Bowl Gouges - The Story of the Superflute


A personal view by Roy Child

Ask ten turners what a bowl gouge should be like - style of grind, shape of handle - whatever and you will get twelve different answers. This confuses beginners and makes a fool out of any egotist wanting to lay down woodturning dogma. To me this is part of the fun and is what is makes my personal view as valid as anyone elses.

Ever since I was in my teens I was interested in the design of gouges and the steel from which they are wrought. I used to come back from school and rough out a few green elm bowls maybe twenty, to earn my supper and pocket money. It was hard work and differences in the shapes and the quality of the steel used in the different bowl gouges I used were very noticable.
old style forged gouge

In those days (1966) gouges were all forged by hand and came in all shapes and sizes. They were all carbon steel as HSS gouges were not yet available. They had to be reground often and I used up quite a few. This is a typical section of a carbon steel forged gouge. I began to experiment with a view to making the gouge last longer between sharpenings and also cut better. I epoxy glued some high speed steel toolbits into steel shafts and ground them to various flute shapes by hand with a cutting disc.

superflute gouge section

Some years later I returned from a brief career with the Marconi Company and did some serious experimentation with gouge shapes. This is the flute section I came up with. It worked really well for me. It has a large radius at the sides blending into a small radius at the bottom of the flute.

 

I had a good friend with an engineering business and he was able to mill out some gouges to my design from round section material. The idea of milling gouges out of the round instead of forging was new at the time - at least it was to me. I used some Government surplus carbon steel which kept a wonderful edge. I have no idea what the analysis of the steel was to this day - it was sold to me as "tool steel". The gouges were taken to a heat treatment specialist in Harlow, Essex to be induction hardened. It was fascinating to see the process. The gouges were suspended in the middle of a coil protruding from one end of a huge box the size of bus. Inside the box were enormous glass valves generating the radio frequency power which, within a couple of seconds made the flute end of the gouge glow bright cherry red. The clamp holding the gouge was precisely controlled by a timer so that the gouge was released the moment it reached the correct temperature and it was allowed to plunge vertically into a tank of quenching liquid - soluble oil and water I think. Every gouge was hardened just right and then tempered. The next job was to take them home and clean them up and sharpen them ready for sale - we sold hundreds by mail order ("we" being Peter Child & Son). I still have a few left. Once the rust is cleaned off they keep a good edge and perform almost as well as high speed steel.

We soon progressed and made a few in high speed steel but at this point Henry Taylor Tools came into the picture. They asked to make the design in Sheffield from M2 high speed steel and they called it the "Superflute". Only Barry Martin could think of that name - something to do with keeping B sharp! The name of course has stuck and these gouges have been made in thousands ever since.

bowl gouge Shortly after the Superflute was launched quite a few gouges with a flute section like this came onto the market. It has two straight side walls with a single radius at the bottom. It is this section because anyone can buy off-the-shelf milling cutters that cut this shape. Suddenly all the manufacturers realized that this was the most economical way to make a gouge. They quickly abandoned the old labour intensive method of hand forging from square stock. Soon the old forged gouges were forgotten and the shape on the left became the "traditional" shape!

The traditional forged spindle gouges were forgotten as well, as all the makers adopted the milling process to make gouges cheaply. Now everyone makes gouges by milling them out of round section material. I am not so sure that it was such a good idea to make spindle gouges out of round but we are all used to them. The recent resurgence of the forged HSS spindle gouge shows how much better the flatter shape is. Both Henry Taylor and Robert Sorby now make some really nice forged HSS spindle gouges. But why does Robert Sorby call them the "Continental" shape?

 

superflute section So what's good about the superflute shape shown here on the left?
The idea is that the large radius at the side of the flute cuts like a large gouge (say a 1/2" gouge) but if you twist it a little and cut with the small radius at the the bottom of the flute you get the same cut as you would with a small gouge (say a 1/4" gouge). As the large radius blends gradually into the small radius you can, at will, vary the radius of that bit of the edge which is in contact with the wood. You have more control over the cutting than you would have with a traditional gouge and you can achieve a higher standard of finish. The small radius at the bottom of the flute stabilises a full cut too. This makes the gouge easier to control when hollowing a bowl and easier to control at the difficult entry point at the edge of the bowl where the bevel is initially rubbing on fresh air.

 

The catch is that this only works if your gouge is ground straight across like (A). This does not cause me a problem as I like my bowl gouges ground this way and this is why the original "classic" HS1 superflute is supplied ground dead straight across. I know that woodturners love to experiment and now, years after the superflute was first made, most turners are asking for gouges with the wings ground slightly back like (B). This is fine but it partly negates the advantage of the flute shape. However the superflute is fortunately very adaptable. The variety of styles of grind people use is remarkable. Remember- if it works for you then it is correct!

What style of grind do I favour? Well I like to have two gouges - one is ground straight across and the other is ground well back with a short bevel at the tip (almost like E but with a steeper bevel to help me take a finish cut inside deep bowls). There is a picture of my own gouges on the next page. If you get a chance, watch John Jordan's video on "bowl turning" to see an excellent explanation of how the two types of grind are used in practice.

 

Styles of grind

So what about the other shapes "C" and "D"? Well "C" is an asymmetric shape which is useful if you are restricted to using the handle of the gouge horizontal - as on a non pivot head lathe where you cannot get the handle down and you want to hollow into a bowl. The left hand wing is ground away a bit to let the other wing do the cutting. The gouge is used on its side with the ground-away wing at the top.
"D" is useful on deep bowls where it is difficult to get round the corner inside the bowl where the side walls join the base. The short bevel enables you to rub the bevel and control the gouge.

Specifications and pricesNext page - grinding

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Copyright 1999 Roy Child

If you think anything I have written here is wrong or you want me to add something to correct the facts please contact me.