Removing tool marks? Who cares? I remember my early bowls so clearly. The pride and joy of simply making a bowl-like shape far exceeded the need to fuss over a perfectly smooth surface.
As time went on, those pesky tool marks, grooves, hills, valleys, and occasional gouge divots needed to be addressed. My bowls didn’t look as appealing with the unintentional texture of tool marks on the surface. In fact, those tool marks made my bowls look amateur and unfinished.
Using a good quality light, shine the light from the side across the wood surface of your bowl. By doing this you will more accurately see tool marks and imperfections on your wood bowl. A good quality lathe light is extremely important.
Before I could fix the tool mark problems, I needed to better understand how those tool marks and grooves in my bowls were being created.
Here’s what I learned: both what was happening and how to fix the issues. I hope these tips for understanding and removing tool marks and grooves help improve the appearance of your bowls as well.
Tool Marks Causes
1. Bowl Gouge
Most tool marks can be avoided by changing how you use your bowl gouges and other tools. As you probably already know, “riding the bevel” is a sacred phrase in bowl turning, and all woodturning for that matter.
There are only three ways the business end of the bowl gouge can contact the wood bowl surface: heel rubbing, bevel contact with clean supported cut or tip contact with unsupported cut. Tool marks are created with the first and last undesirable options. Excessive heel rubbing and tip contact without bevel support make up the majority of all tool marks.
A quick way to check proper bevel-riding technique is to get above your work and look straight down on your tool to review its position. Be sure to have the tool in the exact area you are turning and look at the angle and location of the bevel.
The flat bevel surface should be almost parallel to the bowl surface about to be cut to ride the bevel. Learn all about riding the bevel by reading Riding The Bevel – Bowl Gouge Technique Explained.
If the tip is pointing into the bowl surface and the bevel surface is angling away from the bowl surface, you’re not riding the bevel, and you’ll need to be removing tool marks later.
If this is the case, slowly change the bowl gouge angle by moving the handle until the bevel surface is almost parallel to the surface of the wood bowl.
2. Round Nose Scraper
The round nose scraper can be a savior when it comes to finishing hard-to-reach bowl interior bottoms. But like the bowl gouge, if not used correctly, it, too, can cause undesirable tool marks and gouges. The scraper can also make dramatic divots that require extra turning and material removal to correct.
I use a heavy and sturdy round nose scraper as well as several smaller round nose scrapers when I do my fine tool mark removal. I’ve found this scraper works great and smoothly removes marks, because of its size and mass.
Round nose scrapers work best when the cutting edge is on center, and the scraper is tilted at an angle. If the cutting edge gets above or below center, the scraper tends to catch and tear out material.
Setting the tool rest to the exact height should be carefully done with the lathe off. This will give you time to precisely locate the center cutting line. If it’s difficult to judge the center point, pull up the tailstock and use the center support tip as a guide.
I raise my tool rest up slightly above center so while I’m using the scraper, it’s angled down just a touch. Because the wood is rotating from the top down, if the scraper catches for any reason it will be pushed away because of this slight downward angle. The cutting-edge, even though pointing downward a touch, is still cutting at the center point.
Angling the scraper, while keeping it firmly on the toolset, creates a shearing action that shaves off very fine precise areas accurately. You will know you have this working when the shavings coming off the lathe are fine wispy hairlike fibers.
If the scraper happens to be pointed upwards, instead of flat center or slightly downward, a catch will drive the tool into the wood and make a nasty tear or gouge.
3. Tool Sharpness
This might seem obvious, but I can tell you from experience that forgetting to sharpen tools is also a significant factor in tool marks.
On more than…well, many occasions I’ve been turning and making not-so-smooth surfaces on my bowl, only to discover that my bowl gouge needed to be sharpened. It really is a “duh” moment when I return to the lathe and the next sharp cut makes the wood gently slice and feel like a bar of soap with large curly shavings coming off effortlessly.
Dull tools will not only cut poorly, they actually can begin to burnish the wood surface, which can make ugly marks as well. So follow the simple rule: If you think your tool needs sharpening, it probably should have been done 10 minutes ago.
