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clamping pressure

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Forum topic by NotaJock posted 09-18-2018 12:42 AM 1089 views 0 times favorited 54 replies Add to Favorites Watch
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NotaJock

155 posts in 1246 days


09-18-2018 12:42 AM

Topic tags/keywords: glue clamp pressure

How much clamping pressure is called for when clamping a glue-up?
Tight or barely enough to keep the pieces from moving until the glue sets?
Or somewhere in between?
Thanks

-- Mike in SoCal


54 replies so far

View TimInIndiana's profile

TimInIndiana

105 posts in 287 days


#1 posted 09-18-2018 12:45 AM

View BigMig's profile

BigMig

465 posts in 2760 days


#2 posted 09-18-2018 04:40 PM

“super tight” is too much; I know that for sure. Seeing even squeeze out without forcing teh clamp – that’s about how I do it.
I have see Tommy Mac use a “spring joint” technique – and with one clamp can clamp decent sized boards.

-- Mike from Lansdowne, PA

View John Smith's profile

John Smith

1374 posts in 309 days


#3 posted 09-18-2018 04:48 PM

in my early days, I have actually applied so much clamping pressure
that it squeezed all the glue out of the joint – and the boards fell apart
after the clamps were removed.
so YOU must find that “sweet spot” for each species of wood that you work with
and find what works best for you in your environment.
ensuring that your surfaces to be glued are true and straight and match precisely will be the key.
if you have to force a joint closed – you are asking for failure.
there is no “one way fits all” answer to your question.

-- I started out with nothing in life ~ and still have most of it left.

View pottz's profile

pottz

3148 posts in 1131 days


#4 posted 09-18-2018 06:14 PM

well im probably from the super tight club when i glue up boards,i like firm even pressure,less for soft woods and more for hard woods and ive never had a glue up fail yet.knock on wood-lol.

-- sawdust the bigger the pile the bigger my smile-larry,so cal.

View WoodenDreams's profile

WoodenDreams

129 posts in 58 days


#5 posted 09-18-2018 06:25 PM

It’s easy to tighten down with too much pressure. You want a tight fit. Wrong. You want a snug fit with using the proper amount of glue. The key is straight and matched edges, and properly spaced clamps. BigMig and John Smith are telling you the way it is. www.finewoodworking.com or www.goa.com will show you a video how to example on their sites for free, or check out some youtube video clips.

View rwe2156's profile

rwe2156

3092 posts in 1627 days


#6 posted 09-18-2018 07:33 PM

IMO I think too much has been made about over little regarding this subject. In the real world, you can’t measure clamping force, you just clamp until you get squeeze out, then a little bit more.

That said, I’ve used big time clamping pressure on table top glue ups with my pipe clamps. I’ve never, ever had a glue joint fail in 30 years of ww’ing.

As far as squeezing all the glue out of a joint, I’ll believe it when I see it. You couldn’t do that with a hydraulic press because there will be enough glue remaining in the grain of the wood to still create a bond.

That said, I respect what smarter people than me say, and I’ll read that FWW article, but in the real world in my shop, I doubt it will change a thing.

Kings Fine Working on YouTube as some Titebond information about PSI in clamping.

-- Everything is a prototype thats why its one of a kind!!

View Planeman40's profile

Planeman40

1257 posts in 2908 days


#7 posted 09-18-2018 07:48 PM

Yep, what the guys above say – tight enough to squeeze out the excess glue then stop. I went deeply into this back in the early 1960s when I built a homebuilt airplane. Knowing your life is on the line with what you have made makes you sure to do it right. And if you don’t know, educate yourself very well before building. The EAA (Experimental Aircraft Association) puts out handbooks on the various airplane building processes that are very informative. Back in the 1920s when so many airplanes we built of wood, the US government did a lot of study on gluing wood to insure the safety of the public. This information is still and excellent source of information.

And one more thing. Be sure to spread glue on BOTH sides of the wood to be joined and spread it evenly over the entire glued surface if you want maximum strength. Too may of us just run a bead of glue down one side of the joint and stick it together. To see how slap dash this method is, just do this and then pull the pieces apart. you will often see fairly large spots with no glue.

-- Always remember: It is a mathematical certainty that half the people in this country are below average in intelligence!

