Finish on the edge of MDF

[David Rose]

I just finished a router jig a few days ago for various purposes. Two members are 30" long by 3" wide of 5/8" MDF. After getting the very straight pieces cut and glued, I just made one more little step. I soaked (well MDF won't really soak) one edge with shellac. Before I had gone far, I noticed the warping starting. I thought, "dummy, one edge only?". So I shellaced the other edge. That didn't cure the problem(s). Glued pieces were way out of square and both members with the shellac were very curved. They have stayed that way, though come back some after three days. And the glued angle changed too. I'm off about 1/32" plus over 30" which is unacceptable for my needs.

Should I just leave alone edges with MDF? I wanted to toughen them a little as they will guide the router base. Now I start over. But I don't want to make the same mistake again. Or should I build this thing with plywood as Bill Hylton did? I chose MDF for the smoother surface, but...

David

[Ted Jay]

Couldn't you edgeband or laminate them?

[David Rose]

I really wasn't trying to get that fancy, Ted. I just wanted the edge a bit tougher to resist wear from a router base sliding along it. I just hate building "one time jigs" which I seem to do too often.

I think I will just stick a little UHV (or whatever the initials are) tape on it... if it will stick.

If you meant laminate the original fixture, I could do that also. But the outside edges of the warped pieces would no longer serve as references to square and such.

I've almost got another one built.

Thanks,

David

[Matt Meiser]

I've used glue size on an MDF shelf and didn't notice any problems. It was done after the piece was completely assembled, so maybe that kept everything in alignment?

[Ted Jay]

I really wasn't trying to get that fancy, Ted. I just wanted the edge a bit tougher to resist wear from a router base sliding along it. I just hate building "one time jigs" which I seem to do too often.

I think I will just stick a little UHV (or whatever the initials are) tape on it... if it will stick.

If you meant laminate the original fixture, I could do that also. But the outside edges of the warped pieces would no longer serve as references to square and such.

I've almost got another one built.

Thanks,

David

I didn't think this was a "one time jig" if you were going to the trouble of putting shellac on it. You just wait... your gonna find a project to use it on now that you have the jig made.

[Cliff Rohrabacher]

With good success, I have painted epoxy on some pretty unlikely edges to get water and wear resistance.

I have been itching to try a penetrating epoxy on something like MDF. I just hardly ever purchase MDF.

[Steve Cox]

Most of my jigs have a wear surface of scrap p-lam. I have never had any problems with it.

[David Rose]

now about putting anything liquid on the stuff's edges. I thought I had done that more than once, but now I wonder. That thing warped almost 1/4" before it started settling back with the drying.

David

I've used glue size on an MDF shelf and didn't notice any problems. It was done after the piece was completely assembled, so maybe that kept everything in alignment?

[David Rose]

for the fixture.

David

[David Rose]

I've heard of it, but not seen it. Did you glue it to MDF? And were any of the pieces similar to my 3" x 3/4" x 30"?

Thanks,

David

[Chris Fite]

I use MDF for jigs and fixtures all the time and treat them with shellac. I have not experienced your problem before. Thanks for the warning.

[norman mitchel]

Newbie to the creek, this is my first post. Have been "looking" for a while and appreciate the expertise and helpful assistance being provided. However, on to the question at hand, I don"t know if this will help but a recent magazine article used spackling compound on the edge to smooth it before painting. Apply and sand for smooth finish on ends of mdf.

[Ted Jay]

Newbie to the creek, this is my first post. Have been "looking" for a while and appreciate the expertise and helpful assistance being provided. However, on to the question at hand, I don"t know if this will help but a recent magazine article used spackling compound on the edge to smooth it before painting. Apply and sand for smooth finish on ends of mdf.

NORM...... Welcome
good idea... maybe even use a skim coat of bondo, dries hard and is sandable.

[Steve Cox]

David, p-lam is short for "plastic laminate" more generally known as "Formica" which is a brand name. I've used it for jigs up to 8' in length with no problems. I usually keep some scrap on hand from other jobs just for situations like yours.

[David Rose]

I've got some laying around too.

David

David, p-lam is short for "plastic laminate" more generally known as "Formica" which is a brand name. I've used it for jigs up to 8' in length with no problems. I usually keep some scrap on hand from other jobs just for situations like yours.