The 40/40 bowl gouge grind is a straightforward and useful tool for wood bowl turners and worth trying out.
What is a 40/40 bowl gouge grind?
A 40/40 bowl gouge grind refers to the angles incorporated in the specific sharpening process for this gouge. The bowl gouge bevel angle of the 40/40 grind is 40-degrees, as are the side wing edges. Also, the top slope of the wings to the flute cutting tip is a 40-degree angle.
Why 40/40 Grind
The mechanics of how the 40/40 grind cut wood so effortlessly seems to lie in the angle.
It’s all about the 40-degree angle.
Supposedly if the angle is off more the five degrees from 40, the tool does not perform as well.
A degree or two one way or the other, however, won’t change the cut too much.
To explain the advantage of this gouge, some turners have referenced the similarity of the teeth angles in well-known carnivorous mammals matching this 40-degree angle.
The 40-degree angle seems sloped enough to perform a clean-cut, and the remaining bowl gouge mass at the base of the flute stabilizes the tool during the process.
Think of this more like a slicing cut.
The wood is engaged initially at the cutting tip, but then as the side wing progresses, it acts like a peeler, peeling away material as it enters the gouge flute.
40/40 Slicing Angle
The slicing angle of the 40/40 gouge plays the most crucial role.
For a very visual cutting example, I believe we can look at the infamous Guillotine blade.
Before the Guillotine device was invented, executions were attempted by dropping a straight blade on the neck of the less fortunate.
I say “attempted” because many times, several whacks were needed to complete the job.
Think about what the Guillotine blade is doing.
Unlike the straight blade, the Guillotine is only cutting a relatively small area at a time as it passes through.
The straight cutting edge attempts to cut everything all at once and is quickly overwhelmed and ground to a halt.
At 40-degrees, wood travels up and quickly slices away from the 40/40 bowl gouge design.
OK, let’s leave the beheadings behind and get back to our bowls. 😉
40/40 and Other Grinds
If you’ve read my article, Bowl Gouge Sharpening Angles – SURPRISE ANSWER then you know where I’m about to go.
There is no “right” bowl gouge bevel angle.
As a matter of fact, I recommend you have several bowl gouges ground at different angles for different purposes.
That being said, and in an effort of making a full disclosure, initially I didn’t want to try the 40/40 bowl gouge grind.
I thought I had what I needed with my current bowl gouges, so why mess with another gouge angle?
Now, that I know what the 40/40 gouge is capable of producing, I have a couple 40/40 gouges in my arsenal and will probably have more in the future.
Why should I try the 40/40?
I have several swept-back wing bowl gouges with about a 55-degree front bevel and they work fine for me.
In addition to my swept-back wing gouges, I have a micro-bevel gouge for tougher and deeper bowl angles.
By the way, if you don’t have a micro-bevel bowl gouge (sometimes also called a “bottom feeder” gouge) consider reading this article next.
To be completely honest, I tried the 40/40 grind so I could share the results with you here.
What I discovered was pleasantly surprising!
40/40 Bowl Gouge Advantages
The gouge I decided to shape with a new 40/40 grind was one of my older half-inch bowl gouges. Not too big, but also not too small.
At the lathe, what I noticed immediately, besides the 15-degree body position shift from my 55-degree gouge, was the cut.
The cut of the 40/40 gouge is strikingly crisp!
I expected the gouge to feel different, but I didn’t expect to see that much difference in the cut so quickly.
The other shocking performance was in roughing out material.
As I was roughing the exterior of a large bowl blank with my huge 3/4-inch, 55-degree, swept-back wing bowl gouge, I thought “wait, let me see how the 40/40 handles this?”
Oh. Mine. Goodness!!!
The 40/40 gouge, smaller than the previous gouge I was using to rough by a 1/4-inch, cleared material away like an animal.
I was shocked at the width it was cutting.
It shaved wood away as wide as the side wing and never bogged down!
