Dudenbostel Dovetail Neck Jig

[sliebers]

There is a lot of surface area for glue with the straight dovetail. There are no gaps when it's done right. I use regular thickness HHG to glue it in, and it still binds towards the bottom when installing. I don't think I could use anything thicker. Here's my clamping jig for seating the neck fully during glue up.

[Wes Brandt]

There is a lot of surface area for glue with the straight dovetail. There are no gaps when it's done right. I use regular thickness HHG to glue it in, and it still binds towards the bottom when installing. I don't think I could use anything thicker. Here's my clamping jig for seating the neck fully during glue up.

Do you size your neck joint… like coat the mating surfaces with hide glue and let them dry, (often requiring a bit of refitting afterwards) before then gluing it together? Or just glue it together bare?

[fscotte]

I do a straight joint as well. I wet the joints with water, then lightly sand when dry.

[Wes Brandt]

...for a long time I've sized my dovetails and other surfaces with medium thick glue, warming them a bit with a heat gun first ..they usually swell a little and need to be fit again and always, I remove any glue from the surfaces…

Then when you finally glue it, no or little water is absorbed to swell the various mating surfaces so everything slides together nice and smoothly… though now I see with a non tapered dove tail… you could use that natural swelling to help make the joint fit tighter, in which case you would not want to size it …very interesting...

[sliebers]

Do you size your neck joint… like coat the mating surfaces with hide glue and let them dry, (often requiring a bit of refitting afterwards) before then gluing it together? Or just glue it together bare?

I just glue bare, no sizing or wetting before. I do heat the tenon with a heat shrink gun, and as much of the mortise as I can without burning the binding before I apply the HHG. Might try sizing and see how that works.

[fscotte]

If I glue it dry, I have trouble getting the neck all the way into the joint.

[sliebers]

If I glue it dry, I have trouble getting the neck all the way into the joint.

Sizing the joint makes sense. I'll have to try that on the next one. Are you able to push the neck in by hand to fully seat?

[fscotte]

Absolutely. I see no evidence that a joint that is at least snug, will come loose later. I believe these joints fail for inaccurate jointing, leaving gaps, or a loose fitting joint, or huge gobs of glue to fill areas. Wood on wood contact is as strong as the wood. We know that from tests and experience. If your joint is wood on wood, it will hold.

[sliebers]

Absolutely. I see no evidence that a joint that is at least snug, will come loose later. I believe these joints fail for inaccurate jointing, leaving gaps, or a loose fitting joint, or huge gobs of glue to fill areas. Wood on wood contact is as strong as the wood. We know that from tests and experience. If your joint is wood on wood, it will hold.

I think I've been making the fit too tight all this time? When dry fitting, there is no movement, and the joint would probably hold without any glue. It makes it very difficult to push the neck out when fitting however. A snug joint that is not sloppy makes more sense. Thanks for the information.

[Wes Brandt]

Sizing the joint makes sense. I'll have to try that on the next one. Are you able to push the neck in by hand to fully seat?

I still fit it very tight before gluing and then have to clamp it firmly to get it all the way in but with it sized, the water doesn't get sucked out of the glue so fast and I no longer worry about it getting hung up before seating.

I also find sizing useful when doing neck resets on guitars and etc …I've had a few experiences when I just started using hide glue where the glue swells the joint parts and throws off set a little when it drys, though I may have been using too thin of glue and/or too much warmth those times… but with sizing first, little or no swelling of the wood keeps it all tidy.

[fscotte]

Oh I also use finer grit sandpaper for final sanding. 400 is fine even 600 if you want. Makes for a very smooth snug fit. If youre worried about sanding evenly, just lightly mark the surface with a pencil or use the light reflections to see where youve sanded.

[HoGo]

With straight dovetail there will always be problem with need of all surfaces being perfectly perpendicular to bottom so the neck will insert smoothly. and with any jig used to cut or finish neck dovetail you'll need your body curve perfectly consistent as well. With tapered dovetail you need to get more surfaces to fit all at once, but the joint will tighten automatically and won't bind when gluing in until last 1/16 of an inch.
I believe Don MacRostie uses similar jig to James to shape the outer curve of the body at the neck joint to consistent shape every time but uses custom half-moon cutter in his tablesaw to cut the neck dovetail.
Problem with jigs is that they are rarely universally useful on more body shapes.
I probably couldn't use such jig on my mandolins with tapered dovetail as the slot in the jig would need to be wider tan the neck heel on my necks so that part would not get sanded...
I already posted that I cut my tapered dovetails all by hand, and the harder way (with the body already completely assembled) and when all goes alright I can fit the neck to body within hour or so. This includes 30 minutes of transferring the shape of dovetail to neck and drawing future positions of all centerlines and fret positions needed for correct fit. (I also intentionally angle the neck centerline in Loar style). I'm satisfied when there is wood to wood contact in all critical surfaces and the centerlines and fret positions drawn on both neck and body coincide within the thickness of the pencil lines. It's not that hard to do if you think about each material removal and how it will affect the fit.

[Wes Brandt]

How do you manage to cut the curved parts of the joint by hand Hogo? I've never been able to cut such thick wood accurately with a coping saw but maybe there are really nice blades out there.

This might be of interest to some folks… I had been thinking along these lines for a while… someone mentioned plastic pipe for this but I can't remember who.

…so the other day, I went to my favorite hardware store to see what might be possible and in the remnants bin there was 3' of this stuff, the first thing I looked at… which happens to be exactly 1.9" outside diameter, what luck ...the dimension James mentions in his video (thank you James) for the jig he made…

…also smooth, consistent and rigid, easy to cut…

[HoGo]

How do you manage to cut the curved parts of the joint by hand Hogo? I've never been able to cut such thick wood accurately with a coping saw but maybe there are really nice blades out there.

I use common (cheap) HW store handsaw for this (just like this
https://ae01.alicdn.com/kf/HTB1RTmXK...ade-with-a.jpg
, but in blue color :-) ). With somewhat coarser blade than what it was sold with. I clamp the neck blank to table and just cut close to the lines watching regularly both bottom and top of the neck not to cross the lines. 5 minutes or so of cutting, then goes the final fitting...

I posted more in one of the older threads here:
http://www.mandolincafe.com/forum/sh...ail-neck-joint
I forgot to mention here that I spend some extra time drawing centerlines just after I glue up the rim and cut dovetail into the block and transfer that to piece of thick paper that will later become my template to mark the neck.

[Wes Brandt]

"I use common (cheap) HW store handsaw for this …"

Thanks Adrian… I have one of those but I wouldn't have thought the blades would cut a tight enough curve, however with coarser teeth and more set…. I can see it.

[HoGo]

"I use common (cheap) HW store handsaw for this …"

Thanks Adrian… I have one of those but I wouldn't have thought the blades would cut a tight enough curve, however with coarser teeth and more set…. I can see it.

The original blades wouldn't cut the curve but the coarser blades (something like 1/4" x 8-10 tpi) do it easily. They are sharp and cut easy without need for excessive presure.

[Kennyz55]

I use a knew concepts coping saw like this one.

[HoGo]

Wider blade os the handsaw makes it easier to follow the smooth curve of the cut. Scroll saws and coping saws with thin blades wander too easily and you have to be more careful than with the cheap handsaw...