6 PIN 12 STRING BRIDGE (shared pin method)

Got a new way of doing something? Or maybe an old method that needs some clarification.

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Craig
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6 PIN 12 STRING BRIDGE (shared pin method)

Post by Craig » Thu Jan 17, 2008 1:08 pm

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Bob has asked me advice on my 12 string pin and string spacing as he about to set two of his as "6 pinners".
He suggested I do a tutorial ,so that all interested folk can hopefully benefit.

This tute. will include string & pin spacing , pin hole slotting ,plus some tips on stringing up.


It's not a new idea. Here is a pic. of a Holzapfel , built in 1905

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Both Howard Klepper and Dave White have used this method as well. Thanks goes to them both.
Stringing up may , at first glance, appear a bit tricky, but you soon get onto it , although some may find it difficult. I can now restring quite fast. I've found a couple of tips , I'll explain later.

The advantages are 6 less holes through the bridge and plate. The bridge need not be as big as a 12 pin bridge , so less weight. Less 6 pins - more weight saved !. I did , however, make mine (8mm. thick ), a little larger footprint than a six string guitar, to gain a little more glueing area.
Another advantage is that it is uncluttered. Often as not,12 pin bridges have strings nudging nieghbouring pins. These pins are often difficult to remove because of their close proximity to each other. It's a little congested . The shared pin method also allows you to customise the little gap between the octave/unisons , where as the 12 pin method dictates otherwise.

I used StewMac's oversize Ebony unslotted Ebony pins which are .235" ( 5.97mm.) diameter at their collar.


My method of string and pin spacing are my own. Some may find an easier way, or by using their computer. There are probably string spacing guages that may do the job as well. I customised mine to what I think works well , and simply used pencil and paper ! Others may prefer different gaps/spacing.

First , you must establish what string width you want at the saddle. Because my neck is 1 15/16 " at the nut(alittle more wiggl room for fingerstyle ), my saddle string width is 2 3/8 " ( 60.33 mm. ). Yours may differ , but the method remains the same.
I'll use metric from here on in :

First , make yourself A VERY SHARP PENCIL !!! thus :


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On a sheet of paper, draw two parallel lines to represent the saddle string width Thus ;

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NO. 1, Add up all the string widths (diameters ) in the set you are going to use. I use D'Addario lights , which take up an equivalent area of 6.39 mm. all up.

NO. 2, You must decide what CLEAR gap you want between octave/unison pairs. Thicker strings require more clearance , so I graduated these CLEAR gaps thus ;

E = 3 mm.
A = 2.8 mm.
D = 2.7 mm.
G = 2.6 mm.
B = 2.5 mm.
e = 2.4 mm.

This totals 16 mm. of CLEAR gap all up.

A neck of narrower diminsions than my own may require closing these gaps a little. Some may opt for different gaps . It's up to you . I didn't want too much string rattle. Low " E " needs a good bit !

NO. 3. Add up the total string widths and total gap widths. In my case ; 6.39 mm. plus 16 mm.
This gives me 22.39 mm. of RESERVED width.

NO.4 Subtract that figure from your original completestring width at the saddle. In my case 60.33 mm. ( 2 3/8 " ). This gives me a VACANT area on the saddle of 39.94 mm.

NO. 5. Divide that VACANT area ( 39.94 mm. ) by five, which will give you the CLEAR. equal space between string courses. In my case ; 7.588 mm.

NO. 6. Now we have the figures !
AGAIN, SHARPEN YOUR PENCIL ! :lol: :lol:
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Starting at the left line of your drawing, ( the bass side ) draw a line ( I'll use my figures ) of 4.88 mm. from the left line. This 4.88 mm. includes the width of the 2 E strings plus their CLEAR 3. mm. gap. I realise it's impossible to draw a line to that exact measurement. :lol: :lol: . As near as you can get will suffice.

NO. 7. For the next line ( the A strings ) , Add the 4.88 mm. plus the course spacing of 7.588 mm. , which equals 12.468 mm.
Measure that distance from the very left line ( now our reference line ). and draw a line , as close as you can ,to that distance.

NO. 8. Add a further 4.25 mm. ( width of both ' A ' strings plus their CLEAR gap) to the 12.468 mm.. this equals 16.718 mm.. Draw a line of that measurement ( or as near as you can ) . This will now show the extremities of both the 'E' and 'A' courses.

