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- Herausgeber: Crowood
- Kategorie: Lebensstil
- Sprache: Englisch
This is a comprehensive guide to woodturning which will be of value and help to both new and experienced woodturners.Hugh 0'Neill covers the tools and woods used in turning, the principles of design, the lathe, wood finishing, and the techniques of turning spindles, bowls and decorative works. The book also covers the workshop and a selection of projects including bowls and table legs.
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Veröffentlichungsjahr: 2013
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Woodturning
A MANUAL OF TECHNIQUES
Hugh O’Neill
Copyright
First published in 1989 by The Crowood Press Ltd Ramsbury, Marlborough Wiltshire SN8 2HR
www.crowood.com
This e-book first published in 2013
Paperback edition 1992
This Impression 2010
© Hugh O’Neill 1989
All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, without permission in writing from the publishers.
British Library Cataloguing-in-Publication Data
A catalogue record for this book is available from the British Library.
ISBN 978 1 84797 671 0
Dedication To the Committee and members of the Association of Woodturners of Great Britain for their help, guidance and friendship.
Line-drawings by Terry Hunns Photographs by Kevin O’Neill, Craft Supplies Ltd, and the author
Contents
Introduction
If you are reading this book in bed, in those few quiet moments before sleep permeates the consciousness, then don’t bother. Put the book down, go to sleep and dream of woodturning. You may learn more about the subject that way!
This book is not intended for ‘just dipping into’, nor is it for sitting down to and reading from cover to cover, I first had the idea of writing it some years ago when I did a review of some of the two-day woodtuming courses that are offered in many parts of the country. Leaving apart the fact that some were good and a few were very poor, they all left me with one clear message. You are shown, and indeed try, many things over the two days. You return to your own workshop and try to put into practice some of the things you have learned. Initially you focus upon your own favourite form – it may be bowls, spindles or whatever. A week later you can really only remember about ten per cent of what you were taught. You have a vague idea about another twenty per cent of the basics, but can recall virtually nothing of the finer points that your instructor had passed on to you.
I thought then that what would be useful would be a book which first covers in detail the same ground as the courses, and then goes on into some of the more difficult things that you later have to work out for yourself – like turning natural edge work, equipping a workshop, thinking about design and so on. This book is intended as an adjunct to a short course, not a replacement for one. Equally I knew that beyond describing skills and recording the wrinkles, a little theory might show why we do things the way that we do. This would provide the sort of foundation upon which we all build technique and develop our own unique style. This is what I aim to do in this book.
The book has also been given a ‘what happens next?’ flavour. Once you have the basic course under your belt and can utilise most of the skills demonstrated, you will want to start to move forward. You are not an expert, nor are you quite ready for the expert advice presented on some of the major seminars.
You want to try some of the more difficult techniques like wet turning, natural edge pieces, and maybe hollow spheres. You wish to extend your knowledge of woods and how to use the materials that you can find without always having to go to the timber yard. So I have tried to fill the gap that occurs in the two or three years after the course.
Obviously the book will contain a lot of insights into what I do and the mistakes that I make. Hopefully, however, this is not a book about ‘my way’. Where appropriate, and where known, I have referred to what other (and far more expert) turners do. Although some turners will try to tell you that ‘this is the right way!’ you only have to look at the variety of approaches followed and the ideas expounded by different master turners to know that there is no one way. It is what best suits you that really matters.
Over the years I have set myself up for criticism. It was in the Woodworker magazine that I first said that you can not learn woodturning from a book. I also said that photographs are usually a poor way of illustrating the skills of turning. So why are there photographs here? I have used sketches where they are needed and only used photographs where they do clearly illustrate a point. I still maintain that you can not learn turning from a book. We learn skills by doing and then letting the lessons permeate our subconscious.
Throughout the book there are exercises – these are meant to be tried as and when you read about them – not tomorrow or at the week-end when you are in the shed. You learn turning by getting ‘hands-on’ experience. The structure of the earlier parts of the book are based upon the idea of ‘read a piece, then make a piece’.
Some may be surprised that the book does not start by looking at lathes. In fact I have put the chapter on choosing a lathe towards the end. I believe that the biggest mistake that you can make is to buy a lathe too soon. Such a purchase should not be considered until after you have done some turning.