4. Wood Particulars
Each species of wood turns differently and will have different cutting characteristics. I’ve turned woods that will leave tool marks, regardless of how perfect I attempt to ride the bevel, and I’ve turned woods that cooperate so well I think I could poke at it with a rusty flathead screwdriver and make a smooth surface bowl.
Besides the characteristics of a given species, there are also structural issues to consider. When bowl walls get thin, there can be flexing of the wood, which causes one side to pull away from the bowl gouge while the opposite side smacks the tool. This will obviously leave marks.
To alleviate the smacking issue of thin walls, always work the top thin wall edge of a bowl first. Once the thin area is complete, then proceed to remove additional interior bowl material. Never return to the thin area, because it will be flexing and tool contact is sure to leave tool marks.
5. Natural Edge Trickiness
There are times, especially with the irregular top edge of a natural edge bowl, that we need to be “cutting air” so to speak. When the wings of a natural edge bowl are cut and then the open space between one wing and the opposite wing passes by, this is cutting air.
It’s important to firmly support the bowl gouge on the tool rest to make these air cuts as smooth as possible. The tool rest and guiding hand must make fluid motions on the tool rest without pressing inward.
Pressing inward or not moving smoothly will leave a deeper line on the next wing that comes around. Speeding up the lathe, still at a safe speed that doesn’t cause added vibration, will make these cuts smoother.
Vibration needs to be understood in order to eliminate tool marks. Read this article, all about lathe vibration, next.
However, it’s almost inevitable that there will be tool marks on the wing areas of a natural edged bowl as the tool gets smacked around. Sanding is the best solution for removing these tool marks.
So you have your tool techniques down, and you ride the bevel like a boss. Well, unfortunately, tool marks can still occur. It could be a simple slip on the tool rest or the nature of the wood itself.
Tool Marks Fixes
Here are specific techniques for attacking these pesky tool marks that occur, despite your best efforts riding the bevel.
6. Divot Tool Mark Repair
So you got a nasty catch and there’s a divot in your bowl. It happens to everyone at one point or another, not to worry.
Because most divot catches are deep, they tear out wood fibers, and those fibers go down into the bowl surface. Sanding or finessing a small area won’t work. Learn more about catches and their causes by reading this article.
The area around the divot must be reduced and lowered until all the torn fibers have been removed and the divot area is smooth again. Simply make additional supported cut passes across the wall area that was affected until the divot is no longer visible.
7. Hill Removal
There it is, your fingertip immediately stops on that nasty hill in the otherwise perfect bowl surface. What to do?
When there is only a small area with a slightly raised surface, don’t fall into the trap of thinking one more pass down the bowl wall will take care of it. What will most likely occur if this approach is taken is an exaggeration of the hill area.
Because the riding bevel edge follows the contour of the bowl surface, a simple additional pass will repeat the hill area and remove more material. Instead, we need to address just the hill area.
First, start by identifying the hill. With the lathe off, feel for and locate the high spot or ring edge on the bowl. Touch a pencil tip on that high area. With the pencil resting on the tool rest rotate the bowl by hand. The high spot may be only on a portion or all the way around the bowl. Let the pencil just mark the highest parts.
Position the tool rest as close as possible to the high spot location to give the bowl gouge the best support. When the lathe is turned on, the pencil line should be visible.
This technique is akin to surgery and needs to be treated very delicately. Position the bowl gouge not touching the surface, but with the bevel parallel to the surface area. Then open up the gouge face, so the entire curved cutting edge and bevel is perpendicular to the bowl surface. Again, nothing is cutting yet.
Please note that the bowl gouge presented in an open flute manner to the bowl is the easiest way to make an awful deep catch if pressed carelessly into the wood. Attention must be paid here and think of this as nanosurgery, not traditional bowl turning.
To remove the hill, you will make tiny micro passes from left of the pencil mark to the right across the pencil mark, nowhere else. Essentially you will be shaving the hill away in multiple passes.
