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This is not that difficult and I am sure you will hear more than one theory. This is the method I have been using and one I learned from Dave Nichols of custom pearl. I can assure you that it works very well.
You must first know your line of center from the neck. I use masking tape and mark the tape so in front of the bridge I know where that center line is. Do not assume the tops center is where the bridge is to go.
Once you have center established you can begin the actual plotting of where it should be. You need to consider these variables
1: what action height do you want to go with
2: string gauge
3: the strings physical properties
This effects the placement in that higher action will pull strings sharp , and a heavier gauge seems to need a touch more compensation. I am figuring the placement using normal gauge ( lite and med ) and an action height that is around 4/64 to 7/64
OK, now you know the center, you need to set the bridge on that line and square it up. This is using a 3 degree compensation angle as does martin. I feel this will get you the best intonation that you can get on a fretted instrument. I suggest a 1/8 saddle slot. The heavier slot allows for better single string compensation.
Recap: center line and square
Now follow the line of the first E and low E and center the lines to the bridge holes. I like to have a minimum of 1/16 from the edge of the fretboard. This is to check your bridge pin positions are matching your neck taper. So along the line of the 1st string if I have a 3/32 bridge I will want to position the bridge so the front of the saddle will fall at the position of scale length doubled (nut to 12th fret 12.7 doubled = 25.4 plus 1/8 inch for compensation) The reason we do this is that you are trying to match a dynamic length ( one that is in constant flux ) to a static ( actual fret placement ). So in essence a long scale ( 25.4 scale will place to 25.5 ) This extra length of compensation allows for the strings to stretch as you play them. If I am using a 1/8 saddle I will place the line more to the center of the saddle. I do this for the saddle compensating later. You have more to work with on the 1/8 so this allow tweaking in both directions ( flat and sharp). The human ear will notice a sharp note easier than a flat . I then measure along the line of the lower E and place that 1/8 inch longer than the hi E. So you are looking at the lines along where the string would be placed these measurements. Hi E 25.5 and low E 25.6 For short scale ( 24.9 you want ( Hi E .025.0) 9 Low E 25.125) again this is from the position of the nut to the front of the saddle on 3/32 saddles. On 1/8 saddles you can place the bridge with with the line .25 inside the saddle.
Now you have the bridge located. At this point I drill through the 1st and 6th string holes and pin the bridge so it won't move when I clamp it.
Recap: Center - square - compensated.
Hope this info helps
john hall

tommyboy wrote:This is not that difficult and I am sure you will hear more than one theory. This is the method I have been using and one I learned from Dave Nichols of custom pearl. I can assure you that it works very well.
You must first know your line of center from the neck. I use masking tape and mark the tape so in front of the bridge I know where that center line is. Do not assume the tops center is where the bridge is to go.
Once you have center established you can begin the actual plotting of where it should be. You need to consider these variables
1: what action height do you want to go with
2: string gauge
3: the strings physical properties
This effects the placement in that higher action will pull strings sharp , and a heavier gauge seems to need a touch more compensation. I am figuring the placement using normal gauge ( lite and med ) and an action height that is around 4/64 to 7/64
OK, now you know the center, you need to set the bridge on that line and square it up. This is using a 3 degree compensation angle as does martin. I feel this will get you the best intonation that you can get on a fretted instrument. I suggest a 1/8 saddle slot. The heavier slot allows for better single string compensation.
Recap: center line and square
Now follow the line of the first E and low E and center the lines to the bridge holes. I like to have a minimum of 1/16 from the edge of the fretboard. This is to check your bridge pin positions are matching your neck taper. So along the line of the 1st string if I have a 3/32 bridge I will want to position the bridge so the front of the saddle will fall at the position of scale length doubled (nut to 12th fret 12.7 doubled = 25.4 plus 1/8 inch for compensation) The reason we do this is that you are trying to match a dynamic length ( one that is in constant flux ) to a static ( actual fret placement ). So in essence a long scale ( 25.4 scale will place to 25.5 ) This extra length of compensation allows for the strings to stretch as you play them. If I am using a 1/8 saddle I will place the line more to the center of the saddle. I do this for the saddle compensating later. You have more to work with on the 1/8 so this allow tweaking in both directions ( flat and sharp). The human ear will notice a sharp note easier than a flat . I then measure along the line of the lower E and place that 1/8 inch longer than the hi E. So you are looking at the lines along where the string would be placed these measurements. Hi E 25.5 and low E 25.6 For short scale ( 24.9 you want ( Hi E 25.0) 9 Low E 25.1) again this is from the position of the nut to the front of the saddle on 3/32 saddles. On 1/8 saddles you can place the bridge with with the line .25 inside the saddle.
Now you have the bridge located. At this point I drill through the 1st and 6th string holes and pin the bridge so it won't move when I clamp it.
Recap: Center - square - compensated.
Hope this info helps
john hall

