Dudenbostel Dovetail Neck Jig

[Kennyz55]

Peter Coombe says his jig is 4.5 degrees ."This is my dovetail cutting jig, the idea thanks once again to Lynn Dudenbostel. It is cut exactly to an angle of 4.5deg."


Lynn Dudenbostel said "After transfering the dovetail to the neck, it is placed in a fixture that holds it at the proper angle so the dovetail can be cut on the bandsaw. Shims can be put in on either end of the fixture to increase or decrease the neck angle according to an individuals playing style. For Chris' mandolin, I'm increasing the neck angle slightly because I know he prefers a low action. This will allow a proper /tdidge height with the lower action."

I think Roger Siminofff said 6 degrees.

I'm planning on building a jig to cut my dovetails. How many degrees do builders here use and how do you adjust for lower or higher action?

[sliebers]

I built my first ones with a 6 degree angle from the Siminoff book. I've found that put the bridge very high, (slightly above 7/8") That's with a fairly low action (3.5-4/64") at the 12 fret G string. I've since gone to a 5 degree angle and my bridges end up around 3/4"-13/16" which gives me plenty of room to adjust for high or low action. The standoff height of the neck also affects the bridge height. My standoff height at the 15th fret is about 13-14/32"
Hope that helps. I've measured a lot of F5s, even Loars and found the average bridge height is around 3/4". I feel that 7/8" is too high. Curious what other builders do.

[fscotte]

Recently I've been using 5.5 degrees, but 6 as well. I like more break angle without a massive riser block, so 6 gives me a 7/8" bridge. I'm liking a dry staccato sound, short sustain, so 18 degree break is what I go for lately.

[peter.coombe]

4.5deg is for an oval hole mandolin, I use 4deg for my A5's. 4deg gives a riser block around 10mm higher than the Spruce top and with my arching will give a bridge height of 20mm +-1mm.

[j. condino]

Here is a video showing my version and how I fit it to the body.

https://vimeo.com/149088032

I keep it adjustable rather than a fixed number to allow differences in the arch and ribs. There is a detailed article about the whole system in the upcoming new issue of American Lutherie magazine along with a 1925 snakehead blueprint.

j.
www.condino.com

[Kennyz55]

Here is a video showing my version and how I fit it to the body.

https://vimeo.com/149088032

I keep it adjustable rather than a fixed number to allow differences in the arch and ribs. There is a detailed article about the whole system in the upcoming new issue of American Lutherie magazine along with a 1925 snakehead blueprint.

j.
www.condino.com

Hi Jimmy,
This seems like am amazing system. How do you set the angle and what angle do you set?
Thanks,
Kenny

[Tom Haywood]

Cool jig and systems. My system is to set an old-fashioned T-Bevel to the desired neck angle (usually 6 degrees) using an old-fashioned protractor. When the neck is laid out on the block of wood, I mark the end cut using the T-Bevel and cut it with the band saw while the block is still square on the sides. The cut off piece becomes the angle setter for the neck riser pieces. The T-Bevel stays set for the remainder of the build to check things. I like the volume and tone produced by the 6 degree angle and find that it works well for setups, especially for a bluegrass mandolin. But if it winds up a little less than 6 degrees that's fine. Thank goodness for the Cumberland Acoustic tall boy bridges which can be modified to get the perfect height.

[sliebers]

I'm still thinking of how to build and use such a jig. I only make F styles. The body side of the neck joint is not a symmetrical radius. I'm trying to redraw the body shape to fit a 2" radius, but can't come up with anything that looks right to my eye.
James, do you have any pics of an F style body without the neck to show how you do it?

[HoGo]

The dudenbostel jig works for staright dovetail only. Look for versions of Gibson or Wiens (who copied it) for tapered dovetail.
I personally cut dovetails with simple handsaw. I mark the body on both sides and cut with handsaw very close to lines and clean the surfaces with chisel and sandpaper on straight stick (I make sure the outside of the ribs is smooth and straight along the dovetail for easier fitting). Then transfer the actual shape from body onto thick paper (together with exact position of 13/14th frets and centerline) cut it out as template and transfer on both top and bottom of neck heel lining it up with both frets and centerline (the bottom tracing is moved back to get proper angle) then cut he dovetail with same simple handsaw close to the line. I finish the fitting with sanding sticks gouges or scrapers till all surfaces fit nicely and the centerlines and fret positions are within pencil line, and of course neck projection must be correct. This can take me 1-2 hours half of which is measurement and drawing of the lines. I never felt need to make jig if it won't make it 30 minutes job. Perhaps dedicated cutterhead would be beter way - that's what Gibson is using these days and several other makers (MacRostie etc.) as well.

