Stools from Green Wood

Autumn has come quickly this year (2019) and we're quite far into November and had for the first time temperatures below 5 C during the day. With all the rain over the last few weeks, there is not so much I want to do in the garden and I've put-off more pole lathe work until the weather improves. I made a hedgehog house with Sam using old timber from other jobs and that is now near the hedgerow at the rear of the garden. In between times I have collected locally some felled ash and silver birch green wood with the idea of making some green wood tripod stools. I read the book by Alison Ospina "Green Wood Stools" with lots of photos that gave me some ideas on designs and methodology. I'm not so keen on the stools with bark legs, mainly hazel, and prefer a more finished  approach (that are also illustrated in the book). Alison sets the legs in the base at 90 degrees thus avoiding the problems in drilling at an angle into the base and then uses the flexibility in the green hazel to bend the legs as needed. I wanted to use thicker wood for the legs and set the legs at an angle as I wouldn't have so much flexibility in the legs of the stool. 

The photo below shows a small stool I made on a one day course at Dartington and this was also made of ash wood and shaped with a draw knife and roughing plane.

Tripod stool made of green wood ash, height ??

The legs pass through the top and are held in place with walnut wedges. The legs where shaped with a "rounding plane" so they fitted into the holes in the top. The holes were drilled at an angle using a pillar drill making this bit of the construction much easier. The legs were shaped so that they were thinner at the top and bottom and roughly matched each other. This was done using a draw knife and refined using a large spokeshave plane. I did use sandpaper to finish it off although on the course they discouraged this; I guess it comes down to taste as some like the look of plane and chisel marks. The height of the stool is good for young children (both Sam, 5 years and Esmee, 3 years both use it either as a stool or table). Anyway, my idea was to make a higher stool than this with cross bars to strengthen the leg support. I wanted to experiment with the top as I didn't have large enough material to make it out of one log. For this I intended to join 2 to 3 inch sections together to get a diameter of about 11 to 12 inches and another using 3 radial sections from a large log as shown below.

Five rectangular pieces of ash 2-3 inches wide and about 2 inches thick roughed-out from ash logs originally 20-24 inches long.

Three radial ash sections cut from a single log to a thickness of about 2 inches.

Three ash legs ready to be refined and shaped for the stool . Two of the legs are from one long 22 inch log that was cleaved down the centre and so produced legs with a similar curvature at the bottom. The other leg was from another similar length cleaved log but the shape was somewhat contrived with the axe and drawknife to match the others!!

Tools I used are: 1. Sharpened axe 2. Froe (to cleave but you can just use an axe). 3. Large Draw -Knife. 4. Large flat spokeshave (I find this useful for developing the shape but a smaller draw-knife would do or even a knife). 5. Roughing Plane (Veritas Scrub Plane). 6. Jointer Plane. 7. Rounding Plane. I already had all of these from previous work apart from the Rounding Plane (chairmaker's plane) that is used to make the round tenons on the legs and cross-spars. It is possible to use a pole lathe for this but as the wood isn't often straight it becomes more difficult. Of course it is possible to make straight legs rounded with a pole lathe and then it is a simple matter to cut the round tenons. I purchased a Rounding Plane made by Ray Lles (3/4 inch) (the Ashen Crafts ones are no longer available as new).

I made the top pieces by first cutting into cuboids with an axe and then selecting the best side for the top used a draw-knife and then roughing plane to remove wood to get a fairly flat surface. Finally a used the jointer plane to get a flat surface. I then selected an adjoining surface and did the same but this time using a set-square to get a 90 degrees corner. I then selected a possible thickness and with a marker-gauge marked for the next surface and so on until I had a good shape ready to dry. I wasn't sure how long it wood take to dry so I selected one piece and weighed it at 1 week intervals with it stored in an unheated workshop in the winter (outside temperatures around 10 C). Here are the results:

Week #	Weight/g	% reduction
0	1001
1	973	2.8
2	963	3.8

3                   954                                       4.7
4                   943                                       5.8
5                   943                                       5.8
6                   945                                       5.6
When dry enough, my plan was to finally match the surfaces (with more use of the jointer plane) and  then glue before shaping to a disc but more of that later.