This is a great post John but as usual I'm confused. I am about to set my bridge position on a parlor with a 24.9 scale as outlined by lmi on their scant instructions with the kit. Am I correct in thinking I should measure 25.0 from nut to front of saddle for my bridge position. Or is it just measure from nut to the 12th- then double that and add 1/8th ?

you do have to take the actual measurement of the fretboard you are using. Then along the line of the 1st and 6th string ad the compensation length. Here the variable is the saddle slot width . On the 1st string using a standard 3/32 saddle measure to the front of the saddle with 1/8 you can go in deeper, The goal here is to allow adjustment with the saddle and bridge rotation. If you can set up that you are 3 cents flat you will be in great shape.
In most cases , depending on set up goal. Keep notes , it won't take long to dial in the perfect spot just remember the higher the action the longer the string length so the more adjustment you need on the saddle.

thanks Rick I will make the corrections
Typing late

Runningdog wrote:John -- You said, "Hi E 25.5 and low E 25.6 For short scale ( 24.9 you want ( Hi E 25.0) 9 Low E 25.1) again this is from the position of the nut to the front of the saddle on 3/32 saddles. On 1/8 saddles you can place the bridge with with the line .25 inside the saddle."

I think you mean .025" instead of .25"!

The other numbers don't quite add up to the compensation you recommend earlier but I think you're rounding off to tenths rather than measuring to the hundredth.

I prefer to measure to the middle of the saddle (from front-to-back, i.e. half of 3/32" or 1/8") instead of the front edge. It keeps the compensation factor constant no matter what the thickness of the saddle. You and I differ very slightly in the amount we compensate but it seems like a larger difference because we're measuring to different points. I completely agree that builders should ALWAYS measure the nut-to-12th distance, double that, and add whatever compensation. We see improperly placed saddles literally every day, on guitars from respected builders and from factories (including Martin for almost 10 years!).

Thanks for the input Rick, On my 24.9 scale parlor I'm getting 12 7/16th from nut to the 12th
So, do I just double that and add 1/8th to the centre of the slot ? Or, is is to the front of the saddle slot ?

Many Thanks
Rusty

Does that sound about right ?

Zen wrote:

Runningdog wrote:John -- You said, "Hi E 25.5 and low E 25.6 For short scale ( 24.9 you want ( Hi E 25.0) 9 Low E 25.1) again this is from the position of the nut to the front of the saddle on 3/32 saddles. On 1/8 saddles you can place the bridge with with the line .25 inside the saddle."

I think you mean .025" instead of .25"!

The other numbers don't quite add up to the compensation you recommend earlier but I think you're rounding off to tenths rather than measuring to the hundredth.

I prefer to measure to the middle of the saddle (from front-to-back, i.e. half of 3/32" or 1/8") instead of the front edge. It keeps the compensation factor constant no matter what the thickness of the saddle. You and I differ very slightly in the amount we compensate but it seems like a larger difference because we're measuring to different points. I completely agree that builders should ALWAYS measure the nut-to-12th distance, double that, and add whatever compensation. We see improperly placed saddles literally every day, on guitars from respected builders and from factories (including Martin for almost 10 years!).

Thanks for the input Rick, On my 24.9 scale parlor I'm getting 12 7/16th from nut to the 12th
So, do I just double that and add 1/8th to the centre of the slot ? Or, is is to the front of the saddle slot ?

Many Thanks
Rusty

Does that sound about right ?

Anyone else want to chip in here, I dont want to glue the bridge until I'm 100% sure. I get 12 7/16th from Nut to top of Fret at the 12th. If i double that how much do i add and to where--is it centre of slot or front of slot. The bridge is already slotted and drilled by LMI so I dont have to worry about the compensation there but would really like to get advise on the measurements above
Thanks again to Rick and john and everyone else for the great support so far on this parlor and hopefully will be able to put some pics up soon
Rusty