Headstock Taper and Thickness

[amowry]

The ideal might be for the holes themselves to be oversize enough for the posts to only touch the bushings and clear everywhere else …ream them open just a bit from the back.

As a clarification, I guess this is basically what I do-- the holes in the wood are the diameter of the outside of the bushing all the way through, so the post only touches at the top edge of the busing, on the nut side. There's no reaming, though, it's just a single, straight-walled hole.

[Wes Brandt]

"In other words, the posts have to angle LESS with this method."

I just checked the mandolin tuners and bushings I use and there is more play than I would have thought.

posts = .234 bushing hole = .258 So there is a total of .024 (.258 - .234) "play" and if the post and bush are exactly centered when drilled and mounted from the back, at 90 degrees, the top of the post can be pulled .012 (.024 x 1/2) forward toward the nut.

So if you drill at 90 degree from the front you do end up shifting the top of the hole a small amount away from the nut relative to the bottom and IF the hole is big enough so it the post can go straight through at 90 degrees without binding… and the post comes out and the bushing is moved ~.012 away from the nut …I can see that it can all work out well and it apparently does…

HOWEVER If we were dealing with very precision parts with precision fit though, it wouldn't… it works because we are dealing with what would be considered sloppy work if you were a precision machinist… unless I'm still missing something.

So dang, I have learned something today… good stuff...

[Wes Brandt]

Didn't see this before I posted the last post..

"holes in the wood are the diameter of the outside of the bushing all the way through, so the post only touches at the top edge of the busing, on the nut side. There's no reaming, though, it's just a single, straight-walled hole"

So actually, you can push your tuners towards the nut when you mount them and have them riding right up against the nut side of the bushing at whatever angle or pressure you want within the confines of the system course. But it totally eliminates the which side to drill from question… it becomes irrelevant.

edit ..I take that back… of course the bushings should fit better if drilled from the front, but I've never noticed any problems myself. Now that I think about all this ...it would be best if the posts only touched the bushings and then the plate that the posts are mounted on are the other bearing for the the system.

[sunburst]

...So actually, you can push your tuners towards the nut when you mount them and have them riding right up against the nut side of the bushing at whatever angle or pressure you want...

Yes. I use gravity to place my tuners. The tuners will drop right into the installed bushings, I hold the head stock so that the nut end is down, and gravity holds the tuner shafts against the bushings, then I mark for the screw positions and drill. Actually, it is seldom if ever that the posts all touch the bushings. They are not all evenly spaced at that end even if they are in the plate unless the plate is perfectly flat, the holes are perfectly spaced, and the posts all are exactly 90 degrees to the plate. I assume my drilling jig spaces the holes to within about .004" or .005" as it is designed, though that's probably a bit optimistic, but suffice it to say it is at least as accurate as the spacing of the posts on any set of tuners I've used.
The tuners can be placed so that the posts contact the nut sides of the bushings regardless of whether the peghead is tapered, and I think it is a good idea either way because it reduces deflection of the posts from perpendicular to the plates under string tension, and that can't be a bad thing for smooth tuner function.

[Jim Hilburn]

Here are the Stewmac images showing how Waverlys should be installed and they show it as if it were in a tapered PH. The one with the bushing installed looks like MC Escher drew it.

[amowry]

That's true, you can mount the tuners with the posts bearing against the nut side of the bushing no matter how you drill the holes. I guess I just meant that it happens naturally if the holes are drilled perpendicular to the top.

Wes--"HOWEVER If we were dealing with very precision parts with precision fit though, it wouldn't… it works because we are dealing with what would be considered sloppy work if you were a precision machinist… unless I'm still missing something."

Yes, I'd agree with that-- the bushings are all plenty big so that they can be installed at an angle to the posts without binding. I've seen some older Schallers bushings that have a fairly snug fit, but I believe even those could be installed at an angle.

