Gluing - how long to leave clamped

[Rewound]

White PVA - I have a whole load of stuff to glue together, but only so many clamps. Normally I wold glue, clamp together until the glue started to ooze out, then leave till the next day. But even though the glue might not be fully cured for 24 hours, does it have to remain clamped for all that time? I have experimented an an hour seems to work just as well, but is that so?

and also, how tight should something be clamped? as tight as humanly possible, or will just held firmly do,

 

[Yojevol]

Squeeze it up until the joints are visibly closed. If not under any stress, should be safe to release after an hour. If it is stressed keep it clamped for a few hours.
If you over tighten you may be introducing stresses which then cause movement on release.
I recently looked up the difference between cramp and clamp. A cramp is used to force movement, whereas a clamp merely holds the position. They may be one and the same of course.
Brian

 

[Jacob]

White PVA - I have a whole load of stuff to glue together, but only so many clamps. Normally I wold glue, clamp together until the glue started to ooze out, then leave till the next day.

Some things you can take the clamps off straightaway once the joint is pressed home. Dovetails especially.

But even though the glue might not be fully cured for 24 hours, does it have to remain clamped for all that time?

Not usually.

I have experimented an an hour seems to work just as well, but is that so?

Could be for some things as long as they aren't going to get knocked about etc

and also, how tight should something be clamped? as tight as humanly possible, or will just held firmly do,

Just firmly, unless you are trying to force things together - which could be a good idea with say thick boards for a table top. The wood will be absorbing water from the glue and could be distorting. 24 hours could be good idea.
One key thing is to spread glue over the whole surface of both sides. It's surprising how far it won't spread if you just squiggle it on and clamp - you then find out why it's come apart!

 

[thetyreman]

I'd say minimum of 3-4 hours clamped up, and in colder weather heat the joints up first with a heat gun, it speeds up the curing time, I usually leave glue ups overnight in most cases. You shouldn't need too much pressure if it's a good tight fitting joint.

 

[deema]

If white glue isn’t set after 24 hours, either it’s off, or more likely it’s too cold to be gluing stuff up.
If there is a lot to do, and you need to get in have your considered PU glue? You can get it from 5 min set up to around 45 min. Most are completely waterproof…..and sticks just about anything to anything!

 

[dzj]

Packing tape can exert enough force if it's just a simple 'rub' joint.

 

[Rewound]

The wood will be absorbing water from the glue and could be distorting. 24 hours could be good idea.

a very good point,


I have been gluing stuff up for many years and like most things, I seem to have my own set way, and never really considering another way to what I was may be shown 50 years ago. LOL

Anyways, this is a whole load of offcuts that I have stacked ontop of one another to form a table leg, I will turn it after the glue has set and hopefully get a nice show of end grain from the side of the leg (if that makes sense) I will do a picture when its finished.

 

[Phil Pascoe]

You don't say where you are. Don't forget PVA shouldn't be stored or used at very low temperatures.

 

[The_Yellow_Ardvark]

20% longer than the manufacture gluing times.
Thats what we did when lamiating patch repairs on wooden hull boats.

 

[Rewound]

You don't say where you are. Don't forget PVA shouldn't be stored or used at very low temperatures.

just north of the scottish border, but PVA will still works at these high latitudes.

I think it says not to be used below 12°C, but our workshop is very cold which has concerned me in the past for gluing, and we have experimented down to about +4, and it seems just as succeseful as any other temperature, albeit I think it definitely needs an overnight.

 

[TheUnicorn]

in colder weather heat the joints up first with a heat gun, it speeds up the curing time

I've never heard of this before, how hot are you getting it?

 

[thetyreman]

I've never heard of this before, how hot are you getting it?

haven't measured actual temperature but I just put a heat gun on the lowest setting on the joints for about 30 seconds to 1 minute, seems to work well.

 

[Rewound]

haven't measured actual temperature but I just put a heat gun on the lowest setting on the joints for about 30 seconds to 1 minute, seems to work well.

I do that if using hot melt glue gun

 

[Orraloon]

a very good point,


I have been gluing stuff up for many years and like most things, I seem to have my own set way, and never really considering another way to what I was may be shown 50 years ago. LOL

Anyways, this is a whole load of offcuts that I have stacked ontop of one another to form a table leg, I will turn it after the glue has set and hopefully get a nice show of end grain from the side of the leg (if that makes sense) I will do a picture when its finished.

I am a bit concerned about the table leg having the grain running through rather than along. It will have very poor resistance to sideways forces and could snap off if say dragged as tables often are. I guess a short coffee table leg if kept on the chunky side may work but I would not go there for a full height table. I suppose you could put a bit of steel rod up the guts of it for support.
Regards
John

 

[pgrbff]

just north of the scottish border, but PVA will still works at these high latitudes.

I think it says not to be used below 12°C, but our workshop is very cold which has concerned me in the past for gluing, and we have experimented down to about +4, and it seems just as succeseful as any other temperature, albeit I think it definitely needs an overnight.

4C sounds a bit cold to me. The joints may still appear stuck but they may fail. In winter I use urea/formaldehyde glue as it is far less vulnerable to the cold but I still wouldn't use it under 10C.

 

[Rewound]

I am a bit concerned about the table leg having the grain running through rather than along. It will have very poor resistance to sideways forces and could snap off if say dragged as tables often are. I guess a short coffee table leg if kept on the chunky side may work but I would not go there for a full height table. I suppose you could put a bit of steel rod up the guts of it for support.
Regards
John

my thoughts exactly - however the round bit will only be 250mm long, and have a diameter of 130. it should be OK

Interesting thought for the steel seupport, an M6 threaded bar up the middle would neither be difficult or costly and could help aligning it all up when gluing.

 

[xy mosian]

Interesting thought for the steel seupport, an M6 threaded bar up the middle would neither be difficult or costly and could help aligning it all up when gluing.

With a large washer at each end and some nuts, you could well use that for clamping too.
geoff

 

[niall Y]

For me the introduction of PU glues was a game changer. I no longer needed a large array of clamps, for example, to glue the face frames onto kitchen cabinets. This used to be a prolonged and tedious process, but when I switched to 5 Minute PU, I could release the clamps after a short space of time, and get on with the next glue-up.

When I started out in woodwork, gluing-up was one of those tasks usually relegated to the end of the day, so that the job could be left clamped-up overnight Though this was more for the cabinet -making side of things , as most Joinery items were either pinned ,nailed, wedged, or even star-doweled - so did not need to be left clamped. In fact , what I remember from visiting other Joinery shops , was just how few sash clamps they had; and that these were usually of the heavier, T-bar type.

 

[Noel John]

It depends a lot on the type of wood being used and of course the ambient temperature, hard wood needs longer and soft wood the converse.

 

[Pabs]

Packing tape can exert enough force if it's just a simple 'rub' joint.

aye the blue stuff has a slight elasticity to it, enough for little clamping pressure