Using round nosed scraper at sharp angle ?

[Brice Rogers]

I was finish turning a rock hard Ca. Live Oak platter using a freshly sharpened round-nose scraper with a burr. Although I was getting nice fluffy or wispy shavings, I was still getting a little tear out and some minor catches. So I tried rotating the scraper as it was introduced - - maybe at an angle between 45 and 75 degrees. I was pleasant surprised that it just about eliminated all of the catches and tear out. But holding that angle was a little tricky and I had some tool marks.

Is this kind of a standard thing to do (rotate scraper) when addressing tearout and catches??

BTW, sanding the live oak is a PITA because of its hardness. Lots and lots of sanding - - not a lot of sawdust or removal of tool marks. Kind of like trying to sand a metal file to remove the teeth.

[Curtis Myers]

A negative rake scraper will have the same effect and fine shavings without risk and the excitement as your round nose held at an angle. The burr is everything. For me, a burr put on by a barnishing tool lasts much longer then coming off the grinder. Like upto 10 times longer.

[daryl moses]

You have discovered how to "shear scrape" holding the scraper at an angle will indeed give a cleaner finish cut.

[John Grace]

Brice...As Daryl has pointed out, this is the 'shear scrape' technique and can be a useful technique between final turning and sanding. I found using a scraper in on an angle a difficult tool to control due to being 'on edge' as it were. You may want to consider checking out the video by Robo Hippy on Mike Thompson's fluteless gouge. It's basically a scraper tool with a rounded bottom which I find easier to control on the tool rest. Packard Woodworks also sells something similar in their Taylor woodturning tools section, that one is called the Tracey Owens Finishing tool. But as others have already touched upon, the key...regardless of chosen tool, is razor sharpness and light touches.

[Mark Greenbaum]

I think as the scraper is presented at an angle to the surface (with blade still perpendicular to the plane of the wood), it is acting as a shear scraper. I have used the wing of my larger bowl gouge with a 45 degree angle and handle very low to shear scrape surfaces, and it gets a pretty good surface ready for fine sanding. Experts chime in and correct me if I am wrong, please.

[John K Jordan]

Dry or wet wood?

Nothing I know will work better than a "whisper" cut with a razor sharp gouge, but it does take some control. I control it the best I can then remove any remaining ripples/tool marks in bowls and platters with a curved hand-held cabinet scraper with the lathe off.

But as Curtis mentioned, a negative rake scraper might work better than the round nose. I reground most of my scrapers for this. Here are a few, one made from a Thompson skew. These are especially good for the concave curved inside of a bowl or rim of a platter. A flat scraper works better on a convex surface.

344610

I also use a Hunter Hercules carbide tool for this but the small diameter bit requires a steady hand.

As also mentioned, a freshly sharpened ground back wing of a bowl or other gouge makes a wonderful shear scraper, both inside or outside. It's kind of like an extreme negative rake scraper. Never a catch, removes the finest shavings, generally controls tearout.

I don't know if you did this, but when I see tearout the first thing I do is apply shellac or lacquer-based sanding sealer, make a cut or scrape, then reapply and repeat as needed. Turning wet with sealer (a mess) or oil also works well in some cases. One world class expert told me to spritz with water from a spray bottle.

JKJ

[Brice Rogers]

thanks to all for your suggestions and ideas.

[Reed Gray]

As Daryl said, you have discovered shear scraping, which means you are not rubbing the bevel, and the cutting edge is at an angle to the rotation of the wood. This differs in a couple of ways from a scraping cut. Most of the time a scraping cut is the scraper flat on the tool rest so the cutting edge is at 90 degrees to the spin of the wood. Scraping cuts will always leave some tear out when done on bowl grain type cuts, but can cut amazingly clean on end grain because of how the fiber lines up. I never try to get a finish cut with a scraping cut. If you are sweeping back and forth across the bottom of a platter or bowl, it does a fair job, but still wants to pull rather than cut. Here, a negative rake scraper will do a better job with less tendency to catch or grab. The thing with the shear scrape, since it is at an angle it does a much better job of gently lifting the wood off as you cut rather than pulling it up. Most scrapers have square edges on the bottoms which makes it difficult to sweep across the tool rest. Rounding the bottom edge off to a 1/4 round edge like most skew chisels have really helps it slide along, and of course a hardened drill rod tool rest is better. I prefer a ) nose to a half round profile for my inside the bowl shear scrapes, and a swept back one for the outsides. With the ) or U nose, make sure to drop the handle, and cut with only the lower half of the tool. If you hold it more level, and then start cutting at center height or above, the tool is unbalanced and will catch. Most of the time I use the burr straight from the 180 grit CBN wheel. I have recently discovered that the burr from a 600 grit CBN wheel makes for a better finish cut burr, but is not good for heavy roughing. You can hand hone a burr on, or even hone and burnish.

I am still working with discovering the negative rake scrapers (NRS). They are not as grabby as a standard scraper, but still 'pull' at the fiber. On harder woods they work better than a standard scraper for finish cuts. There is still minimal tear out, but much less than standard scrapers. I am thinking that the shear scrape works at least as well as a NRS, but is a bit more difficult to remove ripples with since the flat on the tool rest has a broader/more surface area cutting edge than the more vertical edge.

robo hippy

[Justin Stephen]

What you described is also how the Sorby shear scraper works. It is basically a rounded "teardrop" scraper you hold on angle. It works well but I use it infrequently as it is a pain in the butt to sharpen.

[Chris Gunsolley]

I was finish turning a rock hard Ca. Live Oak platter using a freshly sharpened round-nose scraper with a burr. Although I was getting nice fluffy or wispy shavings, I was still getting a little tear out and some minor catches. So I tried rotating the scraper as it was introduced - - maybe at an angle between 45 and 75 degrees. I was pleasant surprised that it just about eliminated all of the catches and tear out. But holding that angle was a little tricky and I had some tool marks.

Is this kind of a standard thing to do (rotate scraper) when addressing tearout and catches??

BTW, sanding the live oak is a PITA because of its hardness. Lots and lots of sanding - - not a lot of sawdust or removal of tool marks. Kind of like trying to sand a metal file to remove the teeth.

Brice, personally, I turn my bowls exclusively with scrapers, and one day I had the same revelation. I thought of it as shear scraping with a round nose scraper and I see many others in this thread have noted that. The technique you describe is my preferred technique for finishing cuts, and I think it works really well. If working with soft wood, I'll add mineral oil prior to making the finishing cuts and that helps further in getting the cleanest possible cut when working with those types of woods.

You can use the same technique with dome-ended and flat-ended scrapers on the outside of a bowl, but you're more likely to get a catch with those, so I wouldn't recommend it. I think the round nose scraper works best for this, and that's the one I'd stick with for it.

[Stan Smith]

Hi Brice. I live over 600 mi. north of you and haven't tried to turn any oak. Experienced turners have told me that they prefer other wood that's easier to turn. We have valley, scrub, black, blue, mountain, and live oak hear. A couple of those names may refer to the same kind of oak. One thing that I heard is that live oak was used for ship ribs in the old days. The shipwright would go into the forest and pick out specific branches for various size ribs. For all I know, this could be a legend though. :)

[Robert Henrickson]

One thing that I heard is that live oak was used for ship ribs in the old days. The shipwright would go into the forest and pick out specific branches for various size ribs. For all I know, this could be a legend though. :)

It's true. Live oak was used for the USS Constitution (Old Ironsides).

[Bob Bouis]

A second endorsement for the fluteless gouge (and the video...). It's a great tool, more rigid than a small scraper and easier to use than a big one. You can even make bevel-rubbing cuts with it.