Adhesive for turning?

[Phill joiner]

I've had a lathe kicking around at the back of my worktop for a few years, and after looking at segmented bowl turning it's inspired me to dig it out and have a go. I was wondering what glue you guys use which gives the best results for segmented bowls?

 

[CHJ]

I use Cascamite adhesive, mainly because it does not have joint creep as PVA can with wood/humidity movements.

 

[Phill joiner]

I was wondering if polyurethane glue would be ok. Reason being it sets in 15 minutes and expands into small gaps. It's also easy to machine. I haven't used cascamite for years. Do you still have to mix it yourself?
Also is there an ideal working height for turning. (machine height)

 

[CHJ]

I was wondering if polyurethane glue would be ok. Reason being it sets in 15 minutes and expands into small gaps. It's also easy to machine. I haven't used cascamite for years. Do you still have to mix it yourself?
Also is there an ideal working height for turning. (machine height)

I've never used polyurethane, but I suspect others have, never seen any saying never use it, 15mins is hardly a realistic working time for most segment assemblies.

Never try to turn an item as soon as a glue has gripped, (except maybe CA) most adhesives need 12hrs to cure sufficiently and many manufactures quote 24+ hours before machining.

Gap filling is a thing to avoid with segmented work, glue lines visible after turning, especially if uneven are not conducive to a good presentation.

The oft quoted height is to have the lathe centres at elbow height, personally I find this to be uncomfortable for me and prefer to stand more upright and have the centre 50-75mm higher which suits how I hold an present my tooling.

 

[Happy amateur]

Sue Harker recommends Titebond II for face grain and Titebond Wood Moulding Glue for end grain
to end grain. It is what I use.

Fred

 

[Phill joiner]

Thanks for the info and help guys. Can't wait to get set up now tbh. Dug the lathe out yesterday and dusted it off. It's a table mounted one so I'll have to knock a sturdy one up first.

 

[andersonec]

I use Cascamite adhesive, mainly because it does not have joint creep as PVA can with wood/humidity movements.

"Creep" is usually only ever found on joints which are under constant, heavy stresses and also in joints such as bent laminated timber, it also needs heat to soften the glue and is only ever noticeable on larger joints as any movement on small joints would be fractional, the smaller the join the smaller the potential movement, the wood is more likely to move with humidity before the joint does especially if the timbers are "cross grained".

God knows what is happening to all the joints which have been made with PVA over the years.

Everbuild state their PVA is creep resistant.

Andy

 

[CHJ]

Humidity changes with the simple closed segmented pieces I make are enough to show sufficient joint displacement when made with Creep Resistant PVA to spoil the feel of the surface finish.(you can feel the step at the joins)

 

[Robbo3]

Alan Stratton at AsWoodTurns had movement problems on his latest post "Meanwhile, it seemed that my segments were taking on moisture my the glue and warping while gluing."(sic).
He can also be found on Youtube
- http://www.aswoodturns.com/
- https://www.youtube.com/watch?&v=1WI3P3V97p4

 

[Random Orbital Bob]

There may well be a solution for both zero creep and reasonable speed and that's Hide glue. A friend of mine is a professional guitar luthier and he uses it almost exclusively in his build process for precisely those reasons ie there is zero joint creep and because of the heating/curing process its fairly fast. Well faster than some carpentry glues anyway.

I will caveat this with saying I've not tried it myself so this is a theoretical solution. But the chap I'm referring to is quite the perfectionist and he knows his stuff so I trust his views. However, its somewhat tricky to use.

 

[Phil Pascoe]

If the moisture absorbed from the adhesive made much difference, why doesn't the moisture absorbed from cascamite make the same difference as the moisture absorbed from PVA? They're both water based?

 

[CHJ]

If the moisture absorbed from the adhesive made much difference, why doesn't the moisture absorbed from cascamite make the same difference as the moisture absorbed from PVA? They're both water based?

It is totally dependant upon the size and grain orientation of the pieces as to the effect percentage wise that the moisture present in the glue makes. Cascamite swells the wood just the same as PVA.
On a simple circular ring as used in my boxes it is measurable during the glue-up and subsequent drying/stabilising phase. Hence why I try and prepare rough assembled sections as 'stock' and make sure they are suitably conditioned before final assembly.

To avoid the majority of post glue up and finishing problems associated with wood movement due to humidity changes I endeavour to assemble pieces in such a state of preparation that they will be in compression in moister environments, not in tension in dryer.

If you don't and someone places them in a sunlit room or near a radiator then they will split or open up the glue line.

This is what happens if you mistakenly glue up something that is at 12% moisture and then bring it indoors.
As you can see the wood, both species, split due to tension.