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Thread: shear scraper
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3rd November 2009, 10:17 AM #31GOLD MEMBER
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Thanks Neil. I surmise from the comparison with "horizontal" in the next sentence that you are talking of the 45 degrees tilt as defining the "angle". Did I understand correctly?
If this is so, you indeed confirm in better words what I was saying, I apologise for my poor expression. When I say that producing a shaving defeats the purpose of the technique, you say that the result would be poorer and not a good use of the tool.
Let's see if I can express myself better. The purpose of "shear scraping" is to achieve the best possible finish. My submission is that tilting the tool 45 degrees contributes to the purpose but does not in itself achieve it. This tilt contributes in two ways: helping to cut the grain at an intermediate angle between with and across the grain and helping to hit the surface of the wood in the same way a cabinet maker's scraper hits a flat surface. The best possible finish, and therefore the definition of the technique, is achieved when both aims are pursued.
Nothwithstanding your modesty, Neil, you have a very good standing in the turning fraternity and I am happy to include you among the gurus. I am sure that by observation you will be able to confirm or deny whether indeed the best result is achieved, all else being equal, when "the top surface of the scraper [is pulled] to the surface of the wood at the appropriate angle (acute in the direction of pulling, obtuse if one refers to the penetration of the wood)". If I am talking crap, please say so, I can take it.
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5th November 2009, 04:17 PM #32
Frank - rather than getting into wordsmithing a definition for shear scraping, let's adopt some existing descriptions from established sources. The following all describe what I understand to be shear scraping:
Richard Raffan, here.
This link has lots of good descriptions and tool info by Steven Russell
A collection of descriptions (by the Sydney Woodturners), here
Hope that helps
.....Stay sharp and stay safe!
Neil
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5th November 2009, 05:20 PM #33Retired
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Neil,
I've been playing with scrapers for some time. Well, a long time.
If I do an Ellsworth sheer scraping cut with the tool layed over on its back, I still get ridges. Tiny ones that sandpaper removes almost immediately. But not a great off-the-tool finish.
I much prefer using a scraper flat on the tool rest (no burr, Tormek sharp).
Worked OK at Proserpine on Boree which is fairly hard. (Ken W. insisted I use his radical 45 degree bevel scraper, knowing full well that I was scared of it. stood up for me, until Ken explained his reasoning..... Buggers. )
Or am I doing something wrong?
I know Ellsworth is a fine turner and makes do with just one chisel with his grind. But why bother?
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5th November 2009, 11:19 PM #34GOLD MEMBER
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Sorry for my insistence on wordsmithing, Neil (professional syndrome, I am afraid) but you are nailing the problem with your own words. In my presumption, I want to find, or create if there is none, a definition. What the literature offers, as you say yourself, is descriptions. I want to explain why, not only how, it works. Richard Raffan's description and photo actually are the best so far to support my definition: he mentions pulling the upper surface of the blade towards the surface of the wood. The other descriptions are not very useful, I had already googled them in my earlier research, but none provides any contrary evidence.
Are you trying to tell me that you do not trust your power of observation?
BTW, seems that all the other gurus do not trust theirs either...
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7th November 2009, 11:55 AM #35
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7th November 2009, 12:14 PM #36
I must admit, that by the time I'm down to the scraping my attention is fully on the form and not the technique. More often than not, my eye is on the form on the opposite side of the pieces to where the tool is working. The visual, rather than the verbal, area of my brain is what is being fully exercised.
You are not likely to go too far wrong, Frank, if you adopt the Raffan description/definition. He has very few peers in combining both high level proficiency and very clear writing skills.
.....Stay sharp and stay safe!
Neil
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7th November 2009, 12:36 PM #37Hewer of wood
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FWIW this thread has had me looking closely at where the tear-out occurs on bowl outsides. On two species examined, it's not the end grain - it's close to it after the long grain passes.
This is clearly the point at which the fibres have least support from their fellows further up the surface. Put the tool edge at a shear scraping angle and support is increased by the good offices of fibres closer to the headstock on the same plane.
This is why some turners use eg. a forged spindle gouge with the cutting edge around vertical. The downside is prob. slightly messier long grain but this will quickly scrape or sand clean.Cheers, Ern
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7th November 2009, 01:45 PM #38Retired
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Neil, I do appreciate the long advice / lesson. I type faster than most (the opposite for me when turning). 60 words a minute isn't too bad for a 50 year old???? So I do appreciate your efforts. And all the encouragement given here FOC.
I think I am doing the sheer scraping right. Or so tells me. When I say the tool is "on its back", I probably should have described it as you did. Handle down, flute closed, almost to the point of touching both sides of the tool. Almost. Safe apparently.
As the Ellsworth DVD shows, you can cut up or downhill as the cut is so fine. Dunno whether he's tried it on Boree though.
As for your 15 degree scrapers...... Politely, stick it, Neil. Maybe in 5 years time..... I've got a Ken W 45 degree one sitting out in the shed and I haven't put in anywhere near wood.....
I truly don't know what all this fuss is about re: time and using only one tool. I wander around the shed at my leisure - no production turning pressure - and lope over to the Tormek and sharpen a chisel (10 or more steps, not the recommended 5). For me, that's what it's all about. Turning time should not be about the money - unless, of course, you need it.
I haven't got my turning area ideal, nor the other parts of the shed either for that matter. Plenty of room for another lathe or two (still tossing up between a VL200 short bed and a "modified" shorter-bed 750 Stubby - Jim C. HELP!!!)
Thanks, again, Neil. Most, if not all, of the Mexicans reckon you give great advice.
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7th November 2009, 03:57 PM #39
Agreed, Ern, 'end-grain' was just my shorthand way of saying the tear-out prone area. In my experience it's the transition area just after the end grain begins to become long grain that is the prone area. As you say, this is where the fibres are least supported.
.....Stay sharp and stay safe!
Neil
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