The legs were made from 22 inch length logs split down the middle so the two pieces matched. Each section was cut with a draw-knife to form a rectangular cross section. Then the corners were removed to form an octagonal shape. Further shaping was done with the spokeshave to get a good curvature, uniform thickness and elliptical cross section (as shown in the picture above). Further shaping was done to achieve a leg that was slimmer at the top to accommodate the cylindrical tenon and also at the bottom for standing with ample wood in between for the cross-spar mortices.

This is the first leg that I shaped with 3/4 inch tenon  (2 inches long) cut at the top.

The shape was partly decided by following the grain in the wood so that the bottom of the leg curved out, was thinner at the top and bottom with the thicker part in the centre for the cross-bars. I refined the shape by first marking a circle 1 inch diameter on the top surface of the leg and then shaving wood to get to that diameter. I then used the rotary plane to produce  a taper and 2 inch long 3/4 inch cylinder for insertion through the stool seat. Two sides of the leg were straight (looking at 90 degrees to the stool) so they were reduced first. The other sides had a curvature at the bottom and the leg also tapered at the bottom. I did most of this reduction by eye with the large spoke shave. I finished off with a small spoke shave and 80/240  grit abrasive. The other two legs were done in the same way but using the first leg as a template to develop the right profile.

I then figured out a way to set the legs through the top. First I made a small jig out of some waste redwood. The purpose of this was to align the auger bit at 10 degrees from the vertical to allow a hole to be drilled through about 5 cm thickness seat.

Jig for assistance in drilling leg holes in the seat. I used a traditional auger bit (11/16 th inch diameter) that was about 18 cm long. The guide hole is 13 cm depth set at 10 degrees to the vertical. Note the pencil line used when aligning the block on the seat before drilling. This line also extends over the front and rear faces of the large block.

The small block on top was predrilled by hand and set into the top of the larger block to a depth of about 1 cm and glued into position. This was then used as a guide to drill though the larger block. A centre line was drawn around the large block to aid positioning of the jig.

The jig was tested using a waste piece of 15 mm thickness pine sawn to a diameter of 12 inches. A circle of diameter 12 inches was scribed on the top and a hexagon drawn with sides 6 inches in length.. From this an equilateral triangle was drawn as shown below.

The seat top showing the geometry defining the position of the legs.  This was only a trial with joined pine wood to test the jig and methodology 

The centre of each side of the triangle was marked to show the position of each leg. The jig was then clamped in position on the seat so that the drill contacted the marked position and also aligned in a direction facing an apex of the hexagon to the rear and front of the block (the line also going through centre underneath the block). A board was also clamped to prevent break-through when drilling by hand.

The trial seat with legs partly inserted. With the actual ash seat (about 5 cm thick), the top of the legs will go through the seat and be wedged with beech. Also the stool will have two ash strechers to strenghten it.

I will continue the construction when the seat timber is dry enough.

After about 2 months (see drying table shown above) I decided to continue with the top. I planed the boards with the jointing plane and then joined with glue and dowel pegs. I positioned the dowels using dowel pins to get good alignment. Once set, I planed the top and bottom of the seat to get level and flat with particular attention to the top of the seat. I then used a scribe to find the seat centre and work out the maximum diameter of the seat. I then marked the centre and scribed the seat top. The next job was to cut the seat cylinder using a traditional turning saw. I had tried an electrical jig saw but the seat thickness was too much for the blade and the turning saw was easy going. After that I used a block plane to trim the seat edge to the correct scribed diameter and the smoothing plane to remove any excess wood from the underside of the seat so that it was a uniform thickness.
I then marked out the top of the seat for the leg holes. I did this by drawing an equilateral triangle with the apices on the edge of the circle defining the seat diameter (see picture below). I found it difficult to mark the internal angles of 60 degrees so instead calculated the length of the triangle side (radius from the scribe x square root (3)) and marked the three points. Marking the triangle, the legs holes were marked half-way along each side. I then placed the drill jig with the bit protruding to the mark, clamped it in the correct position and drilled through to a back board. This worked well.