The first pass may contact nothing. This is fine. Gently move the gouge forward a hair and slide your supporting hand smoothly right across the tool rest. The first contacts will probably be very minimal and will also remove the pencil line. This is what you want.
But don’t stop when the pencil line is gone. The base of the hill needs to be shaved away too. With the pencil line removed be sure to keep your focus on the troubled area. Stop the lathe frequently and feel the results. The hill should disappear into the smooth surrounding surface.
8. From Grooves to Smooth
If small hills aren’t the problem and a sea of grooves makes your project look more like a warped vinyl record than a bowl—and this isn’t the effect you were going for—don’t fear, there’s a fix.
Like the previous issue, making further passes may exaggerate those grooves. If a freshly sharpened bowl gouge and smooth bevel riding cut aren’t removing the slots, try this trick.
A shear scraping cut will remove multiple high spots at once without also digging into the low places, eventually making a smooth surface. The shear scraping cut requires a nice sharp edge bowl gouge, so head to the sharpening station before you begin.
Position the sharp bowl gouge with the handle down and the flute almost closed. This is not a bevel supported cut. This is more like shaving with a sharp razor. With the flute nearly closed, or facing the wood bowl surface, angle the bowl gouge at about 45 degrees.
If you’re ready to perform the shear scraping cut, read this article next. You’re going to love the results on your bowl finish.
Similar to the hill removal passes, we need to work across the surface, just removing the high spots slowly. This will take several passes and shouldn’t be rushed.
Watch the top edge of the bowl as you make smooth, tool-rest-supported passes, and you can see the high spots slowly disappearing. Watching at the tool cutting location doesn’t allow for a good viewing angle. This is why it’s a great habit to look up at the top edge of the bowl to see the surface as you cut.
9. Heel Rubbing Tool Marks
If it’s not grooves or divots but burnish tool marks that are plaguing your bowl surface, your bowl gouge may need to be changed or modified.
Smooth lines that have a bit of a sheen to them are burnish marks usually created by the heel of the bowl gouge. When we get into tight spots, it’s possible to be making a bevel riding cut and also rubbing the heel a bit too much at the same time.
One solution for this issue is to change to a different bevel-angled bowl gouge for particular locations on the bowl. Deeper bowls especially have the burnishing problems that will typically occur near the bottom of the curve leading to the bowl bottom. A steeper angled micro-bevel bowl gouge can reach this area without causing burnish tool marks.
Another option is to make a second grind on your bowl gouge. This reduces the bevel area in the heel and makes the bowl gouge capable of turning tighter corners without leaving a burnish tool mark.
Ok, yes sanding is an option for removing tool marks. I know this may seem taboo to some, especially those turners that claim they can turn a bowl in five seconds that is cut so smooth that any sanding would ruin their perfectly turned surface. For the rest of us mere mortals, sanding is a good way to even the surface.
The trick to sanding out tool marks is to not do it with the lathe turning. Yes, you heard me, don’t sand with the lathe running.
Sanding techniques for wood turned bowls covers a variety of things to consider, but the biggest issue here is tackling the tool marks first. Just like trying to fix the occasional hill or grooves with one more pass, attempting to sand these areas with the lathe running will sand the high and low spots equally leaving the same high and low spots, but with more wood removed.
With the lathe off, sand with the wood grain in the particular areas that have high spots. I usually start with 120 grit sandpaper and see if that removes the tool marks. If it does not, I’ll drop down and start with 80 grit.
Use the same philosophy as the other techniques, just focus on reducing the high spots and tool marks. As soon as the high spots are reduced, work through the different sandpaper grits as described in the sanding guide and a smooth surface will quickly appear.
Getting from your first “perfect” bowl to your first genuinely smooth surfaced bowl will not happen instantly. It will take time and many bowls as you learn to diagnose and remedy each particular issue and tool mark that comes up.
Patience, skill development, awareness, and knowledge will all merge to form beautiful tool-mark-free bowls. Hopefully, the tips and tricks listed here will help you along your perfect bowl journey.
– For details of equipment mentioned in this article see my Recommended Equipment Guide.
Thanks and Happy Turning!