Franklin Mystery Screw

[Glenn Demichele]

Although the title of this post would be a great name for a new PF lick, this post is actually is about a freely-turning screw I found under the C6 changer of my '94 Franklin D10.
While snugging up screws underneath, I found that a #8 flat head just spun freely. The threads on the screw show no signs of strippage. The hole was deeper than the screw length, but a longer #8 still didn't grab any threads. Either the screw is the wrong size or type, or there was a nut that fell off the other end. I tried a 10-32, but its too big to fit in the hole. Does anybody know?
Below are pics, E9 and C6. The screw (hole) I'm talking about is underneath the C6 1st string, marked with red (second pic).

[Glenn Demichele]

TTT

[Doug Earnest]

There is usually a gauge in the nut and bolt department of hardware sections.

My keen eye says it's a 10-24. My other eye does too.

[Bobby D. Jones]

What does the ghost screw, Screw into up in the guitar. From the pictures it looks like those 2 screws 1 left and 1 right , Screw into the bar with threaded holes which is the Split Tuning Screw bar.

When working with screws of size 10, There is 2 sizes, There is 10-24 and also 10-32. If the screw goes in and then locks when it hits the threaded hole it goes in, You need to try the other size thread.

Good Luck getting this problem figure out and solved.

[Bobby D. Jones]

I found some other pictures of Franklin steels on the internet. Some on the bars across the back of the changer are solid metal, Some are drilled for Split Tuning hex screws, Can't see on your guitar which it has.

[Glenn Demichele]

Thanks: No solution yet.
The Franklin Mystery Screw is an 8-32. Below is a picture of it next to a 10-32 I bought at the hardware store. My caliper measures the thread diameters of them at 0.1565 and 0.1820 respectively, which is about right for a #8 and #10.
The #10 screw diameter is too big to even to fit through the hole from which the mystery screw came.
I have no splits. The screw layout is different on the C6 and E9. Here are some more pics:

[Jack Stoner]

I looked at what pictures I have of my 82 Franklin and don't see those screws. But there was a change in neck design between mine and yours. Mine is "original" design cut tail like Emmons. Later design the neck was a pseudo wraparound and that mystery screw could be related to securing the neck behind the changer.

My guess.

[Glenn Demichele]

Ttt

[John Haspert]

I'm hoping that Paul Jr. will see this and respond. I'm sure that Paul Sr. had a few other secrets that found their way into his wonderful instruments.

Jim Cohen may also have some ideas.

[Glenn Demichele]

Thanks everybody for your thought and comments. I’m saving the mystery screw until we figure out what it does. Guitar still plays great, but a 747 flies fine with three engines too. Hopefully someone has taken a Franklin apart and can tell me. I do not want to remove any other of the flat heads to investigate because if they screw into a floating nut I’m in big trouble - I don’t know if a 747 will fly with two engines. Thanks, Glenn

[Glenn Demichele]

Ttt

[Bobby D. Jones]

I keep checking this post to see if this problem has been solved.

Have you tried a longer 8-32 screw to check for threads deeper in the hole?

If you measure through the Changer Window to the screw hole, And from back of the guitar to the screw hole. What is at the point where the 2 measurements forms an L where they meet?

Does the guitar have a bar behind the Changer fingers?
Does it have threaded holes for Split Tuning screws to mount through?

Could you post a picture of the Changer from the back and
and side of the guitar would help.

Good Luck in finding a solution the this problem.

[Glenn Demichele]

Thanks. I’ll send more pics, and some drawings with measurements. An 8-32 almost 1/2” longer hits the bottom of the hole without hitting threads first. Seems to me either the imaginary threaded hole was drilled too big for an 8-32, or there was a nut in there that fell off. There is no sign of stripping or metal flakes on the removed Franklin screw.

[Jack Stoner]

My guess is still the pseudo wraparound neck and it was screwed in to that.

My 82 Franklin was a different design and didn't have that screw. I disassembled the E9th neck and changer for cleaning.

[Glenn Demichele]

TTT

[Jerry Jones]

Possibly Tommy Young MAX-TONE mod?

[Glenn Demichele]

Good one Jerry

[Glenn Demichele]

Ttt

[Tony Oresteen]

snip....The screw (hole) I'm talking about is underneath the C6 1st string, marked with red (second pic).
......

I have looked and I do not see any red and can not follow your description. Can you add an arrow pointing to exactly which screw you are talking about?

Thanks!

[Richard Sinkler]

snip....The screw (hole) I'm talking about is underneath the C6 1st string, marked with red (second pic).
......

I have looked and I do not see any red and can not follow your description. Can you add an arrow pointing to exactly which screw you are talking about?

Thanks!

In the bottom picture, you will see a hole that has physically been colored red.

[Jim Hussey]

Did you ever get an answer?

If not – Here you go: The “Mystery Screw” threads into the bottom of a cross bar that spans the changer mounting assembly.

