The Scouts are making some Christmas decorations using LEGO, and we need to stick them on to some metal stands. Could anyone please advise the best glues and process (e.g. sanding, etc.) to join bricks to metal. Many thanks.
Have you considered screwing your decorations to the metal stand, using Technic brick holes to pass the screws? If done properly no harm is done to the bricks, and you will not fear a bad glue joint!
I'm always hesitant to recommend gluing LEGO as it is so much against the spirit of LEGO. Have you considered using the magnet bricks? They come in several regular LEGO brick sizes, and they stick to metal surfaces just fine.
If you must use glue, most glues will readily stick to the plastic, so that is no problem. What you need to check is what glues work well for metal. Personally I would go over to a home improvement store, hobby shop or craft store and ask, as there will be different glues available in different regions/countries.
Depending on how sturdy you need it, then a lot of glues will work. In other words, if this is just going to sit on a shelf, you really don't need tremendous adhesive power.
In this case, I would recommend something like JB Weld or Gorilla Glue. However, make sure you properly prepare both surfaces by roughing them up a bit and cleaning them.
If you need something stronger, I'd look at two-part epoxies that are used in automotive repair. These are specifically formulated to bond metal to plastic. Fusor 116 is one such product.
LEGO bricks are made from ABS, so any glue that will bind ABS to metal will work.
Many thanks for all your help and ideas.
We have experimented with gorilla glue and a couple of others but settled on two part Araldite Rapid, which doesn't take long to set. As they are tree decorations that we are selling to raise funds to build a new building (our old one is rotting away!) they needed to be fairly robust.
Sorry that we are sticking Lego forever, but for every brick we sell we get real bricks in return for our new building!