Replies

1. 
   Runrig | Jul 09, 1999 08:05am | #1

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   True, MDF as such doesn't really have a grain, and with modern glues you should be able to butt just about any two MDF surfaces together and get a pretty good joint. However, joining two cut edges together will probably lead to some glue starvation and subsequent weakness due to the porosity of the exposed edge. Joining a cut edge to a face is stronger, and two faces together should be the strongest. I say that with reservation, because polyurethane glue, for example, has stated on the bottle that a roughened surface is preferable. Most glues work best on a smooth surface.

   Joints such as biscuits, housings (dados,) rebates, (rabbets) in MDF serve at least two purposes. 1. They line the joint up leading to accurate cabinetry. 2. They increase the total area that is glued, ergo, added strength. As with every other joint there is a balance to be found between removing the material from each part to find the best compromise of strength, and accuracy, a whole new topic that I'm not going to go into here.

   Particle board, as you call it, is known in the UK as chipboard, or more frequently, 'Shitboard'. It's best description is crude MDF. Edge to edge joints merely glued are hopelessly weak because of glue starvation caused by the large gaps between all the chips/ particles. The outer surface layers of shitboard have a habit of peeling off under the slightest duress. Joints in particle board/ shitboard are important to impart strength. A lot of KD fittings are used to speed up assembly.

   Anyway, I've never seen anyone make anything out of particle board that was meant to be anything other than temporary, so the cheapest way you can throw it together seems to be the norm. Butt, glue and nail is very common. Chuck it away in a few years time. It was probably junk in the first place!

1. 
   RJT_ | Nov 29, 1999 03:54am | #2

   *It would be impossible to discuss how to join MDF/MDF without knowing the application.