Changr w cross bar.JPG

Changr mounted.JPG

On my guitar, the "Mystery" screw is a round head 8-32 machine screw with a washer. It measures 1” long for the C6 changer. For E9, the same screw measures 1 1/8” long. For your guitar it looks like the mystery screw is counter sunk. The screw circled in RED is the "Mystery Screw". The screw circled in GREEN mounts the end plate to the guitar body

Mystery Screw C6.JPG

My guitar is #082. I suspect your guitar is a higher serial # and may have some changes / improvements. For example, my guitar does not have the allen head socket screw that I see in the photos of your guitar. Also – the panhead screws (GREEN) that are next to the “Mystery Screws” (RED) attach the end plate to the guitar body.

Mystery Screw removed.JPG

So, you do have a 747 flying on 3 engines. I don’t know what was in Sr’s head when he switched from the “cut tail” necks to the “wrap around” style. There has been a lot of discussion about how necks attach to the body and any acoustic interaction between the necks, changers, and the guitar body. From the perspective of “resonance”, I suspect Paul Sr had something in mind when he added the cross bar to the changer support and then added the 8-32 screws through the body from below. You will have to decide if it is worth disassembling your guitar to fix it.

Know this: If you decide to repair this, you will have to remove the neck to get at the changer. To remove the neck, you will have to remove the fret boards to access 6 screws (PURPLE) that hold the neck in place from the top. It’s not as challenging as you might think and there is a way to remove the fret boards without damaging them.

Remove frets.JPG

If you decide to do it, once removed you will have an ideal opportunity to clean the changer fingers. #082 is the second Franklin I’ve disassembled. It was necessary to disassemble both because the changer fingers had become very stiff from years of improper cleaning and lubricating. Once cleaned, the guitar was much easier to properly/accurately tune.

Let me know if you would like more detailed info. I have a lot more disassembly photos and can share some important details like different length screws for the C6 vs E9 necks.

[Glenn Demichele]

Jim: 747 to control tower: Thank you for being the first to confirm that one of my engines is out. Thanks for your effort in explaining my situation, and for all the pictures.
I'm attaching the picture which I think shows what your disassembled guitar shows more clearly. I assume that I can see the edge of this crossbar just under the neck as shown in the picture.

First of all, it doesn't look like the crossbar has shifted.
I discovered my mystery screw when I went to (gently!) snug up all the screws on the undercarriage, and found the mystery screw spun freely. I unscrewed it, and it only came out because the threads were rubbing lightly on the wood body on the way out.

Since my mystery screw threads aren't stripped, nor are they filled with aluminum, I can still hope that the threaded hole in the crossbar is OK, and still lined up because the bar looks to be in the right place. I'll poke around in the hole with a fine probe to see if I can feel what's going on in there, and why my #8 1" mystery screw won't grab anything. I am very relieved to hear there wasn't an inaccessible nut that fell off.

mYSTERYsCREWdIAG.jpg

[Jim Hussey]

Hi Glenn

Your view through the neck does show the cross bar in question and your marking for the mystery screw location is correct. However, even with the mystery screw removed, the cross bar won’t move because it is held in place by 4 screws. 2 screws that come up from the bottom of the guitar (Mystery Screws) and two that are on top of the guitar and screw into the back of the pillow blocks that support the changer axle.

PB screws.png

Because of the pillow block screws noted above you can remove the other mystery screw and compare its length to the one that doesn’t catch now. If it’s significantly longer than the one that doesn’t catch, swap screws and see what happens. If it still doesn’t catch, you have a problem with the threads in the cross bar. It is possible a previous owner had a problem and increased the size from 8-32 to 10-32?

Try a 10-32 (or possibly a 10-24). If that works, you’re back on 4 engines. If it doesn’t work, you are going to have to get eyes on the changer (take the neck off). Or – you can leave it as is and fly on 3 engines!

[Jerry Dragon]

There is usually a gauge in the nut and bolt department of hardware sections.

My keen eye says it's a 10-24. My other eye does too.

I was a machinist for fifty years and my keen eye tells me those threads are pretty raggedy!

[Glenn Demichele]

Thanks everyone:
Here's what I did:
I don't have a tiny borescope, but I took a small needle and could feel some threads deep in the hole. I tried a 1" 10-32 bolt again. It was a LITTLE tight in the hole, but it went in. At first I may have been cutting some SHALLOW #10 threads in the tight hole in the plate, but I carefully kept screwing, and it kept going deeper, and then it got tight when it went all the way in. I'm not sure if it got tight because the bolt was grabbing my shallow threads in the plate, or if it was grabbing threads in the block, but that's where I left it.
I think however that:
It seems unlikely, but my GUESS is that during manufacture, the original 8-32 threads in the block got stripped, so they drilled and tapped it for a #10, but forgot and just put the original #8 bolt back in. There's no way that the force I used to screw in the #10 bolt was enough to drive the #10 bolt into a stripped out #8 hole.