Thread: Screwing into MDF suggestions

A dowel at right angles to the screw works well.

Originally Posted by NCArcher

A dowel at right angles to the screw works well.

As the corbel is glued together and almost ready for painting, I am reluctant to drill into or mark the exterior. I should have done that before gluing the outermost sheets ( 8 sheets of 16 mm MDF) like I did with the dowels that go around the perimeter.

Thanks

Supposedly the best screws for mdf are Confirmat screws, but not sure how well they'd hold on the ends of the MDF like that. Maybe rout a slot under the area where the aluminium bracket is going, and glue a piece of wood to the MDF to give something for the screws to hang onto.

Originally Posted by Marwood

Supposedly the best screws for mdf are Confirmat screws, but not sure how well they'd hold on the ends of the MDF like that. Maybe rout a slot under the area where the aluminium bracket is going, and glue a piece of wood to the MDF to give something for the screws to hang onto.

The cross support dowels are 22 below the outer edges of the corbel. Any screwing that has to be done, must be between the dowels which are separated by 80mm. If I trench the length of the corbel sufficiently for the supporting timber, I will no doubt cut through the dowels.

If I use a 20 mm forstner bit and provide for a 20 mm dowel, at each screw point, however, I would then be screwing into the end grain of the timber, which will still be better than into the endgrain of the MDF.

If I drill a slightly larger hole for a 8 gauge wood screw and then saturate the hole with watered down PVA glue, hopefully the fibres surround the hole will be soaked and provide for a good keying when the screws are later inserted with normal strength PVA. I guess I am trying to create a chemical anchor situation.

Why do you have such a phobia with screwing end grain MDF?
Yes if you just screw straight into the end grain it will split. To make a successful job all you need to do is drill a proper sized pilot hole and there you have It. What is a proper sized hole? If you were to grind off the threads on a screw you would be left with a shaft. That is the pilot hole size!!!
If you are still paranoid....drill a clearance hole for the whole screw, down say 10mm (if using 50mm long screws then into the pilot hole size.
I use long thread screws. They are a parallel sided screw with a Phillips head. The treads go from the point right up to the head. 8# gauge is all you need.
There is no need for paranoia! How do I know? half a life time of screwing components together building kitchens

Why not hold the aluminium in place with glue?

If you want the screws for re-movability reasons, you can drill a larger hole, fill with epoxy, then screw into the 'poxy when its hard.

I've always done this with 3/4" dowel - no chance of the MDF delaminating.

These days I always take a scrap of MDF to Bunnies with me, which has had a hole drilled in it with my Colt 3/4" forstner. Then just go through the cheap 3/4" dowel stock on their shelf until I find a section that is a nice snug fit in my test piece of MDF.

This way I carefully leave all the wildly over/undersize dowel for the rest of you

Originally Posted by chambezio

Why do you have such a phobia with screwing end grain MDF?
Yes if you just screw straight into the end grain it will split. To make a successful job all you need to do is drill a proper sized pilot hole and there you have It. What is a proper sized hole? If you were to grind off the threads on a screw you would be left with a shaft. That is the pilot hole size!!!
If you are still paranoid....drill a clearance hole for the whole screw, down say 10mm (if using 50mm long screws then into the pilot hole size.
I use long thread screws. They are a parallel sided screw with a Phillips head. The treads go from the point right up to the head. 8# gauge is all you need.
There is no need for paranoia! How do I know? half a life time of screwing components together building kitchens

Chambezio, I guess, I am a little paranoid, but at the same time, I like to find out the various options. It can be quite enlightening getting different views from our well intentioned forumites.

There is no doubt that I would have drilled a pilot hole first. Do the screws that you talk about, have a finer thread compared to a normal 8 gauge woodscrew?

Originally Posted by Master Splinter

Why not hold the aluminium in place with glue?

If you want the screws for re-movability reasons, you can drill a larger hole, fill with epoxy, then screw into the 'poxy when its hard.

Master Splinter, your spot on, I am doing this with re-movability in mind. I presume you would drill a pilot hole into the epoxy first.

Each plate will have two key holes, so the corbel will be held by two bolts which are attached to the above canopy. The plate will be slightly angled so that the bolt/plate contact will tighten as the corbel is slid into position.

Originally Posted by Mr Brush

I've always done this with 3/4" dowel - no chance of the MDF delaminating.

These days I always take a scrap of MDF to Bunnies with me, which has had a hole drilled in it with my Colt 3/4" forstner. Then just go through the cheap 3/4" dowel stock on their shelf until I find a section that is a nice snug fit in my test piece of MDF.

This way I carefully leave all the wildly over/undersize dowel for the rest of you

Mr Brush, good idea, I will take the corbels with me to Bunnings. I have got some dowels which I will have to sand down for a snug, but not tight fit.

Thanks for the responses guys. We have got a few suggestion now, it might be an idea to do some experimentation.

Zelk

Zelk
My "weapon of choice" is "Long thread" 8 gauge screws. I buy them from Nover & Co by the box. There is a good selection of lengths in the range. The thread is not unlike a self tapping sheet metal screw. The thread is finer than the typically marked "Chip Board Screw". I prefer the long thread head design as well. If you countersink, the surface is Chip free (If screwing melamine pieces). I find the nibs on the countersink head rough up the surface as you get the screw "home"

Originally Posted by chambezio

Zelk
My "weapon of choice" is "Long thread" 8 gauge screws. I buy them from Nover & Co by the box. There is a good selection of lengths in the range. The thread is not unlike a self tapping sheet metal screw. The thread is finer than the typically marked "Chip Board Screw". I prefer the long thread head design as well. If you countersink, the surface is Chip free (If screwing melamine pieces). I find the nibs on the countersink head rough up the surface as you get the screw "home"

Thanks for that Rod,

BTW, on another topic, as I am planning to use engineered stone ( like Caesarstone) for a bench top, am I better of making a solid plinth instead of using those plastic adjustable legs for the cabinetry?

Zelk

Those plastic adjustable would be fine.....if......you made sure they were placed directly under the gables so the transfer of weight won't bow the bottom shelf. Am I making myself clear? The adjustability makes it easy to instal a cupboard but they create a problem when you want to fit the kickboard. I think you would be better with a solid plinth. You will have peace of mind if you decide to do a dance on the Caesar Stone. I am some what old fashioned with a number of practices.

Another vote for a solid plinth.
In my opinion the advantages are
Easier to install, only one piece to level instead of x amount of cupboards.
Kick board attached to plinth, easier and more solid
More support for cupboards as chambezio pointed out.
Plinth can be anchored to floor and wall, again making it more solid.
If you are building cupboards etc in workshop everything can be sat on plinth, screwed together, fitted and adjusted making it quicker to install kitchen in situ.

FWIW, we have a 5 mtr bench + 3 mtr return stone bench top solid chipboard plinth.

Thanks Rod and Jrock, I can not say that I totally trust these type of legs, even though some kitchen manufacturers say that they are Ok even with stone bench tops. I will probably make the plinth using marine ply and then fix a painted kick-board to it. Another forumite has suggested fixing a board to the wall and and use adjustable legs only at the front of the cabinet.

Zelk