Mid Staffs Woodturning Association Newsletter Issue 23 - December 2007
Wood 'n' things
Editor: Paul Bellamy
Mark Hancock - 'Save the best for last'
The club is always looking for demonstrators, especially those who have not been to the club before or at least not for some time. I don't believe Mark Hancock has visited us before but he certainly lived up to Peter's introduction as 'the best for last', with an evening of fascinating turning coupled with a stream of tips and comments on woodturning.
Mark has gained considerable reputation for his work, as shown by his demonstrations at many of the woodturning shows and a most impressive web site. Tonight was our opportunity to see him 'up close'. He started by saying that his work is mainly artistic, for display and sale in galleries all over the world. The finish required is of the highest standard and not something that could be completed in an evening, so his demonstration would be more about techniques and tips.
Mark works predominantly with wet or green wood for several reasons; it is cheap and plentiful, it cuts easily and it presents an interesting challenge using the drying properties to affect the end result. His preferred timber is oak as many of his pieces are ebonised but tonight he was going to turn a piece of sycamore and make a three legged bowl, the cunning part being to include the legs in the turning.
While setting up the work, Mark explained that he does not like terms spindle or face turning as these can be misleading. More accurate is parallel or cross grain, referring to the direction of the wood fibres.
Mark uses green, or 'wet' wood so his first trick is to centre the work piece on the pith. As the wood dries and shrinks this should be similar around the annular rings and not result in serious distortion. To achieve this, Mark had already rough turned a large piece of sycamore to the size required, with it centred on the pith. The drive centre was hammered into the wood, while it was on the bed of the lathe. As Mark said, "never hammer the wood onto the headstock or you will damage the bearings".
The piece was
roughed out using a spindle roughing gouge. These must never be used on cross
grain as they are forged steel and could fracture, with disastrous consequences.
Mark quickly got down to the basic shape, a large diameter main body with a
spigot on the tailstock end for mounting in the chuck. This was tidied up using
a swept back gouge but the rest of the piece was left to be finished after it
was reversed onto the chuck as it might not run true. Before screwing the chuck
onto the headstock spindle Mark inserted a dead centre to make the spindle solid.
This is especially good practise when turning heavy, out of balance pieces.
The end of the piece was tidied up to give a flat face, then Mark worked on refining the outer profile of the bowl. It's difficult to get a good finish on green wood as the fibres are still pliable A shear cut can be used to perfect the form/shape of the piece with the aim of achieving a flowing curve but this needs good tool control. Mark's solution is to use a cabinet scraper. This is used direct from the grinder which leaves a burr on one side. However, the wood will take this off very quickly so it is not worth burnishing but use the same side up each grind. You need to be careful with woods such as ash with different spring / winter growth or you will get ridges on the surface. The cabinet scraper can also be used on dry wood for both form and finish.
To shape the inside
of the bowl, Mark used a spoon auger to bore a hole to the required depth, ready
to use a specialist hollowing tool.. These spoon augers aren't generally available,
Mark got his from
Once the hole was bored, Mark used a Munro Standard Hollowing Tool to remove the rest of the waste. This has an edge protector to govern the depth of cut and Mark recommended this should be set to a quite small gap. If you set it too wide, it will not prevent clogging, in fact it will make it worse as it will not be able to break the shavings as they are cut. These tools also have an articulated head which allows the cutter to get into undercuts, so they are very versatile. Mark also likes the Hamlet 'Little Brother' tool. However, there is a plethora of hollowing tools and he suggested trying them before you buy one as none of them are cheap.
These hollowing tools are unsupported i.e. they don't have a bevel to rub, so it is difficult to avoid ribbing. This can be hidden by painting the surface black. It is also important to hollow in stages to stop movement during turning. Cut in an inch at a time until you are close to the finished diameter, then cut the next stage. This leaves plenty of wood to support the piece as you work and prevents it going out of round. To finish the interior Mark used the cabinet scraper again but stressed it MUST be kept in trailing mode. The cabinet scraper is also effective at removing the pimple many of us get on the bottom of a bowl
With the inside
of the bowl finished, it was reversed onto the chuck and the tailstock brought
up to the base for support. In addition, Mark secured the work to the chuck
with masking tape. Now he could work on the section that would become the legs.
Using a spindle gouge, he turned the base section, leaving a wooden cylinder.
This is difficult as the tailstock is in the way but Mark leaves this in place
as long as possible for the extra support but eventually he parted off the waste
cone of wood.
Now he could
get in to the bottom of the bowl but he needed this part to match the outer
curve and the 'leg' piece was in the way. To 'see' the curve, he used a profile
gauge, normally used for tiling, pushed onto the end of the work and the curve
was easily checked. And to get a crisp corner, where the base met the inside
of the legs, he used a pointed gouge, taking care to keep to the curve.
Once Mark was happy with the profile, the legs could be marked out. He reminded us that odd numbers of things are generally more pleasing to the eye, so his bowl would have three legs, not two or four! There are other benefits of three legs but that's another discussion.
The waste was cut away using a Japanese Trim Saw available from Axminster Power Tools. It cuts on the pull and so makes it easy to support the cut as you make it. After that the surface was smoothed with a microplane. "Don't worry if you go too far and mark the base, just make it a feature", and Mark then cut some radial grooves in the base.
That was the woodturning completed but the piece wasn't finished. Mark wanted to add texture to the outside surface. For this, he uses a propane gas blowtorch. This is hotter than butane, but if you can get a hotter flame, acetylene for example, that would be even better! The wood was put on a heatproof mat, and should be clear of any dust and shavings. Mark also had a welder's glove to allow him to move the piece around while it was still hot. It didn't take long to char the whole surface and Mark explained that this gives a textured surface with Oak by burning out the softer areas more than the harder areas. You could also ebonise wood chemically. Woods like oak, with high tannin content, will react to a pickling solution of iron in vinegar. This is easy to make by putting steel wool in a jar of vinegar and leaving it for several days to react but don't screw on the lid as it gives off a gas and would explode from the pressure.
After the bowl had cooled, Mark used a pine brush to remove the carbon created by the blowtorch, and to polish and burnish the surface, highlighting the grain patterns.
As well as ebonising
Mark uses acrylic paints and gilding to enhance his pieces. He recommended the
company Tiranti (http://www.tiranti.co.uk/) for gold leaf supplies and uses
transfer leaf as this is much easier to apply than loose leaf. The advantage
of good quality gold leaf is that it will not tarnish, leaving a glistening
finish that will be good for years. The leaves are cut into strips to make it
easier to apply to the inside of bowls and these are tamped into place using
a cotton ball wrapped in a silk scarf. After that, a soft brush can be used
to remove any loose gold and push it into any blank spots.
Whether or not you approve of embellishments to the wood, you cannot deny Mark's work is most impressive. And we all got a lot of tips and tricks from his demonstration to the extent that I foresee numerous purchases of cabinet scrapers, steel wool, vinegar, profile gauges, blow torches etc., over the Xmas period. Thanks, Mark, for an excellent evening.