I was assembling a cabinet today and screwed the screws into the other panel,the did the same thing on the other side and moved it slightly and every screw blew out of the panels all 8,4 on each side,Looking at where the screw went into the panel it only caught maybe 1/8" on the edge of the panel. the panels are 1/2" thick BB ply. any Idea why this happened.I'm using the kreg jig K3 set at 1/2" and kreg screws says they are for 1/2".
Is this the right way to attach? I did A, but is B a better way?
Drill the pocket hole as shown in "B".
The screw should be directed "INWARD", away from the edge.
When a screw is directed toward the OUTSIDE edge, as in "A", it may blow thru.
Make some tests with the drill bit boring a 1/16" shallower.
I use the "micro jig" when joining 1/2" material.
It's a good practice to make sample test pieces, before proceeding to the final work-piece.
This method helps to insure you're getting acceptable results.
In that same situation, I've put screws in both ways, depending upon which way would make them harder to see. For example, if the cabinet is against the wall then I'll put them in from the outside edge so you do don't see the holes from the inside. I don't think which side you drive them from matters. The bigger issue is getting enough of the screw into the joining material without going too far.
I think your best bet would be to take a couple pieces of scrap that are the same thicknesses of your actual cabinet sides and do some test fits.
I've often had to "tweak" my drill collar settings beyond what the jig recommends you to use. Often, wood just isn't the thickness it is supposed to be due to moisture, metric/imperial differences, etc.
"B" is always better - points the screw into the 'meat' of the wood.
That said, you can often get away with "A" with thicker material. Probably 80% of the time with 3/4" ply.
Rare that "A" will reliably work with 1/2" ply.
Trust me, I've learned this lesson a few times when making drawers with 1/2 stock ;)