YOU NEED TO USE A CHIPBOARD SCREW DRIVEN INTO A PILOT HOLE DRILLED INTO THE CENTER OF THE EDGE AND IDEALY THE WEIGHT WHICH THE SCREW CARRIES SHOULD BE IN THE VERTICAL PLANE OF THE BOARD TO PREVENT SPLITTING AS IT WOULD IF THE WEIGHT WAS APPLIED AT RIGHT ANGLES TO THE BOARD.
UNFORTUNATELY I AM NOT AT ALL SURE IF THE "PAN HEAD" TYPE SCREW YOU WISH TO USE IS AVAILABLE IN THE CHIPBOARD TYPE SCREW.
THE LENGTH OF THE SCREW IS DEPENDANT ON THE WEIGHT THE SCREW IS TO CARRY (I WOULD HAZZARD A GUESS AT 30-40mm WILL SUFFICE AND THE EXTRA DEPTH WOULD HELP WITH THE SPLITTING PROBLEM) AND THE DIAMETER SHOULD BE NO MORE THAN (4mm) BUT AGAIN IS DEPENDANT ON WHAT YOU ARE FIXING.
DRIVING A SCREW CLOSE TO THE EDGE OF THE BOARD IS NOT RECOMMENDED AS THE BOARD IS SURE TO SPLIT SOONER OR LATER EVEN IF A PILOT HOLE IS USED TO PREVENT IMMEDIATE SPLITTING OF BOARD.
AFTER ALL THAT, I'VE PROBABLY PUT YOU RIGHT OFF!!!
I haven't tried this screw for that type of job but i fit solid wood floors and screw them down when possible.
I use a screw called tounge-tite which may work for this type of job.
These screws are good as the are long but very narrow as they are designed to also going thought the face of the floor without leaving a big hole. When i screw them into solid wood they don't need pre drilling and don't ever split the wood so the design must be good for narror screwing spaces. They only come in boxes of 200 and cost about Â£7. The only place i have been able to obtain these is from howarth timber. They are brass and the head is tiny. They have a star shaped screwing bit (Included in box of screws)
Alda, regarding weight distribution, I want to attach a panel on the top of a carcass, but leave a gap between the panel and the top of the carcass. The panel overhangs the edges of the carcass by about 2cm and I had planned on screwing into the edge of the side panels of the carcass instead of the surface of the top horizontal surface panel. There will be four screws (one at each corner).
Yes, I am very worried about it splitting. So, from the additional info provided above, what diameter of screw would be best to use and what length?
Joiner_Mike, thanks for the suggestion; I'll look into those screws.
I haven't found anything called 'carcass screws' at B&Q, but they do have something called black japanned screws, which has a 'pan head'. What are these for?
Is it possible to tell just by looking at a screw whether it is single or twin thread? I have looked it up, but all this pitch and lead business hasn't really provided an answer.
TO MAINTAIN A GAP BETWEEN THE SURFACE PANEL AND THE CARCASS
THERE WILL HAVE TO BE SPACERS/WASHERS INBETWEEN TO REQUIRED SIZE.
ASSUMING NO LATERAL LOADING, AS THE PANEL WILL BE "RESTING" ON THE SPACERS/WASHERS WITH THE SCREWS GOING THROUGH THEM AND INTO EDGES OF CARCASS, I WOULD SUGGEST USE OF SCREWS
3-4mm DIA X 25mm+GAP+ PANEL THICKNESS=LENGTH OF SREW.
YOU COULD USE COUNTERSINK SCREWS HERE IF YOU ARE WILLING TO USE COUNTERSINK WASHERS OR ENCLOSED SCREW CAPS ON THE SURFACE INSTEAD OF PAN HEAD SCREWS.
YOU COULD USE ANGLE BRACKETS SECURED TO INSIDE OF CARCASS AND UNDERSIDE OF SURFACE PANEL AND POSITIONED TO GIVE THE GAP YOU WANT.
THESE BRACKETS COULD BE SECURED IN PLACE WITH
2.5-3mm DIA. X 12mm LONG SCREWS, COUNTERSINK OR PAN HEAD AND ALL FIXINGS WOULD BE HIDDEN FROM VIEW.
AT THE POINTED END OF THE SCREW, IF YOU LOOK CLOSELY YOU WILL SEE THE "START OF THE THREAD". IF THERE IS ONE START THEN THAT IS A SINGLE THREADED SCREW AND IF THERE ARE TWO STARTS THEN THAT IS A DOUBLE THREADED SCREW.
I've seen the types of screw info many times at various websites, but don't understand why they don't suggest a screw for carcasses. I'm assuming that chipboard screws are for the actual chipboard only but need something that takes the melamine face into consideration.
pilot drill the correct size and countersink the hole should give you no problem. i am not aware of any screws specifically designed not to split the melamine in this type of situation and am not sure how they could work if they did exist!