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Screwing MDF
Hi All
Having problems with putting screws into the edge of 18mm MDF. I've tried correct size pilot holes and special MDF screws from SPAX but I still get splitting and a slight bulge where the screw is. Special MDF screws are best (or least worse) but still noticeable. Any tips? Dave |
david lang wrote:
Hi All Having problems with putting screws into the edge of 18mm MDF. I've tried correct size pilot holes and special MDF screws from SPAX but I still get splitting and a slight bulge where the screw is. Special MDF screws are best (or least worse) but still noticeable. Any tips? Dave If its possible clamp 2 pieces of wood either side of the MDF where the screw/s are being inserted. |
david lang wrote:
Having problems with putting screws into the edge of 18mm MDF. I've tried correct size pilot holes and special MDF screws from SPAX but I still get splitting and a slight bulge where the screw is. Either don't, find another way to do it, or use a tap (which you could make out of a screw), with clamping as suggested by "ben". I guess drill'n'fill'n'screw would be fiddly. |
On Sun, 18 Sep 2005 19:42:58 GMT, "david lang"
wrote: Having problems with putting screws into the edge of 18mm MDF. That's because you can't. If you absolutely must, drill and glue hardwood plugs in there. Ideally drill the plugs through the face perpendicular and screw across them, like a wooden knock-down barrel nut. Don't do anything to MDF that puts a tensile force across the laminations. It might not delaminate today, but it will do. |
Andy Dingley wrote:
On Sun, 18 Sep 2005 19:42:58 GMT, "david lang" wrote: Having problems with putting screws into the edge of 18mm MDF. That's because you can't. If you absolutely must, drill and glue hardwood plugs in there. Ideally drill the plugs through the face perpendicular and screw across them, like a wooden knock-down barrel nut. Don't do anything to MDF that puts a tensile force across the laminations. It might not delaminate today, but it will do. Heh! MDF does not have laminations, its compressed fibres. |
david lang wrote:
Hi All Having problems with putting screws into the edge of 18mm MDF. I've tried correct size pilot holes and special MDF screws from SPAX but I still get splitting and a slight bulge where the screw is. Special MDF screws are best (or least worse) but still noticeable. Any tips? Dave If youre screwing with MDF youre screwed already. Use something decent NT |
In article ,
ben wrote: Don't do anything to MDF that puts a tensile force across the laminations. It might not delaminate today, but it will do. Heh! MDF does not have laminations, its compressed fibres. Still delaminates, though. ;-) -- *He's not dead - he's electroencephalographically challenged Dave Plowman London SW To e-mail, change noise into sound. |
ben wrote:
Andy Dingley wrote: Don't do anything to MDF that puts a tensile force across the laminations. It might not delaminate today, but it will do. Heh! MDF does not have laminations, its compressed fibres. It splits quite easily into thinner bits. Take, say, a 12"x1" bit of 1/2" MDF. Flex it severely, and see how it breaks. You know how your finger-nail sometimes flakes? Same thing. |
david lang wrote:
Hi All Having problems with putting screws into the edge of 18mm MDF. Any tips? Drill 2mm holes and use panel pins with a smear of glue on them. |
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On Sun, 18 Sep 2005 20:44:22 GMT, "ben" wrote:
Heh! MDF does not have laminations, its compressed fibres. MDF is pressed in sheets, rather than rolled. The pressure is applied in one axis and so there are two strong tensile directions and one weak one. You can (pointlessly) argue the semantics of "laminated" and whether it means that such a material _must_ be formed by laminating flat sheets together, but the simple upshot is that MDF has inbuilt planes of weakness and disassembles into laminations, no matter how they were formed. |
Thanks for the input chaps. No magic bullet then.......
Plan 'B'. I'll try cutting a 6mm deep dado in the sides & screwing through from the outside - hopefully the tight fit of the shelf in the dado will stop the splitting. I'll try that tonight & report back! Dave |
On Sun, 18 Sep 2005 20:44:22 GMT, "ben" wrote:
Heh! MDF does not have laminations, its compressed fibres. Slightly OT.. It's worth mentioning that it is now thought that dust from some types of MDF *could* be carcinogenic, due to the glue used to bond the fibres. It's therefore very important to wear a face mask and cut it in a well ventillated area. sponix |
david lang wrote:
Thanks for the input chaps. No magic bullet then....... Plan 'B'. I'll try cutting a 6mm deep dado in the sides & screwing through from the outside - hopefully the tight fit of the shelf in the dado will stop the splitting. I'll try that tonight & report back! Dave I've built mdf shelving with Scewfix Powerdrive carcass screws, straight into the end grain with no pilot hole. As long as you're dead centre, and at least 2" inches from the edge, you should get away without bulges. Boxed in 1000s, so not something you can try out easily. Maybe B&Q Warehouses would have something similar in smaller packs. I've never had much luck with "mdf screws". |
On Sun, 18 Sep 2005 19:42:58 GMT, "david lang"