Stool top after gluing boards together and making leg holes. The top has to be shaped and prepared for making the leg stretchers.

I then marked bevels on the top and underside of the seat using the scribe (about 6 mm from edge) and with a marking gauge marked about 6 mm from the top and 1 cm on the edge side of the seat. I planed these with a block plane and tidied with a large spoke shave.

The next step was to prepare a stretcher between two of the legs. To do this I installed the legs to the correct positions and marked their orientation on the tops. I then judged a vertical position of the stretcher that looked right and measured the distance from the bottom of the seat and marked this on both legs. I put the stool on the bench with the seat at the bottom and legs up. Because the legs are slightly different I was careful to locate the centre for the holes for the stretcher on the inside of the legs and then mark the line around the leg to estimate the position of the hole on the outside.  This line needed to be horizontal (i.e. parallel to the floor) and hence at an angle to the surface of the leg. I also estimated this angle with an adjustable square. The next stage was to drill the holes for the stretcher in both legs. This proved straight forward by clamping the leg in a vice and adjusting the angle of the leg in the vice so that the drill would be central on the leg and also horizontal. To do this I used the ratchet on the brace and kept a close eye on the direction of the bit relative to the bench top. Hence it was easy to keep the drill bit horizontal (measure against the bench top) and central on the leg. Once the drill screw pierced the opposite surface, I reversed the leg and drilled from the other side to produce a clean hole.

I made the stretcher by using the draw-knife to make a round blank of about the correct length for the stool. I then shaped it so that the end fitted into the 3/4 inch Rounding Plane and the centre was large enough to accommodate the cross-stretcher. I then used the Rounding Plane to shape the ends of the stretcher to a depth of 5 cm (the diameter of the legs). Finally, I used a large Spokeshave to shape the stretcher and make it symmetrical ready for fixing as shown below.

The first stretcher installed ready to mark the second one. It is of course necessary to remove the legs to install the stretcher. The stretcher still needs to be finished and fitted with glue and wedges.

The cross stretcher was made in a similar way but this time the hole in the first stretcher was made smaller (9/16 th inch) because of the smaller diameter of the stretcher compared with the legs. I formed the shape of this on the pole lathe, reducing the last 1 1/2 inches to 9/16 th measured with Vernier calipers. I then used the 3/4 inch Rounding Plane for the other side of the stretcher and shaped the rest with the large Spokeshave. Obviously it is important to measure the distance between the leg and the first stretcher so that the uniform diameters at the end of the new stretcher extend far enough. In fact it would have been easier to make the whole stretcher with the lathe although the oval shape at the centre of the stretcher would have been lost. It only remained to drill the appropriate holes. This seemed a little daunting at first because of the non-regular shape of the legs and the angles involved. However it was straight forward, basically putting the stool together to the marks previously made, and then finding the centre of the first stretcher and using a steel ruler and spirit level to locate the centre on the opposite leg. I then used a plastic flexible ruler to mark the opposite side of the stretcher and leg and sliding bevel to get the angle on the leg. The holes were drilled with a brace using the work bench and sliding bevel to judge the angles and direction.

The stool legs with both stretchers installed and ready for finishing and installation with beech wedges.

Now (beginning of July) five months later and the parts were left in the workshop over the winter and spring. It only remained to put the stool together, install wedges in the joints, glue and finish.

Finished stool after treating with Shellac, Dutch Oil and Wax. 

The final construction was made more complicated because the Ash had dried further after shaping and making the joints. I made the mistake of making the joints prior to complete drying and so the tenons were smaller than ideal. Although I had left them two month to dry, that is clearly not enough or perhaps the higher temperatures in the Spring and Summer had some effect. With the foot-stool (see below), I made the tenons after the wood was dried longer and obtained a snug-fit.  Also the top had moved a little and had to be planed flat again. In retrospect, the top should have been joined after drying. In future when working with greenwood, I will do the main roughing-out and pole lathe work with the fresh wood and then allow it the dry slowly by sealing the end grain. After drying I will then do the joinery. Assessing the dryness of the wood is pretty crucial to the joinery.

