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Clamping Pressure for 2 Piece Body

SmidgeBass

SmidgeBass

Jan 5, 2015
8
1
44
#1
Hey everyone!

I have had about a day's look and search through the forum for this and couldn't find anything. Sorry if it has already been posted and I couldn't find it.

I am wondering about the clamping pressure required for gluing a 2 piece body.

This might seem a little weird but while looking for some clamps I noticed that the Irwin range have pressure ratings and wondered could I save a bit of money and go for something that was rated at around 100kg's or do I need the big 270kg ones.

I understand that too little pressure and the glue seam will be rubbish but I have also heard that too much pressure creates a weak seal.

What are your experiences with this? Thanks!
 
#2
I use F-shaped bar clamps and put the screws to it as hard as I can, until I can't physically turn the handles anymore, and I have not yet had a glue joint fail. I think you would have to tighten them down with pneumatic clamps to to starve the joint of glue.
 
#3
SmidgeBass said:
Hey everyone!

I have had about a day's look and search through the forum for this and couldn't find anything. Sorry if it has already been posted and I couldn't find it.

I am wondering about the clamping pressure required for gluing a 2 piece body.

This might seem a little weird but while looking for some clamps I noticed that the Irwin range have pressure ratings and wondered could I save a bit of money and go for something that was rated at around 100kg's or do I need the big 270kg ones.

I understand that too little pressure and the glue seam will be rubbish but I have also heard that too much pressure creates a weak seal.

What are your experiences with this? Thanks!
Click to expand...

I've used the orange "Pony" pipe clamps for years on various furniture projects, and just snug them down by hand until they feel "stiff" to me (you don't need to reef on these things with a cheater bar), and I've never had a glue joint fail. The people I know who have had issues with glue joints on their projects are those that only put a tiny bead of glue down because they don't want to clean up too much "squeeze out". Titebond is cheap, use liberally. :D
 
#4
I use these Invalid Link Removed

I use 8 or more of them on an average body, and tighten them as tight as I can get them. They are dirt cheap and work well, HF sells some crap, but these are a gem. Some people may tell you a myth about a dry glue joint caused by over tightening your clamps. That is an absolute myth, there is no way a human being could possibly tighten a clamp tight enough to squeeze out all of the glue.
 
#5
Hopkins said:
I use these Invalid Link Removed

I use 8 or more of them on an average body, and tighten them as tight as I can get them. They are dirt cheap and work well, HF sells some crap, but these are a gem. Some people may tell you a myth about a dry glue joint caused by over tightening your clamps. That is an absolute myth, there is no way a human being could possibly tighten a clamp tight enough to squeeze out all of the glue.
Click to expand...

Agreed, and I use the same clamps for bodies.
 
#6
I use these:
17f7012s2.jpg


2 or 3 for a body.

But think most important is jointing your wood correctly.
 
#7
Hopkins said:
I use these Invalid Link Removed

I use 8 or more of them on an average body, and tighten them as tight as I can get them. They are dirt cheap and work well, HF sells some crap, but these are a gem. Some people may tell you a myth about a dry glue joint caused by over tightening your clamps. That is an absolute myth, there is no way a human being could possibly tighten a clamp tight enough to squeeze out all of the glue.
Click to expand...

I also use these and have good success with my glue joints. Another good thing to consider with HF clamps is that if they have issues (bar bends, etc.) they are guaranteed for life. I was a little aggressive with them on one job and bent the bars a bit - a short trip to the store and they replaced all of the clamps no questions asked.
 
#8
michaelwayneharwood said:
I also use these and have good success with my glue joints. Another good thing to consider with HF clamps is that if they have issues (bar bends, etc.) they are guaranteed for life. I was a little aggressive with them on one job and bent the bars a bit - a short trip to the store and they replaced all of the clamps no questions asked.
Click to expand...


They are going to bow when you tighten them, They have all straightened back out
 
#11
Just to keep things lively and to be a contrarian...

There is also the infamous "rub" joint which involves not applying clamps at all, rubbing the glue onto the surface of the wood and letting gravity apply the pressure. I hear it makes a pretty decent joint, providing the wood is properly prepped, jointed and glued.

That having been said, I don't have a whole lot of experience with 2 piece body joints. I would find a rub joint to be a bit terrifying for a bass body, knowing that pressure is one of the things that causes wood glue to work, and that pressure helps make glue lines invisible.

In my own experience I have a tendency to over clamp (I think) which kind of forces the joint to glue up well, but not exactly perpendicularly to the bottom (or top). I think the pressure and water in the glue causes it to swell a bit making the line clean and even, but not perpendicular. Of course I also expect my technique isn't the best.
 
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#12
Deep Cat, that might work OK with hot hide glue. It contracts slightly as it dries and hardens, so assuming the surfaces are properly jointed and prepared, you can make very tight joints with hot hide glue using relatively little pressure as compared to what would be necessary using white glue.
 
#13
Deep Cat said:
In my own experience I have a tendency to over clamp (I think) which kind of forces the joint to glue up well, but not exactly perpendicularly to the bottom (or top). I think the pressure and water in the glue causes it to swell a bit making the line clean and even, but not perpendicular. Of course I also expect my technique isn't the best.
Click to expand...

Hrm, when you're clamping, do you clamp from both sides of the piece, or just one side? I've found that if you clamp from one side you tend to get a little "bow" in the piece, where adding clamps to the other side tends to pull it back even since you have equalized the presure/tension on the joint.
 
#17
HaMMerHeD said:
Deep Cat, that might work OK with hot hide glue. It contracts slightly as it dries and hardens, so assuming the surfaces are properly jointed and prepared, you can make very tight joints with hot hide glue using relatively little pressure as compared to what would be necessary using white glue.
Click to expand...
+1, as i understand it the "rubbed joint" is only a hot hide glue thing, and even then only when there isn't a big structural demand on the joint.
 
#19
Jake72 said:
Hrm, when you're clamping, do you clamp from both sides of the piece, or just one side? I've found that if you clamp from one side you tend to get a little "bow" in the piece, where adding clamps to the other side tends to pull it back even since you have equalized the presure/tension on the joint.
Click to expand...

I clamp both sides, of the piece, top and bottom and I use a few cauls as well. I don't tend to get much bow (anymore) The problem I have is more that the actual joint line when viewed on edge shifts a few degrees from perpendicular despite being properly and squarely jointed. 90 degrees before clamping, 89 degrees after, if you take my meaning. The "line" also isn't even from one end to the other. One end might be 89 degrees and the other is 87 degrees. I contend this is a function of clamping pressure, a freshly jointed edge, and the moisture in the wood glue, but I also expect there can be a whole host of errors I'm making as well.

I think I ought to make a go at epoxy and compare my results.
 

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