What adhesive – that shrinks when it sets – do you recommend for melamine laminate sheets?

[JasonBModerator @jasonb]

900 x 2000 breakfast bar would come close if you went the worktop route but you would have to buy the whole 2m length

Melamine or Laminate top is nice if you are glueing up on it as it is easier to wipe off excess glue

[Tim StevensParticipant @timstevens64731]

One factor which needs to be considered, too, is the range of conditions in which the bonded parts will exist. Several clever adhesives are modified (or destroyed) by heat or cold, vibration, or by solvents, including everyday cleaning chemicals. Advice offered in the absence of detail like this may be nugatory. Or worse.

Cheers, Tim

[larry phelan 1Participant @larryphelan1]

The glue I used years ago was called "Cascamite", and it did exactly what it said on the tin [or sack, in my case ]

I t was cheap, simple to use, and never failed. I used it to bond plastic laminate to chipboard and mdf board and for wood -to-wood joints. For sheet work, I used a rubber roller, being faster and giving a better spread.

Dont know if it is still around, I no longer do that work, but it might be worth looking into.

As I remember, it was made by Borden Chemical Co.

Might not be what you are seeking, but worth a try.

[Donald MacDonald 1Participant @donaldmacdonald1]

No, Hopper, the whole point is that my sheets of MDF already come with melamine glued to both sides. And that is why I am needing to bond melamine to melamine. Single sided would warp all over the place, with every change in atmospheric temperature & moisture.

No, the MDF is definitely melamine (gads!)

…and it is 18mm thick and A0 sized and on the table I have it flexes just enough to be annoying.
No, I want a smooth & easily cleaned working surface, not plywood, for a whole variety of reasons.

It will need to withstand direct sunlight temperatures ranging from -5 (in storage) to +40C.

A lot of glues would work if only ONE side is plastic. "Cascamite" is a "Powdered urea/formaldehyde resin glue" so sounds like a powder which is activate by adding water. It sounds brilliant.

But I am keen if possible to use up some of my existing glues of which I now have quite a collection.

If my 2 tubes of J-B weld aren't going to be enough, maybe I'll just us some epoxy resin glue.

Donald

[JasonBModerator @jasonb]

Another option would be Cyano, 50ml bottle of one of the "mitre" adhesives or bottle of ZAP would be enough to run a continuous straight bead every 50mm, don't do circles as you will bet air trapped. You would not need the activator.

I've used it enough times to stick various trims to MFC and NFMDF and it usually pulls the thin melamine layer off the substrate if you try and pull them apart

[Dave SParticipant @daves59043]

If 3/4” dual faced mdf flexes annoyingly on the current table I would suggest the current table is likely to be the issue.

Dave

[Grindstone CowboyParticipant @grindstonecowboy]

Agree with Dave S. Like a building, it's only going to be as good as the foundations. (Waits for someone to come up with an example that disproves it… )

Rob

[not done it yetParticipant @notdoneityet]

KISS Principle. Screw them together?

[Donald MacDonald 1Participant @donaldmacdonald1]

Posted by not done it yet on 31/03/2022 16:51:50:

KISS Principle. Screw them together?

Buying a new table is definitely not KISS!

Not screws because:
A) I want to use the whole of the both of the top faces and any screws will be hard to flatten off.
B) I want to make sure that the centres does not bow out from each other.

But good point about using lines not circles, Jason. I shall definitely use that.

Don

[Frances IoMParticipant @francesiom58905]

can you screw from underneath ? or is the intention to turn it over when you have badly scored one side.
If 16mm backed MDF flexes then you need to apply less pressure or strengthen the base – sounds as tho you are trying to work on a folding card table.

[HopperParticipant @hopper]

I agree with Frances above ^^^^^  It seems like way overkill or overthinking on gluing two pieces of board together in order to create a surface on top of an existing bench for the very simple purpose of resting a cutting mat. If it is this difficult — two pages of forum discussion with not one suggestion being "just right" — something is wrong at basic principles level.

Edited By Hopper on 01/04/2022 07:30:17

[Ramon WilsonParticipant @ramonwilson3]

It seems to me that the use of JB Weld in this situation is rather a waste of the product.

The thing to bear in mind once this gluing of two surfaces together – to provide a flat one – is the inability to part them if it does warp. Not suggesting it will but am saying it might – too late then.

