Slotted Bridge Pins vs Slotted Holes

[jacm81]

This is related to my last post: https://www.acousticguitarforum.com/...d.php?t=528786

Basically, I need to get my bridge pin holes reamed out for oversized pins. The question is, should just have the holes reamed out for bigger slotted pins or should I go for slotted holes and use unslotted pins?

[charles Tauber]

Why do you believe that you need oversized bridge pins?

As I discussed in your previous thread, the preferred method is slotted holes with unslotted pins, which force the ball end of the stings out of the hole and against the bridge plate. The worst arrangement is unslotted, untapered holes with slotted, tapered pins, the arrangement currently standard on Martins.

[John Arnold]

Four good reasons for using unslotted pins:
1) Unslotted pins are more durable. Without the slot, they are inherently stronger. They can be installed in any orientation, which means the string ball is not pressing on the same area of the pin each time they are installed. With slotted pins, the string ball is pressing on two knife edges, which tend to distort or break off with use. The slot in the pin means the string is bent at a sharper angle at the ball, placing more pressure on the pin. This also increases the wear on the pin.
2) Unslotted pins reduce wear on the bridgeplate. The string ball rests squarely on the bridgeplate, instead of on the edge of the hole.
3) Slotted pins have a slot that will clear the largest (6th) string. That means a loose fit on 5 of the 6 strings. Using unslotted pins and a slotted bridge means that each slot can be sized for that string. This better fit means less chance of wear.
4) Most bridge pins are tapered so that the diameter at the bridgeplate is slightly smaller than the string ball. Without the slot, this means that the hole will have to be a bit larger than the pin at the bridgeplate....where the fit is most critical. This normally means a straight hole, or a hole that is tapered on the upper side, but straight at the bottom. Either one will create a problem with the pins leaning over, and possibly having the string ball jam into the hole. Slotting the bridge and bridgeplate will allow the string ball to pass through a smaller hole that will be a closer fit for the pin.
One way to make this work better is to use strings that have a ball with rounded edges, like DAddario. They will pass through a smaller hole....whether it is slotted or not.

Martin used unslotted pins until 1944. I have repaired many, many prewar Martins that had their original bridgepins in good functional condition. The bridgeplate wear on these guitars is often nonexistent or minor. This is extremely rare on Martins made after 1944, where damaged pins and bridgeplates are the norm.

It is possible to reduce the size of the pin holes by coating them with super glue. After the glue cures, the holes can then be taper reamed to fit smaller pins.

1930's Martin style unslotted pins are slightly larger than modern slotted pins. This style of pin is available from Stew Mac (Waverly), or from Elderly (Antique Acoustics 1930's type).

[lar]

I have a 2011 (?) Gibson AJ with slotted pins. It sounds like getting solid pins and slotting the bridge would be beneficial to the longetivity of the bridgeplate. Or I could just use the same (stock) slotted bridge pins turned 180 degrees I suppose (although as John pointed out, the pins themselves would not be as durable).

I can't imagine it would be expensive to have a luthier slot the bridge. Any idea of the rough cost? My only issue would be finding someone who knows how to do this correctly and not make things worse. In that sense, it may be best to leave things as they are.

Am I correct in that slotting the bridge will change (increase) the break angle of the string over the back side of the saddle? Which is generally considered to be a good thing?

BTW: Briankimsey.com has some nice photos of seated balls in various bridge configurations (after going to his site, select 'lutherie', then 'slotted bridges'.

[charles Tauber]

Originally Posted by lar

I have a 2011 (?) Gibson AJ with slotted pins. It sounds like getting solid pins and slotting the bridge would be beneficial to the longetivity of the bridgeplate.

In some circumstances, yes. However, the first thing that should be done is to have tapered holes that match the tapered pins. Martin doesn't do this anymore. The initial reply and discussion related to a Martin guitar in which the OP was having some issues.

If the tapers match, with care, in a non-slotted bridge, one can ensure that the ball ends of the strings are fully seated against the bridge plate, rather than in the holes. Doing that will minimize longterm damage to the bridge plate. Not as ideal as sloted holes with unslotted pins, but likely adequate in most cases.

Or I could just use the same (stock) slotted bridge pins turned 180 degrees I suppose (although as John pointed out, the pins themselves would not be as durable).