You cannot know what to look for until you have tried various machines, and you can easily end up making an expensive mistake. Even more to the point, you cannot choose a suitable lathe until you know what sort of turning you are going to focus upon – and this will only crystallise after you have done some turning and tried various styles.
I started with a lathe attachment for a Black and Decker drill. It was given to me by a friend whose fence I had repaired (and I owe the lady in question a life-long debt of gratitude). As a lathe it was a good start because it was so bad! It very quickly showed me some of the things to avoid in my next lathe. It also became a challenge, presenting a never ending range of problems to be overcome. My second lathe, an Elu DB 180 was also not a deliberate choice made after careful consideration, but an unexpected bargain that I was offered. Despite its several faults and inadequacies, it soon paid for itself. It also showed me precisely what I wanted in my third lathe.
Now I use a massive old Wadkin RS which is marvellous, and it is supported by a Multico which was cheap and cheerful. Neither are perfect – perfection in lathes does not exist – everything is a compromise. Neither are they necessarily likely to suit you, your needs will probably be very different to mine, but they do suit me – at the moment! However, I already have plans for my next two!
So to get started beg, borrow, hire, or rent time on someone else’s lathe. Go on a short course to a centre where you can try several lathes. Try the exercises in this book on a friend’s lathe. Then sit back and think. Only then should you consider purchasing your own.
I have written this book with another theme in mind. I was a beginner when I first put a ‘carpentry’ chisel to wood forty-nine years ago at school. I was a beginner when I went on the two-day courses, I am a beginner now and I will be a beginner the next time I go into my workshop and on every occasion after that. I know that I will always have things to learn, ideas to try out, mistakes to make, and new skills to develop. Sometimes I put to one side all the short-cuts that I have been shown, and start again from basic principles; this way I unlearn some of the bad habits which come with familiarity. So this book is for beginners – novice beginners, five years experienced beginners; even, hopefully, a few hoary old pro-beginners.
Perhaps my biggest learning experience in recent times has been the writing of this book. It has made me think through what I do, and analyse all the whys and wherefores of every bit of technique that I use. Some aspects did not stand up to the examination – clearly they were bad habits that had crept in and become firmly established. So to every reader I have to say, ‘Thank you! Thank you for making me a better turner.’
Finally, you may find there is some repetition in the contents. This is quite deliberate. We learn by rote, by practice, by analysis, by use, and by frequent recall. Nobody takes in everything the first time, so some key points of practice have been reiterated as a lead into considering some variations or related topic. There are also some things that we cannot remind ourselves of often enough. I know one turner of many years experience who, as he switches on the lathe for the first time each day, says, ‘Remember to keep the bevel rubbing.’
So let’s begin with a little ‘hands-on’.
1 Getting Started
It is workshop time!
Yon will need a plane, a chisel, a mallet, a sharpening stone, a vice (or means of holding the wood), and some scraps of timber. A bit of old deal will do.
Start with the plane. Hopefully the cutting edge is a little dull from when the kid tried to smooth a bump off the concrete path. Set the blade to give a coarsish cut – the blade clearly showing below the shoe of the plane. Now take a cut along the grain of the piece of deal. With considerable effort you will produce a coarse, broken ‘shaving’. The ‘finished’ surface of the wood is torn, and fibres have split away. With the plane in this condition we won’t even try to make a pass across the end grain – it probably would not cut at all however hard you push.
Now give the iron a few rubs on the sharpening stone and then fix it back into the plane. This time set it fine – only the merest edge of the blade will be showing, In fact if it is set fine enough you will probably detect the blade edge more by feel than by sight. This time, as you make a pass along the wood, you will find that with very little effort you can produce a long, fine shaving and the surface of the wood will be smooth and polished.
Try also a pass across the end grain. You will not produce a shaving but rather fine ‘sawdust’. Unless the blade was super-sharp the cut face may be flat, but it is likely to be ‘pitted’ where each fibre of the grain has been torn away from the adjacent one. The corner may have broken away where the plane exited from the pass.
Cutting along and across grain. (a) Cutting along the grain, the chisel parts the long fibres from their neighbour. A flat bevel rubs on the cut timber and prevents the edge digging in deep. The result is a clean cut and fine shavings. (b) Working across the grain, the chisel slices off the ends of the grain which break away as ‘sawdust’.