View pottz's profile

pottz

3148 posts in 1131 days


#8 posted 09-18-2018 09:27 PM



IMO I think too much has been made about over little regarding this subject. In the real world, you can t measure clamping force, you just clamp until you get squeeze out, then a little bit more.

That said, I ve used big time clamping pressure on table top glue ups with my pipe clamps. I ve never, ever had a glue joint fail in 30 years of ww ing.

As far as squeezing all the glue out of a joint, I ll believe it when I see it. You couldn t do that with a hydraulic press because there will be enough glue remaining in the grain of the wood to still create a bond.

That said, I respect what smarter people than me say, and I ll read that FWW article, but in the real world in my shop, I doubt it will change a thing.

Kings Fine Working on YouTube as some Titebond information about PSI in clamping.

- rwe2156

i totally agree,if my projects start falling apart then ill change my method.

-- sawdust the bigger the pile the bigger my smile-larry,so cal.

View CWWoodworking's profile

CWWoodworking

146 posts in 326 days


#9 posted 09-18-2018 10:54 PM

I think the glue on both pieces is kind a malarkey. Put a thick bead on one piece and smash it together and pull it apart. You will have plenty on both pieces. I will glue close to 1000 panels this year. No failures.

More important is a good joint and thick bead. Glue is cheap.

View Planeman40's profile

Planeman40

1257 posts in 2908 days


#10 posted 09-18-2018 11:47 PM

Could be malarkey. Try building a homebuilt airplane and betting your life on your method of gluing. If it works for you, go ahead. Glue tests by engineers say differently.

-- Always remember: It is a mathematical certainty that half the people in this country are below average in intelligence!

View Tony_S's profile (online now)

Tony_S

924 posts in 3230 days


#11 posted 09-18-2018 11:50 PM

Starting with cleanly, properly milled material, apply enough force that the joint closes tightly. If you’re unsure, re-tighten slightly in 20/30 seconds. If you get any squeeze out on the second try, the first wasn’t tight enough. It doesn’t need to be anymore complicated than that.

You also don’t need to apply glue to both surfaces on a simple edge or face glue up…and…it’s absolutely impossible to squeeze all the glue out by over tightening. Not even to the point that the glue joint will suffer to any significant degree in relation to the strength of the wood you’re working with.

-- It is the mark of an educated mind to be able to entertain a thought without accepting it. Aristotle

View Redoak49's profile

Redoak49

3529 posts in 2135 days


#12 posted 09-18-2018 11:57 PM

How careful you need to be about glueing certainly depends on what you are doing. If you are doing an airplane, you need to be super careful. But if just two boards, anything goes.

View jbay's profile

jbay

2678 posts in 1046 days


#13 posted 09-19-2018 12:08 AM


Too may of us just run a bead of glue down one side of the joint and stick it together. To see how slap dash this method is, just do this and then pull the pieces apart. you will often see fairly large spots with no glue.

- Planeman40

Do it all the time. I guess you need to use a bigger bead.

100% agreement with Tony

View Planeman40's profile

Planeman40

1257 posts in 2908 days


#14 posted 09-19-2018 12:21 AM

You guys are probably right. I over do almost everything. But – I can honestly say that In the 60 odd years I have been woodworking I can honestly say I can’t remember one of my glued joints failing over the years. But then I am an old man and there are a lot of things I can remember any more. ;-)

-- Always remember: It is a mathematical certainty that half the people in this country are below average in intelligence!

View CWWoodworking's profile

CWWoodworking

146 posts in 326 days


#15 posted 09-19-2018 12:27 AM



Could be malarkey. Try building a homebuilt airplane and betting your life on your method of gluing. If it works for you, go ahead. Glue tests by engineers say differently.

- Planeman40

Gladly. Based on true numbers, my failure rate is 0%. Even if I had 1 panel fail, that is .1%. That’s better than almost any production part. Most mass produced part manufacturers (non life threatening) aim for less than 2%

I do this for a living so speed is key. This is an extremely low risk practice.

At the pace I glue panels together, there is a much higher chance I miss a season split or hair line crack, than a glue joint failure.

But hey, to each is own. Your probably not changing and I know I’m not.

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