NO.9. Continue this through all the courses. The string set package figures are handy here, to add up each individual string width.
TAKE ALL MEASUREMENTS FROM THE VERY LEFT LINE !
When finished , your drawing will have equal spacing between courses and will looksomething like this ;


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Excuse the pics. My camera makes the lines look a tad bent ! :?

It wuld be impossible to draw your lines to the exact decimal points ,BUT, for CALCULATION PURPOSES , it is important you should use all decimals , so that you end up with equal spacing . Drawing lines as close as you are able will suffice.


We can now use this drawing to transfer the bridge pin spacing.

AGAIN SHARPEN YOU PENCIL !!Image


Measure and mark with a tiny dot , the centre of eachcourse. You can now transfer tose dots to yourbridge , by pricking the dots through with a sharp pricker or scribe. Line up centre lines of the drawing with your centre line on your bridge. In my case , I pricked through to a piece of scrapwood I used as a drilling template to drill the bridge pin holes.

Rather than have all pins in line , you can easily have a curved line for your holes by drawing the centre dots on your drawing in their respective curved position, as I did on mine.

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Again these line may appear to curve because of the camera shot.


NEXT ; SLOTTING THE BRIDGE PIN HOLES.

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Post by Craig » Thu Jan 17, 2008 1:57 pm

SLOTTING THE BRIDGE PIN HOLES ;



This isn't the easiest of tasks, as we are not making a single slot as in a 6 string guitar.
I used a slot saw from StewMac ,along with an array of others I made from mini hacksaw blades and jigsaw blades etc. What ever you have lying around. The StewMac one has a kerf of .8 mm..
I adjusted the kerf on some blades be beating the saw's teeth "set"


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I found StewMac's to be very good ! . Note the saw on the left with a little masking tape on the blade's back edge to save marring the back of the hole.

Measure the string diameters at their windings just past their ball ends. It's surprising how some of the thinner strings still require quite a wide slot.

I also use needle files . I purchased this tiny set from a hobby/model shop . They have to be fairly narrow to fit in the pin hole.Alternativley, you could maybe gring down the edges of a larger set.

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IMPORTANT !! ; Practice on scrap first !. I know we often hear this advice , but in this case, it' a MUST !!

I made up a scrap sandwich of Rosewood/Spruce/Rosewood to the same dimensions as the bridge/soundboard/plate , and drilled and reamed the holes to duplicate the guitar exactly. I pleased I tryed this practice run first , before attacking the actual guitar !!!!!!!

I started ( with a slot saw) at the lower end of the hole.
You will find the saw wanting to drift toward the centre of the hole, which is to be avoided at all costs. In fact , it is better to encourage the saw to cut more towards the side of the hole , rather than staight ahead. Keep the saw upright at all times , with nice 90 degree strokes. I drew pencil marks at the top of the holes where I wanted the slots to be , as they are slightly different with each hole. Once you have the slot kerfs started. stop and inspect the kerf/slot. Carry on if you are happy with it , or adjust your cutting angle accordingly . A light ( low temperature) inside the guitar is welcome here , to inspect your handywork. It'll out line your slot quite well when looking from above.

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You want the front of the hole completley untouched and the web( between the slots ) to be the same width as the gap between the paired strings ( or as close as you can get ).
With the thicker strings, this means the slots are nearing the outer width of the hole itself.
Once the saw has cut sufficient depth . I move on with the needle files to refine the actual slot.
Check the slot with the corresponding string . and try placing the bridge pin in to see that it seats well.After you are happy with it , move to the other string slot in the pair, and do likewise.

You want it to look like this :


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NOT THIS !!!


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NOTE ; If the gap in the pair didn't quite end up as you had hoped , a slight adjustment can be made by ramping the slots later on.



NEXT ; STRINGING HER UP

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Post by Craig » Thu Jan 17, 2008 2:33 pm

STRINGING UP


I like to have the ball ends seated this way ( as does Dave ) but it probably isn't really necessary.


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To attain this and to also aid in stringing up , I place the first string of the pair , into the hole andwhen it's lines up in the above fashion , put the bridge pin in place, give it a light tug , and bend the string around the top of the bridge towards the saddle.It will then sit ( almost ! ) :lol: happily there.
Take the bridge pin back out , and insert the string's partner. You soon get the knack of it , although there may be some folk ( the type that are " all thumbs " ),experience some difficulty. It's a bit tricky.

Well, that's all folks ! If Dave or any others can offer more , please feel free to contribute.

