Jig bases: bow, cup, twist

[PerranOak]

I'm trying to build a collection of useful handtool jigs.
I have a mag (American) that has a nice design for a planing board, etc.
They recommend plywood as it is very stable.

I made the first one from ply and it twisted within a few days.

The next I made from 18mm MDF. It bows every day then I store it on a flat board the other way up and it bows back - mostly!

What is going on!? Is there any "super stable" material we can get here that is good for jigs?

 

[Digit]

I use exclusively Paxolin for those very reasons.

Roy.

 

[Paul Chapman]

The next I made from 18mm MDF. It bows every day then I store it on a flat board the other way up and it bows back - mostly!

When I make jigs and similar stuff from MDF, I usually lip it with soft wood, glued on with biscuits. This stops any bowing, stops the edges from getting damaged and stops it absorbing moisture. Also helps if you rub some wax on it. Here's a shooting board I made that way and it's stayed completely flat, whether I store it flat side down or on edge

Cheers :wink:

Paul

 

[PerranOak]

Cheers both.

Paul, even that top one that is not edged?

 

[Paul Chapman]

Paul, even that top one that is not edged?

The top board doesn't go right to the edge, so is unlikely to sustain any physical damage, and I wax the edges to stop it absorbing any moisture.

Cheers :wink:

Paul

 

[newt]

Here is another example

 

[Derek Willis.]

Use moisture resistant M.D.F. you will find it a lot more stable, that's all I ever use.
Derek.