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.

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.

Notes & Comments

Information regarding Grindstones

Rake Angle Grinding

The best shape for the edge is slightly convex or flat.

Good	Slightly Convex - best shape	Flat - acceptable shape
Bad	Overly Convex	Concave
	Cause: excessive grinding on the front edge.	Cause: excessive grinding on the wings/sides.

---

40/40 Grind Using a Tormek

Grinding the Top of the Cutting Edge

Henrik Franck Stampe provided this set of instructions for making a 40/40 grind using a Tormek grinder. He noted that this helps get a flat edge on the wings as shown in the picture to the left. As he also noted: trying to control the wing shape using precise side-to-side movements is difficult, oftentimes leaving the wing edges a mess.

Step 1: Grind the top of the cutting edge flat

Settings: Hole A | JS 4 | P ~45

Place the bowl gouge “upside down” in the SVD-186 (bowl gouge's flute opposite the screw knob, as shown in the picture to the right). This is a bitt fiddly, but it is quite possible. Set the tool's projection in the SVD-186 to around 45mm.

Using the side of the grinding wheel, grind the top edge flat, very carefully and very little at a time. This is shown in the picture to the right (click on the picture to see a bigger version).

Step 2: Grind the cutting edge

Settings: Hole A | JS 2 | P 75

Place the bowl gouge in the SVD-186 in the more typical fashion (bowl gouge's flute towards the screw knob). Set the tool's projection in the SVD-186 to 75mm.

Grind the cutting edge using the face of the grinding wheel.

Image courtesy Tormek

Longer Wings?

The wings can be extended for a greater rake angle by the way you grind. The rake angle is increased when you spend more time grinding on the wings, and when you increase the amount of swing you use when grinding.

The diagram to the right shows this movement.

Glenn Lucas' video, Avoiding common problems when sharpening woodturning tools, is a good one to review before proceeding down this path. A link to that video is below.

Tool Too Short?

When the tool gets too short to be held by the jig, you can grind off the top as shown in the upper tool in the picture to the left. This flat area allows for the jig to hold the tool without the tool slipping or rotating.

And when it gets even too short for that, consider making it into a round negative rake scraper (great for bottom corners of boxes), a beading tool, or a point tool.

• 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 are 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. Sebastien 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). In this episode we learn how to use the Tormek MB-100 Multi Base to sharpen a completely flat bevel ▼, on the side of Tormek's diamond wheels DC-250, DF-250 and DE-250. For some tools, such as 🎻 luthier knives,🔪 Kiridashi knives, v-tools, chip carving knives and Japanese plane irons, a completely flat surface on the bevel is preferred over a slightly concave, which you get when you sharpen on the rounded part of the grinding wheel. For some people this is more of a personal preference.

  Regardless of what might be the reason to want a flat bevel, Sèbastian and Wolfgang show how to achieve it with your Tormek wet sharpening system, They will 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)