Saturday 2 May 2009

Paington Zoo bench. 2

The timber has been sitting outside my workshop waiting for my other jobs to be finished so I can complete making the bench.
I selected the two most suitable pieces of 3 inch thick planks, one of which had a slight backwards curve in, the other was thicker but straight. Ten minutes with the chainsaw and both pieces had the same curve. After raising them off the ground with a couple of logs, the centre line and overall shape were marked in chalk. I like working with chalk, as it can be rubbed off and lines redrawn quickly and easily.

I cut the left hand side back piece with a chainsaw and placed it on the right hand side piece, again using blocks of wood to keep it level. Using a black marker pen I marked the final profile.

This was cut, then both pieces were levelled up on the blocks and clamped together using sash cramps. Using a technique called 'kerfing-in' the chainsaw was run down the centre wavy line. This is a way to get 2 boards to fit snugly together -well, almost - especially as I was using a chainsaw and not doing a straight cut.

The outside profile was cut and the two planks were made consistently thick by holding the chainsaw bar as if I was going to cross cut the wood, and swinging it rapidly from left to right. You can get a very good finish this way on any plank of wood.

I want the bench to have a natural tooled finish, without any sanding, so all surfaces are worked with an adze. When done well, an adzed surface is not smooth and regular, but it presents a tactile, faceted and natural surface texture.

I enjoy using the adze, it is held in my right hand against my hip. This is the fixed pivot point. My left hand holds the handle half way down, and the left hand lifts and pushes the adze up and down. The adze swings in an arc, and the bottom of the adze is curved so a thin scoop of wood is cut off. The only down side, is that I sometimes suffer from back-ache and so I use it for short periods of time. The two back pieces took four sessions, about an hour in total.

The sun came out, off came the jumper, the edges of the two seat backs were draw-knifed into shape. Green oak is very easy to work with hand tools, and it is a real joy to work without to much physical effort.

The two smaller back posts are cleft to form triangular cross sections. These are hewn into shape along with the front legs and are given an adzed finish.

I have a dedicated splitting axe, an ex-army one with a protective metal casing where the handle joins the head. This axe is blunt and I have been known to bash rocks open in Lime Regis to find fossils with it.
My favourite axe is the Gränsfors Bruk carving axe, the blade profile is perfect and is a good weight for spoons or heavier hewing. With most hewing and adzing work I work across the grain, this avoids the cutting edge from following the grain of the wood and going off course.

The mortices had to cut by hand as the wood was too wide to fit into my morticer. Once a mortice is marked out I drill out as much of it as possible, and using large framer's chisels I cut the sides square.

Dave came along for a day to give me a hand, here he is cutting a blind mortice in one of the two shorter back posts.

As the wood is shaped by hand with axe and adze, the marking out of mortice and tenons takes a little bit longer, as nothing is square. For this reason the shoulders of some of the tenons had to be kerfed in for a tight fit, I have found this to be the fastest way of getting a good fit.

Once all the joints are pegged together with wooden dowels, I use the draw-boring method to achieve a very tight fit, I cut off the top of the tenon if it protudes too far through the mortice. I use an adze again for this, the wood is green and so it only takes a couple of strokes.

The back posts and legs are all finished and it is time to fit the seat, more on this in my next post

1 comment:

  1. Man,that looks like a lot of work! Also looks like fun. I learned something new in kerfing in the tenons. All the woodworking shows I have watched I've never seen anyone do that. A very useful technique.



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