Yes, of course, you can remember all that from your early days of woodworking – probably from school. Nevertheless try it again now and as you do so tell yourself:
‘One: blunt tools tear wood, and with the power and speed of a lathe the tearing is likely to be even greater than this.
Two: taking deep cuts also tears wood and requires much more effort.
Three: fine cuts are easy.
Four: fine cuts with sharp tools leave smooth finishes.
Five: a really fine planing cut with a sharp tool leaves a finish more “polished” than will the finest grade of sandpaper.’
And as you go off the edge on the end grain and the corner breaks away:
‘And six. Wood that is unsupported and is cut across the grain, parts along the fibres and tears away.’
There is another little test that is worth doing to further illustrate this point. Take a clean paintbrush and stroke the ends of the bristles across the edge of a table. To start with, and through the middle of the stroke, the bristles will be bent back but will stay together as a mass. However as you get to the edge the remaining bristles will lodge on the table edge and will part right away from the mass. This is exactly what happens when you cut across end grain of a piece of wood. In fact it is worse. The fibres of the wood cannot bend as do the brush bristles; so they tear apart, break off, and leave the surface pitted.
In a nutshell what you have demonstrated for yourself is a substantial part of the theory of tool choice and tool control in woodturning.
Cutting end grain – even with a fairly sharp chisel.
Of course there is a difference between a plane (and a carpentry chisel), and the lathe and its tools. Indeed there are two fundamental differences. First, with the plane there is the body and shoe plate to prevent the blade digging in or taking too deep a cut. The second difference is that you move the plane and keep the wood fixed. In essence, with the lathe it is the other way around. You move the wood and keep the tool (and the lathe) still – or at least you try to!
So let’s see how we can emulate the plane when we are using tools without the assistance of the depth-controlling shoe plates. It is back to the workbench time!
This time use an ordinary chisel; you might as well start with it nice and sharp – we already know that ‘blunt tools tear wood’. Try two things. First rest the bevel of the chisel on the surface of the piece of wood. Now, holding the chisel handle firmly with one hand and with the finger and thumb of the other gripping and steadying the blade, push the tool along the surface of the wood. Keep the bevel flat and rubbing on the surface of the wood and you will not take off a shaving but you will polish or ‘burnish’ the surface.
Take another pass. This time raise the handle of the chisel the merest fraction until the edge starts to cut into the wood. Now you do take off a fine shaving but, providing you keep the bevel rubbing behind the cutting edge, you will still burnish the wood. The chisel glides easily along, and passes through the wood quickly. If it doesn’t then go and sharpen the tool!
The third pass is going to take much more effort. Increase the angle of the blade, push harder, and the chisel digs in, taking off a thick shaving and leaving a slightly rougher surface. The chisel pass was much slower. Too steep an angle or loss of control of the blade and you dig in and the pass stops.
Last exercise. Cut a small mortise into the wood – a rectangular hole. Keep the faces vertical. You will probably have to use a mallet. Note how the cut across the end grain leaves a clean polished face (if the chisel is sharp enough) whereas the cut made along the grain tends to break away long splinters. The chisel did not pass through the wood, but proceeded in a series of short jerks with each mallet blow.
So, what are the lessons here?
1 The chisel bevel should be kept in contact with the wood as it:
(a) Controls the depth of cut (just like the shoe of the plane).
(b) Leaves a clean cut and burnishes the surface of the wood.
2 Once the edge of the blade is unsupported by the bevel rubbing on the wood behind the cut, the edge digs in.
3 When cutting along the grain with a tool that is anything less than razor-sharp, then you tend to lift up and tear through the fibres rather than slice them.
4 In fine cuts the chisel moves much more quickly, whereas with coarser cuts chisel speed is lower and the effort required is greater.
Probably the only principle of turning that the exercises have not now demonstrated is that the corners of the edges of tools can catch on a rotating work piece and dig in.
If you always have these principles in mind, you will usually know what sort of tool to use to do different turning jobs. You can work out where to set the lathe tool rest, and even the speed at which the lathe should be run.
So let’s take our first look at the lathe. A few moments ago we saw that the difference between the plane and the lathe was that with the former the tool moved and the wood remained still, whereas with the lathe it is the opposite way round. It is both as simple as that, and yet as complicated.
