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Hanger bolt question
http://luthiersforum.com/forum/viewtopic.php?f=10101&t=38929		 Page 1 of 1
Author:  murrmac [ Mon Jan 14, 2013 1:50 pm ]
Post subject:  Hanger bolt question
Just wondering what is the preferred length of hanger bolt used by those who employ this method of neck joint.

Over here we have a choice of 60mm or 50mm (M6) metric hanger bolts, although for some weird reason the wholesalers don't call them "hanger bolts" over here ..

So (for US builders) what length do you like, I would imagine that 2" would be just on the short side and that maybe 2 1/4" - 2 3/8" overall length would be about right ?

Also, what I would really like to know is ...what is the length of the wood screw on the bolt you use, and what is the length of the machine screw ?

I am, of course , aware of the necessity for dowel reinforcement in the heel, I just wondered if the lower bolt fully grasped the dowel, or whether maybe a longer bolt was necessary for the upper connector ? I suppose what I am really asking is "how far back from the face of the neck heel is the forward face of the dowel ?
Author:  George L [ Mon Jan 14, 2013 1:57 pm ]
Post subject:  Re: Hanger bolt question
Oooh, excellent questions... Eat Drink
Author:  murrmac [ Mon Jan 14, 2013 2:04 pm ]
Post subject:  Re: Hanger bolt question
Thanks George ..

One further thing which I meant to ask is ...do you guys leave the heel length over size, drill the dowel hole, insert the dowel, and then cut to length, or do you not find that necessary? By "heel length" I mean the length measured from the headstock, not the "body height " ...
Author:  Barry Daniels [ Mon Jan 14, 2013 2:17 pm ]
Post subject:  Re: Hanger bolt question
I am just starting to use hanger bolts, but the dimensions you asked for obviously depend on the size of your heel and the thickness of your head block. What works for one builder may not work for others. I plan on drawing every thing out and using a bolt that fits. But I too would be interested on what Mario and others may be using.
Author:  Ron Belanger [ Mon Jan 14, 2013 2:28 pm ]
Post subject:  Re: Hanger bolt question
murrmac wrote:
Just wondering what is the preferred length of hanger bolt used by those who employ this method of neck joint.


I use a bolt longer than needed and then cut it to just reach the depth of the washer and nut.

murrmac wrote:
Also, what I would really like to know is ...what is the length of the wood screw on the bolt you use, and what is the length of the machine screw ?


I think the real strength in this connection is where the screw is in the dowel, so the length needs to be at least 1/2 inch. On the bolts I use it is generally 1 inch or more, I think normally about half the length of the bolt; the machine screw is the other half.

murrmac wrote:
am, of course , aware of the necessity for dowel reinforcement in the heel, I just wondered if the lower bolt fully grasped the dowel, or whether maybe a longer bolt was necessary for the upper connector ? I suppose what I am really asking is "how far back from the face of the neck heel is the forward face of the dowel ?


As I mentioned above, the strength of this joint is having both screws fully in the dowel, I put the dowel in my heels 1/8" from the face. I do this after I cut the heel to the proper length and angle.
Author:  Tom West [ Mon Jan 14, 2013 2:42 pm ]
Post subject:  Re: Hanger bolt question
The bottom hanger bolt should engage with the dowel because that is the one taking the most rotational force from the strings.
Tom
Author:  murrmac [ Mon Jan 14, 2013 2:45 pm ]
Post subject:  Re: Hanger bolt question
Ron Belanger wrote:
As I mentioned above, the strength of this joint is having both screws fully in the dowel, I put the dowel in my heels 1/8" from the face. I do this after I cut the heel to the proper length and angle.



Thanks Barry, and thanks Ron.

I suppose I am still stuck back in my cabinet shop days, when, if you machined a mortise in a door stile, for example, you always left a "horn" on the end of the stile and then cut the surplus once the rails had been fitted ...I was kind of thinking that drilling and fitting the dowel might be similar ...
Author:  Darrel Friesen [ Mon Jan 14, 2013 4:14 pm ]
Post subject:  Re: Hanger bolt question
I cut the tapered tip of the woodscrew off so that the threads engage right to the bottom of the blind drilled hole in the heel and completely through the dowel.
Author:  murrmac [ Mon Jan 14, 2013 4:18 pm ]
Post subject:  Re: Hanger bolt question
Darrel Friesen wrote:
I cut the tapered tip of the woodscrew off so that the threads engage right to the bottom of the blind drilled hole in the heel and completely through the dowel.


That makes a lot of sense ...depending on the depth of your neck block it might be necessary to implement similar surgery on the machine screw end ?
Author:  mkellyvrod [ Mon Jan 14, 2013 4:30 pm ]
Post subject:  Re: Hanger bolt question
I agree with George - excellent questions, and I appreciate the responses. Didn't realize until recently that so many appear to be using these various types of screw and/or bolt fasteners. I'm only two deep into builds, and both are classical guitars; since I'm still such a newbie, I think I'm going to stick with the slotted heel block for at least two more classicals, but I'm considering a butt type joint for a steel string. Just trying to soak this all up, and appreciate all the input on this thread and other recent ones as well. Thanks to all for sharing.

Marty [clap] [clap]
Author:  ChuckB [ Mon Jan 14, 2013 5:15 pm ]
Post subject:  Re: Hanger bolt question
It really depends a lot on the size of the head block, where exactly you place the cross dowel, if you use a tenon, and if you are recessing the nut. That said, for me a 2" hanger bolt works, 1" of it goes into the heel of the neck, through a !/2" tenon and a !/2" maple cross dowel. As has been said, best to make a drawing. FWIW Collings has been using hanger bolts and a tenon for some time now.

Also, I drill and install the maple dowel on the neck blank before shaping.

Chuck
Author:  Joe Sallis [ Mon Jan 14, 2013 5:54 pm ]
Post subject:  Re: Hanger bolt question
what I'm not completely sure about is, do you drill the bolts into the neck to correspond to the neck angle? What I mean is, should the bolts protruded from the neck perpendicular with fret board or are the holes drilled at, for example a 1 degree angle, or dosent it matter very much as long as the cheeks of the neck are at the right angle? (hope you understand, difficult to explain these things sometimes!)
Author:  Bryan Bear [ Mon Jan 14, 2013 6:05 pm ]
Post subject:  Re: Hanger bolt question
Joe Sallis wrote:
what I'm not completely sure about is, do you drill the bolts into the neck to correspond to the neck angle? What I mean is, should the bolts protruded from the neck perpendicular with fret board or are the holes drilled at, for example a 1 degree angle, or dosent it matter very much as long as the cheeks of the neck are at the right angle? (hope you understand, difficult to explain these things sometimes!)


I drill perpendicular to the side surface the neck is butting against, though you would be amazed at jsut how much room for error there is.

As for lenght, as others have said, I cut off the pointy end of the wood screw plus however much more I need to in order get the machine threads to end where I want them to. Naturally, the heel block thickeness is part of the planning too. . .
Author:  ChuckB [ Mon Jan 14, 2013 7:27 pm ]
Post subject:  Re: Hanger bolt question
Joe, the bolt holes are drilled perpendicular to the head block, and perpendicular to the bottom of the tenon. When routing the tenon on the neck, make sure you set the proper neck angle in your jig so the cheeks are at the correct angle, and on my jig I can route the bottom of the tenon to match the top of the neck block / body. Then simply drill the holes in the neck perpendicular to the bottom of the tenon...Hope that makes sense.

Chuck
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