Thread: Sheer scraper - sharpening angle?

Hi Danny,
I use scrapers like they are going out of fashion (a lot). Sharpening them has become second nature and I never check the angle when I sharpen them. Your question got me interested and I just went out and measured the angle on several of them. So, my sharpening angle varies between 32 degrees and 40 degrees (off 90 degrees). I turn a wide variety of timbers with this angle range from very hard woods to soft woods and it works fine for me.
I see in Mike Darlows book "the practice of woodturning" he uses a 20 degree angle.
I guess it just comes down to what works for you.

Robo Hippy has a youtube clip on sheer scrapers. Think he mentions his preferred angle but I found the clip well worth a look. I have had a couple of attempts at sheer scraping and have been using a regular scraper with a bevel angle of about 70 deg sharpened on 180 grit wheel to give a burr on the edge. With the tool presented at the right angle I was able to get those fine wispy shavings and take out much of the torn grain.

Tony

Al Stirt a US turner who demonstrated at the AWSA congress here in South Africa uses sheer scrapers a lot. A pdf of his angles (looks about 60/70 deg) is available on his website
Student Resources
He uses a diamong stone to remove the burr put up by grinding then puts a controlled one back with a carbide rod (similar to the burr on a cabinet scraper). It works very well
Richard

Originally Posted by artful bodger

Hi Danny,
I use scrapers like they are going out of fashion (a lot). Sharpening them has become second nature and I never check the angle when I sharpen them. Your question got me interested and I just went out and measured the angle on several of them. So, my sharpening angle varies between 32 degrees and 40 degrees (off 90 degrees). I turn a wide variety of timbers with this angle range from very hard woods to soft woods and it works fine for me.
I see in Mike Darlows book "the practice of woodturning" he uses a 20 degree angle.
I guess it just comes down to what works for you.

Interesting - I am also a bit of a scraper nut, and without measuring, my guess is mine would be in the same range (some with a bevel on top as well, but not all). Will try to check this afternoon and see!

Thanks all - that confirms my suspicions that a 'blunt' angle is likely the way to go, with careful attention paid to the burr. I will be playing around with some options, hopefully plenty of time for turning over the xmas/new year period!

Danny

BTW, going to try to remember to put some chisel pics up when I get handles on and some sharpening done - if anyone's interested and I don't get photos up over the next few weeks, remind me!

I recently posted my views on scraper angles in another thread, here.

Without getting too technical, the primary grind angle on a scraper is not as important as the 'burr' angle, ie if you leave or make a burr on your scrapers.

Burr durability depends on how much it has been hard burnished. The burr off an Alox wheel is likely to be fragile compared to one off a diamond or CBN wheel or plate. Adding the burr with a hard carbide burnishing rod also makes it more durable. Years ago I did some controlled tests to prove this to my own satisfaction. I reported those results here way back then, but probably lost with the changes to the forum software since then.

Makes sense to me! I am going to experiment with raising burrs while I'm playing with angles and scraper shapes (will have both round and square blanks).

Don't have a burnisher, but I'll try burrs off CBN wheels and diamond paddles.

Originally Posted by NeilS

I recently posted my views on scraper angles in another thread, here.

Without getting too technical, the primary grind angle on a scraper is not as important as the 'burr' angle, ie if you leave or make a burr on your scrapers.

Burr durability depends on how much it has been hard burnished. The burr off an Alox wheel is likely to be fragile compared to one off a diamond or CBN wheel or plate. Adding the burr with a hard carbide burnishing rod also makes it more durable. Years ago I did some controlled tests to prove this to my own satisfaction. I reported those results here way back then, but probably lost with the changes to the forum software since then.

Agreed, and the more you grind away from the 90' the more fragile the edge becomes. Its the burr that does the work, I grind mine around 85-90.

After seeing the sharp angles used by Richard Raffan and Vic Wood I started grinding mine to 45 degrees and find it works really well.

Josh, with your 45 degree chisels are you sheer scraping or normal (or both)?

Originally Posted by rtyuiop

Josh, with your 45 degree chisels are you sheer scraping or normal (or both)?

I use it for both but I haven't done much sheer scraping with it (or at all) so I can say how it compares to other angles

Haven't spent much time in the shop lately (too hot!) but I finally got some experimental sheer scrapers made and had a quick play around with them - these are what I was mucking around with:





My observations (all based on experience with an australian cedar bowl I was playing with):

Tried a very 'blunt' grind first -my normal scraper angle, ~30 degrees but done on both sides, so maybe a 120 degree angle in the end - could barely get it to cut, so went to ~45 degrees on both sides for a ~90 degree point, which was much more satisfactory.

Raising a burr with a burnisher (timberbits and their 15% off sale ended up being expensive!) was probably the single biggest factor I saw in how effectively they cut, outside of technique. Going to have to practice using the burnisher on a rounded tip tool though!

The round blank with a rounded tip chisel (the middle one in the photos) was by far my favourite. The square tips made things very dependent on tool rest height being exactly right, and the square blank meant I couldn't alter the angle easily. The round tip and round blank also meant I could 'tune in' angles vertically, horizontally, and how the chisel was rotated. I could also cheat with my sharpening, and if the burr had gone on one part of the blade, just start cutting with another area.

I do think the other shapes might be better suited to spindle work, but not sure if they would be superior in any way to my normal combination of a skew and some traditional scrapers.

So - long story short, I really like the combo of a burnisher and a round chisel with a rounded, 90 degree tip. Bear in mind this was all of a couple of hours playing around, and all on one bit of wood, so my current opinion might be completely wrong in other circumstances!

Cheers,

Danny

I've found that the steel quality makes a difference too.

Some of the ones I've made from cheaper tools are almost square at the bevel, while others of 'better' steel won't really cut until sharpened more acutely. Now that you mention burnishing - which I don't do - it seems obvious that the cheaper steel develops more of a burr off the wheel... they cut well for a while but quickly lose their edge.

FWIW, I also prefer a mildly rounded cutting edge on round stock. It gives you soooo much more control of the cut.

Originally Posted by Skew ChiDAMN!!

Some of the ones I've made from cheaper tools are almost square at the bevel, while others of 'better' steel won't really cut until sharpened more acutely. Now that you mention burnishing - which I don't do - it seems obvious that the cheaper steel develops more of a burr off the wheel... they cut well for a while but quickly lose their edge.

That makes sense to me - these are thompson (I was just in the US for work so grabbed some while I was there), so it makes sense they would be in the latter category, and maybe that explains why burnishing made such a difference!