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Shear scraping with rounded bottom tools.......

Odie

Odie

Panning for Montana gold, with Betsy, the mule!
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When I first saw this diagram, I thought to myself this makes perfect sense......until, I realized this is a two dimensional diagram, with a tool used strictly perpendicular to the cut, being applied to a three dimensional application. In practical application, a standard scraper can be presented to the wood and the cut can be just about anywhere along the cutting edge, depending on how it's presented. I would think this would apply to either a standard flat bottom scraper, or a rounded one.......

Just how valuable this concept is, is up for speculation. I wouldn't know for sure, because I haven't spent the money and tried these rounded scrapers......so, everything is strictly speculation from my point of view.

If the purpose is to "remove wood", I can see there may be a valid reason for the rounded shaft. From a safety perspective......it just may be a good thing for "catch" prevention. However, now we are mixing purposes, because normally one would keep a standard scraper flat to the tool rest, if removing wood is the purpose. Shear scraping has another purpose, and that is not to remove wood, but to create as fine a surface as possible before sanding. In the case of the latter, the shearing action is done with such a light touch, that I would question the necessity for rounded tools at all.

Anyway, I'll leave it there, and let anyone who wants to comment on these things, to register their input now........

......and, thanx! 😀

ooc
 

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I think I'll make one and try it out. Theory seems ok but I want to see what the learning curve is before I spend much money on a new tool. Beside I need something to try out my belt grinder on. I'll let you know.
Bill
 
Bill,
Use a handle - with a 3/4" dia. piece of drill rod for a shaft - use your grinder to make a flat spot on the end of the drill rod - drill and tap a hole for a 10-32 bolt in the middle of the flat - When you buy your drill rod from Enco, purchase an 18" piece of 1/8" thick x 1 1/4" flat stock. Cut and make a small cutter from the flat stock. - drill a hole for the 10-32 bolt - do a quick heat treatment and you are all set - You will only spend about $30 and have enough for about 3 tools (with the drill rod cut at 12" long). And have a bunch of flat stock to make many more tips.

For a handle, I use my Stewart arm brace. Easy to control. If you have the Stewart "Hooker" tool, you do not need to make a drill rod shaft. With the bend of the hooker tool over the tool rest you can make the shear scraping cut on the inside of a bowl.
Hugh
 
I can see where it makes a certain amount of sense. Sorby has one that works like this, it also has a flat side for regular scraping.
There are also tools with broad flat sides, tilted for shear scraping.

All give you probably a more certain contact of the tool on the rest
 
Wonderful stuff. I'm not concerned, because I use broad sweep gouge where the bevel supports as I shear cut. As to whether a cylinder is more unstable on a rest than an edge on a scraper, it would seem to me that both make equal contact. Edge or tangent, it's only a line.

http://i35.photobucket.com/albums/d160/GoodOnesGone/Forged-in-Use.jpg

Why scrape if you don't have to?
 
There is a traditional tool that the Oregon Coast Myrtle wood turners use that is called 'the Big Ugly' tool. It is tantung steel that is sliver soldered onto a piece or 3/4 inch bar stock. Think of one of the carbide tipped tools that you can sharpen. On the square bar stock, it is a bit top heavy. I want to make some for experimentation, and would put the cutter on a piece of round bar stock where it is cut half round to mount the cutter/tantung.

As for the standard scrapers, I wouldn't bother with the round back, but I do round over the square corners on the bar because for the finish shear cuts, I have it up on edge, and it is more stable on a rounded edge than a square one, and it moves across the tool rest with a lot less friction. I have a couple of skews that came this way.

robo hippy
 
I call it a fluteless gouge but the idea of a round nose shearing the wood works very well. IMO The tool very well to almost a perfect cut that doesn't need sanding... the down fall is you need tool control so the finish cut isn't wavey... I could get about 3 inches before it goes south.
 
Doug Thompson said:
I call it a fluteless gouge but the idea of a round nose shearing the wood works very well. IMO The tool very well to almost a perfect cut that doesn't need sanding... the down fall is you need tool control so the finish cut isn't wavey... I could get about 3 inches before it goes south.
Click to expand...

Howdy, Doug.......