Tenon Undercut Tool
There are many tools that can create a nice undercut for the dovetail on a bowl tenon.
But most of those tools require stopping the use of your current gouge and switching tools.
I usually use a detail-ground spindle gouge to shape my tenon dovetail angles.
However, I was surprised to discover that the 40/40 gouge can undercut just enough to make a very nice dovetail tenon angle. All without switching tools.
40/40 Grind Disadvantages
With the many advantages of the 40/40 grind gouge, there are a couple of disadvantages.
I’m hooked on shear-scraping the final bowl exterior surface to get an almost perfectly smooth finish off the gouge.
I share all the details about the shear-scraping cut here in this article. It’s worth reading.
While you can do a little shear-scraping with the short wings of a 40/40 gouge, it really isn’t designed for shear-scraping like the swept-back 55-degree bowl gouge.
That being said, the smooth cut straight from the 40/40 gouge is so good, it almost doesn’t need to be shear-scraped.
Also, the 40/40 grind needs to be hand-sharpened.
Hand-sharpening can be a bit of a disadvantage, but after a couple of times at the sharpening wheel, hand-sharpening is pretty simple.
I’ve also designed a unique 40/40 Gauge that aides tremendously and takes the headache out of sharpening.
Preparing to 40/40 Sharpening
We need to set up the sharpening platform before we begin to shape or sharpen the 40/40 bowl gouge.
The only additional hardware needed at the sharpening station for the 40/40 grind is a sharpening platform.
If you already have the Wolverine Vari-Jig Sharpening System, then you should also have the Wolverine sharpening platform.
Wolverine makes a stand-alone sharpening platform, here’s a link if you need one.
I know some turners that like to have separate platforms and vari-grind jigs locked and set for different specific tasks.
While this might not be the most cost-effective approach, having a dedicated grinder platform tightened and locked to 40-degrees can be convenient to just slide into the track and begin sharpening without the need to measure angles.
Accurately Setting 40-Degree Angle
As you probably are guessing, we need to set the sharpening platform to 40 degrees.
The adjustable protractor I use that works great for checking bevel angles on gouges, doesn’t work so well for setting up the grinder platform.
Because we only have the sharpening wheel to measure from, the protractor is pretty much useless.
Don’t worry, I designed a unique DYI 40/40 Gauge.
This gauge is straightforward, yet very powerful.
NOTE: Be sure to do all the following adjustments with the grinder turned off and not moving.
Place the DIY 40/40 Gauge on its side or vertical, and simply adjust the sharpening platform angle until the curved face touches the sharpening wheel flush.
The sharpening platform is now precisely set to 40 degrees.
We will also, need 40-degree reference lines on the platform itself.
Not to worry, the DIY 40/40 Gauge also has this covered.
Place the DIY 40/40 Gauge on the platform and mark the angled sides to the platform.
I like to use blue masking tape, but you can also draw lines directly to the platform using the gauge edges.
Set up of the 40/40 sharpening platform is that easy using the DIY 40/40 Gauge.
If you’d like to be able to set up your platform this easily, click here to order you DIY 40/40 Gauge now.
40/40 Bowl Gouge Shaping
If you are reshaping an older gouge or shaping a new gouge, there is one trick you need to do first, before anything else.
You need to initially establish the top 40-degree top wing profile angle.
(top 40 degree angle ill)
With the sharpening platform set to 40 degrees, as described above, place the gouge upside down on the platform.
Be sure the two sides of the flute are resting flush to the sharpening platform surface.
Gently slide the gouge forward until the nose is making contact.
You can slightly rock the tool up and down as you shape the top 40-degree angle.
Once the path from the top of the flute to the tip of the nose is one flat continuous edge, you can stop.
By establishing the top profile, we can clearly see the shape of the cutting edge. Now, only the excess material around the cutting edge needs to be removed to form the final edge.
Now we can proceed to sharpen the bevel angles.
Top Angle Touch-Up
Occasionally, it is a good idea to re-establish this top 40-degree profile angle.
