Footed Ogee Bowl
Thursday 25 September 2008
Mark Baker turns this delicate bowl
Natural-edge work is something that most turners will try, if only to see what can be made from an odd log that has sat in the corner of the workshop for ages. Natural-edge pieces do not have to be made from whole logs, where the grain is running parallel to the rotational axis of the lathe, as with spindles. They can also be made from wood that has the grain running at 90 degrees to the axial rotation, as with most bowls.
This little project is an excellent introduction. Using a log of apple, we are going to make a small natural-edged bowl, and in this case the grain is running as in a spindle.
This is an unseasoned log, so we can explore the techniques of turning wet or green wood. Apple cuts well when dry, but, like most woods, it cuts exceptionally well when wet. Finishing, however, is less easy; we will look at techniques to overcome this.
Instead of using a roughing gouge followed by a spindle gouge, we will use a bowl gouge. The log is very out of true, and the toolrest may be a long way from where we need to work, so the extra blade thickness comes in very handy to reduce vibration. A spindle gouge will also be used, but only on the foot. The foot does not follow the convention of being between 1/3 and 1/2 of the overall diameter; instead, it is small and delicate, in keeping with the overall form.
Glossary Rollover a term to view its definition
- Bowl Gouge
A cutting tool with a deep flute and a heavy cross-section. These are normally made from round bars and the flute is milled out. The round bar fits into the handle thus giving the tool a great deal of strength to enable it to overhang the toolrest a long way in order to hollow out deep bowls. Its primary function is for faceplate - or bowl turning - but it can also be used in spindle work. The bevel angle is ground to suit the user but is anything between 40 degrees and 80 degrees. Traditionally, bowl gouges are ground straight across, but many turners prefer to grind the wings back. There are many terms for a swept back bowl gouge - fingernail grind, O'Donnell grind, Irish grind, Ellsworth grind, lady's finger - to name a few. There may be subtle differences in these grinds, but generically they are all bowl gouge grinds where the wings have been ground back.
- Parting Tool
As the picture shows, there are several different types of parting tool - three of which are shown here. On the left is a narrow (3mm) parting tool which is very useful when parting work where the least amount of grain mismatch is desirable, for example when parting the lid from the base in box making. The middle tool is a straight sided, standard parting tool and the one on the right is a diamond parting tool where the widest part of the tool is at the cutting edge. This can be advantageous when cutting deep grooves because it means less of the tool is rubbing on the sides of the groove. Parting tools primary task is to part wood off in spindle work but they are also used to cut tenons or spigots and grooves. They can also be used to cut beads.
As its name suggests, scrapers scrape the wood rather than cut it and generally leave a poorer surface finish on the wood than cutting tools. Unlike cutting tools, do not use the bevel rubbing technique with a scraper. In fact the 'bevel' is really a clearance rake and allows the cutting edge to come to a sharper edge. Sharpen or hone it often and take very light cuts with a scraper. You should get shavings; if you are only getting dust, resharpen it. Scrapers come in all shapes and sizes - square edge, round nosed, French curve, box scrapers and hardwood scrapers. The picture shows a 1/2 inch round nosed scraper.
- Spindle Gouge
Modern day spindle gouges are made in the same way as bowl gouges - from a round bar of M2 high speed steel with the flute milled out. The flute is shallower and more open than that of a bowl gouge. Traditionally spindles gouges were forged from a flat, rectangular sectioned bar and some manufacturers have started making a modern day version of this, commonly known as the Continental Style spindle gouge.
Like their name suggests, spindle gouges are used to cut details such as beads, coves and fillets on spindle work.
The view from above emphasizes the irregularity of the log
- The technique of shining light through the wood to reveal the wall thickness can be used on all forms of wet turning. With natural-edge work I find it easier to apply the finish once the piece is off the lathe
- If the piece were larger than this, you would not be able to make the finishing cuts from top to bottom. Instead, after removing most of the waste, work down in 1–2in (25–50mm) sections, finishing off each section before going on to the next. Working in this way, you will be able to achieve a uniform wall thickness without being hampered by flexing or distortion of the walls
- When cutting the bark edge, the gouge will not be in contact all the time. Do not apply too much pressure, and do not alter the initial angle of cut: you will soon be back into solid wood and have full bevel contact again
Diagrams Click an image to enlarge