THE FINISHED PRODUCT ( before intonating the saddle)



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A close up , but before I ramped the slots

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Here's a picture of the back ,, for no other reason other than , I just wanted to show it off ! :lol: :lol:


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Cheers to all, Craig Lawrence

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kiwigeo
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Post by kiwigeo » Thu Jan 17, 2008 5:07 pm

Excellent post thanks Craig

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Post by Graham McDonald » Thu Jan 17, 2008 6:08 pm

My only suggestion is to think about the space between the courses. I got some very useful feedback about one of my bouzoukis from one of my customers about this. He said it feels a little more comfortable if the space between the courses is a bit wider on the bass strings, and a little narrower between the higher courses. The space between pairs looks about right, but you might try 7mm for the treble course up to 8mm on the bass side. here is a diagram of the spacing on one of my five course bouzouki/citterns.

Hope this is useful

graham
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Post by Graham McDonald » Thu Jan 17, 2008 6:09 pm

OK, here's the picture

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Post by Tom Morici » Thu Jan 17, 2008 7:19 pm

Craig,

Thanks for taking the time to show how this is done, clear and well illustrated. Great job!!! Your work is top notch.

Tom

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Post by Dave White » Thu Jan 17, 2008 7:23 pm

Craig,

Great tutorial!! I haven't got much to add. For the slotting I like to use a thin Bosch jigsaw blade as I found the Stew mac one a little fragile. I put my left hand inside the sound hole and hold both the top and bottom when I cut which gives me more control. I haven't worked up the courage to try it with the blade in the jigsaw as some other builders do :?

I'm going to a workshop tought by Gavin Davenport at the beginning of February so I will have the chance to see how the slots on the guitar/cittern I made for him are holding up after a year and a half.
Dave White
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Bob Connor
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Post by Bob Connor » Thu Jan 17, 2008 10:21 pm

Thanks very much for that Craig. An excellent tutorial.

It'll be put to good use in the next few weeks.

Cheers

Bob

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Post by Rick Turner » Tue Jan 22, 2008 3:05 pm

I absolutely agree with this method. I don't build many acoustic 12s, but when I do, they get 6 pins and 12 slots.

On my Renaissance semi-hollow 12s, we run six holes through the body for the strings, and then we use 3/32" (just under 2.5 mm)brass pins to separate the string pairs behind the saddle. Works great.
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Post by Serge » Tue Jan 22, 2008 4:24 pm

Many many thanks Craig, a 12 strings is in my projects for the future, what a great tute bud, great details and great pics of your work too!

Serge
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Post by BillyT » Tue Jan 22, 2008 4:47 pm

Thanks Craig! Nice work too!!

The only pinned 12 I've seen had double pins, I like this much better!

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Kim
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Post by Kim » Tue Jan 22, 2008 6:34 pm

Wow, what a great tutorial Craig, thanks for the effort mate this is a first class presentation and one worthy of the tutorial section.

Cheers

Kim

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Post by sebastiaan56 » Tue Jan 22, 2008 7:28 pm

Yup, its a keeper, very clear, precise and very relevant to where I am up to on #1

thanks Craig,

Sebastiaan

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Post by Sam Price » Wed Jan 23, 2008 3:21 am

Great tutorial, thank you for taking the time to share this information. Wow, this forum is amazing!!

I used the same technique for my Celtic Cittern, which I still play on a daily basis; I borrowed the idea after seeing David White's double-coursed instruments designed the same way.

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Post by Craig » Wed Jan 23, 2008 10:40 pm

Thanks for the 'thumbs up' everyone , and also Graham and Dave for their contribution.

I have a new appreciation for those who post tutorials . I didn't really realise how time consuming they are to put together.

I must say that I am really enjoying playing this guitar . So much ,that my six string are almost ignored. I encourage all to start work on one immediately ! :lol: I'll bet you won't regret it . This thing is very alive , and hard to stop playing. Also ,I think it makes me sound better than I actually am . :lol: ( which is a very very good thing !) :lol: :lol:

Cheers Craig

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Post by Rick Turner » Thu Jan 24, 2008 3:01 pm

Craig, one warning, though. If the Disney folks see what you've drawn, you might be getting a nasty letter in the mail re. their copyright ownership of all images of Mickey Mouse...
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Post by Sam Price » Sat Jan 26, 2008 1:55 am

Dave White wrote:
I'm going to a workshop tought by Gavin Davenport at the beginning of February so I will have the chance to see how the slots on the guitar/cittern I made for him are holding up after a year and a half.
Dave, it would be great if you PLEASE give a general report on this instrument!!!

have a great time!!

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