Jointer and Synthetic Materials

[jschen]

I've been reading that you shouldn't use a jointer on MDF and Plywood. What's the reasoning on this? Is it because it dulls the blades fast? I ask because I use those two materials quite often in my projects.

[jonmulzer]

Is it because it dulls the blades fast?

Quicker than you could say that sentence. Why would you need to joint sheetgoods?

[Pappy]

If you need to 'joint' the edge on ply or MDF use a router and a straight edge. Spiral trim bits leave a clean edge.

[jschen]

Quicker than you could say that sentence. Why would you need to joint sheetgoods?

I am always having problems cutting the boards square so when I join (box) them they never seem to butt up correctly. I probably need to just practice more in cutting but thought a jointer might solve part of that problem.

[eddy merckx]

I am always having problems cutting the boards square

Hmm, lots of questions. Are you using a tablesaw to make the cuts? Are the edges out of square with one another (not exactly 90 degrees) or are the edges kind of wavy?

Eddy

[LinuxRandal]

I am always having problems cutting the boards square so when I join (box) them they never seem to butt up correctly. I probably need to just practice more in cutting but thought a jointer might solve part of that problem.

Are you using the factory edge? They aren't always square. You can use that, to trim the other edge (needs two points of contact to be flat enough), then flip it to trim your original edge, so they are parallel.

[bfrikken]

From my experience, I recently salvaged a bunch of MDF from a neighbor who was going to throw it all away. These were very big pieces, most being 60"x48". The problem was that the original person who installed them used a nail gun and split every exposed edge. On top of that, not a single cut edge was cut straight. So in an effort to save as much material, I cut close to what I desired my width to be. Then I took a straight edge and a router with a straight bit, and trimmed my first true straight edge. That became my first edge to cut the other side of on my tablesaw. Since I needed narrow, yet long boards, I then cut the ends off with my mitre sled. Far as I can tell, they are square and edges are straight. My first attempt, I walked my board from the fence first pass through, but I cleaned it up with another pass.

[jschen]

Hmm, lots of questions. Are you using a tablesaw to make the cuts? Are the edges out of square with one another (not exactly 90 degrees) or are the edges kind of wavy?

Eddy

I have been using a straight edge and circular saw for the bigger 2' x 4' panels and then a table saw. The edges are out of square. I may need a better fence on my table saw but I do have it aligned to the blade. Like I said I think I need more practice and perhaps better technique.


I am working on a router table so I may be able to square up my edges with that. If I do jointing on my router table do I need to keep this jointer? Perhaps spend that money on a better fence on the table saw.

[drumpriest]

Why would you need to joint sheet goods?? 3 words.. bent wood lamination... It's technically plywood, but you often need to joint an edge on it, and it's really mostly practical on the jointer. But yeah, it'll kill knives in a hurry.