screw size

[Bradley Rogers]

I'm doing a cabinet job and I'm using 1/2 birch plywood and I bought screws for that thickness but they don't seem to work right. Any ideas would be helpful. Thanks in advance.

[Jay Boutwell]

Hi Bradley, When working with the thin plywood and you are drilling the holes to the correct depth with a correctly set jig and using the correct length screw the ply should draw together without any incident.  The one thing that may hamper your work with this is that since birch plywood is soft you must remember to reduce the amount of torque that you apply to the screws. There are fewer plies, unless you are using Baltic birch, than in 3/4 inch plywood so the 1/2 plywood does not offer the same amount of resistance to the screw insertion and will require to you to reduce the driving force.  If you apply too much then they will either strip out in the thread or the ply will split or separate . Since you did not offer any indication as to what it is doing that makes you feel that is  not working right I can only guess.  If there is something else that is happening please let me know what and if possible send a couple photos and I will do my best to figure out the problem.  Remember also that if you are using course thread screws the threads are very aggressive in the birch plywood.  If the screws are exiting the threaded end then you are boring the holes too deep or you are over driving them.

[Bradley Rogers]

I've got everything set to 1/2 but the screws seems to short and won't bite.

[Jay Boutwell]

Bradley, That means that the pocket hole is not drilled deep enough.  The 1/2 ply requires a carefully set drill bit depth setting as there is very little room for error.  I suggest that you check the actual thickness of the plywood as many ply woods that are sole today are marketed as 1/2 " 5/8 " #/4 are actually not that thickenss.  Everything is still metric in European countries and the actual thickness is not as thick as they are stated.   If it is 1/2 thick then I would increase the depth of the drill bit a by a fraction.  Be careful here as you can easily drill through your jig base.   The way I insure that I do not drill through is to drop the drill bit into the jig without the drill and check the tip of the drill bit in relationship to the jig base.  The way I do my bit setting is using a nickel and with the jig set for 1/2 inch in this case.  I set the nickel on the base and then lower the bit down on top of the nickel and then set the stop collar so that the bit stops at this point when you drill the pocket hole.  This means that you should get a proper hole depth without drilling into your jig base.  This gives you about hole that is just shy of the point penetrating through the ply which would be about 1/8 th inch.  So see this is why it is very critical in 1/2" plywood.   I use Kreg's micro jig block for drilling the 1/2" plywood holes and the screws for the 1/2 ply which are a smaller diameter as well as the Jig drill bit and never have any trouble.  I use the same set up method as described above.

You stated that you were not getting any bite.  Take a look at the threaded portion of the hole and see if there is tear out or no indication of any thread at all.

Take a scrap piece of plywood drill the pocket hole and see  if bit tip is coming through he pocket hole.  It should not come through as this prevents you from getting a good seal between the two pieces. Then run a screw into the pocket hole and see how far it is coming through the pocket hole.  with a 1/2" piece of ply wood scrap set the drilled piece on top of the scrap (this would be the piece that the screw is screwing into)  This will give you a picture of how far the screw would screw into the piece.  Let me know what you find out.

[Bradley Rogers]

I will for sure let you know. I won't be able to till this evening when I go to my workshop.