Watching some of Richard Raffan's videos I noticed he has his scrapers at 45 degrees and uses them pretty aggresively. I've always sharpened my standard scrapers at about 70 degrees. Wondering what others are doing and thoughts?
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Scraper bevel angle.
- Thread starter Tom McDonnell
- Start date
john lucas
AAW Forum Expert
I use 45 degrees for 2 reasons. O. Is it seems to raise a good burr. Not necessarily a stronger burr just one that's easier to raise. Second is the easy way of raising the burr. My too is ground at 45 degrees on both sides. So I flip the tool over and grind off the old burr. Then flip the tool and grind a new burr. Works for me but I use a scraper only to refine a surface.
I wonder why most turners measure their scraper angle from the top instead of the bottom of the tool steel......?
It really makes little difference how it's measured, but to grind a bur on the scraper, it's the bottom edge that indexes to the platform......therefore the bottom edge should be the key to determining the angle of a scraper grind. Would it not?
Anyway, my scrapers are all about 75° when measured from the top edge, or about 105° if measured from the bottom edge.
This makes for a more robust bur, whether it be a ground bur, or a manually raised bur. Either way, I feel the bur is longer lasting, although more pressure is needed to raise the manually raised bur, and slower swing times at the grinder is necessary to raise a substantial ground bur. (I note here that none of my scrapers are ground straight across at the cutting edge......even those that appear to be straight have an almost imperceptible curve to them. This is because IMO they are more manageable in use when ground to a curve vs an absolute straight across grind.)
@Tom McDonnell
To my thinking, your grind at 70° is very usable, and there is no difference in actual performance between the bur you are getting when you compare it to the Raffan 45° scraper. The only real distinguishable difference is the longevity of the bur, and the mechanics of how it's attained.
I invite you to do some practical experimentation and verify the information I'm suggesting......and see for yourself!
=o=
It really makes little difference how it's measured, but to grind a bur on the scraper, it's the bottom edge that indexes to the platform......therefore the bottom edge should be the key to determining the angle of a scraper grind. Would it not?
Anyway, my scrapers are all about 75° when measured from the top edge, or about 105° if measured from the bottom edge.
This makes for a more robust bur, whether it be a ground bur, or a manually raised bur. Either way, I feel the bur is longer lasting, although more pressure is needed to raise the manually raised bur, and slower swing times at the grinder is necessary to raise a substantial ground bur. (I note here that none of my scrapers are ground straight across at the cutting edge......even those that appear to be straight have an almost imperceptible curve to them. This is because IMO they are more manageable in use when ground to a curve vs an absolute straight across grind.)
@Tom McDonnell
To my thinking, your grind at 70° is very usable, and there is no difference in actual performance between the bur you are getting when you compare it to the Raffan 45° scraper. The only real distinguishable difference is the longevity of the bur, and the mechanics of how it's attained.
I invite you to do some practical experimentation and verify the information I'm suggesting......and see for yourself!
=o=
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79 Degrees.
In 20 years of symposia and demos watching the best of the best once again I repeat that the number of times I heard and saw a pro using a scraper and say that the burr only last seconds but then he uses it for minutes then puts it down and later picks it back up and uses it more. The burr is over rated! I have a scraper by my lathe that hasn't been near a grinder for at least a year or two. When I need it I pick it up and use it and it still does the same job, its only taking off a thou or two. What is the angle? I have no idea it just has one angle so it is always pointed down from the tool rest and that angle probably changes a degree or two in use. When it quits leaving a surface I don't like I'll sharpen it again.
Measuring tool angles can be confusing. I prefer to specify the included angle. Most can understand that 90° won’t cut (or at least very much) and can appreciate the smaller the included angle, the sharper it as - although it may not hold an edge as long. The included angle concept works with both standard and negative rake scrapers. There are several gauges on the market.
I used to use anything under about 80° but have since gone a lot lower. I just checked one of mine with one of my angle finders and it’s at 65°.
Reading others comments, 45° sounds very acute for a scraper. I’ll give it a try at some point.
I now though remove the grinder burr on my scrapers and hone the edge. I then press a burr on it with my home made version of the Veritas Burnisher for Woodturners. I just bought the 10° carbide pin and made the rest. I’ve found it a game changer if you can hone the edge first. I use an 800g belt on my belt grinder.
I have my scrapers all at about 65 degrees, which is at 70 on my robo rest. This is how my scrapers all came from the stores. Tomislav has his at 45 degrees, his turning channel is excellent by the way... He seems to get much cleaner surfaces with his scrapers than I do with mine. May have to try a 45 degree scraper eventually, if I remember....
As for burrs, the grinder burr is excellent for heavy roughing cuts on bowls. Not really worth burnishing. For shear scraping, then a burnished burr seems to work better. I can hog out a 12 inch bowl with one sharpening. With my Big Ugly tool, I can rough out for half a day. That is because of the tantung on it. Stellite is another good metal for that.
robo hippy
As for burrs, the grinder burr is excellent for heavy roughing cuts on bowls. Not really worth burnishing. For shear scraping, then a burnished burr seems to work better. I can hog out a 12 inch bowl with one sharpening. With my Big Ugly tool, I can rough out for half a day. That is because of the tantung on it. Stellite is another good metal for that.
robo hippy
Anything less than 90" will work. A smaller "included" angle on both standard and NRS gives a little more clearance below the edge for situations like scraping the inside of a bowl. I have some close to 70 and some a little less than 90. They all work.
BTW, there are different paths toward raising the burr. I don't use the grinder burr but always remove it and burnish a burr. The type of steel can make a difference - I use mostly Thompson 10V steel. Long ago I used the Veritas bench burnisher but now use only hand burnishers - it' great for monster conventional scrapers - then moved to hand-held burnishers. For several reasons my favorite now is the french-made Arno.
JKJ
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I’ve used a burnished scraper for stock removal and it works very well. As for “not worth it”, it surely is because the burr lasts much longer than one straight off the grinder, and you can go back to the burnisher a couple of times before needing to go back to the grinder. I’m expecting my scrapers to last a whole lot longer. 😉
Quote fail, apologies.
As Robo notes both Richard R and Tomoslav seem to get good surfaces from the way they use their scrapers. I do use a burnished burr and shear scrape for a finish but if when I use a scraper like they do....torn grain and lots of sanding.
As Robo notes both Richard R and Tomoslav seem to get good surfaces from the way they use their scrapers. I do use a burnished burr and shear scrape for a finish but if when I use a scraper like they do....torn grain and lots of sanding.