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DBurns

Cello Neck Dowels Information

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   Hi 

Can anyone that has pinned their cello neck, a la David Burgess Method, tell me how far back the center dowel is and at what angle to drill at?

 

Working on planning for my first cello.

Thanks

 

 

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Hi,

I use two smaller carbon fiber rods on either side of the center line, rather than one larger one in the center. I also run a c.f. strip down the center of the length of the neck. The combination of the two is similar to the bent c.f. piece demonstrated awhile ago in the strad, but much less expensive.

The pieces in the heel sit about 10mm above the bottom, and follow the angle all the way back, ending about 10mm from the button. So the angle of the holes is the same as the angle of the heel. 

Carbon fiber comes from here:https://dragonplate.com

Anyway, that's what I do.

Good luck!

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   Hi 

Can anyone that has pinned their cello neck, a la David Burgess Method, tell me how far back the center dowel is and at what angle to drill at?

 

Working on planning for my first cello.

Thanks

 

Hi DB - I've repaired a number of broken cello necks by drilling a 16mm dia. hole parallel to and as close to the outside of the heel as I dare - then gluing in a "slip-fit" maple dowel using structural epoxy as the adhesive.

 

I gave your question some thought and  I think that, on my first cello, I'll make a 10mm wide slot into the end of the heel and glue in a piece of maple that has it's grain running at right angles to that of the neck - i.e. laminate the heel. That will improve the tensile and compressive properties of the heel and reduce any movement due to string tension.

 

Finish the bottom of the groove as a semi-circle to avoid any stress raising corners.

 

cheers edi

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Thanks for the information.

90 degrees!  Got it!

 

I am making jigs right now, and thought I would make the "David Burgess" style drilling jig for Cello neck dowels, from Trade Secrets article in The Strad magazine.

I do not want to make a mistake and drill in the wrong spot!

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From a repair standpoint I really hate dowels in necks.  I deal with a lot of broken cello necks, and when a neck has a dowel in it the dowel is an obstacle for repair.  I am not convinced that a dowel provides adequate reinforcement to a previously cracked neck, and the fact that it is not reversible is a problem for me.  I haven't read the article you reference, but I'm guessing that the dowel in a new instrument is expected to prevent shifting of the neck angle over time.  I have a bass in the shop right now that has a broken neck heel and it had been previously repaired at a well respected bass shop with 2 ebony dowels 1/2" diameter and at least 40mm deep on either side of the crack.  Didn't prevent the neck from breaking again.  

 

I know David has a great reputation as a maker, and I know other well respected makers use dowels in new necks.  I don't see a lot of modern American instruments in my shop, so my comments on dowels is more of a general statement, not directed at the practice in modern making.  

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Thanks for the information.

90 degrees!  Got it!

 

I am making jigs right now, and thought I would make the "David Burgess" style drilling jig for Cello neck dowels, from Trade Secrets article in The Strad magazine.

I do not want to make a mistake and drill in the wrong spot!

DBurns, I'm not sure the holes are 90 degrees to anything. The photo below gives an idea of the angle and location I use for the thickest and most important dowel. The idea is to get it as close to the outside surface as you dare, in the area where the neck has the least support, and is most susceptible to bending.

 

IMG_1917%20reduced.jpg

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Thanks Everyone ....

I will be working on a neck that is not finished until after it is joined to the body, so I am guessing right now how to drill this thing with enough clearance, but not too much.

I want to put dowels in the neck so that the neck does not go all over the place with wild swings in humidity.

 

My guess is that the neck heel angle is about 83 degrees, so I will try and use an 83 degree angle for the 10mm diameter dowel.

I guesstimate from David's picture that about 50mm back from the end of the neck heel will do.

 

Once I have a finished neck, calculating the right angle and dowel placement will be easier.

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Lovely varnish, David.

Thanks, Christopher.

 

 

 Thanks Everyone ....

I will be working on a neck that is not finished until after it is joined to the body, so I am guessing right now how to drill this thing with enough clearance, but not too much.

I want to put dowels in the neck so that the neck does not go all over the place with wild swings in humidity.

 

My guess is that the neck heel angle is about 83 degrees, so I will try and use an 83 degree angle for the 10mm diameter dowel.

I guesstimate from David's picture that about 50mm back from the end of the neck heel will do.

 

Once I have a finished neck, calculating the right angle and dowel placement will be easier.

Several things I'd like to mention:

 

Doweling the neck won't reduce changes from humidity fluctuations all that much, because much of the change is due to dimensional changes in the top and back as moisture content varies. What it will do is make the neck much more resistant to long-term bending under load, or "creep", particularly under high humidity conditions, which renders wood much creepier. :D  

 

I don't know if I mentioned this in the Strad article, but I first started experimenting with neck heel reinforcement after doing a cello neck graft in the Weisshaar shop, and finding that the neck projection had dropped about 10 mm within a year. This was extreme and unusual, but all cello necks do it to some extent. If they all did it the same amount, one could just compensate by setting the neck too high by a certain amount, and trimming the bridge periodically as the mutha drops. But they don't all change the same amount, and I don't know of a reliable way to predict how much they will drop.

