The Bevel

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The Bevel:
Andy Coates looks at what is it, why is it important and how do we use it to aid our turning practice?

Andy Coates looks at what is it, why is it important and how do we use it to aid our turning practice?

Those who are new to woodturning are inundated with advice and information from a wide range of sources. Most will be at odds with other information, which is difficult for the fresh novice to understand, and a lot of the information is littered with buzzwords and phrases, most of which are never fully explained. There are two such stock phrases that come up time and again: ‘the bevel must rub’, and ‘technique doesn’t matter; it’s the results that count’. Well, let us discard number two right now. The truth is that you will never safely achieve what you hope to if you do not have a firm foundation in technique. The first phrase, however, is worthy of further comment as it is important but rarely expanded upon.
First we need to understand what the bevel is: the bevel is the angled area of tool after the cutting edge, on the underside of the tool. It is in fact the bevel that creates the cutting edge by creating a ‘sharp edge’ between itself and the interior flute of the tool. The line formed where the bevel ends and the shaft is unaltered is referred to as the ‘heel’.
Think of a pencil… you create a point on a pencil by carving a bevel on the wood around the lead. By altering the degree of the bevel you can create a sharp or a blunt pencil point. The longevity of that point is a compromise between sharpness and angle of the bevel. So it is with woodturning tools. 

How is the bevel formed?
When you buy your woodturning tools they will come pre-ground, often ‘ready for use’, so for the novice it is not necessarily apparent how the bevel was formed, or for that matter, why it was.

Milled round bar bowl gouge with tip removed to show cross section

On a bowl gouge, the shaft under the flute is ground anywhere between 40–60°

As the ground area, the bevel, increases, it travels towards the flute

We can see clearly here how the bevel produces the cutting edge. The angle of the bevel can affect both the sharpness of the edge and its resistance to wear. A sharper edge will dull quicker, but cut cleaner. In order that the cut is consistent, and repeatable, the bevel needs to be continuous and of a single facet, and the length of the bevel also has a part to play; a shorter bevel may be easier to control. The size and shape of the flute also have a role to play. A larger radius flute, for instance, will invariably produce a poorer cut, and a flute with a tight base radius will form a more pointed nose shape, which may be difficult to control. However, in every variant the role of the bevel remains consistent: supporting and directing the cutting edge.

The bevel is formed
Having looked at how and why the bevel is formed, we now need to look at how it can impact our turning practice. Essentially the role of the bevel is to support the cutting edge and direct it in the cut; this is how
we achieve the shape we want rather than the shape the tool dictates.

Rubbing the bevel
‘Rubbing’ can be a misleading term for a novice. It may seem to indicate some backward and forward motion, as for rubbing wax onto wood, when in fact  it simply means that the bevel should have contact on the wood, supporting the cutting edge through the cut, and through bodily direction from the user  cause the tool to impose shape to the object being turned. This may be full or partial bevel contact; the important thing is that it does contact, i.e. ‘rub’, the wood. If only  the cutting edge is in contact, the cut will be uncontrollable and potentially dangerous. Let us look at a simple tool to see how this works.

When it meets the flute, the angle between the bevel and the flute creates the cutting edge

This style of grind is called a ‘traditional’ grind. There a number of variant grinds for bowl gouges

The bevel and shaping the outside of a bowl with a bowl gouge
The bevel is the key to producing shapes and it is only by developing skills in controlling it that we can hope to realise the shapes we conceive in our mind. Think of the bevel as a SATNAV for the cutting edge; without it the cutting edge is unlikely to reach its destination by the best route.

When ‘facing off’ a blank in the chuck, the area of bevel under the flute can be used to help produce a flat surface. The cut is a push cut and the flute is facing away from you pointing to about 2 on an imaginary clock face in front of you. The cut will be flat and true

When beginning to shape a bowl the tool is anchored with the hand on the toolrest and pushed into the wood at an angle. As soon as the cut begins, the bevel comes in to play to support the cutting edge. This provides stability and control

If all you do is push the tool forward you will end up with a flat-sided cone, the angle of which will precisely match the angle on the tool as it takes the path of best support and least resistance

In order to impose a shape on the wood you need to apply pressure on the bevel. If you gently pull the handle towards you as you feed the tool forward, the bevel will drive the cutting edge in a gentle convex curve. If you push the handle away from you, the curve will be concave

The bevel and shaping the interior of a bowl with a bowl gouge
The bevel on any turning tool is not a single point, it is a plane that progresses around, or across, the shaft of the tool, sometimes varying in size, as on a bowl or spindle gouge; learning to understand what this means and how to manipulate it should be high on the skill acquisition list.

