Double Bevels on Turning Tools
Double Bevels Overview: Many years ago in Junior High School, I recall my difficulties in free hand grinding a single bevel on some of my turning tools. At the time, we had a 10" dry grinder in the schools woodshop, which was equipped with a teensy-tiny angle platform on the front of each wheel. The tool rest was so small in fact, it was a challenge to even rest one finger on it to steady the tool when grinding.
Using a double-beveled 5/8" Irish ground bowl
gouge to hollow the interior of a 16" Honey Mesquite bowl.
More often than not, my bevels were a nightmare of multi-facets and blued edges. Each time my woodshop teacher would come by my lathe, he would remind me to strive for a single bevel when sharpening my chisels and not to overheat my high-carbon steel tools.
While the old school mantra was to always grind single bevels on your turning tools, in recent years this has evolved into a new methodology – one that recognizes that there are times when having more than one bevel on your tool is just what the Doctor ordered.
Single Bevels vs. Double Bevels
Most of us are well aware of the benefits of using a single bevel on our turning tools. Manufactured sharpening jigs have greatly contributed to the overall ease in woodturning by eliminating the need to learn to sharpen freehand. Having a consistent bevel on your tool makes the tool much easier to use. It also allows you to get the "feel" of the tool much faster than freehand ground bevels with multiple facets.
Having said that, there are times when a single bevel can be limiting, or even counter-productive to your turning efforts. Double bevels can allow you to use the tool to perform intermediate and advanced turning tasks that would be difficult, if not impossible to achieve with a long single bevel.
If you have never worked with a double beveled tool before, go slowly at first. The shortened bevel length takes a little time to get used to, but when you do, you will find that it is a very easy modification to put on some of your tools. If you are new to using tools with more than one bevel, try it on one tool at first. Some of my tools have permanent double bevels on them, but most are only ground with two bevels when necessary.
Think of these types of tool modifications as additional tools in your toolbox, ready when and if needed. Just like your current tools, different approaches to the same basic tool are necessary in some situations. For example, a standard Allen head wrench. It works great most of the time, but encounter a nut with very little clearance, or one where another object partially blocks the head and a ball end Allen wrench is the better choice.
The same is true with double beveled turning tools. A regular scraper ground with a single bevel might work 99% of the time, but try to use it when deep hollowing end grain through a small opening and a double beveled scraper is the way to go. Having experience with a broad range of tool configurations allows you to choose different tools as necessary. Here are a few tools that I find useful to grind with double bevels from time to time…
Note: Double bevels in the following photos have been highlighted with a black marker for easier viewing.
This 1.5" round nose scraper was double
beveled for end grain hollowing in small openings.
When using thick scrapers to perform end grain hollowing (on a box for example), the thickness of the scraper can cause clearance issues when working inside smaller openings, as the lower part of the scraper blade may hit or rub the inside wall of the box. One easy way to eliminate this challenge is to grind a double bevel on the lower part of the bevel. This will remove some of the bulk of the thickness, while maintaining the rigidity necessary for clean cuts when hollowing a long distance off the tool rest.
Negative rake scrapers offer increased control
and a very smooth cut and have
become very popular in recent years.
Negative rake scrapers are another situation where two bevels are used to good effect on scrapers. Negative rake scrapers have both a top and a lower bevel edge, which allows the scraper to produce very smooth and controllable cuts on turnings. Negative rake scrapers have gotten a lot of buzz in recent years and are another great option to consider in certain turning situations.
This Irish ground 5/8" bowl gouge
features a 1/16" double bevel.
Bowl gouges can also offer the opportunity to add a double bevel on your tool. The long bevel on bowl gouge can cause several challenges, depending on the shape and size of the form you are turning. One challenge that many new bowl turners face is scoring lines on the inside of their bowls when hollowing. Scoring on the inside of a bowl is usually caused by the sharp edge transition between the lower face on the bevel and the bottom of the shaft.
