Screws for MDF?

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Jeff

Jeff
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I've never built a cabinet from MDF mainly because I'm gun-shy about how to hold them together. Rabbits and dados instead of butt joints are probably a good idea and wood glue could be TBII or TBIII.

Which screws to use is my question. I've read that regular wood screws could work but the preferred screws are "Spax" or "Confirmat" types. What's unique about these screw type designs (deeper/coarser thread grooves?) vs a regular wood screw which makes them better for MDF? What's your experience with both? TIA.

Here are McFeely's "Spax" screws and they look almost like a regular#8 wood screw (untapered shaft).

https://www.mcfeelys.com/screw-fastener-web-store/shop-screws-by-brands/spax-branded-screws.html?p=2&screw_recess=65&screw_thread_size=82
 
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Gotcha6

Dennis
Corporate Member
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I've found the key to the screw used in MDF is the pilot hole you make, preferably tapered and countersunk head. Also, screws should be coarse thread. Glue works best on face to face surfaces and not edges. Best corner joint IMO would be an interlocking miter or a variation thereof. You could possibly get an advantage using glue on that.
 

Rwe2156

DrBob
Senior User
Jeff,

I've used both. Spax makes screws specifically for MDF which work well. They have a smaller head diameter/countersinking not necessary.

With flat head screws splitting or crushing along the edges are an issue.

IMO MDF does better with butt joints if you use a rabbet or dado just be aware the reduced thickness can be an issue when screwing.

I always use glue. Presize the edges first.
 
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danmart77

Dan
Corporate Member
DQ
Other than speaker cabinets I pass on MDF. Others like it but I think the cost difference between a good ply and mdf is not enough of a factor for me.

I don't like the weight factor either for cabinets.. especially the one destined to be hung on the wall.

Glue? Good old yellow glue. You don't need the T2 or T3 for interior MDF cabinets.

Others my differ here.
 

ehpoole

Ethan
Corporate Member
DQ
Confirmat screws were specifically engineered for MDF and are designed to function a lot like a steel dowel in terms of their performance, so they are considerably chunkier than your typical screw. They have very deep coarse threads. However, to really function well you must also buy the specialized drill bit that drills the multi-stepped hole required for the screw (without you will have to carefully drill the shank, shoulder, and countersink in three distinct steps to the proper depths). They are commonly available in both the 1/2” and 3/4” MDF sizes, so you want to use the screw that most closely matches the material thickness you will be using. Each size Confirmat screw has its own matching drill bit that matches the profile of that screw.
 

KenOfCary

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Ken
Staff member
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What Ethan said. If you're going to use screws in MDF, Confirmat with the special drill bits is the way to go. You can also get little plastic snap-on covers for them so you can paint right over them if painting the MDF.

You can usually buy a starter kit that includes the screws, bit and plastic caps in a package.
 

Rwe2156

DrBob
Senior User
Confirmat screws were actually designed for dissasembling/reassembling cabinets. They are kind of a combination dowel/screw.

Lots of other screws will work just as well.

I've used standard wood screws like McFeeley's and Spax in MDF they work just fine. You just have to be very careful of blowing out the ends of a board or overtightening. That's where the Confirmats excell.
 
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