Thursday, February 23, 2012

Thinning on top

For the next board I'm going to make it a bit thicker because I'll be using it in higher wind conditions and in the surf so I want to make sure its up to the task. It's still only going to be 8mm thick but the 33% increase will increase the stiffness of the unlaminated core by around 60% which means around 30% stiffer overall.

My dilemma has been that I've previously tried thinning the 6mm planks that I have using 40 grit sandpaper on a random sander and also using an electric plane and with my emerging woodworking skills the result has been uneven or excruciating long.

To get the 8mm I've decide to thin all the 6mm planks to 4mm because this will mean they are the same thickness as the rail material I'm using so no problems of having to sand it down to avoid bridging and 2mm veneer of paulownia seemed too flimsy to work with and I imaged it would be easy to break. Also, 2 layers of 4mm will be relatively easy to bend while they are not glued together.

So, I took the idea that Fibre n Foam showed in his video of making a jig for using the router and clamped it to the table saw table I made for the HandyCut saw. I used the rail material to set the depth of the router and whao hoo, homemade thicknesser.

The first piece I did was a bit uneven. Only a fraction of a mm but enough to see the obvious furrows. The 4 tips I picked up which lead to the last 2 planks looking almost perfect where

i) make sure you clear the saw dust and shavings off the surface the plank passes over. This is enough to cause the furrows as it makes the surface uneven

ii) make sure the wood plank is pressed flush against the sliding surface by bending the the end of the plank up and so forcing the section near the router bit hard against the surface. A better solution would be to have guides either side of the router to force the plank hard against surface. I'm thinking HDPE strip held down by a compressed spring would be perfect.

iii) If you stop or take pressure of the plank around the router area the bit can easily lift up slightly and the router will put a crop circle on the wood. Feed it through continuously and at a constant rate.

iv) The largest router bit I could find was only 20mm diameter and so I had to keep repositioning it. It only dawned on me half way through that each time I repositioned it I could turn the board around and thin out same section on the other half of the plank. This sped things up.

The final plank was near perfect. The surface was roughed up a bit but I left some extra thickness on there to let me sand it down later.

1 comment :

  1. Something that will hold down timber when cutting or thicknessing is a feather board, easy enough to make youreself too.