Upon removing the neck mentioned above, I found that the surface which goes against the block, which had originally been planed flat, was now concave (a clear indication of bending), with most of the bending concentrated in the upper portion. Again, this is something you'll find upon removing just about any cello neck. The difference this time was that I had planed it flat myself, so I knew it had started out this way, versus the possibility of it not having been flat in the first place.

 

The angle:

I like to angle the dowel a little more than  you've described, so that the area where the dowel bottoms out at the bottom of the hole, will be more to the center of the heel, rather than having the entire length of the dowel running close to the outside wall. The idea is that any stress concentration at the end of the dowel will be better supported this way, and that less reinforcement of the outside wall is needed in this area anyway, because resistance to bending in this area is provided pretty well by the  block (as long as the glue joint remains solid). This is just an idea, I don't have experimental evidence that angling the dowel so it ends more to the center of the heel is actually better.

 

A lot of people have measurements and jigs for drilling the holes on a drill press, and doweling before the neck is inserted and trimmed. Once you've got this set up correctly, I think it's a more reliable way of doing it. The reason I don't do it this way myself is that it's so easy for the glue to travel quite a ways through the endgrain, that upon trimming the heel to final dimensions, there's a high likelihood of exposing a glue-sized area, creating a highly conspicuous  "glue ghost" which is impossible to get rid of. It doesn't hurt anything, it's just really ugly. When I apply filler and varnish first, there's enough of a barrier that the glue never finds its way to the surface.

 

I suppose the ideal way would be to drill the holes first on a drill press jig, before the neck is inserted (which would allow better precision), and wait to glue the dowels in until after the instrument is varnished. Assuming these holes would still be straight. ;)  (just thinking out loud)

 

Since so many people are doing this now, with so much accumulated experience, it might be a good idea if I brought it up with the group at the Oberlin Violinmaking Workshop, to see if some sort of consensus has developed on the best way to do this, in the 40 years since I first started doing it. Time and experience march on.

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Thank you for your post!

Most helpful in straightening out my thinking.

I have heard of Cello necks having a mind of their own, and I am hoping for a relatively calm experience when my turn comes.

I will keep away from getting to close on the first time doweling, so I do not get the Glue Ghosts.

 

Thanks again ...

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How does the dowel method fair compared to a spline ?

 

 

Hi Ben - at present I'm flat on my back on a heated under-blanket trying to will my L3/L4 vertebrae to stop annoying the nerves that feed out from between them.

 

Anyway while lying here - thinking - and catching up with Pegbox chatter - and jus' thinking - I have had second thoughts about the sense of using a spline insert in the heel of a new neck. 

 

I was tempted to consider the spline method because it strengthened the forward edge of the heel against movement in compression. While thinking it over, I realized that since the grain in the end-block runs at right angles to that in the neck, any movement due to compressive stress is already being handled. 

 

A 40mm long dowel at the "flat" of the heel will stiffen that short bit of the heel that stands between plate and fingerboard.

 

- to answer your question - dowels would be quicker and less intrusive.

 

 

Notes: Cello Neck Repair Method

 

The quickest neck repair (drilling the hole, making and fitting a dowel) took me less than 2 hours in total - but spread over 3 days.

 

Remember the Old Woodworkers Adage - " A full day between glue and loose"!

 

Step 1 - reglue the break/neck mortise back home using hide glue. If luck runs your way the break will be near invisible.

 

Step 2 - drill hole, make and insert dowel

 

Step 3 - clean up, trim the dowel and slightly countersink the top of the dowel to ensure clearance to the finger board.

 

I stumbled into doing these repairs the usual way - the oldest repair shop in Cape Town asked me to come and look at a cello where the previous repair had failed. It was a through-bolted repair that had become loose, allowing movement across the break.

 

Well - it's always easier to come up with a "better" when you are looking at a "not-good-enough". 

 

I brought the "victim" home and spent some time in formulating a theory of how the original failure had occurred, a second theory to account for the failure of a bolted connection and more time in measuring the Lever arm, calculating the Moments due to String tension,  the Stress distribution in the heel caused by the change of Areas due to the heel shape, Maximum allowable stresses of Maple in tension and compression, Shear strength of epoxy glue, Allowable stress in the glue joint, Area of glue joint - you know, the normal baggage that Mechanical Engineers carry around in their minds...

 

Anyway the end result was a 16mm dia maple dowel inserted as close to the surface of the heel as possible.

 

The pics below are of another repair. This one had a wood screw up front and a wooden dowel towards the outer edge of the heel.

