Official Luthiers Forum!

Thanks to everyone for their contributions to this illuminating thread.



Genuinely curious Hesh - why do you say 3 degree pins superior to 5 degree?

Although I briefly used 5 degree pins when I started building I soon ended up settling on 3 degree, which I use to this day. I could never discern much practical difference between the two and switched more because I became a loyal customer of a vendor who mainly stocked 3 degree pins, rather than any perception that 3 was a better design for pins.

So it's nice to hear that my expedient decision was correct But why?

Hey Josh: Great question and the difference between 5 and 3 degree pins in terms of the benefit is admittedly a nit but building a fine guitar can be all about lots of nits now can't it. . This comes from our friend Mario P. who back in the day offered the why 3 degree unslotted pins are superior to 5 degree unslotted pins.

It has to do with how we use a 3/16" drill bit to drill the pin holes and how less of a taper (3 degree) more completely fills the hole at the depth of where the pin becomes proud of the bridge plate.

The entire purpose of unslotted pins over slotted pins is the unslotted pins push the string ball more completely onto the surface of the bridge plate and off the pin hole edge that we drilled where slotted pins let the string ball eat that edge away over time causing damage. Since 3 degree pins push the string ball even more away from the pin hole edge than 5 degree pins and more firmly on the flat of the bridge plate even less wear and damage over time is possible.

Again you're 95% there with the benefits of unslotted pins with 5 degree pins but that last 5% or so is available to us by going with 3 degree unslotted pins.

Hopefully this will make sense from what I wrote here. We have illustrations of this on our walls at our Ann Arbor shop to show clients why they need bridge plate caps and replacements because of the ravages of cheap slotted plastic pins. I'd show some pics and graphics but we are closed this week because of the annual Ann Arbor Art On A Stick BS Art Fair.... The thing draws over 1,000,000 people all just milling around and wanting to talk at us so we leave town and lock down.... .

Anyway good on you for using 3 degree unslotted pins your instrument's serviceability quotient just went way up Josh!

I saw the same argument a few years ago when I was doing a bit more in terms of dredging the OLF and MIMF archives, and advise El Heffe that his pin angle choice was sub-optimal. His response to me was to prove my thesis. The following is a summary of my work, the defense of that work, my eventual conclusions, and my counter-argument:

The gap generated between surface of pin and edge of the bridge plate pin hole opening varies with the bridge thickness, bury of the pin head (is the ring under the head proud, half proud, or full-bury), pin angle to the base of the bridge (90 degrees is the usual), top thickness at the bridge, bridge plate thickness, diameter of the pin under the ring, height of the ring, and finally, pin taper.

For a 0.350" thick bridge, a 0.110" thick top, 0.100" thick bridge plate, and a 90 degree pin configuration, the total inserted distance for the pin is 0.560", less the bury on the ring. We aim for the pin to be 50% buried in the pin hole chamfer, reducing the inserted distance to 0.535" with a 0.050" tall ring (this is the measured ring height on AA 1931-1939 unslotted pins and about what the standard StewMac ivoroid, ebony, and tortoid pins run.

The AA and StewMac pins run about 0.220" nominal diameter under the ring, so with distance run of 0.535", the pin diameter at the inside surface of the bridge plate is 0.174" and hole diameter is 0.188", for a gap of 0.007" between the face of the pin and bottom pin opening of the plate.

For a 3 degree pin of 0.220" diameter under the pin, that gap goes to zero, while for diameter of 0.200" (the diameter of most of the common thermoplastic three degree pins seen on Asian imports, the gap reopens to about where the 5 degree, 0.220 pins would be, illustrating why both diameter under the ring and taper angle matters.

So I'll advance a counter-argument:

- I don't believe a gap of less than about half of the string ball diameter matters (ball diameter for D'Addario strings are about 0.160"), with the string ball oriented to - if free to do so - roll along the string. In this case, the point of contact of the ball with bridge plate would be clear or well clear of the edge of the pin-to-plate gap, depending on the aforementioned variables.

- Further, even with the string ball twisted 90 degrees to that orientation, the chamfer or radius on the edges of the ball (I measure D'Addario string balls as having an 0.080" width and 0.015" radius edge treatment) would make contact with bridge plate clear of the edge of the pin-to-plate gap, provided that gap is no greater than the sided width of the chamfer or the radius.