[peter.coombe]

The dudenbostel jig works for staright dovetail only

Not really. The bandsaw cut is straight, but I cut a caper by hand after the bandsaw cut so my joints are all tapered dovetails. Cutting the taper is easy peasy, but fitting it and getting everything straight and at the right angle takes at least an extra hour, usually more, sometimes much more if you screw it up and have to shim.

[j. condino]

Just tilt the table on your bandsaw; taper problem solved. Almost every bandsaw made since 1900 has tilt adjustable trunions.

If you have asymmetry in your designs, make asymmetric jigs. To me, the neck angle is not a single set parameter. It is a function of the arch height, the overstand, and the whole design intent of that mandolin.

No matter what system used, you need to be flexible and creative. I went from a miserable, challenging process that would eat up the better part of a day in frustration with inconsistent results to one that has very even predictable results and only takes about 15 minutes with a smile on my face. Call up the guys at Stew Mac and tell them you want that jig. They have seen the video and think it is irrelevant...


Jimmy???

[Bluetickhound]

James, if you ever consider making a batch of those jigs for sale, please PM me as I would gladly buy one. I have been able to improve every aspect of my (very limited number of...) builds but the dovetail is whipping me. I watched your video several times and that jig is legit. If StewMac isn't willing to pay you for it my guess is that they are feverishly trying to come up with their own version of it for an inflated price....

[j. condino]

Gotta Bridgeport mill? If so, we can make up a batch together. Better to give them away than deal with money. People seem to get crazy grumpy these days as soon as money gets involved.....

The reason that video exists is because I submitted it to several of the major tool and jig suppliers / producers in the country. Every single person who made traditional dovetails and then used mine both here and at the big lutheir nerdfests like GAL and ASIA has requested one- some rather aggressively. The video was my sales pitch to get them to produce it. I already have mine and I'm not setup nor do I want to become a producer of them. The general outcome of all my interaction with the other big guys who do things like that is they are mainly guitar centered companies who sell a lot of guitar items and that mandolins are generally a waste of time to them so they are not interested. There are dozens of fine guitar dovetail jigs on the market, but nothing for mandolin nerds...

Fitting a mandolin dovetail has its challenges, but with practice you can get good at them. This jig saves you about two dozen failed attempts before you get the hang of it. I also build and restore double basses- fitting a neck on one of those well is a LOT of work- probably 20 times the surface are of a mandolin neck joint! Like a lot of things, I'd guess that someday I'll see another person trying to make a buck off it and claim it is their idea. What is that old saying about imitation being the best form of compliment....

Either way, it seemed like a good idea that the rest of the community could benefit from, so I put it out there for free. I'm also in the process of updating my old websites and putting out a "blueprint of the month" for free where my goal is to start releasing some of the 100s of blueprints I've done over the years on some of the greatest instruments in the world from famous collections and museums that most other folks will never get a chance to handle. As much as I like issuing them with the GAL, it takes a huge amount of work to prepare a commercial blueprint. 'Better to get them out there than to have one person get them all when my I keel over and Mrs. C burns them in the woodstove with all of my old Brazilian rosewood.....

Peachtree city is just a few hours from Asheville; drop by for a visit sometime and you can see it in action or give it a test run and you can see the other versions that I worked out before this one.

j.
www.condino.com
www.kaybassrepair.com

[Bluetickhound]

That is a very kind offer and next time I am up there (I used to go to the GSMNP frequently but haven't been in a couple of years) I will definitely give you a heads up. I'm ashamed to say I live just down the road from Marty and have yet to pay him a visit...

[Inklings]

James, +1 on the admiration for the jig, and the willingness to send a few dollars your way if you change your mind and have a few made up. Thanks for making that video, and sharing with us - so much to learn, and that is a real help.

[David Houchens]

5 degrees

[amowry]

Great video, James!

[Marty Jacobson]

Great video, James!

Whomever machined that jig must be an absolute whiz.