The lathe takes the effort away – it moves the wood under power and (usually) in a predictable, ‘fixed’, rotary direction. As the lathe does the work, we can spend all our time, concentration and effort on controlling the tool. However you can stop a plane or a chisel in mid-cut – it is not so easy to stop a modern, high-power lathe in mid-rotation. Because it is moving the wood fairly fast, everything happens much faster. The merest slip with a tool edge can cause a disaster in milliseconds. There are stages in turning where the edge of the wood is only a blur – you have to make some guesses and go in boldly. Lathes are ‘decisive’ and they require decisive operators.
The biggest consideration of all is the obvious one. Lathes move the wood, but can only do so in a circular motion – so we can (broadly speaking) only produce round (or oval) objects with the lathe. So, while we think of chisels and planes as travelling in feet per second, we normally convert the feet per second of the wood passing the lathe tool into revolutions per minute of the lathe. What governs the choice of the speed of rotation that is used is still, effectively, the speed of the wood passing the tool tip as measured in feet per second.
There are optimum speeds of traverse of cutting tools across wood; and there are similarly optimum lathe speeds. As a basis, the rougher or coarser the work, the slower the speed we use. The finer the work the higher the speed. Within this framework we try to keep the speed of the wood past the tool fairly constant. This means one thing above all others – that the bigger the diameter of the wood we are turning the slower the speed of rotation that we have to use if we are to keep the rim speed (the speed of the surface of the wood past the lathe tool) roughly constant.
If you read some of the published recommendation of master turners you will find considerable variation. First, and not surprisingly, you find that each gives a recommendation on basic lathe speed. Some provide tables relating the diameter, and the length of the piece to the speed. They also differentiate between face plate and ‘between centres’ work. However not only will you find major variations, but also several inconsistencies.
Most of the well-known turner/authors recommend rotational speeds which give somewhere between 20 and 30 feet (6 and 9 metres) per second for the actual wood surface to be passing the turning tool. One turner, however, has a table which gives a rim speed range of from 1ft 6in (45cm) per second to 65 feet (20 metres) per second.
In subsequent chapters we will look at tables of recommended speeds for different types of turning and different sizes of workpiece. These will show the theoretical speeds as well as the actual speeds that I use, because it is the nearest that I have available on my lathe.
You may find some of the speeds on the high side. Don’t worry. Find a speed that you are comfortable with even if it is somewhat slower. If you feel that you could go a little higher, and are confident about the firmness of the mounting of the wood, then go higher. In broad terms the higher the speed, the easier it is to get a good finish. The limitations are questions of safety and the speed with which mistakes can occur (and the distance which a piece of wood will travel if it does break free from the lathe).
There is another point to watch. Turning at high speed does set up stress in the timber and if there are any hidden flaws the wood may fly apart. It happened to me recently when demonstrating with an 8in (20.5cm) diameter 4in (10cm) thick yew bowl blank; it very nearly had disastrous consequences.
In broad terms you can use the more desirable faster speeds when turning between centres because the wood is more securely held in place. You can use faster speeds for shorter workpieces because there is again a more secure mounting. You should do roughing at half the speed of finishing turning for a similar sized piece of timber because of the strain that roughing puts on timber, mountings and tools.
If we start with the base line of aiming for a standard cutting speed of 25 feet (7.5 metres) per second, the following table would hold good for a 2in (5cm) thick bowl blank or a spindle of up to 6in (15cm) in length. Looking at a table like this causes many turners to realise that on smaller items – say 6in (15cm) diameter and down – they do not turn fast enough. It also shows up the inadequacy of many lathes which have clearances capable of accepting 12 to 14in (30 to 36cm) diameter blanks but the lowest speed that they offer is 800 r.p.m.
You may also have identified another problem. Let’s say that you are turning an 18in (45.5cm) diameter bowl. You set the lathe to 400 r.p.m, which gives a rim speed of 31ft/sec. But what about that sweeping cut where you are trying to get a nice tear-free finish on the inside base? As you near the centre the effective cutting speed is continuously decreasing. At 2in (5cm) out from centre the wood is travelling at about 3½ ft/sec.; at an inch you are down to 1.7ft/sec – hardly the speed at which to make a clean shearing cut with a tool as crude as a wood-turning gouge!
Table 1 Lathe speeds for different diameters of work.