With repeated hand-sharpening, the top edge of the wings can drift a bit off from 40-degrees.
It’s common for one wing to become shorter or taller than the other.
This technique checks and resets the top 40-degree gouge angle.
40/40 Bowl Gouge Sharpening
With the platform set to 40 degrees as we covered above and with the top wing angle ground to 40 degrees, we are ready to sharpen the rest of the 40/40 gouge.
Unlike using a jig, we will not try to do a full sweeping pass across the sharpening wheel to shape the 40/40 gouge.
Instead, we will work on each wing separately and then blend the two sides together as we sharpen the nose of the gouge.
Side Wing Sharpening
Besides setting the platform correctly to 40 degrees, here is the next most crucial step.
The bottom inside flute needs to be parallel with the platform.
Start by sharpening one of the side wings on the 40/40 bowl gouge.
When sharpening the side wing, the flute needs to be parallel and should not be fully closed to the sharpening wheel.
With the flute parallel to the platform, begin sharpening the gouge wing until the bevel meets the top angle.
You can rock the wing slightly left to right (perhaps less than 1/32 of an inch or 1-2mm) as you sharpen the side.
When one wing is complete, switch to the other side and repeat the process.
The top cutting edge needs to be nothing more than the side wing bevel meeting the top edge of the inside flute.
If you see any flat surface visible near the top of the bevel or along the flute, continue sharpening.
I think there’s a “nose to the grindstone” joke in here somewhere. Ha!
Once the side wings are sharp, the only thing left is the gouge nose.
Keep the bottom of the gouge flush to the sharpening platform surface and swing the nose across and around to blend the two side wings.
Make light passes and don’t force the gouge into the sharpening wheel.
Remove material until the front bevel edge blends continuously across the top edge of the gouge.
Just like the side wings, the nose needs to have a crisp cutting edge that is formed by merging the front bevel with the inside flute.
If any facets, bumps or flats spots appear along the cutting edge, keep sharpening.
You are done sharpening the 40/40 gouge when there is a crisp clean cutting edge that wraps from the left-wing, across the nose, and along the right side.
After sharpening the 40/40 gouge a few times, you will be able to smoothly roll the tip from left, across the nose, and complete the right-wing in one pass.
I suggest, now that you have sharpened the 40/40 gouge, go try it out for a bit.
One of the aspects of this bevel angle is the width of the bevel and how much material it removes. This can be good or less desirable, depending on how you turn.
If you’d like to use this gouge for tighter curves, especially inside a bowl, it might be helpful to reduce the size of the gouge heel.
I use the platform as a general guide and rest my hands there as I remove the gouge heel.
Position the gouge tip up a bit on the sharpening wheel and freehand this grind by rocking the heel left and right on the sharpening wheel.
The top cutting edge bevel will be shortened as you remove the heel. How much you reduce the bevel is up to you.
The shorter the bevel, the tighter the gouge will be able to turn without burnishing, or worse, being forced off bevel while cutting.
Looking to better understand how “riding the bevel” works? Check out this article next.
40/40 Bowl Gouge Grind Conclusion
I must say I was a bit reluctant to give the 40/40 grind bowl gouge a try.
But after developing the DIY 40/40 Gauge, which I needed to quickly set up the platform, and then trying out the bowl gouge, I’m hooked.
I still have my other bevel angled bowls gouges, but I’ve been finding myself grabbing the 40/40 gouge pretty often, and I really like the results.
You’re Probably Going To Want To See These Too:
BOWL GOUGE SHARPENING ANGLES – SURPRISE ANSWER
BOWL GOUGE BASICS – BEGINNER GUIDE (PARTS, USE, SIZES, GRINDS)
5 TOP REASONS NASTY CATCHES HAPPEN WHILE TURNING WOOD BOWLS
Try it out the 40/40 grind for yourself, if you haven’t already and let me know what you think of the 40/40 bowl gouge.
Please, leave a comment below.
Thanks and Happy Turning,