# How to edge join MDF



## Chris Curl (Jan 1, 2013)

I am starting to plan building my router planing jig (http://www.woodworkingtalk.com/f27/router-planing-jig-165546/), and am considering using 3/4" MDF for it. 

I have never worked with MDF before, so I don't know what to look for or think about when using it. 

So, what is the correct way to make an "L" corner using MDF, joining the edge of one piece to the face of the other piece? Just glue? Glue and screws? Glue and brads? No glue because glue would cause the MDF To swell? Something else?

HELP!


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## bargoon (Apr 20, 2016)

I use mdf all the time for jigs. I used to use biscuits and glue but now I just use Titebond III glue and 18ga brads. I've had no failures and the glue doesn't swell the mdf.


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## J_L (Apr 22, 2014)

Most jigs I just screw together. MDF included. However, screwing into the edge of mdf can be tricky. You have to predrill before screwing otherwise it will split and separate around the screw. But predrill too much and the screw won't bite. 

I typically use dewalts countersink bits with the stop collar set so the drill bit ends just shy of the screw length.


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## MT Stringer (Jul 21, 2009)

Chris I pre-drilled pilot holes with a countersink bit, glued and screwed the "gantry" together. Hope this helps.
Mike


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## woodnthings (Jan 24, 2009)

*3/4" mdf?*



Chris Curl said:


> I am starting to plan building my router planing jig (http://www.woodworkingtalk.com/f27/router-planing-jig-165546/), and am considering using 3/4" MDF for it.
> 
> I have never worked with MDF before, so I don't know what to look for or think about when using it.
> 
> HELP!


If you buy a full 4 X 8 ft sheet of 3/4" MDF you will need a crane and a forklift to move it around. It's overkill for your planing jig because while 1/2" may bend of it's own accord, the minute you put the sides on it will stiffen right up. I would stay with 1/2" and even that sheet will weigh a whole lot. ... been there done this. 
Our member @Marv makes some beautiful jigs from 1/2" Baltic Birch and he was kind enough to give me one of his extras.


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## ducbsa (Jul 6, 2014)

I have seen where the MDF is drilled at right angles to the screw and a dowel inserted and probably pilot-drilled to provide something for the screw to bite into.


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## Chris Curl (Jan 1, 2013)

woodnthings said:


> If you buy a full 4 X 8 ft sheet of 3/4" MDF you will need a crane and a forklift to move it around. It's overkill for your planing jig because while 1/2" may bend of it's own accord, the minute you put the sides on it will stiffen right up. I would stay with 1/2" and even that sheet will weigh a whole lot. ... been there done this.
> Our member @Marv makes some beautiful jigs from 1/2" Baltic Birch and he was kind enough to give me one of his extras.


My local HD/Borg sells 4x4 sheets of MDF in both 1/2" and 3/4". If 1/2" is strong enough, I'll go with that. Thanks.


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## Chris Curl (Jan 1, 2013)

responded to the wrong thread ... sorry


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