NDIY's and others suggestion of screwing is to me the most logical. Correctly done the screws can be equally spaced to ensure even pressure across the area and the heads countersunk enough to either be flush or filled over. The original poster does say that for most of the time it will be used under cutting matts so screws shouldn't be an issue.

The environment would appear to present a challenge with -5 to + 40 and relevant humidity changes – another thing to be considered.

I have in my workshop a very flat bench top – MDF on top of MDF on top of Chipboard – all screwed together. It is checked for flatness and warpage each time I build a model – so far the stability has remained since I placed the last layer on

 

 

 

As always the pics are to assist the recommendation but what I do does require an absolutely flat working surface – the above has proved admirably successful for me.

Someone suggests this is probably being over thought, yes the question was about which glue type to use but it's time to think outside the envelope perhaps.

 

Regards – Tug

 

 

 

Edited By Ramon Wilson on 01/04/2022 08:04:11

Edited By Ramon Wilson on 01/04/2022 08:11:55

[HopperParticipant @hopper]

Ramon – not overthinking at all for your purposes where you are using it as a jig/fixture base for building large complex structures that must be dead flat/straight/true, such as airfoil sections as shown. But for resting a cutting mat as the OP describes — not so much.

[Ramon WilsonParticipant @ramonwilson3]

Hi Hopper,

Maybe so but the principle's the same – the object is to get two pieces of board together to provide a flat surface without it warping or delaminating. My approach is on the basis of once bonded it's bonded – if a warp does then ensue it rather defeats the object – atmospheric conditions can, and will, play a part in trying to do what you want to prevent..

FWIW all the MDF two layer bases I make for my plastic models are screwed together for the same reason but – 'yer pays yer' money etc.

Tug

[HopperParticipant @hopper]

Yes indeed good from that point of view. And as you say, screw holes could be filled with bog and filed/sanded down flat,

What kind of screws work best in MDF though? Ordinary wood screws? Chipboard screws? Or are there special MDF screws?

[Ramon WilsonParticipant @ramonwilson3]

I use basic 'Screwfix' silver screws but I'm sure any 'modern' parallel thread screw would do. I would think an acrylic filler for the melamine surface would be best. If done with care they would be hard pushed to see let alone feel.

T

[HopperParticipant @hopper]

Yes I suppose they have all that stuff available that cabinet makers etc must use when doing kitchen cabinets etc with Melamine. Just a matter of prowling the local hardware store or home reno shop.

[CirclipParticipant @circlip]

Yep, the idea of having the boards double sided to help stop bowing is good. taking facing off the two surfaces to bond to each other solves that, still faced on outer sides after bonding. Problem is, however you do it, without a laminate press you can't ensure, at that size they will be flat parallel faces. Unfaced 32mm MDF is available so you could face both sides with laminate using 'Cascomite' (Ahh remember it well for making toy boats) but when mixed, add a few drops of Meths to disperse air bubbles in mix.

Regards Ian.

[Donald MacDonald 1Participant @donaldmacdonald1]

Thank you for all your thoughts.

Frances – no, for a number of reasons I intend to use both sides.

Yes, I am working on a folded table, but it HAS to be a folded table. [For the love of God, please don't anyone else suggest buying a whole new table – KISS!!]

Hopper – And no, as I have already said, I will not JUST be using it under a cutting mat. Please stop over-thinking your answer and just attempt to answer the question. If you have nothing of value to add please then please don't!

Raymond – To state the obvious, the more sheets that are bonded together the less likely they will be to warp after they have been bonded together. But if & when it does warp after I have bonded the 2 sheets together, I shall cross that bridge.
But IF gluing fails then screws, pref from one side only & filling them carefully could be done. But I would much rather have a complete, sound melamine surface if I can. Also unless I put a screw in the middle of my sheets (thereby screwing up a perfectly good nice, flat, easily cleaned melamine surface) it will be more likely to warp with screws than with adhesive.

In truth the only reason that I have not yet implemented gluing option is that my MDF sheets are in use underneath ongoing projects!

I have yet to check whether there is any slight pre-existing warping in my MDF sheets when removed from the table, buy if so, then I shall of course arrange them back to back so as to cancel each other out as much as possible.

Don

[Dave SParticipant @daves59043]

A very simple, low cost solution to a wobbly folding table that you cannot replace is to work on the floor.

Making an 1 1/2” thick piece is unlikely to fix your problem.
3/4” is already quite heavy and very stiff.