Yes, I guess a "fluteless gouge" is a good way to visualize how the cutting edge is applied....in a micro-sense!

....But, as you say, it's "tool control" that makes it all happen. There is more to it than just the physical aspects of the steel to wood. For one, everything must be done to insure the tool glides on the tool rest with the minimum of friction, or bumps.....and this means paying attention to the smoothness of both the bottom surface, and bottom corners of the scraper.....as well as the surface of your tool rest.

It doesn't stop there, because an important element of the equation is how your arms, hands, and entire body flows with the cut. This part is major.....and, only can come with practice, and experience. There are times when it helps to brace your body, or knees on the lathe itself, but this isn't always the case. You may increase stability by only "flowing" with your knees or hips/up, but when you do, your total arc of movement is smaller. I remember a video made by John Jordan back in the 90's, where he was talking about the importance of "wide stance"......and, by actively paying attention to this, it has helped me improve the slow smooth flowing motion that is necessary to make a scraper do it's best.......

ooc
 
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Yep, round(ed) noses are a good thing. They control the pressure required to enter wood by confining it to a small area. Think tangent. Any tool with a rounded sharpened portion takes advantage of this reality. The other reality for everyone is that higher-angle cutting requires more pressure than lower angle(s) if available. Both will do the job, as the owners of York pitch and low angle smoothers will attest.

What turners commonly refer to as scraping is really high angle cutting, as opposed to what cabinet workers refer to as scraping, where the curl makes the operation into a low-angle. To get the same angular relationship on a turning is extremely difficult, as those who have used cabinet scrapers can verify. It would almost require the handle to lead the nose.

So we're stuck with a compromise of sorts where we can effectively lower the cutting angle by shearing, rather than leaving broadside into the rotation. Here's another candidate in the how best to control the tool category from Dave Hout. http://www.packardwoodworks.com/Mer...ore_Code=packard&Category_Code=tools-crn-hout Uses the flat spot on the bottom to support. Better than either cylindrical or square edge, but, where available, still higher than slipping a long-bevel tool underneath and slitting your way through.
 
I shear scrape on convex and flat shapes with two tools

the Ellsworth ground gouge and an Al Stirt ground square nosed scraper( it has a slight radius.) These tools both have a radius.
I use them with the bevel 90 degree to the wood and the long cutting edge on the tool about 45 degrees to the rotation of the wood.

These tools have the small contact point which cuts well and you can shift to a sharp spot on the tool as you work. These tools are also fair curves nicely avoiding the wavy surface Doug mentioned.

The tool shown in the diagram looks a lot like the Sorby Spinlde master.

A few years ago I experimented with using a shallow gouge ground upside down as a scraper. Put the flute down on a platform an grind the tool at about an 80 degree angle. The tool is used either flat on the tool rest with flute down or at a 45 degree angle. the curved scraping edge leaves a clean surface. I've practiced enough to get a sandable (220) surface with an Ellsworth gouge most of the time. For really troublesome wood with wild grain I pull out the Stirt scraper and then my hair.

if you ground the tool shown with the flat edge on the bottom it might give better results.

-al
 
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someone years ago made what appears to be an upside down spindle gouge. Think of a flattened U turned up side down. Then it is sharpened like a scraper with the bevel down and top edge has a burr. You cut with either the right or left side. This gives you a shear cut but you have constant support on the tool rest so I can't imagine a catch. I've always wanted to make one but never have. Maybe this spring while the weather is nice I can get out the forge and finally build one.
 
Joaz Hill. IIRC he used it to scrape progressively deeper by leading with the cuticle end of the fingernail, following deeper to the rounded nose. Added dimension in that the rise in the tool (opposite the flute) effectively skewed rearward, doing the same progressive deepening.

It's the same principle as the cut I do with the flute of the gouge away from the wood. Tilt and skew. Nothing new. It's the way everything was done before we got cylindrical.

http://i35.photobucket.com/albums/d160/GoodOnesGone/Peeling-Outside.jpg This one's deep enough to show how the opposite side of the nose meets the wood.
 