Edit--just saw Jim's post with the photos. Yes, that drawing of the bushing doesn't seem to show the gap resulting from being installed in a hole that is not perpendicular to the face of the headstock

The drawings show a "stepped" hole, and I'm not sure what the purpose of that is, but that would prevent the post from being angled in the hole. If the holes are perpendicular to the face, the hole does have to be a single size all the way through. That's why they say the tuner baseplate wouldn't mount flush.

[sunburst]

...The drawings show a "stepped" hole, and I'm not sure what the purpose of that is...

I don't know either, but I suppose the purpose is so that they can drill a tiny hole just big enough for the tuner post to fit through, and I really don't know what the purpose of that would be. Once loaded by string tension, the tuner post is pulled slightly diagonal, with the front part of the shaft bearing against the bushing in the peghead and the back part of the shaft bearing against the opposite side of the hole in the tuner plate. A small enough hole in the peghead would prevent that, friction would be increased because of the post bearing on the wood of the peghead, and the effort required to tune the instrument would be increased. Minor misalignment would go from being small problems to being bigger problems...human sacrifice, dogs and cats living together, mass hysteria...

[amowry]

[HoGo]

Here are the Stewmac images showing how Waverlys should be installed and they show it as if it were in a tapered PH. The one with the bushing installed looks like MC Escher drew it.

I think they suggest it so folks buy their drilling jig and and the fancy bushing reamer...
This way IMO is one of the safest way to get into problems. Most of binding tuners I've solved were dona that way. The small hole through wood is especially problematic. Often changes in humidity can cramp the post in the snug wood hole or gunk or oil (when folks try lubrication when tuners are tight) will harden in the hole into sticky mass making it turn even harder. their installation of bushing can be source of problems as well (especially using arbor press) no matter how yoiu drill hole for the bushing if you press it in it will want to align with the top surface (ebony is hard and flat against the edges of the bushing) so it will often compress the softer maple on one side inside the hole so the top seats flush with ebony. Result is simple, misalignment between the 1/4" hole in wood and 1/4" hole in bushing and this is asking for trouble as your tuner posts now bear at least against three or four points and any slightest imprecision in drilling the four holes will cause binding.
I do much like Andrew described. I drill 8mm (roughly diameter of the bushing) all through the headstock (I drill from top to back on drillpress through exactly marked positions on headstock face) perpendicularly to back and just ream the holes a bit so bushings seat neatly. When I insert the tuners from the front of the headstock as test they drop in freely right down with baseplate against bushings, this lets me know the bushings are in the right place. The holes in bushings of most modern tuners are large enough to accomodate the slight angle of headstock back (those old 1/2" long Schaller bushings were really tight, newer shorter version works fine). The tuner posts bear at just two points - one is the mounting plate and the other one is top edge of bushing. No more is needed, actually any more contact can just get you in trouble.
This is allustration I made some time ago (laft is bushing installed into hole perpendicular to back and teh other is with the bushing seated well against front of headstock), you can see that all you need is slightly loose hole in the bushing.

[tom.gibson]

Excellent drawing. That sums it all up for me.

[Tom Haywood]

Sums it up very well for me, too. The drawing on the left shows the bushing problem I described based on the taper, which led to asking why the taper is necessary. Drilling from the face perpendicular to the face has been my preferred method (I failed to list it in the various methods I've used for the taper), which explains why I have not had bushing problems until this recent one where I followed the instructions and drilled from the back. The idea that the posts SHOULD lean in the bushings did not occur to me, nor did I consider that the holes should be more than 1/4" diameter for the posts to avoid binding. I was concerned about the potential difficulty of seeking replacement for a faulty tuner if it was not installed according to the manufacturer's printed instructions. There was no intention to attack anyone's method or reasoning, and I apologize if it sounded like an attack. This has been a very educational thread. The take away for me is that the taper is aesthetic, it does not present a problem for tuners if the holes are drilled close to the size of the bushings, and no problem for bushings if the holes are drilled from the face unless they are screw on bushings (which I haven't seen on any mandolins so far).

[amowry]

Sounds like a good summary to me! I didn't read anything that sounded like an attack, and this thread has been educational for me too!