Tablesaw with a fine blade and zero clearance insert. Add a strip of 2" painters tape over the cut line. Lots of tricks out there. Search cutting melamine or laminate, same idea. No jigsaws!

 

Tablesaw, with the good side of the board facing up.

 

That is MDF most of the time, it usually cut pretty clean. A quick wipe with a sanding sponge.

 

You've gotta make a 12" cut across a board 72" long? That's a PITA and a little dangerous on a table saw. I'd use a circular saw with a high tooth count blade. Use a large speed square as a guide, if you need to. Practice first on the waste. Cut good side down. Use blue tape on the cut line if needed. That stuff cuts pretty easy.

 

I made the cut with a circular saw, and the cut was clean.

However, the board was factory painted on one side, and since I use painting tape to protect both sides for the cut, when I pulled the tape off after the cut, the tape removal itself pulled paint off the board...didn't expect that LOL.

 

I cut a 3x4' piece out of a 4x8' sheet the other day with a regular circular saw with a 60 tooth blade, and was very satisfied with the cut. After block sanding all the edges, I couldn't tell the factory cut from mine.
What is your project ??

 

What is your project ??

 

Find a round knockout that was recently removed from a junction box and use the sharp edges of the knockout. The knockout has to be one that was very, very difficult to remove. 😁

 

I cut a 3x4' piece out of a 4x8' sheet the other day with a regular circular saw with a 60 tooth blade, and was very satisfied with the cut. After block sanding all the edges, I couldn't tell the factory cut from mine.
What is your project ??

John, I try to simplify and generalize my questions down to the most basic form so it doesn't get on a tangent. The actual project in this case doesn't matter because I had similar situations came up in various projects in the past that I "resolved" in different ways by some not as successful as others.

For a plywood sheet this is not difficult but if it's a piece of very thin fiber it's a different story.

One time I took two pieces of steel bar and clamped the fiber board in between and took an angle grinder and cut across it using the steel bars as stop. That didn't give me clean result and had left burnt mark on the fiberboard edge.

I tried to use a razor blade and scored repeatedly and after 3 blades and scoring over 20 times it was not even ha;f way through the 1/8" board.

This time the circular saw cut looks good except the paint tape I used tore some paint off it.

 

except the paint tape

I use 3M auto body tape, light green in color but I doubt color makes a difference. I don't know the model # of the tape but I can look if you have a need. I can leave this tape on for weeks at a time. It's not as cheap as blue painters tape. Knock wood....no matter the surface, I've never had a problem.

FWIW...Don.

 

Anything too thin, even thicker stocks, no problem cuts by cutting over sacrificial table with blade depth set just 1/8 more than the stock. Circular saw, better than 30-40 teeth. Go in at full rpm.