Interesting thing about the Craft Supply video that Al posted. You can but the fancy tools shown, or like me, you can make all of those cuts with standard inside, outside, and round nosed scrapers. The diagram shows the tool contacting the wood at center line. Duh, that is dangerous. Use a round nose scraper, and work on the lower 1/4 of the tool. Safe and simple. Round nose will work either way, and the inside or outside tools are more specialized.

robo hippy
 
one tool away from greatness

I heard Don Geiger explain that he bought a particular tool when he was "one tool away from Greatness."

That rings true for lots of us until we figure out that proper use of a 1/2 side-ground bowl gouge and a 3/8 spindle gouge and you can turn any outside shape and end with a surface that needs little sanding.

It is tempting to buy a tool to solve a problem rather than spend the time learning to use the tools we have.
It is rare ti find a tool that doesn't work.
It is also rare to find a new one that is must have.
Tool makers have such an easy time with us.

happy turning
Al
 
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I made one out of a piece of O1. Useless as a fluteless gouge or spindle master (vs. conventional tooling), but it does make a very nice small scaper that I use to clean up the inside of small end grain boxes.

I pull a micro burr with a diamond hone and it is awesome...

S
 
Steven Antonucci said:
I made one out of a piece of O1. Useless as a fluteless gouge or spindle master (vs. conventional tooling), but it does make a very nice small scaper that I use to clean up the inside of small end grain boxes.

I pull a micro burr with a diamond hone and it is awesome...

S
Click to expand...

What I have found with O1 is that unless you heat treat and temper, the burr doesn't last long enough to see if it worked.

I guess if the nose of the tool is rounded also, then there is only a little contact point to catch and roll the tool, so it would be less likely to catch. Given an opportunity, I can still make it catch. I'm good at that.
I did design a tool that was square and had a diagonal on it, like a beginners Jordan sheer scraper. No holding the tool at a specific angle, just lay it flat and sweep. Problem with a square tool, you would need to resharpen it upside down to go the other way.
 
Steve Worcester said:
...Problem with a square tool, you would need to resharpen it upside down to go the other way.
Click to expand...

OK, I was doing good until then, but now I am confused. If you have a square tool ground diagonally and you are sweeping left-to-right, and you wanted to sweep right-to-left, couldn't you just rotate the tool 90 degrees counter-clockwise? Any burr you had would still be up.
 
Steve Worcester said:
What I have found with O1 is that unless you heat treat and temper, the burr doesn't last long enough to see if it worked.

I guess if the nose of the tool is rounded also, then there is only a little contact point to catch and roll the tool, so it would be less likely to catch. Given an opportunity, I can still make it catch. I'm good at that.
I did design a tool that was square and had a diagonal on it, like a beginners Jordan sheer scraper. No holding the tool at a specific angle, just lay it flat and sweep. Problem with a square tool, you would need to resharpen it upside down to go the other way.
Click to expand...

I case harden mine in mineral oil. Heat with a torch and dunk. I never temper it, since I'm not hardening all of the way through. It takes a pretty good edge, and when I wear away the hardened part, I just reheat it and do it again. I only use it on small boxes, so it lasts "long enough" and is easily renewed with a 1200 G diamond hone. Rolled over to about 10 o'clock, it cannot catch if you swing the handle (it's a negative rake scraper!)

Steve
 
Oh, I do love the smell of hot steel in the morning! I love new tools but I have found I really only need about 6 or 7 and a "bit" of practice...well that's no fun, what about, he who dies with the most...? I use a small forge 12 x 6 that gets to about 2600 deg in 8-10 min. I use all kinds of steel including cpm 10v from Crucible (only for small stuff). The most fun is just playing, some tools work others are a total waste of time..for me, because what works for some will not work for others. I love hook tools I can clean out an end grain box in no time. However, I have friends who are great artisan that hate them. So it really come down to finding, using and practicing. I really like practicing. Besides our customers could care less how you get to the end product, just so long as it's pretty. Well that's what my wife says anyway. :cool2:
 
John Lawson said:
OK, I was doing good until then, but now I am confused. If you have a square tool ground diagonally and you are sweeping left-to-right, and you wanted to sweep right-to-left, couldn't you just rotate the tool 90 degrees counter-clockwise? Any burr you had would still be up.
Click to expand...

Uhmm, maybe. Yes.
 
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