So in summary:

- I don't believe the sort of gaps generated with common bridge/top/plate thicknesses and pin installations would cause pin taper angle to become meaningful in terms of plate damage at the edge of the pin hole, although

- For longer inserted lengths generated by overly thick bridge/top/plate or pin ring and head left standing well proud of the top, the gap might grow large enough to be of concern

- Pin diameter at the bottom of the ring (or head, for a pin without a ring) matters...a skinnier 3 degree pin will have the same gap as a thicker 5 degree pin

Finally, according to the engineering brain trust here in the shop, withdrawal force for a tapered pin increases as the angle of taper decreases, so all other conditions being equal - something never seen in reality - the 3 degree pin will not only require greater force to remove, but will generate a greater 'spreading force' on the bridge with equal insertion force. This seems to me to be less of a concern with a fitted hole, as that force is evenly distributed.

_________________
For the times they are a changin'

- Bob Dylan

My head hurts now.

I am in the process of disassembling and rebuilding a 76' J45 and it has already shown me why you just shouldn't do a few things. A major sticking point for me is that it is always a bad idea to glue every single surface of your neck. that includes the sides of the guitar, the checks of the neck, and every other orifice imaginable. Glue the dovetail, fingerboard extension, and that's it. There is no reason to slather everything else with glue unless you just hate repair people.

It will be fine...just some momentary math. There...all better!

_________________
For the times they are a changin'

- Bob Dylan

Woodie wrote:
"I saw the same argument a few years ago when I was doing a bit more in terms of dredging the OLF and MIMF archives, and advise El Heffe that his pin angle choice was sub-optimal."

Hi Woodie,
I read your counter argument, and although I agree the difference between 5 degree pins and slimmer 3 degree pins is negligible, properly fitted 3 degree pins may be very slightly better as the bridge plate wears and the radiused portion of the ball ends come in contact with the bridge plate. This is largely a theoretical argument because careful placement and orientation of ball ends is not done. The argument that properly sized and fitted 5 degree pins (if available) would not have a "gap" at the bridge plate and would be equally serviceable as the fatter 3 degree pins could also be made.
The use of the term "sub-optimal" implies that there is an "optimal" solution that is at least somewhat better than what is proposed, not merely no worse than it. I didn't see that mentioned.
Ultimately I think we are engaging in an activity the shampoo industry has been trying to eliminate.

I've already shown most of my work, and the trig is Sesame Street level at best (Oscar Had A Heap...), so it did not make sense to include that calculation. I'd love to hear your ideas on how much wear might be necessary to present an issue, as well as what string ball orientations might generate the worst cases for wear.

Optimal? I believe at the time I discussed this with El Heffe, I suggested that pinned bridges were not worth the trouble, but after too many set-ups and related work on Breedloves and other ridiculous instruments (the Babicz radial string monstrosity still gets my vote for worst of the worst), I have revised my opinion of late...Mr. Somogyi's pins are a bit hefty for my tastes, but they do fill the pin hole completely.

_________________
For the times they are a changin'

- Bob Dylan

When it comes to how much bridge plate wear will present an issue I think when the plate is so thin it is no longer protecting the fibers of the top from being damaged it is time to repair or replace it. In my opinion the worst cases for wear will be caused by the normal variation of the string ball placement every time the strings are changed, but I don't see a good way around it. Others may have a different opinion that is better informed.
Does your Boss (El Jefe) have some characteristics in common with a certain Cuban Dictator besides the love of fine cigars?
I hold the same opinion as you regarding the Babicz guitar. It never made sense to me. I do however use a pinless bridge on my travel guitars, which may not make sense to some. It is good that you are not dogmatic in your thinking and are willing to revise your opinions as experience dictates. So often we don't see the trees in the wood pile before us.
As I mentioned in my last post I think the argument between using 3 or 5 degree pins is one of splitting hairs. Ultimately the bridge plate is a "wear" item, similar to a fretboard, and although with proper care it's life can be extended, it will eventually have to be renewed.

As far as I can see, bridge pins are toggles. The ball end bears against the side of the pin, pushing it sideways and preventing it from popping out. Under the circumstances there's no need for the pin to fit tightly into the hole; even a somewhat loose pin will be pushed sideways and keep the ball end in place.

Bridge pins are wedges, and, as woodie pints out, the smaller the included angle the greater the wedging force. A line of six pins along a single grain line can exert enough force to crack a bridge if they're in too tight.

It's often said that tight pins sound better, but I have yet to see a blind study that demonstrates that. I suppose it's possible for a very loose pin to vibrate in the hole, which could cause a buzz or dissipate some energy at that particular frequency. Any other mechanism for a lose pin to affect the sound presupposes that there is some string signal being transmitted to the pin, and I have seen no evidence of that either.

It can be argued that we're talking about 'small' effects, and those things add up, but in this case I can't see much of a case for any effect.

Where's the emoticon for 'duck and cover'...?

