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If you use cross dowels/barrel nuts with your bolt-on mortise and tenon neck, I have found that the bevel on the head of the bolt can cause problems while setting the neck. Filing it off will give you a little wiggle room and seat the full head on the neck block.

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Good judgement comes from experience. Experience comes from poor judgement.

Good tip Casey. I chamfer the edge of the hole in the neck block to get around that problem but I might try it your way next time.

I'd be concerned that the loss of material there might compromise the strength of the fastener, kind of like grinding down a weld bead -- it loses its inherent strength. I never cared for those bolts, so I switched to 1/4"-20 socket head cap screws and washers. http://www.mcmaster.com/#socket-head-cap-screws/=ym29vm


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Mountain Song Guitars www.mountainsongguitars.com

Good tip about the fillet affecting the alignment. But it's easier to just chamfer the hole with a counter-sink bit....unless you forget to do that before the top and back are glued on

There are short, hand-held chamfer tools that fit easily into the sound-hole should you forget. I don't know everything about fasteners, so maybe it's not an issue, but would rather avoid introducing a stress riser or other weakness at the joint of the head and shaft.

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"Building guitars looks hard, but it's actually much harder than it looks." Tom Buck

I suppose chamfering the holes would be my approach but I think the altered bolt would be strong enough in this application. If a bolt on neck is seeing enough force to break that bolt with the extra metal removed, the guitar is in trouble. I suspect you would be fixing wood long before you would have to replace that bolt.

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

Clearly, for those who cut their slots after body is finished, chamfering is a tough proposition. I'd like to see a picture of such a handheld tool please. Makes a lot of sense. I noticed in my last builds neck alignment was perfect until last couple of bolt turns. Never noticed the fillets.

Mine looks like this one, Mike. Forgive the cheesy guitar in the pic... I snatched it off of ebay...

I use mine a lot actually, for the bridge where the pins are inserted, and to easy the edges of the tuner holes for example. The results are not as perfect as one would produce with jigs/drill press, but I kind of like evidence of hand work.

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"Building guitars looks hard, but it's actually much harder than it looks." Tom Buck

That looks just like a countersink that you would use with a drill press, chucked into a file handle.

Alex

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"Indecision is the key to flexibility" .... Bumper sticker

This thread reminded me of a long standing question that's been rolling around in the back of my mind for a while. How much pull is actually exerted on the neck bolts? Because the strings pull in a line that is so close to the body, the majority of the string tension is pulling the neck into the body and only a small part is trying to rotate the neck upwards. If I remember how to do vector analysis of force diagrams properly from college physics, then assuming a 24.5" inch scale and total string tension of 160 lb, the upward component of the force at the nut is only around 2.5 lb. Using the 14th fret as the lever fulcrum point, the ratio of the length of the neck from the nut to the neck body joint to the distance from the top surface of the body to the lower bolt in the necks of my guitars gives a lever arm effect of about 5 to 1. So, if I had only the bottom bolt installed, the outward force on that bolt would only be about 12.5 lbs. I doubt that two of your bolts with the bevel removed would be in much danger of failing even if they were weakened some by removing the bevel.

Maybe someone has already addressed this on the forum before. If so, I hope my calculations are in the same ballpark.

I use #10-24 x 1 1/2" allen head bolts, which don't have a bevel, with a brass washer and recess them into the head block using a reverse spot facer.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

That is not the concern. And I am not sure there is a concern. When the fillet is ground away, you are creating potential stress risers. I think the concern is that you could twist the head off while tightening (or removing). But who cares? Break one or both, the neck is still coming off. I doubt, however, you could ever get to where you were applying enough torque to break it.