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Hand fit dovetail
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10128&t=27729		 Page 1 of 1
Author:  Haans [ Mon Jun 07, 2010 1:48 pm ]
Post subject:  Hand fit dovetail
Can't remember, but someone a while back wanted some photos of dovetail work. Here's how I do it with a straight dovetail...
The dovetail is marked on the box and cut out on the bandsaw. While I'm at it I cut out the scroll too.
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Next I clamp the neck to the box, align it, then using a Xacto #11 mark out the dovetail on the neck. Then I cut out the male part.

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The rest is all fitting and filing till it slides in. Lastly, I cut the heel depth so it's flush to the bottom and It's all ready for the back.
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Lastly , I check the angle...
Pretty simple really, but a lot of hand work to fit it.

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Author:  Dave Stewart [ Mon Jun 07, 2010 2:13 pm ]
Post subject:  Re: Hand fit dovetail
Great stuff Haans....love pics like this.
Just curious..do you have a special jig to hold the neck at a specific neck angle (relative to the f'board surface) while you bandsaw the tail?? (...or maybe the angle's zero for mandolins. For archtops, it's about 4 1/2.)
Author:  Haans [ Mon Jun 07, 2010 3:41 pm ]
Post subject:  Re: Hand fit dovetail
Looks like I forgot one photo.
Dave, if you will notice, the back end of the neck before the tail is cut is at a 5-1/2 degree angle, and the bottom of the heel is 90 degrees to that angle. When I put it on a riser (to clear the peghead) it automatically cuts the tail at the required 5-1/2 degrees.

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Author:  Dave Stewart [ Mon Jun 07, 2010 5:31 pm ]
Post subject:  Re: Hand fit dovetail
Ahhh... that makes sense!
I think this is great (& I don't even make mandolins)... elegent in it's simplicity. Maybe should be in tutorials for posterity.
Author:  JJ Donohue [ Mon Jun 07, 2010 6:34 pm ]
Post subject:  Re: Hand fit dovetail
Beautiful!!!

Thanks, Haans...this is just what I need to see. You just made my mandolin project a bit less stressful!
Author:  Chris Oliver [ Tue Jun 08, 2010 10:58 am ]
Post subject:  Re: Hand fit dovetail
Haans wrote:
Looks like I forgot one photo.
Dave, if you will notice, the back end of the neck before the tail is cut is at a 5-1/2 degree angle, and the bottom of the heel is 90 degrees to that angle. When I put it on a riser (to clear the peghead) it automatically cuts the tail at the required 5-1/2 degrees.



Haans... it appears that you do not use a compound dovetail here because you have extra support/glue to the back plate?

Do you use a compound dovetail on A style necks that do not finish flush to the back side of the rim and sit higher with a heel cap ... like a guitar?
Author:  Haans [ Tue Jun 08, 2010 1:01 pm ]
Post subject:  Re: Hand fit dovetail
Thanks guys, glad if it can help. Since I will no longer be building mandolins much I'm petty much an open book.
Chris, I use straight dovetail on all my mandolins. It's just easier. When you have that many compound planes to work through, a tapered dovetail is just another trouble. It's also very easy to set the height of the neck off the top riser block this way. Lots of builders and wannabees make the mistake of setting necks too high, and end up with bridges that are too tall. Then you have to deal with too much down pressure on the top, and that will kill the tone.
That ebony jig is a great little tool. The screw is adjustable and it is just a 3/4" chunk of ebony glued to a tapered maple piece (that simulates frets + action) and a chunk of old fretboard on the bottom. Set your desired bridge height with the screw, and as you fit the dovetail, check it with the jig. When you glue the neck on (after the back is on, just clamp the jig to the neck and make sure the screw is touching the top at the bridge spot.
Author:  Chris Oliver [ Tue Jun 08, 2010 3:26 pm ]
Post subject:  Re: Hand fit dovetail
Thanks Haans. That is definitely a time saver... and in some instances, a hair saver. At least I haven't pulled out all of my hair yet setting mando dovetails.

Have you had any trouble with necks rising? I'm guessing no, but...
thanks again.