The underside of this bowl gouge is marked with three lines. Number one directly under the flute, number three near the top of the bevel close to the cutting edge and number two between these two

An entry cut would see the cutting edge of the tool enter between one and two. The back of the tool shaft is anchored with the thumb and the tool is pushed forward into the wood. As the cut progresses, the tool handle is pulled back to your body

As the cut progresses the handle is gently twisted towards you so that the tool cuts at position three. This moves a shorter area of bevel onto the wood, allowing more control around the curve. You may still struggle at this point

A common solution to the problem is to grind the heel off the tool, creating a ‘secondary’ bevel. The aim here is to produce a shorter bevel which will travel around a tight curve much easier

This new bevel, blackened here for clarity, is not used in turning. It is simply a relief grind to provide a smaller working bevel to allow tighter curves to be traversed

The spindle roughing gouge (SRG)
The SRG is a tool with a large flute, a bevel at approximately 45°, and unusually for a woodturning tool, a tang with which the tool is mounted in a handle. This tool is only ever for use on ‘spindle stock’ – where the axif od the grain is parallelto the bed bars – chair legs  and so on, and never for faceplate mounted work – where the grain rubs at 90° to the lathe bed – bowls and dishes and so on. Its primary function is to turn square stock down to a cylinder in preparation for applying shapes and features with a spindle gouge or skew chisel.

The bevel is formed at about 45° to the shaft, and is ground in what is called a ‘straight across’ style

The flute of the SRG is deep and open. This facilitates the rapid removal of shavings from the roughing down operation

If you were to present the SRG at 90° to the workpiece you can see that only the sharp edge is touching the wood. This would be uncontrollable in the cut

Presented somewhere between 10 and 45° to the workpiece, the cut becomes controllable as the bevel supports the cutting edge

Working from the left off the end of the workpiece (supported by the toolrest) take gentle cuts. This will produce a clean cut

Same tool, different bevel
The same tool may be ground with different bevel styles for different tasks. Here, a pair of identical 10mm spindle gouges have a ‘long’ and a ‘conventional’ grind. The longer grind works well for detail work in tight corners, while the conventional ground tool is a good all-rounder for spindle shapes. The longer grind can be achieved by hand but is easier to produce using a dedicated jig. It is advantageous to have one of each on your tool rack. Bowl gouges can ground in a similar manner too.

The bevel on spindle work
The bevel is perhaps at its trickiest to control on spindle work and accordingly can take some time and effort to get the better of, but one thing is certain, it will pay dividends far in excess of the investment in time and effort.

Just as on bowls, the bevel must be controlled in order to dictate shape. Here the tool was simply pushed in to the wood. The resulting shape is simply a facsimile of the bevel angle. The tool has made the cut

In order to use the bevel to form a cove, the tool is presented at an angle, pivoting at the centre, and the tool handle is pushed to the right and fed slowly out as the cut deepens. The bevel describes an arc that the cutting edge follows

The cut should end at the midpoint of the cove to prevent cutting ‘uphill’, or against the grain

The tool is moved over to the opposite side, and using an opposite angle the cut is taken in the same fashion. As the cut progresses the tool is twisted in the opposite direction to end with the flute roughly pointing directly
upwards, though at a slight cant

Here we ‘feather’, or blend, the two cuts together to create a flowing shape ending at the middle, and lowest point of the cove

To produce a bead on a spindle the bevel of the spindle gouge is equally important. The bevel ensures the cutting edge describes the shape if presented correctly

Limitations
In writing this article I am aware that I have cleverly avoided one of the primary areas of discussion in  respect of bevels on woodturning tools; that being bevel angles. This was a conscious decision. Most woodturning tools come pre-ground with a perfectly serviceable bevel angle and if the novice woodturner maintains that angle they are unlikely to hit any great problems in respect of that angle. It is highly likely that as your skill level and understanding increase, you will begin to alter pre-set angles to ‘tune’ your tools to your own style, stance, and presentation. You may already have noted, for instance, particular grinds that appear to be the same but have different names; these are largely the result of slight alterations made by one turner in preference to the angle and style of another.  Each works, but in a slightly different manner. In time you may develop your own angle/style combinations that differ from the norm.
In the meantime, you can trust the tool manufacturers to have ground the tool in one of a number of suitable styles and angles. Your main concern will be maintaining those angles when you  re-grind the tools… and that is a whole other article.

Remarks
This can only be a cursory look at the bevel, and I have not covered the skew, scrapers, or parting type tools. The bevel of the skew and the parting tools can be utilised in much the same manner as described for the gouges already mentioned, while scrapers do not utilise the bevel at all; it is simply the manner in which the ‘wire edge’ that does the cutting is produced, and thereafter plays no part in the use of the tool.
The bevel is paramount to achieving the shapes we intend in a safe and controlled fashion, and mastering it will benefit your technique tremendously and allow you to dictate shape on the wood rather than have the tool dictate it for you, which is rarely an appealing outcome. There are other factors which influence the bevel, such as body position, style of tool hold, wood type and density, wet or dry wood, flute shape, steel/tool quality and of course, ability, but with a basic understanding of the principles most of these factors can be anticipated and overcome.

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