Later we will consider some of the special problems of turning different woods, particularly burrs and knotty materials, and the requirements of turning natural edged or ‘waney’ pieces. In general I find that I prefer to work at half to three-quarters of the normal speed for a given diameter when I am working on ‘scrubby’, ‘pippy’, or rough woods.
There are some other basics to consider whilst talking about lathe speeds. Green wood cuts more readily than dry timber but it requires sharper tools to cut through the fibres and is more likely to tear when cutting across the grain. However, the sap does have some lubricating property.
Dense, tropical hardwoods blunt the tool very quickly and respond best to the use of smaller tools, lighter cuts and a higher speed of rotation. Some woods, such as Iroko, are particularly aggressive.
One thing is certain. When the wood first goes into the lathe – when it is not a perfect round, when it may be square or have warts, bumps or dents on it – then it must be turned slowly. Remember the chisel exercise. In roughing you are taking deep cuts in a series of jerks as each protrusion passes the tool. You are not concerned about the surface finish, you just want to remove wood! Deep cuts means slower cutting speed – or, on the lathe, slower revolving speed.
If the normal speed for the diameter that you are turning is ‘x’ then when roughing down, drop the speed to half ‘x’. For instance the normal speed for shaping and finishing an 18in (46cm) diameter bowl is 400, but for roughing the outer rim it would be only 250 r.p.m. A 2in (5cm) spindle may be worked at 2,000 and even higher; but it should be roughed from a square to the round at about the 800 mark.
So to conclude this chapter, let’s try that. If you have never used a lathe at all then it would be useful at this stage to read the first few pages of the later chapter on lathes just to become familiar with the names of the parts.
Any sort of timber will do. In fact for practice it is a good idea to use poor wood, not because you will be ‘wasting’ it anyway, but because the poorer the wood the more precise you have to be with your tool control if you are not to end up with torn surfaces.
It is useful to befriend a local builder and ask for any off-cuts – the ends of floor joists and rafters provide useful practice. If it is used wood watch out for the nails, and for early practice avoid the knotty pieces. A second source of good practice wood is a local window-frame maker. They often have pieces of Meranti and other low-grade hardwoods which are quite suitable for general practice and for the making of tool handles. Frame-makers will give you a bag full in return for the occasional handle.
For this exercise we want something about 2in (5cm) square and 9 to 12in (23 to 30cm) long. If the wood is not roughly square it is worthwhile squaring off on a saw table as this saves turning time.
We are going to turn this piece ‘between centres’ – that is, with the headstock drive in one end and the tail stock point supporting the wood at the other. This is also known as spindle turning as with chair legs, banister rails and so on. The closer you can get the centre axis of the wood to align with the axis of rotation of the lathe, then the less wood will be wasted and the larger will be the diameter of the spindle you are left to work on. So first find the centre of the ends of the piece of wood.
There are three ways of finding the centre of a squared piece of timber:
Finding the centre of a square section.
(a) Guess.
(b) Link diagonal corners.
(c) Use a centring gauge.
Guessing is OK and some people are very good at it. For most it wastes wood! Linking diagonals is readily available, cheap and takes only a few seconds. Using a centring gauge is fast and reliable, once you have made a gauge! For now we will adopt the linking corners approach.
Using a steel ruler link the diagonally opposite corners and scribe a line with a sharp, hard grade pencil or an awl point. Repeat, linking the other two opposite corners. Where the two lines now inter sect is the centre of the wood. You can use the same method for rectangular, square, or nearly squared wood. Next use a centre pop to indent the intersection point. A four or six inch nail makes a good ‘pop’ for this purpose. Repeat to find centre on the other end of the wood.
Finding the centre of the squared timber by linking the diagonally opposite corners.
Marking the point of intersection with a centre punch.
It is important that the drive spur is firmly indented into the wood. Do not hammer the wood on to the spur whilst the latter is mounted on the lathe – this very quickly damages the lathe spindle bearings! It saves a lot of time if you have a spare spur for punching the drive end of the wood. Using a rubber hammer will avoid damaging the spur.
Indenting the drive spur to give a firm seating. Use a rubber hammer to avoid damage to the spur threads, or use an old spur. Never do this by hammering the wood on to a lathe-mounted spur.
Offer up the timber to the spur on the lathe. Bring up the tailstock until the point sits in the centre popped mark on the outboard end of the wood. Clamp the tail stock, wind in the quill and lock it in position.