 In all it was a challenge to take a log of Ash and use the intrinsic shape to make the curved legs and choose wood for the top. By splitting the log I was able to get some matching symmetry for two of the legs. The geometry to get the mortices correct is difficult but possible given some flexibility in the placement of the stretchers.

Square footstool.

I also decided to use some of the ash to make a square footstool of similar design to the solid seat stool described in the book by Jack Hill ("Country Chair Making"). For this I used the three larger timbers described above and joined them with dowels. First I got the surfaces square using the jointing plane and then used dowel pins to locate the holes for the dowels. The boards were then cut to approximately the chosen size (about 9 x 9 inches) and then glued / clamped. When the top was dry I marked out the top and planed the main surfaces flat, first with the roughing plane and then the smoothing plane. The final board was 1 3/8 inch thick and 9 x 9 inches and perfectly square.

I didn't follow the dimensions given in Hill's book for positioning the leg. I increased the angle from 20 degrees to 25 degrees and then calculated the position of the legs across the diagonals. This was 3.1 inches on the bottom side of the seat and 3.7 inches on the top (measured from the corners of the seat) with a stool height of 8 inches.

The footstool seat with one of the leg holes drilled. A new drill guide was made (shown on the right) using some waste beech so that it could be clamped to the top of the seat with the centre line along the diagonal.

Drilling a leg hole using a 1 inch auger and jig to get the correct angle.

I then made the four stool legs using silver birch branches. These were from some pruning from a nearby orchard and about 4 inches diameter with the bark on. I decided to shape these on the pole lathe. I cut them to about 11 inches in length and used the axe to remove the bark and side branches. I then marked the centres and turned about 2 cm on each end on the lathe and then used a draw-knife to make a cylinder between the two turned ends. I then turned the legs (I was aiming for a stool height of 8 inches) allowing 2 inches for the tenons (I turned to 1 1/8 inches to allow for shrinkage) and shaped so the maximum diameter of 1 1/2 inches was 4 1/2 inches from the top of the stool. I turned the lower part of the leg to mirror the upper and reducing to 1 1/8 inches at the foot of the stool and allowed about 1 inch spare to adjust the height as needed.

Silver Birch stool legs immediately after turning. The top tenons are shown at the bottom. The ends of the legs were coated with beeswax and put in a paper bag to dry together with some shavings from the lathe. The plan is to refine the legs when they are dry and make the 1 inch tenons accurately with a rounding plane. The legs can still be mounted on the lathe for adjustments and sanding as needed.

Now about five months later having left the wood in the workshop over the winter and spring. I prepared the top of the stool using a scraper and sand paper down to 350 grit. Because of the varied grain pattern, the scraper worked better than a plane. I put the legs back on the lathe to do the final preparation of sanding and marked two concentric rings with the skew chisel. The legs had not cracked or distorted but the top of the stool had a slight concave that I rectified by planing.  The next step was to use the 1 inch rounding plane to form the final shape of the tenons. I had to use a spoke-shave to get the slope on the legs to fit the plane as without doing this the plane caused some tearing of the wood. I did one leg first and from this did more work on the pole lathe to shape the upper part of the other legs for use with the rounding plane. Each leg was then fitted into the mortices by making fine adjustments to the tenons using sandpaper to get a close fit. 

The stool was then put together and the lines for the wedges to fit the legs were marked so that they went across the grain of the top to avoid splitting the top when tightened. I prepared wedges from some waste beech, sawed the wedge-cut in the tenons, glued the legs in position and inserted the wedges. It was then only a matter of sawing off the waste from the top of the legs, chiselling them to fit flush with the top and doing the final preparations before treating with Shellac and Dutch oil.

Foot stool; Ash top and Silver Birch legs.