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Just started working on my very first neck :) The scarf joint is ready I think ( i see no light through it) ((spanish cedar planes so nicely even with a not very sharp iron))

Going to glue it using LMI white, thats what I have here atm.

Clamped with the traditional twine and wedges method.

Any advices on this ? Should i put a lot of glue, or spread even a very thin film ?  How much pressure ? Just enough to put out the excess glue, or wedge it to oblivion ?

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Build log

Thanks for the tips! Going to prep the wedges and a dry test.  The surfaces should be clean, and I'll plane again just before glue-up. 

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Build log

I use fish glue for this now (collagen glues for everything), but when I did use LMI I spread an even film on both surfaces with a roller. And clamped with four cam clamps and ensured squeeze-out all around. Todd's right the cumpiano system of clamping works well.

T clean up the surface prior to gluing, just run a scraper over it, no need to plane.

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

Thanks both of you.   It seems to be very hard to do so far, it keeps slipping out and so on. I need to devise a stop at each end, first. 

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Build log

I don't have real good pictures, these are all I have of this process.
You need to be able to lock down the neck and headstock. This is how I do it. I hope this helps.

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"An adventure is only an inconvenience rightly considered. An inconvenience is an adventure wrongly considered." G. K. Chesterton.

I will buy a couple books soon I hope - but I had to glue it today :)

I managed to do one of my monster improvised jigs: first clamped half of it in a small mobile vise, then put the whole contraption in the big bench vise. I spread the glue as evenly as possible with a credit card and I have squeeze out all around. Will see tomorrow how many gaps they are in there   Luckily both ends have a couple inches of backup so i can redo it if it goes wrong.

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Build log

We do a couple of dozen necks a month in maple and mahogany this way with LMI white glue using nothing more than three or four hand spring clamps. We then put a couple of maple splines in across the joint. No problems...

That would lead me to believe that high pressure is not an issue in this joint, with that glue.  Do you think it would maintain strength without the splines added?  

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Waddy

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Sound Clips of most of my guitars

By spline you mean a wood rod? I suppose they are inserted in the center, between the two lines of tuners.  Probably 15mm deep for an 18mm headstock. Or right through it if a backplate is applied later.   This is a great backup to add! Thanks. 

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Build log

Waddy I would imagine the surface prep is the key. if the surfaces are very good, you can get a thin glue line by just rubbing them a bit around. The splines would be mostly backup mostly, even if they add more strenght to the joint. Also the head plate must be adding a lot of extra strenght to it. 

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Build log

I guess my question wasn't worded too well.  My point of the question was, with only the pressure of hand spring clamps, does the joint have the same strength that say, 2000 lbs of clamping pressure would give?

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

[QUOTE=WaddyT] I guess my question wasn't worded too well.  My point of the question was, with only the pressure of hand spring clamps, does the joint have the same strength that say, 2000 lbs of clamping pressure would give?
[/QUOTE]
Waddy,
I've seen this discussed before. It seems that when glue manufacturers specify lots of clamping pressure, they are doing it because too often the surfaces are not prepared correctly - clean, flat and smooth. With a properly prepared joint, it seems that lots of clamping pressure is not necessary and will be harmful if too much of the adhesive is driven out of the joint.
Bottom line, with a well prepared joint, enough pressure to hold the parts together will work.
Remember that vacuum clamping works great and only gets up to about 14 psi.

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"An adventure is only an inconvenience rightly considered. An inconvenience is an adventure wrongly considered." G. K. Chesterton.

Thanks, that's exactly what I was wondering.  So a freshly scraped joint with enough pressure to close the joint (squeeze out excess glue) is all that is required.  I assume the same is true for colligan type glues, which in turn would tend to suck the joint together when drying.

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

You can use too much pressure with this type of joint too.  Even if you load it up with glue, you can get a starved joint by clamping it quickly with too much pressure.  The bulk of the glue gets squeezed out and the end grain soaks up the rest (in mahogany anyway, spanish cedar may even be worse with the bigger pores although I don't have the direct experience there).  I like to to spread glue on the end grain and let it sit and soak in for a good 30 seconds or more before clamping.

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We just use nicely machined surfaces. On the peghead part it's off the planer; on the neck scarf cut it's off the table saw. We'll use two maple splines, one on either side of the truss rod slot. I have a dual dado saw blade affair with a center guide on a custom table saw blade insert. Piece of cake...

I think we can all over-intellectualize some of this stuff and forget that there are simple solutions that work just fine.

Good point.  Thanks Rick!

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

Hmm, 30 seconds ?

I actually spent some time spreading the glue on one surface, and I made it very thin. Then spreaded the other, and then I realized the first had sucked most of it, with the color turning from white to redish.  I put a finger on it and it was very sticky, I assumed it is ruined so i scraped it off and planed again.... 

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Build log

Sorry, should have said 30 seconds mated before clamping although open air should easily be fine for that long with lmi white glue.

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Steve, thanks a lot for the pictures. I have to admit I do not have any clamp atm. Poor excuse of a luthier I am :) 

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Build log

While that Cumpiano clamping method is all fine and dandy, and works fine, it's messier, fiddlier, and less easy to 'get perfect' than just using two or three strips of good 'ol masking tape.

Seriously.

I'll let Ant Setchell's blog (good online buddy of mine, he's almost ready to start branching out into acoustics, so I'm sure he'll show up here eventually) do the explaining with photmapictureythings.

http://www.setchellguitars.co.uk/ant/blog/?p=121

I like StewMac's brown stuff for this, because it's a bit thicker/stronger, but plain old 3M does the trick just fine.

Also, I've never managed to starve a titebond glue joint, although maybe that's because I do most of my clamping with wood cam clamps.

I'm with Mattia on this. Tape...

We put a 1/4" width of polyethelene plastic (or that high molecular weight plastic) the truss rod slot in the neck shaft aligned with a matching slot in the peghead, put a couple of pieces of flatback binding tape on either side, and clamp with spring clamps.   

I swear i would tried to tape it but I ran out of it earlier today.

For that matter, I have glued a back with just tape and it worked great.

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Build log

"Also, I've never managed to starve a titebond glue joint, although maybe that's because I do most of my clamping with wood cam clamps."

Me either, except a scarf joint on a neck.  I like to use lots of pressure to keep the glue line almost invisble.  Large C-clamp cranked pretty hard.  I had 2 different people at Healdsburg this weekend ask me if I use a 1 piece neck and even when I tried to show them the joints at the scarf and heel, they couldn't see them (the light wasn't great though).  But I've also had a scarf joint come apart in my hands.  Squeeze out all around and no glue in the joint.  Letting it sit a bit before clamping has worked fine since then.

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http://www.chassonguitars.com

Rick: do you scarf your headstock onto the 'back' of the neck blank, or 'on top' of the blank (ie, headstock is one piece, scarf is in the neck shaft). If it's the former, I'm not quite getting how/where the plastic alignment bar comes into it all.

I scarf a shaped peghead onto a machine shaped shaft. So the peghead goes on top.   It's a system that I set up around the use of a pin router for making parts, and it's incredibly efficient as I can machine shape the neck shaft, then cut the scarf; machine a nearly complete peghead; glue it on, and then there's minimal carving to do in the hand stop area.   

Someday I'll figure out where to stick photos so I can post them.