By doubling up you double the weight but the stiffness will only go from very stiff to really very stiff…

If 3/4” is not stiff enough then you really have to question the supports or the force you are putting in.

Doubling the weight on a suspect support is dubious from what little information you have supplied.

Dave

[Ramon WilsonParticipant @ramonwilson3]

Well far be it from me to disagree with you Don but I think you will find that if two flat surfaces (as you describe) are screwed together there is far less likely hood of them warping than if bonding for the simple reason that each layer has the ability to stretch/shrink without directly influencing each other but as said 'yer pays yer money' etc..

If you want to potentially waste two (or more ?) sheets of faced MDF in order to find out by all means do so. Something tells me however that had you screwed them together from one side only you would be well into being able to use it by now – one side nice and clean with an un-interrupted surface to use as such, the other 'unclean' side to be used under the cutting mats.

Whatever I think you must have garnered enough information and help from the replies to your call for help on here to enable you to make a firm decision by now – good luck with it how ever you do it

Ramon – No Y No D BTW – and usually referred to as Tug 

 

 

Edited By Ramon Wilson on 01/04/2022 16:53:32

[PackmuleParticipant @packmule]

When formica was all the rage we used a glue called Thixotropic made by evo-stik.

[SillyOldDufferModerator @sillyoldduffer]

To my mind Donald's post just after midnight yesterday changed the question completely.

If I read his second post correctly, the question is how to improve the rigidity of a table-top, not 'Which shrinking glue is best for sticking sheets of MDF together (without warping)?'

Warping is not the same as sagging. Warping occurs when two sheets expand at different rates due to heat or humidity. A good way of stopping it is to let the sheets slide: this is why bridges have expansion joints.

Sagging is when a girder (or table top) deflects due to it's own weight, and a load. Benches and kitchen worktops are kept flat by having multiple supports underneath, and although a comprehensive frame can't be built-in to a folding table, putting temporary props underneath might be a satisfactory solution.

Sag is reduced in proportion to the depth of the girder, so another way of approaching this is to glue deep narrow ribs between the two sheets. Ribs increase the effective depth of the table-top, reducing sag, and the extra depth is obtained without adding much weight. Welding two strips in a 'T' is much more rigid than welding them into a single flat:

Wood might do, otherwise deep Aluminium I-beams. Another observation, in a ribbed sandwich the lower sheet can be thinner than the top sheet, or even wires. This is because the top sheet is in compression and has to resist buckling, unlike the lower sheet which is in tension.

In engineering it's usually best to start with the actual requirement. Otherwise everyone ends up wasting time producing complicated solutions to the wrong problem that don't work very well! Apologies if I've misunderstood, but it appears this requirement is more about designing a bridge than choosing glue.

Dave

[HopperParticipant @hopper]

Posted by Donald MacDonald 1 on 01/04/2022 15:20:49:

Thank you for all your thoughts.

Frances – no, for a number of reasons I intend to use both sides.

Yes, I am working on a folded table, but it HAS to be a folded table. [For the love of God, please don't anyone else suggest buying a whole new table – KISS!!]

Hopper – And no, as I have already said, I will not JUST be using it under a cutting mat. Please stop over-thinking your answer and just attempt to answer the question. If you have nothing of value to add please then please don't!

Perhaps you should try stating your problem clearly in the first place instead of — once again — drip feeding often contradictory information as members spend their time coming up with solutions for your partially described problems that never seem to be up to your exacting standards

You can't hope to do precision — certainly not to the standard you aspire to — work on a folding table. A length of 4" x 2" timber wall studding cut up and screwed together will make a stout table frame an four legs for your MDF boards and cost about the same as one or maybe two cups of skinny soy latte coffee. Could be made with hinged legs for folding up. Or hinged off the wall with two outrigger legs. A bit of lateral thinking should solve most of your problems.

And being rude to those spending their time trying to help you is probably not the way forward, either on the forum or in life.

 

Edited By Hopper on 01/04/2022 22:28:18

[Michael GilliganParticipant @michaelgilligan61133]

If I was in the unfortunate position of needing to produce a metre square, flat and negligibly deflecting under its own weight, cutting board: I would start by looking at honeycomb and/or foam cores.

But I did work in a vibration test facility, so I may possibly have a head’s start, Donald.

MichaelG.

[Author]

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