 

The wood screw was totally redundant - it is in an area that only sees compression. I removed it, drilled and inserted a 12mm dia maple dowel.

 

Then I drilled through the first wooden dowel and inserted the 16mm dowel.

 

I suspect that the first dowel was glued in with hide glue. The failure was most likely due to the working window was too short. Epoxy resin gives you almost 30 minutes

 

 

In later repairs of this type I removed the broken part of the neck, cleaned up the exposed gluing faces until I achieved a seamless fit and them reglued the parts together. This is both quicker and easier than having to sand the mismatched joint flush and re-touch the varnish.

 

post-98-0-38510100-1462178168_thumb.jpg

 

post-98-0-64330600-1462178222_thumb.jpg

 

post-98-0-45359200-1462178281_thumb.jpg

 

i) I eyeball the angle and send down a 5 - 6mm pilot hole followed by a 16mm spade bit - quick and nasty. 

 

ii) Make a dowel that just slips nicely down the hole, chamfer the edges and file a flat down the length to allow trapped air to escape.

 

iii) Trowel epoxy into the hole and spin the dowel on its way down, remove and repeat a couple of times to ensure that you have full glue coverage and that all dust is thoroughly mixed into the epoxy.

 

iv) Trim dowel and countersink the top of the dowel slightly to ensure clearance to the fingerboard. 

 

Unfortunately I haven't had the opportunity to monitor the behaviour of a repair after time but no returns to date.

 

cheers edi

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How does the dowel method fair compared to a spline ?

 

A spline is how i started out, and I actually think it is a better way. I switched to dowels when I no longer has access to a table saw with a wide blade to cut the kerf, and when I also started thinking about how lethal it could be if the saw launched the neck in my direction while making such a heavy cut. :o

 

A carbon fiber spline would probably be better yet, but I didn't like the idea of what it would do to my tools as I planed the back of the heel, and the fingerboard gluing surface.

 

IMG_1912reduced.jpg

 

I think I told the story before about the first cello I did this way. It ended up in Rene Morel's shop about ten years later for a new bridge. I had set the neck in high, assuming that it would come down some, as they always had in the past. But it didn't. I got a call from Rene saying something like,

"Daveed, I has zees cello from you, and zee neck ees too high. You always do nice work, so what happen?  You make bad meestake?" :lol:

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Hi David, when you did the spline what type of glue did you use?

Either Titebond, or regular hide glue. Can't remember exactly, a lot of time has elapsed. :blink:

Of course, Titebond has known creep issues.

Epoxy would probably work fine, but we didn't have much long-term experience with it for woodworking, in the 1970s. I'll add that epoxy properties are all over the map, and one can't just say that "epoxy is epoxy". Some epoxies can creep too, and others don't seem to suffer so much from that.

 

One thing I always worry about though, when using epoxy on wood, is the time the glue takes to set up, versus how much time the glue has to soak away into the wood, leaving a less than ideal bond. When bonding metals, we don't have that issue.

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   Hi

I have worked in Golf with epoxies, and even with metal to metal contact, we found that epoxies are not all created equal.

It is a little embarrassing to have a client bring back 2 clubs instead of 1!

So I think David is making a really good point about "epoxy is epoxy" from my experience.

 

We found 1 epoxy that worked on metal to metal contact that was very expensive, but worth it ..... in the end.

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A spline is how i started out, and I actually think it is a better way. I switched to dowels when I no longer has access to a table saw with a wide blade to cut the kerf, and when I also started thinking about how lethal it could be if the saw launched the neck in my direction while making such a heavy cut. :o

 

A carbon fiber spline would probably be better yet, but I didn't like the idea of what it would do to my tools as I planed the back of the heel, and the fingerboard gluing surface.

 

IMG_1912reduced.jpg

 

I think I told the story before about the first cello I did this way. It ended up in Rene Morel's shop about ten years later for a new bridge. I had set the neck in high, assuming that it would come down some, as they always had in the past. But it didn't. I got a call from Rene saying something like,

"Daveed, I has zees cello from you, and zee neck ees too high. You always do nice work, so what happen?  You make bad meestake?" :lol:

This looks fantastic. I understand not wanting to do this on a table saw, but why not saw the mortice by hand and fit the tenon to it. Even if your mortise slot isn't perfectly parallel, the tenon could be planed for a snug fit

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   Hi

I have worked in Golf with epoxies, and even with metal to metal contact, we found that epoxies are not all created equal.

It is a little embarrassing to have a client bring back 2 clubs instead of 1!

So I think David is making a really good point about "epoxy is epoxy" from my experience.

 

We found 1 epoxy that worked on metal to metal contact that was very expensive, but worth it ..... in the end.

Thanks for weighing in. Considering all the time and effort it takes to make a decent cello, I'd consider epoxy cost to be a very minor consideration. Well, maybe not, if will cost me 1000 bucks or something.  :D

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