Set the tool rest so that it is parallel with the length of the wood and sufficiently far from it so that there is 1/8in (3mm) clearance between the rest and the corners. The height of the rest should be such that it is just below the centre axis of rotation of the lathe (to be precise, about ¼in (6mm) below centre height). Rotate the wood by hand to check that all corners are clear. Always, after every adjustment of the tool rest, turn the work piece by hand to ensure that it clears the rest.
Tool rest position for roughing down.
The tool that you want is the roughing gouge – that is the big, deep fluted one. You are going to start with the tool in a position where it could not cut anything. Rest the gouge with the flute vertically upwards, and with the underside of the blade bridging across and resting on both the tool rest and the top of the piece of timber. It should be near the right-hand end of the rest and towards the right-hand end of the timber. The tool should be at between 30 and 45 degrees to the axis of the lathe with the blade pointing to the left. The tool handle will be down at about 20 degrees from the horizontal.
Start the lathe, hold the gouge handle firmly in one hand and bring the tool down into the position just described. As each corner of the wood hits the underside of the blade it will bounce. To dampen out the bounce place the first two fingers of your free hand on top of the blade over the rest, and press the blade on to the rest.
At this stage as you look at the turning wood there will be two images. There will be a dark core and a fuzzy or blurred corona. The core marks the round diameter you will get down to, the hazy part is where you have the rapid interplay of the corners of the wood and the spaces between. This is the wood that you will have to remove.
Now, draw the blade back slowly. There will be a point at which the underside of the blade is no longer on the wood but now the bevel rubs. Again it will be bouncing on the corners of the rotating timber and it makes a sound like a world war one aeroplane engine. There are still no chippings coming off the wood. This is what is known as the ‘bevel rubbing’ position and, whatever the cut or the tool, this should be the starting position every time you take a tool to a piece of wood.
So, you always start with the tool firmly on the rest and the bevel rubbing. This is the control position and avoids the huge dig-ins you are likely to get by pushing the tool straight into the turning wood. Remember – over the top, and then draw back.
Once you have a feel for the chattering bevel rub, then draw back the handle of the tool a fraction further. Immediately, chippings will start to fly.
Bringing wood to the round with the roughing gouge – ‘roughing out’. (a) Tool rest is1/8in(3mm) from the widest part of the wood (check by hand-spinning the wood). (b) Start with the back of the tool resting across the tool rest and rotating the wood. (c) Draw back the gouge until the bevel rubs on the wood, then draw it back a fraction further until cutting starts. (d) Angle of 45° at which normal roughing will later be done.
Keeping the tool firmly down on the rest move it slowly sideways. As the turnings fly, the hazy corona reduces in diameter. You are taking off the corners! Stop the lathe and have a look.
Roughing with a massive gouge. The blade is positioned to an angle of 45 degrees to the axis of the wood.
Start up again. Tool on the rest, bevel rubbing, and then draw back to start the cut. This time as you move the tool sideways roll it on its axis so that the flute is not vertically upwards but is just off the upright. Point the open flute in the direction of the cut. Continue the cut by moving the tool sideways on a line parallel with the lathes axis. As you reach the end of the timber (or that part of it within the compass of the tool rest) angle the tool the other way, again tilting the flute in the direction of cut and move sideways to make a cut in the opposite direction.
The cutting zone is at about 10 o’clock.
Roughing with a large bowl gouge.
Repeat this, back and forward, until the corona just disappears and you can now see a sharp outline of the turning timber.
Testing for round. The tip of the thumb must point in the direction of rotation.
You can check to see if you have completed the rounding out without stopping the lathe by resting the thumb lightly on the top of the rotating piece. Have the hand over the far side of the workpiece with the tip of the thumb pointing towards you. You will feel bumps if the corners have not quite gone.
Words of caution! A finger caught between the timber and the tool rest can be lost! Always have the tool rest close to the timber and make sure that the tip of the finger (or thumb) is pointing in the direction of rotation and never against it. Always keep it well clear from the rest, and make sure that your sleeves do not catch.
So we now have a cylinder. Stop the lathe and look at the finish. If you are using poor timber it is extremely unlikely that the finish will be good.
