Bowl Gouge

When a work lifts your spirits and inspires bold and noble thoughts in you, do not look for any other standard to judge by: the work is good, the product of a master craftsman.

Jean de la Bruyere

40/40 Grind

The “40/40” grind is advocated by Stuart Batty (Allan's son), and is used by his protégé Ashley Harwood. They both advocate hand grinding on a platform set for 40° (a number of companies make such platforms).

My experience is that this shape is very useful for the really hard woods used in ornamental turning. Examples include African Blackwood and Desert Ironwood (both with Janka hardness measures > 13,000 N).

As shown in the diagram to the right, the wings are not swept back as far as the diagrams below, but the α remains the same. Also, the wings (on the rake) are recommended to be flat, not convex. This is because the wings are not a key element of the style Stuart uses for his work (unlike that advocated by David Ellsworth). I have found it difficult to produce truly flat wings; mine are more convex. This has not decreased the usage of the tool's grind shape for me.

Stuart Batty has a number of great videos on Vimeo showing his SB Tools, including some on sharpening.

Henrik Franck Stampe provided a set of instructions for adding a 40/40 grind using a Tormek grinder.

Flute Note: The bowl gouge sold by Ashley Harwood has a parabolic flute. Feedback I've seen regarding this grind shape has noted that the parabolic flute seems to work best for this grind. Additional feedback I've read is that a U-shaped flute does not work well with this grind.

The profile shown to the right with long swept back wings can be achieved by adding more side-to-side swing of the tool when sharpening it (i.e., grinding the wings further back for a higher rake angle -- more information about this is in the comments below).

The Tormek handbook, Water Cooled Sharpening of Edge Tools, advises that this grind shape is not recommended for starter-level turners as it can be somewhat aggressive, but many others feel that 40° is the optimal grind angle (except for bowl bottom gouges, where 60° is recommended).

Note: I do not see this grind discussed often in woodturning fora or at woodturning tool sharpening events.

The Tormek handbook, Water Cooled Sharpening of Edge Tools, recommends that this grind shape is for turners of all skill levels.

Others feel that 40° is a far better grind angle (except for bowl bottom gouges), especially if pursuing a multiple bowl gouge workflow.

Note: I do not see this grind discussed often in woodturning fora or at woodturning tool sharpening events.

The "Irish" profile with swept back wings was pioneered by Liam O’Neil, and can be achieved by adding more side-to-side swing of the tool when sharpening it (i.e., grinding the wings back further).

Allan Batty recommended this angle, though Stuart Batty noted that his father's recommendation for this angle was based on his production work being made easier (vs. using a second bowl gouge for bowl bottom work).

Stuart's stories of working for his father are worth the price of admission to his classes (oh, and the instruction is good too).

This is a good grind for bottoms of shallow bowls.

The wings do not need to be swept back, and indeed the rake angle may tend towards 80°.

The larger edge angle is beneficial when turning deeper within bowls.

Tom Wirsig noted that this angle, coupled with a U-shaped flute, is best for figured woods, also noting that it must be very sharp (see also, "Tips for Turning Figured Woods", in the October 2022 edition of "American Woodturner"). Tom also recommends a shape where the wings are not swept back, with the rake angle tending towards 80°.

This is a good cutting angle for bottoms of the bowl, especially a deep bowl.

The rake angle (wing sweep) will look like the one shown above for 55°.

The “Ellsworth” shape, made famous by David Ellsworth (one of the founders of the American Association of Woodturners - Member #1) has wings which have a very pronounced convex shape.

David turns a lot of wet wood for the objects he makes, and I have found that this shape works well for such turning. I have also found that this shape is not as usable for really hard woods (i.e., Desert Ironwood or African Blackwood).

These wings are a key element of the style David uses for his work (unlike that advocated by Stuart Batty).

Flute Note: The bowl gouge developed by David Ellsworth has a parabolic flute. Feedback I've seen regarding this grind shape has noted that the parabolic flute seems to work best.

Other feedback notes that a U-shaped flute works well for this, especially for the bottom of a bowl. That same feedback also noted that the α could be as high as 75° - 80°. Also, the wings would not be swept back for this use.

Slightly Convex - best shape

Flat - acceptable shape

Overly Convex

Cause: excessive grinding on the front edge.

Concave

Cause: excessive grinding on the wings/sides.

• Jeff Farris' Presentations
  • Sharpening with the Tormek SVD-185 Gouge Jig (YouTube video)
• Alan Holtham's Presentations
  • Tormek SVD-186 Gouge Jig (YouTube video)
• Glenn Lucas' Presentations
  • Avoiding common problems when sharpening woodturning tools (YouTube video). Glenn's video is quite well done, especially explaining about what causes concave surfaces on the cutting edge of the bowl gouge, and how to avoid it.
• David Peters' Presentations
  • Tormek SVD-186 Gouge Jig Review and Comparison to the 185 (YouTube video)
• Tormek Presentations
  • Tormek Live Sharpening Class - Part 4 - Carving Knife & Carving Tools (YouTube video). Wolfgang and Sèbastian from Tormek go through the sharpening of carving knives and various carving tools such as v-tools, carving gouges and short wood chisels.
    • The commentary that starts at 10:40 about setup of the Tormek SVM-00 Small Knife Holder Jig is excellent.
    • Around 24:00, there is a discussion on sharpening hook knives (with the grind on the outside edge). Sharpening the inside edge must be done by hand, or using the method advocated in The Complete Guide to Sharpening (1996) by Leonard Lee.
  • Tormek Sharpening Classes: Part 5 - Woodturning Tools (YouTube video). Want to learn how you get your woodturning tools razor-sharp? In this week's sharpening class we take a closer look at the tools for the woodturner; Gouges, skews, parting tools, scrapers, cutters and more. Sèbastian and Wolfgang will show you the methods for sharpening all these turning tools and how you achieve repeatable edges every time. Stay tuned and hit us with your questions during the stream.

• Tormek Presentations (continued)
  • Tormek Live Sharpening Class - Part 9 - Sharpen a flat bevel with Tormek MB-100 on a diamond wheel (YouTube video). Sèbastian and Wolfgang show how to achieve a flat bevel with your Tormek wet sharpening system, They also touch upon the differences between the different types of bevels.
  • Tormek Sharpening Classes: Part 23 - Reshaping woodturning tools on a bench grinder (YouTube video). In this episode of the Tormek sharpening classes we explain how you can quickly and with full control, re-profile your turning tools on your bench grinder. The BGM-100 Bench Grinder Mounting Kit allows you to use the same jig settings as on your water-cooled Tormek sharpening system. It is therefore easy to do the rough shaping on the bench grinder and then continue to sharpen and maintain the edge of your Tormek machine.
  • Tormek AngleMaster WM-200 (YouTube video)
  • Tormek Short Tool Jig SVS-32 (YouTube video)
  • Tormek SVD-185 Gouge Jig (YouTube video)
  • Tormek Turning Tool Setter TTS-100 (YouTube video)