Friday, 25 February 2011

As I was saying....

....the sides of the cabinet are made by laminating pieces together and putting them in a veneer bag.  I'll show you.

The veneer bag is a heavy weight plastic bag which is connected to a vacuum pump which sucks all the air out. Anything that is in the bag will then get squashed by the atmosphere around us. In theory you should be able to get 1 atmosphere of pressure, but in real life you only get about 0.8 atmospheres which is enough.

The picture shows one of the curved cabinet sides being made.  Inside the bag goes a large flat piece of material, in this case a piece of white faced chipboard.  On this sit the former which has the shape I want to produce - in this case a simple curve. On top of the former sits the pieces I am laminating. Shove it all in the bag, switch on, leave for a few hours for the glue to set and the result is a panel that has the shape of the former. Easy.

As the curved panels are only 8mm thick, by themselves they would not be strong enough. To beef up the cabinet sides, the curved panels are glued to curved ribs that are in turn glued to a flat panel. This then gives the cabinet side the strength required. The flat side becomes the inside of the cabinet, while the curved side is the outside of the cabinet.  I must remember this during the glue-up and make sure I don't get it the wrong way round!

Before the cabinet is glue together, I have to drill evenly spaced holes on the inside faces for the shelf supports.  These need to be drilled accurately otherwise the shelf will not sit right and wobble.  To do this I use a jig and a router.  The jig is simply a piece of ply wood that has holes drilled into it at a regular spacing.  On the base of the router a guide bush is screwed. This is a circular collar of metal that has an outside diameter the same as the diameter of the holes I drilled in the ply.  You see where this is going?  The jig is clamped to the cabinet side, the guide bush sits in the hole and the router is then used to drill the hole.

This picture shows me doing a dry fit of the cabinet components before I do the glue up.  It is always good practice to do a dry fit, as once glue up starts it is too late to fix any problems!

You can see how the curve of the cabinet sides is mirrored  by the curve of the legs. Another reason for this dry fit is that I need to have the four legs completely sanded to their finished state.  The reason for this is I am going to fume the oak to make them go a dark chocolate brown.  Once fumed, I can't start sanding down the legs otherwise I could sand all the colour away.

To fume wood, you need to expose it to ammonia vapours.  Ammonia is horrid smelly stuff and not nice at all - the fumes need to be contained to get the best effect on the wood.  Hence, you can either fume in a sealed plastic box or make a fuming tent. I did the latter.

The tent I made is a simple MDF frame that is covered in heavy weight plastic.  A plastic flap is pulled over the top and seal with brown packing tape. It reminds me in some way of the first fish tank I had when I was much younger.  It was one of the glass-and-frame types that existed before the all-glass versions you see now days. My Dad got if for me. He found it in a friends garden. It was in a right state. All the iron rusty, glass broken.  He did a repair job on it, got the rust off, painted it, replaced the glass.  It looked good as new once finished!

Anyway, back to the oak and fuming.  Here is the method. Place the wood to be fumed in the tent. Get some ammonia. Wear lots of personal protection equipment. Pour some ammonia into plastic trays. Place trays in tent. Seal tent up. Wait 24 hours or until you have the desired colour (which maybe before 24 hours if only a light fuming is required). Remove oak.

Once the wood comes out of the tent, it really wiffs of ammonia.  I left the legs for a few days to air off before I coated them with oil. After that it was the carcass glue up!

So this is the state of play.  Carcass glued together. Doors on, but not finished as I have to make the handles.

Ah the am I going to do that......