Try an experiment. Make sure that the tool is sharp and make a pass or two with the gouge at a different angle to the axis. You will find that there is an optimum. If too much towards the right-angle you get small chippings and a rough finish. Too fine an angle and you get fine ribbon shavings and burnished wood, but it takes a long time to get much off. Somewhere between, the cut is quite fast, the turnings are larger, and the finish is reasonable. The more that the alignment of the gouge is angled to the axis of the lathe the more the bevel rubs, and the more rubbing there is the better the finish.
Using the roughing gouge to round out a squared section equates broadly to the use of the chisel in our first exercises. The bevel is rubbing then we lift the handle slightly to get a cut. Some people use the roughing gouge more as a scraper, just chipping flakes off the corners. Why have a gouge in this case?
Perhaps, now we have a cylinder to work on, it is time that we looked at the other basic tools of woodturning.
2 Woodturning Tools
Chisels and planes cut wood. They peel off slices. According to the type of wood, the angle of approach to the grain, and the sharpness of the tool, you get either long, thin peelings or short, thick ones. If you use a rasp to shape wood, you tear off mini chips which look like sawdust.
In woodturning most of the tools that are used work in a planing fashion; they include chisels, skew chisels, gouges, and beading tools; we do, however, also approximate the rasp in that we also use tools called scrapers. There are some turners who only use scrapers, and others who regard scrapers as taboo! In fact each and every tool has its uses: and its problems!
CHISELS
The simplest chisel for the tool maker to make is, of course, a square-ended flat chisel with a single bevel. However, such a tool is useless for getting inside rounded corners and under the rims of bowls. So turning chisels are made into a variety of shapes to handle different types of jobs. Flat chisels have angled ends to work across the surface; these we call skew chisels. Corners are cut back and the whole blade is rounded into a semicircular section to give what we call gouges. By having the sides of the chisel blade bent up to the gouge form, we can keep the corners out of the way when cutting into concave recesses. Gouge bevels are ground at different angles to enable them to get deep inside rounded forms.
Scrapers, too, are profiled into various forms to get into round or square corners or under the lip of a recess. Sometimes we grind scrapers to special profiles to produce particular cuts or beadings.
Let’s start a detailed examination of the different tools with the simple chisel. A conventional woodwork chisel has a square end and has the bevel on one side only. The woodturning equivalent normally has an angled end and has a bevel on both sides. The reason is simple.
If you took a square-ended chisel and went straight in at right-angles to the axis of rotation, the chisel would not cut while the bevel was rubbing. The moment that the edge caught, the wood would peel, the bevel would cease to rub and the pressure of the shaving on the top of the blade would force the blade deeper into the wood and in no time at all you would have a horrendous dig-in.
In order to keep the bevel rubbing we angle the blade to the axis of rotation (as we did with the roughing gouge). This way we also keep the corners clear by making sure that the cut is being taken somewhere near the centre of the edge. Obviously with a square-ended blade the whole tool would have to be held at a fine angle to the axis – it would almost be lying along rather than across the tool rest, and would be difficult to control. The tool handle (and our knuckles) might come close to the rotating wood, and the end of the handle would probably foul the tailstock. By grinding the edge at an angle we can maintain the correct angle at the cutting edge while having the tool at a more acute angle to the workpiece.
A 20 degree skew means that the edge can be presented to cut at 45 degrees to the axis of rotation while the tool handle is only 25 degrees from the right-angle.
The double-sided bevel means that the chisel can be worked from either end of the workpiece into both left- and right-handed corners (a substantial degree of ambidextrousness is invaluable to a woodturner).
The skew chisel is used in two basic ways. One is for planing down the outside of a cylinder working almost along the grain; the other is for cutting into corners, as on facing cuts, or making a round ‘bead’ where the cut is across the end grain.
How to get a dig-in! (a) Starting position, with the bevel rubbing on rotating wood – no cutting taking place. (b) Bevel still rubbing to support the blade, but the tool has been brought back until the tool edge just lifts fine shavings off the surface. The tool edge is now being pushed down into the wood by the shavings but the rubbing bevel and tool rest prevent dig-in. But – (c) The tool is drawn further back – no support from the bevel. Added pressure from shavings forces the blade down. It pivots on the tool rest and the handle is forced up. (d) The blade is pinched between the wood and the rest – it may wrench the wood off the mounting.
