Cutting oak veneered mdf

[barbershopper john]

Over the years I have done many projects using 18mm oak veneered mdf and have created some great stuff. However today I started a project with mdf from a different supplier , the veneers are great but after I have cut through it the cut Is convex from top to bottom which means a but joint between two pieces leaves a small gap on the faces.

Has anyone else had a similar problem? Can anyone explain what is going wrong? How can I rectify things?

The saw is a ts55 with a fresh blade in.

Can anyone help?

Cheers John

 

[ear3]

[member=14113]barbershopper john[/member]
Just curious why you suspect it might have something to do with the material as opposed to being an issue with the saw -- or more likely the rail -- itself?

Have you confirmed that your current setup will produce straight cuts in other material?

Over the years I have done many projects using 18mm oak veneered mdf and have created some great stuff. However today I started a project with mdf from a different supplier , the veneers are great but after I have cut through it the cut Is convex from top to bottom which means a but joint between two pieces leaves a small gap on the faces.

Has anyone else had a similar problem? Can anyone explain what is going wrong? How can I rectify things?

The saw is a ts55 with a fresh blade in.

Can anyone help?

Cheers John

 

[Doug S]

Did you just cut the pieces straight off the full sheet? Even though it's MDF there can still be tension/stress in the sheet. Sometimes it's best to cut the pieces slightly over size to release the tension then cut them again to the correct size.

Doug

 

[Russty]

are you saying the mdf bulges out in the middle of the thickness? does it feel fluffy in the middle where the material is less dense? some lower quality mdfs are like that. not sure of a solution to that though other than trying to sand it flat.

 

[Stone Message]

Over the years I have done many projects using 18mm oak veneered mdf and have created some great stuff. However today I started a project with mdf from a different supplier , the veneers are great but after I have cut through it the cut Is convex from top to bottom which means a but joint between two pieces leaves a small gap on the faces.

Has anyone else had a similar problem? Can anyone explain what is going wrong? How can I rectify things?

The saw is a ts55 with a fresh blade in.

Can anyone help?

Cheers John

Hi John

Veneered MDF and some other laminated products can have tension in them after manufacture. When you start cutting a sheet those tensions get released and often lead to cuts that should be straight being slightly curved.

In order to routinely avoid this cut your sheet up not into exact sizes but 4 - 6 mm over size. Then trim down to the finished size. It is not as time consuming as it sounds but does help you avoid the problems that you have observed.

Good luck.

Peter

 

[lwoirhaye]

This has been called a "dust cut" and I have had more than one argument with a person online who believes sheet goods cut straight.  While cuts in MDF and plywood often come out straight enough for further processing, when further processing tests that tolerance a wise craftsperson might hedge his or her bets by cutting a bit oversized and letting sheet goods move overnight.  An edge over perhaps 36" will show this movement sometimes - enough that it can be a problem.

I edge band with a press and it forced me to pay attention to this.http://www.woodcentral.com/bparticles/edgebanding2.shtml