Pins, generally, aren't expensive. However, if you have suitable pins that aren't worn, just turning them around is fine. No need to run out and buy new pins.

I can't imagine it would be expensive to have a luthier slot the bridge. Any idea of the rough cost?

Should be under $50.

Am I correct in that slotting the bridge will change (increase) the break angle of the string over the back side of the saddle? Which is generally considered to be a good thing?

"Slotting" is different than "ramping". Slotting doesn't change the break angle much. The purpose of ramping holes is usually to increase the break angle.

Alan Carruth's work suggests that beyond about a 6 degree break angle, the angle doesn't matter much. If the angle is too large, it increases leverage on the saddle tending to force the saddle to lean forward. In some cases, that can crack the bridge at the sound hole-edge of the saddle slot.

[Arthur Blake]

Originally Posted by John Arnold

Four good reasons for using unslotted pins:
1) Unslotted pins are more durable. Without the slot, they are inherently stronger. They can be installed in any orientation, which means the string ball is not pressing on the same area of the pin each time they are installed. With slotted pins, the string ball is pressing on two knife edges, which tend to distort or break off with use. The slot in the pin means the string is bent at a sharper angle at the ball, placing more pressure on the pin. This also increases the wear on the pin.
2) Unslotted pins reduce wear on the bridgeplate. The string ball rests squarely on the bridgeplate, instead of on the edge of the hole.
3) Slotted pins have a slot that will clear the largest (6th) string. That means a loose fit on 5 of the 6 strings. Using unslotted pins and a slotted bridge means that each slot can be sized for that string. This better fit means less chance of wear.
4) Most bridge pins are tapered so that the diameter at the bridgeplate is slightly smaller than the string ball. Without the slot, this means that the hole will have to be a bit larger than the pin at the bridgeplate....where the fit is most critical. This normally means a straight hole, or a hole that is tapered on the upper side, but straight at the bottom. Either one will create a problem with the pins leaning over, and possibly having the string ball jam into the hole. Slotting the bridge and bridgeplate will allow the string ball to pass through a smaller hole that will be a closer fit for the pin.
One way to make this work better is to use strings that have a ball with rounded edges, like DAddario. They will pass through a smaller hole....whether it is slotted or not.

Martin used unslotted pins until 1944. I have repaired many, many prewar Martins that had their original bridgepins in good functional condition. The bridgeplate wear on these guitars is often nonexistent or minor. This is extremely rare on Martins made after 1944, where damaged pins and bridgeplates are the norm.

It is possible to reduce the size of the pin holes by coating them with super glue. After the glue cures, the holes can then be taper reamed to fit smaller pins.

1930's Martin style unslotted pins are slightly larger than modern slotted pins. This style of pin is available from Stew Mac (Waverly), or from Elderly (Antique Acoustics 1930's type).

What an excellent summary. Thank you, John.

[lar]

Thanks for the Gibson advice Charles. I talked with a luthier at a local shop today. He said my options would include:

1) have him make ramps in the bridge so the string won't be at right angles coming out of the bridge (which could break strings if it is close to a right angle), and then string-up w/o using the slots in the pin.

OR

2) just turn around my slotted pins now so the slot points away from the saddle, and see how it works. The strings naturally will (and probably have already) ground a natural ramp - he said. But if not, and strings start breaking, then have him ramp the bridge (option 1).

Is #2 reasonable?

OP - I think I took a Gibson fork in the road. My apologies.

[charles Tauber]

Originally Posted by lar

Is #2 reasonable?

The "usual" method is to drill holes, taper them to match the bridge pins, then used slotted pins. Properly fitted pins fit in the holes without space around the pins. The slots in the pins accommodate the diameter of the strings. With an unslotted hole, with unslotted pins, there is nowhere for the string diameter in the hole. That is the purpose of the slotted pins.

Alternatively, one can slot the holes to accommodate the diameter of the string, then use unslotted pins.

Unless you have a lot of wear in the pin holes, enough to accommodate the diameter of the strings, simply turning the slotted pins around won't allow for the diameter of the strings - unless the pins don't properly fit the holes. Pin holes don't usually wear sufficiently to accommodate the diameter of the strings. Properly slotted, the pin holes are slotted right through from bridge to bridge plate.

Unless you have insufficient saddle height, you generally don't want to ramp the holes. You might want to slot the holes.