wrote: Hi All Having problems with putting screws into the edge of 18mm MDF. I've tried correct size pilot holes and special MDF screws from SPAX but I still get splitting and a slight bulge where the screw is. Special MDF screws are best (or least worse) but still noticeable. Any tips? Dave Hi, Have a look at the woodfit site, they have loads of fixings for this sort of thing, eg: http://www.woodfit.com/product_info.php?cPath=16&products_id=1184&Name=Ch ipboard+Fastener+-+12mm+-+Nylon http://www.woodfit.com/product_info.php?cPath=16&products_id=185&Name=Con firmat+Screw+-+7+x+50mm http://www.woodfit.com/product_info.php?cPath=16&products_id=176&Name=Hi-Lo+Screw+-+8+x+55mm http://www.woodfit.com/product_info.php?cPath=14&products_id=161&Name=Bar rel+Nut+-+plastic+-+Beige http://www.woodfit.com/product_info.php?cPath=14&products_id=171&Name=Kli x+Cam+for+15+to+17mm+board Also some good tips he http://www.canadianhomeworkshop.com/toolbox/toolbox_mdf.shtml If just a few holes I'd try giving the screws a good coat of molten wax then dropping them in oversized pilot holes filled with epoxy. After the epoxy has set the screw should home out (hopefully!) and allow the other bit to be fastened on securely. Would need trying on some scraps first though. cheers, Pete. |
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Try drilling and then screwing with 2 inch drywall screws from B &Q with a
dab of pva glue. Done all cupboard door hinges this way and no bulging or splitting "Pete C" wrote in message ... On Sun, 18 Sep 2005 19:42:58 GMT, "david lang" wrote: Hi All Having problems with putting screws into the edge of 18mm MDF. I've tried correct size pilot holes and special MDF screws from SPAX but I still get splitting and a slight bulge where the screw is. Special MDF screws are best (or least worse) but still noticeable. Any tips? Dave Hi, Have a look at the woodfit site, they have loads of fixings for this sort of thing, eg: http://www.woodfit.com/product_info.php?cPath=16&products_id=1184&Name=Ch ipboard+Fastener+-+12mm+-+Nylon http://www.woodfit.com/product_info.php?cPath=16&products_id=185&Name=Con firmat+Screw+-+7+x+50mm http://www.woodfit.com/product_info.php?cPath=16&products_id=176&Name=Hi-Lo+Screw+-+8+x+55mm http://www.woodfit.com/product_info.php?cPath=14&products_id=161&Name=Bar rel+Nut+-+plastic+-+Beige http://www.woodfit.com/product_info.php?cPath=14&products_id=171&Name=Kli x+Cam+for+15+to+17mm+board Also some good tips he http://www.canadianhomeworkshop.com/toolbox/toolbox_mdf.shtml If just a few holes I'd try giving the screws a good coat of molten wax then dropping them in oversized pilot holes filled with epoxy. After the epoxy has set the screw should home out (hopefully!) and allow the other bit to be fastened on securely. Would need trying on some scraps first though. cheers, Pete. |
Rob Morley wrote:
Why not just glue it? I've made bookcases that way that held themselves together even without glue, which makes the gluing up pretty easy. It's really an assembly thing, difficult to glue up without screws in my somewhat cramped workshop. Dave |
david lang wrote:
Thanks for the input chaps. No magic bullet then....... Plan 'B'. I'll try cutting a 6mm deep dado in the sides & screwing through from the outside - hopefully the tight fit of the shelf in the dado will stop the splitting. Plan 'B' worked a treat! Applied glue to the dados (Titebond 11) and used 3.5 x 40 SPAX 'M' MDF screws from B&Q. No splitting on the trial run and virtually no expansion on final assembly. Straight in no pilot holes at all. SPAX 'M' screws aren't cheap mind, £5:98 for 100 - but they do what they say on the tin. Joints are as tight & strong as they could be - jobs a good un! Dave |
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In uk.d-i-y, Rob Morley wrote:
In article , says... david lang wrote: Thanks for the input chaps. No magic bullet then....... Plan 'B'. I'll try cutting a 6mm deep dado in the sides & screwing through from the outside - hopefully the tight fit of the shelf in the dado will stop the splitting. Plan 'B' worked a treat! Applied glue to the dados (Titebond 11) and used 3.5 x 40 SPAX 'M' MDF screws from B&Q. No splitting on the trial run and virtually no expansion on final assembly. Straight in no pilot holes at all. I've found that can cause a small bulge where the screw goes through the dado which pushes the joint apart slightly. I don't understand where a dado comes into the picture. Did I miss something? Just curious. -- Mike Barnes |
david lang wrote: It's really an assembly thing, difficult to glue up without screws in my somewhat cramped workshop. I thought -all the way through this thread, that you were talking about putting screws near the end of the face of the MDF. (You need to pilot drill and countersink screwing through the face of that stuff. And you need to keep as far from the edge as possible. 3 inches is getting close.) MDF is a medium density fibre. That means laminations that are not even tightly bonded. An example of well bonded fibre board is Formica. OK that is a different medium entirely. I doubt though that you would get screws into the end "grain" of higher density fibe board. What you need to do is put some architrave or 2x1 on the uprights where the shelves are going to sit. Remember when measuring out for them that you need to keep them the thickness of the shelf down. You want a 10 inch space from the top of the bottom shelf to the bottom of the next shelf up for books that are 8 inches high. So with a 3/4 inch board as the shelf the batton needs to be 10 3/4 inches from the top of the batton for the next shelf up. (Another point to note is that shelves over 2 feet long need either extra thickness board or some other sort of extra support. A nice edging strip will act as a feature and help keep dust out of the shelf below.) |
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