What are your opinions/experiences with pocket screws and MDF? I just predrilled a pile of rails, but the stiles were splitting when i’d screw the rails to them. I’m feeding the screw nice and slow and even. I’m using kreg brand self tapping screws and i have the joints clamped nice and tight. i’m going to try predrilling through the pocket hole into the stiles and see if that does it, but while i ate lunch i figured i’d see what folks here though of using pocket hole joinery (and glue) with MDF (for face frames in this case).
Jesse David
Replies
You should be using a screw that you would use for soft wood... a very coarse threaded screw. If that is the kind of screw you are using I can't explain the problem.
Hi Jesse D ,
IMO you will compromise the structural integrity of the face frames with MDF as opposed to solid wood faces. Also your screw may not be centered and closer to one side then the other , hence causing the splitting action . The screw in MDF will take little racking or abuse before breaking or cracking .Unless the MDF frame is to be screwed to the wall or otherwise held solidly , your better way is to use wood , Alder , Soft or any Maple Poplar or other paintable woods.
good luck dusty
The face frames'll be attached to sturdy cabinets attached to the wall, so there shouldn't be much racking action. I wouldn't trust pocket screws to hold mdf together under strain. But in this application, used with glue i think they'd be fine, except for the splitting.
And yes to the above poster, i am using coarse 1 1/4" self tapping screws.
Jesse David
to hold mdf together under strain..I use veneer faced MDF quite a bit..
For case panels I use a LockMiter bit (I love it) but I have set-up blocks I use to set the bit depth..If I have to screw into the edge (which I try to avoid) I route about 1 inch deep and glue a hunk of hardwood scrap in there..I have never had a joint failure...I am not sure of their real name, I call them 'Dog-Bone' fasteners..
They work well but more work than just a hole/slot with hardwood in there...
I have a lock mitre bit, and i've found some great uses for it, but i take a lot of time in the set up. What is your system witht he set up blocks? Different thicknesses of wood routed at the correct depth, so that you can easily match the depth again, or what?
Jesse David
I usually use the mdf or ply based Veneers.. They are pretty much the same size all the time.. I have a box with drawers..Hunk of the wood, two set up blocks for cuts that I thought perfect...I just use 3/4 inch or whatever it is now.. Why I keep a sample of the original wood.. Just in case the thickness changes.. I have NOT seen any from where I get my stock..Folks bitch about the lock mitre bit.. Like any joint.. Either ya can do it or NOT! Yes you need some spaCe for the panel for the Vertical cut but a high fence and 'away you go!'Just make sure the vertical held panel does not hit a rafter or a pipe!
Edited 8/8/2005 1:29 pm ET by Will George
MDF splits so easily that you probably cannot get pocket screws to work. Hardly any types of screw will work in MDF. I think you are better off with a different fastening method.
I like to use staples and glue. The staples only have to hold it for the glue to dry, which is stronger than any fastener. Nails and screws just tend to cause splitting, and bulging. The staples does less damage to the MDF, and when it is spackled and painted it looks just as good as if you had mortised and tenoned it, and it may be just as strong.
Shame on you for using MDF, Jesse. Pre-drilling into the other piece is your best chance for avoiding the split. I don't use pocket screws for faceframes, I prefer FF biscuits for utility grade work. I won't use MDF for anything but disposable jigs, too heavy, too weak and I hate the dust.
Beat it to fit / Paint it to match
I think you are way better off using an inexpensive wood like poplar for your face frames. It paints nicely and you won't have problems with splitting. But if you are settled on using MDF, are biscuits an option -- or even dowels?Before you give up on the pocket screws, try fiddling with the depth of the hole you are drilling (a collar should have been supplied with your bit). Once you have the holes drilled in the one piece, fit them together, and run your drill (without the jig) through the piece you have already drilled (with the jig), and into the piece you are fastening it to (which I assume is the one where you are getting the splitting).********************************************************
"I tend to live in the past because most of my life is there."
-- Herb Caen (1916-1997)
MDF tends to split whether or not it's pre-drilled, in my humble experience.
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