These scored lines are very difficult to remove when sanding, but are easily prevented with the addition of a small secondary bevel on the bottom of the bevel. This softens the edge transition and prevents scoring the inside surface when rubbing the bevel to make your interior profile. This secondary bevel is usually very small, 1/16" or less in most cases is sufficient. Some turners use a handheld hone to soften the edge on their bowl gouges; others prefer to use the grinder. Either way works well.
This modification has become so popular with woodturners that some companies have jigs that can produce a uniform secondary bevel. The Tormek water grinder offers this option on its SVD-185 gouge jig. Once the initial bevel has been established, the jig is readjusted to produce the secondary bevel.
While most of these double bevel examples can be employed as needed, adding a secondary bevel on bowl gouges is a good idea to consider on all of your bowl gouges. If you do not feel comfortable grinding it, you can use a small diamond hone or hard stone to soften the transitional edge on the bottom of your bowl gouge bevels. You will find that your sanding protocol will be much easier when your bowl gouge has this modification, especially when working on softer hardwoods.
Production spindle gouges are often double
beveled to make sharpening easier.
Spindle gouges are rarely ground with two bevels, but there are times when it can be useful – on production spindle gouges for example. If you use production spindle gouges you know that the extra steel under the flute makes for a very long bevel when sharpening. Most turners using these specially made spindle gouges double bevel the tool to make it easier to sharpen.
In my studio, I use production spindle gouges on occasion and all of them are double beveled. The primary bevel is still rubbed in the traditional manner when turning. The secondary bevel is not rubbed and is there to make it easier to sharpen and for clearance in tight areas when cutting coves and similar design details on spindles.
Note: Production spindle gouges feature much more steel under the flute area when compared to a traditional spindle gouge. They are typically used by professional spindle turners when turning production spindles. The extra steel under the flute of the gouge adds extra rigidity to the tool when it's used a long distance off the tool rest.
A traditional spindle gouge has a much shorter range that it can be used unsupported off the tool rest, before vibration compromises the cut quality. Production spindle gouges allow you to work larger spindles with deeper profiles without vibration concerns when working with the tool a long distance off the tool rest.
Skews are often ground
with a double bevel to reduce scoring
when turning shallow curves.
You might not think skews would be a good candidate for a double bevel, but the addition of a tiny secondary bevel in one specific area on the tool can greatly improve the quality of the cut off this remarkable tool. Skews are for the most part, a difficult tool to master for most woodturners. One friend of mine refers to his skew as "El Diablo," Spanish for "The Devil."
While it is true that the skew for most turners is one of the most difficult to master, it is also one of the best tools you can use when turning spindles. A tiny secondary bevel can be added to the top corner (long point) of your skew to make this versatile tool even better.
This tiny secondary bevel prevents the skews top corner from scoring the blank when making shallow curves. In effect, you are softening the sharp edge transition from the bevel to the side of the skew -- in the top corner. Just like when you soften the edge transition on a bowl gouge with a secondary bevel, this helps to prevent scoring the surface of the timber when turning.
How About You?
If you have developed or use a double bevel enhancement on any of your tools, email me and let me know how it is working for you. If possible, send me a quick digital photo as well, since it can be difficult to describe a particular grind on a tool without a photo. I would love to hear from you!
Safety Note: Always follow all manufacturers safety instructions before working with your lathe, or any of the tools or products you may use. If you are unsure about any operation, obtain competent professional instruction before proceeding. Use and wear all necessary safety devices during turning and observe safe woodturning practices to prevent accident or injury.
|Steven D. Russell is a professional studio woodturner, teacher and writer. He has written numerous articles for international woodturning magazines, which have been published in more than 78 countries around the world. Steve has demonstrated in numerous cities across the United States. His studio, Eurowood Werks, specializes in bowls, platters and hollow forms with unique visual and tactile treatments. |
Steve is also a regular featured writer for the Guild of Master Craftsman's "Woodturning" magazine, published in London England. Woodturning magazine is the world's leading magazine for woodturners. Look for his monthly articles covering technical topics, or project based articles in each issue.
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