MDF - Can it edge jointed ?

[Art Travers]

Wondering if this is possible...

[Steve Schoene]

Yes, but it will be murder on the sharpness of the jointer knives, and light cuts are called for. It comes in 4'x8' or even larger sheets so you should never need to join two edges.

[Pat Germain]

I know my jointer manual clearly stated to not use plywood or particle board on the machine. So I don't. That's all I know.

[Jeff Duncan]

Edge jointed or edge joined?
Edge jointed I would take as meaning run it over a jointer to get a straight square edge. This can certainly be done but would not be friendly to your knives.
Edge joined, meaning gluing two pieces together on the flat, is also possible. But to give a better response I would need more details. What kind of piece, how's it going together, sizes, all that good stuff.
JeffD

[Art Travers]

I had glued up two MDF 3/4" x 27 x 19 boards including imbedded two metal strips ala
Mr Sawdust to minimize warping for a router table. I had tried this once before and failed miserably. So in this instance I took a couple of MDF Boards lying around in my shop and tried it again ..and it worked. And yes I also used cauls to flatten out the boards. However, in my haste and not thinking it was going to work I did not straighten any of the edges. Now i need at least one good side so that I can square up the table.

[Greg Hines, MD]

If you are trying to smooth up an edge of a piece of MDF, it is usually easier to use a router and straight edge than to use your jointer. The router bit will do a good job of smoothing it, and you don't risk dulling your jointer knives, which is common with man-made products.

Doc

[Peter Quinn]

I'd edge joint one edge using a router and a carbide bit with a straight edge guide. Otherwise use a part of your jointer knives you don't need much and plan on having your knives sharpened soon, as MDF is rough on HSS, it joints just fine but one or two passes will dull a 3/4" groove into your knives that will make itself obvious next time you pass hardwood over the machine!

[Tom Henderson2]

I had glued up two MDF 3/4" x 27 x 19 boards including imbedded two metal strips ala
Mr Sawdust to minimize warping for a router table. I had tried this once before and failed miserably. So in this instance I took a couple of MDF Boards lying around in my shop and tried it again ..and it worked. And yes I also used cauls to flatten out the boards. However, in my haste and not thinking it was going to work I did not straighten any of the edges. Now i need at least one good side so that I can square up the table.

Why not just make a light cut on the table saw?

-TH

[Julian Wong]

Art,
You don't need to edge joint MDF on the jointer. All you need to do is to run it though the table saw to make sure that you have a relatively good and straight cut on both pieces you want to glue together. Need not be perfect as jointed edges.

When you glue it up, use good clamps and tighten it down well. The MDF fibers are soft and will compress enough to give you a good bond. Of course, use enough glue on both edges becayse MDF edges suck glue like crazy.

[David DeCristoforo]

It can be done. But in my shop anyone that gets near any tools that have a cutting edge (TS excluded) with a piece of MDF gets slapped in the back of the head.

[Matt Ocel]

It can be done. But in my shop anyone that gets near any tools that have a cutting edge (TS excluded) with a piece of MDF gets slapped in the back of the head.

Why's that Yoshi? I personally don't use MDF much but you can't cut it with a Karate Chop.:D
All kidding aside why the bad wrap on MDF.

[glenn bradley]

I had glued up two MDF 3/4" x 27 x 19 boards including imbedded two metal strips ala
Mr Sawdust to minimize warping for a router table. I had tried this once before and failed miserably. So in this instance I took a couple of MDF Boards lying around in my shop and tried it again ..and it worked. And yes I also used cauls to flatten out the boards. However, in my haste and not thinking it was going to work I did not straighten any of the edges. Now i need at least one good side so that I can square up the table.

Draw a straight line and follow it within about 1/16" with a jigsaw. Clamp a straight edge down and run a router with a spiral bit along to clean it up. My .02.

[Peter Quinn]

If I understand the OP's second post he has face glued two pieces of 3/4" MDF with steel stiffeners between the laminations for a router table top, and now needs to create one good edge to begin creating a square panel. So final thickness is 1.5"?

I'm now thinking a long straight line sled on the table saw might be the best way to clean up one edge.

[Chris Padilla]

It's times like these that I like to drag out the trusty Holtey to clean up those MDF edges. ;)

Lottsa ways to skin this cat and most have been highlighted here:

(1) Table saw
(2) Guided Circular Saw with clean, sharp blade
(3) Jigsaw close to the line, clean up with router/flush trim bit
(4) Jointer

MDF is basically glue, some more glue, and sawdust. Glue is like sandpaper to metal...it wears it down. Hence, it is tough on one's blades. Plywood is similar but it has much less glue in it.

Have fun...and dust collection is a MUST with MDF...nasty, nasty stuff....

[David DeCristoforo]

"All kidding aside why the bad wrap on MDF."

Bad rap? What bad rap? I didn't say anything against MDF. All I said was don't be running it through my machines. You want to run it through your own? No problem. they're your machines.... Is this just a personal thing? Yep. But I will concede that sometimes it's ok for jigs and mockups.

[Matt Ocel]

"All kidding aside why the bad wrap on MDF."

Bad rap? What bad rap? I didn't say anything against MDF. All I said was don't be running it through my machines. You want to run it through your own? No problem. they're your machines.... Is this just a personal thing? Yep. But I will concede that sometimes it's ok for jigs and mockups.


Roger That!

[George B. Tracy]

If you have one of the "Pro" clamp n tool guides (about 5 1/4" wide) clamp it over one of the ends so it overhangs the edge of both sheets and run it through your tablesaw using the guide indexed to the fence.

I have a 54" and the 99" I use it to "joint" rough stock all the time and for things like you're doing now. Clamp and tool is apparently gone but CIAO makes the same thing only a bit narrower in width in their "PRO" line.