be deep enough to a bearing though.

That's just the point. The rout doesn't even go throu the mahogany all the way, let alone have enough room for a bearing.
I can't add a link from my cell phone, but if you go to my website I have a photo of the control cavity under complete bodies that shows this.

[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.

[alk-3]

Originally Posted by gtrmaker

Yes, Chris does also state that "This can be hard to see or even feel with your fingers, so I recommend examining the alignment of the potentiometer posts by removing the knobs."

I believe what he says is correct because I've also read somewhere on a forum a post that one of the top "experts" on 'burst authentication alludes to this same feature as one of the tells of a fake and that he does the inspection by feel.

I've pondered this quite a bit to envision the fixture that they would use to perform this operation and I have not quite figured it out.

I have also heard that the pot holes were drilled stright down on a press and then reamed by hand to angle them, so removing the knobs and examinigthe pot shafts would still reveal angled pot shafts, but no v carve.
I think you're rght about how they might have achieved tha carve, in that it would be very dificult. It would be simple enough to make two fixtures, one for each side of the v and use it on the pin router, but getting them to meet at the point of the v PERFECTLY and not just some of the time, but EVERY time is beyond concievable to me. Not to say it would be impossible, but I would think there is a better way, but none that I can think of using the machinery they had at that time (no CNC).
I would love to hear from someone who can actually check it out hands on.

[gtrmaker]

I think I've figured out the how in theory and the thing that makes it possible is that this secondary route was done with an overarm pin router hence the bite marks from what most believe is the chuck. Control cavity routing was done when the laminated body blank was still unprofiled. So, the angled template would have been attached to the flat unarched top surface of the body blank which could have easily had a minor secondary angle in it that was made to contact the table sort of in a rocking motion. If so, then this type of route could not be replicated with a router fixture attched to the back of the guitar because the router base could not follow the fixture's inverted 'V' shape in the same fashion.

This sounds plausible to me.