Shear Scraping to the rescue. Do pesky tool marks plague your final turned bowl surfaces? Well, this article is going to be a treat for you!
The shear-scraping bowl gouge technique is probably, initially, the most awkward and yet useful wood bowl turning move ever conceived. At first, the shear scrape feels 100% wrong, but wait until you see what it can do.
Why even use a shear scrape? The
Bowl Gouge Shear Scraping
When you hear the term shear scraping, you might be thinking of a traditional scraping tool like a round nose scraper. Yes, traditional scrapers can make a shear scrape, but we’re going to do it with a bowl gouge.
The swept back wings of a bowl gouge are multi-functional as cutting edges, but when flipped over they become scrapers.
Shear scraping is a surface refining bowl gouge technique and not a central shaping or roughing move. Don’t try to shear scrape a bowl until it has been roughed out and the final shape is established using more traditional bowl gouge techniques like the push and pull cuts.
This article is all about making shear scraping cuts with a bowl gouge. If you’d like to see how to make a shear scrape with a round nose scraper, read this article too.
Learning To Shear Scrape
Shear scraping does not come easy, at least not for me. I remember trying to pick up this skill and getting frustrated because I just couldn’t get it to work.
A fellow turner, Tom, would come by and casually say, “here, like this,” as he would position my bowl gouge and make clean shear scrapes effortlessly.
I guess that did give me the confidence that at least my tool was capable of making a shear scrape, even if I wasn’t yet.
Practice and persistence are definitely critical factors in learning to shear scrape.
Over the last few hundred bowls or so, I’ve scrutinized and analyzed how a shear scrape cut works, and in this article, I’m going to do my best to give you a head start on learning to shear scrape.
Shear Scrape Warnings
Before we go much further, we need to make a few things clear, for safety’s sake.
Never place the bowl gouge at the angle we will be discussing, while the flute is positioned like a traditional push cut. If the gouge contacts the bowl at this angle an amazingly nasty catch may occur, and we don’t want that to happen.
Only approach the bowl surface with the flute “closed” which means the flute is completely facing the bowl surface. You should not be able to see the bowl gouge flute at all.
The second warning is to only use the shear scraping technique on the bowl exterior, never on the interior of a bowl. Yes, technically if a bowl has a wide open flat rim, it could be possible to shear scrape a portion of the inside. But for now, stay out of the bowl interior.
Starting From Scratch
Remember when you made your first cut with a bowl gouge? Remember that strange, scary feeling when you felt the force of the bowl blank engage with the tool?
Over time that initial bowl gouge cut was replaced with new smoother cuts and you learned and acquired all the motor/muscle and hand/eye coordination skills needed to make those cuts with little effort.
The skills used to make traditional bowl gouge pushing and pulling cuts are super necessary to know, but they do not apply to the shear scrape.
To learn the shear scrape means to
Learn from my mistake.
A mistake I made while learning to shear scrape was to think that the shear scrape is similar to a push cut, and I only needed to make a few little modifications. This thinking is probably what caused a short time to pass before I got the shear scrape where I required.
Unique Bowl Gouge Technique
Think of the shear scrape as a one-of-a-kind bowl gouge technique, unlike anything you currently know.
The skill of making a push or pull cut is most likely almost second nature to you now.
Try to think of the shear scrape like the first time you placed a bowl gouge in the rotating path of a bowl blank. Learning to shear scrape is an entirely new skill.
Just like the various tools you possess, the shear scrape will become a completely different cutting technique you will own and be able to use when it’s needed.
Before we can get into the steps for making a shear scrape, we need to talk about the tool we will be using, a bowl gouge.
2. Bowl Gouge Shape
There are as many possible shapes for the end of a bowl gouge as there are people turning bowls. And in case you’re wondering, there is no right bowl gouge angle. Take a moment and read this article about bowl gouge angles to better understand this issue.
When it comes to shear scraping, there are bowl gouge angles that work better than others. Short and steep bowl gouges offer a small side wing and aren’t usually used for shear scraping.
The ideal bowl gouge tip used for shear scraping has long swept-back wings. The wings of the bowl gouge are what will be doing the shear scraping.
Straight or slightly upward convexly curved side wings work best for shear scraping. Wings that are concave or too convex will offer problems.
If the side wings of the bowl gouge are concave, there won’t be a straight enough area to shear the bowl surface, and the point made at the back of the wing will most likely dig into the bowl surface.
On the other hand, if the bowl gouge wings are too convex, only a small point at the apex of the convex curve will be doing any scraping. Instead of scraping an area, this type of wing will only scrape a thin line and most likely leave new tool marks.
I use a bowl gouge angle of about 55° with long swept-back wings. To learn exactly how I shape and sharpen this bowl gouge, see this article which shares how to make this grind angle.
3. Shear Scrape Tool Rest Position
When we make a traditional push cut on a bowl, we usually position the tool rest close and parallel to the surface to be cut. When we shear scrape, there’s a slightly different way to adjust the tool rest.
The tool rest needs to support the bowl gouge not near the cutting tip, like a push or pull cut, but instead further down the shaft of the tool.
Because the bowl gouge will not be taking much force during the shear scraping process, we don’t need the tool rest positioned as we do most every other time we make a cut.
Think of the tool rest more as a guide or aid that will be keeping the tool in line for us. The tool rest assures we keep the bowl gouge where it is needed.
And because the bowl gouge is going to be presented at a steep angle with the cutting action up higher away from the tool rest, we need to angle the tool rest at about a 90-degree angle to the bowl gouge.
Unlike a traditional push cut, we will not be able to quickly work around the entire surface of the bowl without moving the tool rest as we progress. The tool rest will need to be moved frequently to work in each area around the bowl surface.
