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Best Way to Screw MDF Together???

75751 Views 13 Replies 13 Participants Last post by  radioelectrico
So I'm building Norms Deluxe Router station and while building the fence portion I'm having to drive screws into MDF. Now of course I pre-drilled all my holes but for some damn reason the MDF keeps splitting! Any suggestions guys? I went larger on my drill bit but I'm almost drilling out the size of the threads at this point.

I spent a ton of time cutting all the MDF and had one 3"x3" block just split right in two.

- Ugh

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I have had this problem as well and solved it by using a clamp when putting screws into the end grain. This seems to stop the splitting and allows the screw to bite and hold.
Confirmat screws work well for MDF. There is a special tapered drill bit to match the profile of the screws. I think McFeelys, Rockler of Woodcraft sell them.
I agree with Vincent. I recently put together a bookcase out of MDF and used Confirmat screws with great results. You can check my projects page for the bookcase, but I bet I put in ~40 screws with only one causing splitting. I got mine from McFeely's and they offer a kit that comes with the needed stepped drill bit, screws, and plasitc caps.
If you must screw MDF, Vincent and Derrk are right on.
The problem you are having is why I don't use MDF for projects like that. That said, I do use a lot of MDF, but not for those applications. Even if you solve the problem now, how well is it going to stay together long term.
I would hate to think I spent that much time building something that may not last, in order to save a few dollars. It seems like every time I go cheap, it costs me in the long run. Mdf certainly has its place, but often it's not worth the savings. I realize I go overboard, having access to good materials, but I've got a lot of experience, learning the hard way what doesn't work.
By the way, you may be able to redesign and do a joint other than screws. Without seeing the fence, I'm not sure what. Could you post pictures?
I agree with vince and Kent
I'll second Kent. although confirmat are the way to go with screwing MDF. I think for the long run - you're better off finding another solution to joint these, or use a different material - esp. since this is for the fence for your router table which should stay true for the long run.
My experience with MDF is similar to the comments above.
It's just not a good chioce for structural projects.
I dont hesitate to use it for jigs or patterns or even counter tops but it is really just pressed cardboard at best and has no shear strength to speak of.
Yes. there are sharp screws to make it fit together but any lateral force on the joint will just cause it to split eventually.

Particle board is a bit stronger but still wont take much twisting without breaking the fasteners loose.
p.s. there are also various grade of MDF out there and the reall cheap stuff is not a good choice for your project.

Hello Brad I to feel the same as everyone else I have used mdf and I,m feel it has it place don't know if that's in my shop with that said I to have had the same problem as you what I did to fix is drill out screw hole that is strip out and drill to 1/4 inch and glue in dowel and then pre drill and put screw in I have done this myself work good but not something you don't what to do all time it a way save your project and you time, money to hope this helps
It is also important not to locate screws within about 2 inches from the end to avoid splitting the MDF.
Have you tried Spax screws? I bought some on a whim at Home Depot and have used them in both 1/2" and 3/4" MDF with great results and no pre-drilling. They have a special screw made just for MDF. As someone else has mentioned, though make sure you're at least 1-2" from the ends.
If yoou need 7mmx50mm Confirmat screws at a really reasonable price that are not packaged in over the top priced retail packs…give us a call.
They are not on our web site.
as stupid as this may sound.

MDF has a "grain", two kinds of grain,......."face grain" which is the big 4' x 8' surface and "edge grain" which is the edge surface that runs around the perimetr of the 4' x 8' sheet.

Screwing "into" face grain is almost always strong as an Oxen. Screwing into edge grain is almost always a disaster in waiting especially oif they are structural in nature as opposed to "pretty" aesthetics.

To avoid "splitting" try joining it, instead of nails and screws, use biscuits, rabbets, dadoes, grooves, and glue, clamps… splits and strong like "Bull"

I like confirmate screws as they have their place but I am certainly not convinced they work when applied into edge grains of MDF.

I glue everything first, overnigth an then screw the mdf nly to reinforce the joint.
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