I see the ball end as the "toggle" rather than the pin being such. For the ball end to have complete bearing on the bridge plate the pin should fill the hole completely and not allow the ball end to be half on and half off of the bridge plate, as a loose pin might do. As Woodie pointed out the difference between a 3 and 5 degree pin when properly fitted is rather miniscule. I won't argue the sonic effects of loose pins vs. tight pins, and believe a well fitted pin is neither loose nor tight.

I know the factual assumptions I am about to describe are probably not what repair folks normally see, but I will ask the question anyway:

If we start from the assumption that a builder of a new guitar has a reamer of a specific taper (pick one), and the builder intends to use unslotted bridge pins of a taper that matches the reamer, and the builder carefully reams the bridge pin holes to allow the bridge pins to fit snugly at the proper depth, and the builder puts well-cut string slots in the bridge, is there any practical difference between 3 and 5 degree bridge pins? Won't they both fit into their respective holes the same way, and fill up the entire hole, thereby not allowing the string ball end to creep up into the bridge pin hole?

I definitely allow for the probability that I am missing something, and I fully appreciate that lots of guitars do not have the beginning advantages I described. But if I build that part of the guitar right, does the taper matter? I'm just not seeing it.

Yes Don , but I did run into a problem on an early build where 5 degrees pins resulted in too small a diameter at the bottom of the bridge pin holes for the ball ends.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

That ia a common ailment of bridge pins that are not "fat" enough to start with. You have to first drill the pin holes to the minimum size needed for the balls to pass through and then ream the drill holes to fit the pins. Chamfering the pin holes in the bridge allows the pins to seat further down which can help. Something I do is fill the slots on the 10 cent plastic pins I use with slips of corian and make slotless pins that are a little fatter on the lower end. With a notched bridge it helps keep the balls on the bridge plate.

Yep drill the pin (and string ball) hole first, I use 3/16th".

Woodie is correct that the difference between the fit in the hole of the 3 and 5 degree pins is negligible. I originally called this a "nit" several thousand words ago.

Clay is right that this little bit or nit (the difference between 5 and 3 degree) does keep the string ball bearing more firmly on the flat of the bridge plate but then so will either five or three degree unslotted pins.

The only point that I think is important here is use unslotted pins and of course have the conversation as to why you are doing this with the guitar's steward and you can save a bridge plate. I think that I have eight acoustic guitars here in my condo and all of them are fitted for unslotted pins.

I'll add that one of the more common reasons why acoustic guitars shed bridges is that the bridge pin holes get damaged by this exact thing happening. The use of slotted pins permitting the string balls to start to migrate upward through the bridge plate into the top. It can cause the pin holes to be so very damaged that a physical crease in the bridge plate forms connecting the holes and eliminating the flat surface topside (on the top) for the bridge to be glued, properly on. The money part of the bridge, the back edge releases and the bridge starts to peel off.

Now we have a lifted bridge, damaged bridge plate, a possibly traumatized steward/cuctomer who loves the guitar and all that it now means to clean it up.

Just use unslotted pins, 3 or 5 degree please and your instruments may look like the 1870's Martin that we had here and some of our students saw that had zero bridge plate damage and unslotted pins.

Yes for the most part. This is that "nit" that I mentioned and the trig that Woodie mentioned. There is a minuscule difference in how well the two respective tapers fill the 3/16" drilled hole at the precise depth (bridge height, top thickness, plate thickness). The difference with the five degree taper permits the string ball ever so slightly greater access to the pin hole edge but again it's a ..... nit. Either taper in unslotted pins is a huge improvement over the use of slotted pins.

Now some of you may find it interesting why pins are slotted at all.

If you have not used unslotted pins you have not yet had to slot the bridge, top and plate for the strings. It takes a few minutes to do, I use cut-off 6" old strings with the ball end to do the fitting along with some shops made files and a small saw. There is a bit of skill required to make it look deliberate and uniform and fit effortlessly and well.

This entire step was eliminated for f*ctories when someone invented cheap, mass produced slotted bridge pins. One size fits all (when it never really did) ruled the day.

So what if 15 years later bridges are peeling up it wasn't the person's problem who invented the cheap, mass produced plastic bridge pin.

Sigh...

I think that may be the salient point here: once the switch is made to solid pins and ramped/slotted bridge, any bridge plate wear seems to progress much more slowly.

The El Heffe spelling is intentional...it's a running gag/commentary on the boss's horrible Spanish language skills, which seem at odds with the amount of time he spent in Central and South America doing what heaven only knows for a special something or other back in the 1990's. As far as I can tell, his abilities in Spanish are limited to ordering beer, getting directions to the bathroom, demanding that you drop your weapons or die, and offering some pretty awesome insults involving both family relationships and farm animals. Hilariously bad, really.

_________________
For the times they are a changin'

- Bob Dylan