4. Shear Scrape Tool Angle
At first, the angle of the bowl gouge was the most challenging concept for me to grasp. By thinking I was only slightly modifying the push cut, initially, I just wanted to drop the handle a little bit. That was incorrect.
The angle of the bowl gouge for a shear scrape is pointing up. The handle needs to be positioned against your thigh. Not your belt line or the side of your ribs, as I tried at first, instead place the handle at your thigh.
Yes, at first, it seems completely wrong holding a bowl gouge in this position.
If you were to apply a degree to the angle of the bowl gouge, with straight up and down being zero degrees, I would guess the gouge is somewhere between 40 to 50 degrees while making a shear scrape.
5. Shear Scrape Cutting Head Position
The cutting head of the bowl gouge needs to be facing the surface of the bowl while making a shear scrape. The flute is completely closed and facing inward towards the bowl.
This is not a bevel supported cut. A shear scrape is a scrape created by the underside wing top edge only.
Both wings of the bowl gouge can touch the bowl without any problem. However, it is the bottom or underside wing that will do the scraping. The top wing needs to be lifted just a bit off the surface.
A common misbelief is that if the top, or lead wing contacts the surface, there will be a catch, but that’s not the case. The best thing to do is to make contact with both wings to prove to yourself that you won’t get a catch when the first wing touches.
6. Bowl Gouge Height
The bowl gouge head needs to be well above the center line so that only the underlying wing is making contact with the bowl surface.
If the gouge tip is too low, the curved nose of the bowl gouge might contact the bowl surface and cause a catch.
On the other hand, if the gouge is positioned too high, then the full wing might not be engaging the bowl surface. And the point where the side wing ends and blends into the bowl gouge shaft may rub and burnish the wood instead of scraping.
7. Switching Hands
To make the shear scrape even more different than a push cut your hands can be in opposite locations on the bowl gouge.
Because your thigh will be bracing the bowl gouge handle a bit, you can use either hand to maintain tool contact with the tool rest and the opposite hand can guide the scraping wing.
Depending on where on the bowl exterior you are performing a shear scrape, you can switch hands and even change scraping wings of the bowl gouge.
While working the right side of a bowl exterior, I may have my right hand at the top of the bowl gouge and my left hand guiding on the tool rest. In this position, I’m scraping with the right wing of the gouge.
As I work around to the bottom or headstock side of the bowl exterior, I can switch hands and guide along the tool rest with my right hand and manage the scrape with my left. In that configuration, I’m scraping with the left wing of the bowl gouge.
8. Shear Scrape Motions
What you are looking for, when making a shear scrape is the lower wing to engage and make a clean scrape against the bowl surface. Once a scrape begins, you can move the tool back and forth to work and shape or clean a particular area while maintaining the wing contact.
Keep the bowl gouge tip steady and use the tool rest as your guide. If the bowl gouge tip bounces away from the bowl apply a bit more pressure to hold it steady.
Unlike a push or pull cut, the shear scrape is essentially shaving fibers off the bowl surface. Because of the steep tool angle, only minimal resistance will occur when the tool engages, so catches are almost nonexistent.
There are really two things you can use the shear scrape to achieve, subtle bowl shape refinement and surface cleaning.
Refining Shape Shear Scrape
Refining the shape of the bowl may require a bit more aggressive shear scraping. However, since this is a steep angled scrape, the amount of material being removed will be minimal.
If the shape of the bowl needs significant adjustments, revert to a push or pull cut or possibly a scraping cut. See this article to understand the four main bowl gouges techniques better.
Making shape refining shear scrapes will require a bit more pressure against the scraping wing of the bowl gouge. The motion of the tool during a shear scrape can move forward or backward, and you can incorporate a slight inward and outward action as well.
Use your entire body since the tool handle is connected to your thigh. Move freely by bending your knees and shifting your weight from left to right to achieve fluid motion.
Cleaning Shear Scrape
If you are removing tool marks or cleaning up the bowl surface, you will be doing basically the same thing as above, but with more subtlety.
Think of shear scraping for cleaning the surface as shaving. It really is the same thing.
Light, gentle passes will create the most ideal finished surface. Try not to be too aggressive with cleaning shear scrape passes.
Stop the lathe and check your progress. If a high spot still exists, use a pencil to mark it and make it more visible. Then position the tool rest and bowl gouge so that you can best access and level the high spot.
9. Shear Scrape Confirmation Evidence
The best part about making a shear scrape is that there is a “green light” indicator when you do it correctly-shavings.
Even though this is a scraping technique, with a sharp bowl gouge, you will create shavings. And the cool thing is these shavings are like angel hair, super-fine and curly.
When you begin, if you are making more dust than shavings, that’s ok, it happens to all of us.
Move the bowl gouge to a slightly different angle, roll the flute closer to the bowl surface, or shift your body a bit one way or another.
When you are shear scraping, you will know it because you will be producing thin wispy shavings. Take note of your tool angle and position then repeat that move over and over.
Soon you will acquire the motor muscle memory to make a shear scraping cut whenever you like. And once you see how smooth the final finish can be, you will most likely use the shear scrape frequently.
Shear Scrape Summary
Yes, the shear scrape is an unusual and awkward technique at first. However, this weird technique added to your other wood bowl turning skill sets will make you a bowl turning superhero.
Give it time and lots of practice and shear scraping will become second nature. You’ll probably wonder how you got by without it for so long.
Shear scraping is a finishing move used on wood bowl exteriors that can leave the surface so smooth, sanding might not be required. And if you do decide to sand, you can most likely start out at 220 or even 320 grit as your first pass.
Shear scraping is not a beginner technique nor a natural skill to master quickly. Hopefully, this article lights your path a bit clearer and makes the art of shear scraping a little easier for you to learn.
Leave a comment below and share your experience with shear scraping.
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