Wait a second... if you're not using a compound dovetail, how do you keep the cheeks firmly on the neck block? Do you jam wedges in the dovetail while using the slipping sandpaper method, eventually gluing in the wedges? How tight do you attempt to get the cheeks against the neck block? So many new questions for a new, to me, method of attaching the neck. gaah
Author:  Haans [ Wed Jun 09, 2010 6:49 am ]
Post subject:  Re: Hand fit dovetail
Chris, thin slivers are stuck into the dovetail when glueing, but the cheeks are glued also. This is not like a guitar dovetail. Mandolin necks aren't built to come apart easily, and don't need to. Necks don't pull up. It's more important to get a tightly glued joint. Mandolins are finished with the neck on.
Author:  Chris Oliver [ Wed Jun 09, 2010 7:02 am ]
Post subject:  Re: Hand fit dovetail
Haans, I hoped you would respond that way. I spend so much time trying to get the dovetails undercut and then sneak up on them. I should be cutting them to be a close fit and then shim them as you instructed. This would save alot of time going in knowing you're going to have to shim them anyway, so just get them close instead of under. I never seem to get over the fact that the necks don't usually budge on mandos and always want to make the repair easier. Much conscious effort is required!
Author:  Haans [ Wed Jun 09, 2010 8:47 am ]
Post subject:  Re: Hand fit dovetail
Very, VERY rarely is a neck reset done on an arched mandolin, Chris. They usually have maple necks with a truss rod, many times ebony strip down the center, are 10" long, and have the break angle bisected by the bridge more or less. Guitars just have a different set of forces going on.
Author:  Arnt Rian [ Wed Jun 09, 2010 9:05 am ]
Post subject:  Re: Hand fit dovetail
Thanks, Hans! This looks (a little) less overwhelming than the tapered dovetails, maybe something even I can tackle. I've been doing the Siminoff style joint, which is for sissies really ;) This metod allows you to carve that elegant cocave shape on the side of heel, which the Siminoff one doesn't, without too much hassle.

Hey Hans, now that you're mostly retired from mandolin making, feel free to share anything you can think of. This is great stuff! bliss
Author:  Chris Oliver [ Wed Jun 09, 2010 9:32 am ]
Post subject:  Re: Hand fit dovetail
Arnt Rian wrote:
I've been doing the Siminoff style joint, which is for sissies really ;)


uh... ohhh... beehive
Author:  Haans [ Thu Jun 10, 2010 7:00 am ]
Post subject:  Re: Hand fit dovetail
Arnt, I'm open for any discussions.
I should say that the object is to get a tight sliding fit. You have to sneak up on it just like a guitar dovetail, but like a guitar dovetail, if you screw it up a little bit, you can always use shims. You can see that the dovetail above is pretty tight (neck is sitting lower than the riser block), and with a good fit, you have to use a clamp to draw down the neck after the glue is spread.
Author:  WudWerkr [ Thu Jun 17, 2010 8:18 am ]
Post subject:  Re: Hand fit dovetail
Beautifull work on that one . looking forward to hearing a clip of her singing ! [:Y:]
Author:  Chris Oliver [ Tue Jun 22, 2010 3:34 pm ]
Post subject:  Re: Hand fit dovetail
I gave Haans' method a try not long after his posts above. Here is what I experienced.

Here it is with a semi-tight fit. A few small wedge shims were made to draw the heel in as it is forced down during gluing.
Attachment:
Dsc01041.jpg


Here it is with glue slathered everywhere...not knowing how long this operation would take to complete, I didn't use hide glue.
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Dsc01043.jpg


Here I am forcing in the top wedges to draw neck even tighter.
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Here it is with most of the glue squeeze out wiped clean.
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Here it is with fretboard installed, strung up and playable with a fly enjoying the blond look.
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A few things I learned in this method.

  • You need to apply your wedges/strips evenly. While clamping, the neck pulled slightly off to one direction. This was due to the wedges I used inside the joint being differently sized...even though just slightly.
  • This neck had enough room to move side to side a bit. This allowed the neck to twist while it was being clamped down into the joint. I was able to get it mostly straitened out and it is not as critical on a mandolin with fretboard extender that is being shaped to meet the angle of the neck in the next operation, but should be addressed. In the case of this mando, the neck is tilted slightly counter-clockwise when looking down from the headstock. I chock this up as an added feature to more easily get at the G string... you know, like on master fiddles.
  • The clamping method I used to draw the neck down into the neck block could have been improved. For the next, I will make a cawl to help put more pressure where needed. I would have liked this neck to drop down about an 1/8" more than it did at the time.
  • The last thing I noted once strung up and attempting to tune. The top dropped far greater than I had expected it would and my bridge height is pretty high. I'll have to anticipate that extra 3/16" on the next one.


If the high bridge did affect the tone, this one would have tone off the scale. The current sounds coming out of it are wonderful and fat. I didn't thin the top plate. I actually left it a little thick under the bridge and just right at the thinnest area along the rim.

It is built with a lutz spruce top sourced from Shane Neiffer, local hard maple back and sides, local walnut accents and cocobolo accents. The headplate and fretboard are African blackwood. The tailpiece is from Bill James, ebony bridge and golden era tuners from StewMac, bone nut from cow, moo.
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