I'm making, let's say, a 3-sided box using particle board. It's to be used as a "stand" per the plans. I'm thinking of using glue and pocket screws. Is this the best way, or should I put in screw some hardwood cleats to the particle board, then screw the other piece to the cleat? Each piece is 1/2"-thick; what size screw?
Hi, if you are using the 1/2inch particle board the use of glue is a must as well as using pocket hole joinery. If gluing raw to raw you are ok using a good quality glue like tight bond. It there is any plastic coating such as common is a lot of the furniture in the market of today then you must use a different glue such as "Roo" glue to bond the wood to plastic glue. As for screws I would use the 1 inch screw as anything else will be stretching it for screw length.
As with any joinery practice the use of cleats always make a tighter and stronger joint. I would use something like 3/4 " and use again glue and most likely again the 1 inch screw. Even though you are running the screws at an angle the risk of the 1&1/4 inch screw is again is taking a chance of penetrating the material.
If possible you could increase the cleat thickness and then go to the 1&1/4 inch screw. This depends on the design of the project.