[Dale Ludewig]

Was it you, Marty? The outside radius is pretty cool. A CNC'ed cutter could make short work of that, but kind of expensive for a one-off.

[j. condino]

You guys are making it harder than it needs to be. Just go to your local old geezer tool sharpening shop and have them regrind a big router bit; costs maybe $25. Anyplace that sharpens and cuts shaper bits can do it in ten minutes. I made several variations of them before this one was made. I used the cnc to make a very accurate version of my working model AFTER I had the kinks worked out. We'll keep the whiz's name a secret so you guys leave him alone; just give credit to where you got the idea from. There are already several other of my things floating around on the web that other folks are making $$$ on; low style points.

The goal is for everyone to make better mandolins, not get distracted with too much jigs and tooling nerdiness. Go over to the guitar forums and they completely miss the point and have a jig for every step of the process but very few of them seem to actually play the guitar. The first priority is to learn how to build something well. Once you work out a reliable method, then a jig can help you with efficiency and repeatability. Too many people get sidetracked on the jig aspect and wind up with some amazingly efficient production of mediocre things. This one is nothing- you should see the four foot tall welded version that I have for double bass necks. If the mandolin version saves me three hours, that one saves me three days per neck.

My grandfather was a patternmaker; I'm a mandolinmaker (who occasionally finds it necessary to make a good pattern jig)!

j.
www.condino.com

[Bluetickhound]

My idea is a lot less dramatic (and I'll be interested to see how well it actually pans out...). Cut about 4 or 5 identical blocks out of hardwood to shape, glue them together to form the jig and sand/file it to one long consistent shape. Easier said than done, I suspect but I'm going to give it a go and if it crashes and burns.... I'll tell everybody it was my idea all along. If it works, James will get full credit.

[Wes Brandt]

Here is a video showing my version and how I fit it to the body.

https://vimeo.com/149088032

I keep it adjustable rather than a fixed number to allow differences in the arch and ribs. There is a detailed article about the whole system in the upcoming new issue of American Lutherie magazine along with a 1925 snakehead blueprint.

j.
www.condino.com

How do you get a tight fit with a straight dovetail… ? I've always relied on the taper to pull it all together tightly.

I can see the appeal of it being much easier to cut and I can see where it would be less of an issue that the dovetail be quite so tight when you have a much larger glue surface on the heal end of the dovetail that glues to the back…

[RobH]

I'd like to revive this discussion because I'm also curious about using a straight dovetail. Should the back be glued on first and does the button act as a stop? if not how is the neck held at the proper standoff? Are there any disadvantages? Do you need dowels like the Siminoff joint?
Rob

[sliebers]

I use a straight dovetail. I get the fit and standoff height with the back off, then trim the heel flush with the back block. It takes me a lot of time to get the fit tight and still have everything pull tight. Sometimes I have to glue very thin maple shims to the neck tenon to make it tight at the bottom. The advantage of a straight dovetail for me has been an adjustable standoff. Once I get the standoff and bridge height established, I can use the button as a stop when I glue the neck in. I've now refined my dimensions and archings so the standoff/bridge height has been consistent from build to build. The fit ends up being so tight that I have to use a press clamp to seat the neck fully once glue has been added. I'm going to take some time on the next build to try some different joints, maybe a tapered, or possibly something like Ellis does.

[Wes Brandt]

No matter which dovetail you use, one thing you can do is leave your neck blank roughed out but unfinished and a little oversize in all dimensions, then concentrate on getting the joint and heel fitting well everywhere… then if needed you can plane the neck to the correct standoff height, correct set and then draw the center line, finalize nut position, neck thickness, peg head angle, install the truss rod etc. This way you're not trying to get the set angle, centerline and standoff AND the dovetail / neck heel fit all perfect at the same time.

I haven't used it yet but the straight dovetail is interesting to me for simplifying the work involved for this style of mandolin and because you do have a large surface area of the dovetail that glues to the back, I believe it adds a lot of strength where you want it… significantly more than the tapered joint which gets quite small at the back.

Also, you could use extra thick HH glue and warm everything up and keep it warm when you glue it… so it is more likely to fill any tiny gaps in the straight dovetail joint than regular thickness glue… regardless, I always use a long clamp from top of the peg head to the tail of what ever instrument I'm gluing the neck onto, after whatever other clamps I use are on, to be sure the visible joints are tight as possible.