Sheer scraper - sharpening angle?

[rtyuiop]

Hi folks,

Going to play around with reshaping a few tools to be dedicated sheer scrapers (going to try out some round blanks and square blanks reground diagonally).

Anyone have any thoughts on preferred sharpening angle? My only data point so far is what sorby does with their multitip tool (which I don't mind, but I like a dedicated tool instead of having to change around cutters etc.), which seem to be 90 degrees - at least that's convenient and easy to remember!

Cheers,

Danny

[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.

[tony_A]

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

[Richard Hodsdon]

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 (http://www.alstirt.com/Pages/Student%20Resources.html)
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

[rtyuiop]

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

[rtyuiop]

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!

[NeilS]

I recently posted my views on scraper angles in another thread, here (http://www.woodworkforums.com/f8/curved-scraper-round-carbide-cutter-218004#post2058223).

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.

[rtyuiop]

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.

[hughie]

I recently posted my views on scraper angles in another thread, here (http://www.woodworkforums.com/f8/curved-scraper-round-carbide-cutter-218004#post2058223).

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.

[Woodturnerjosh]

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.

[rtyuiop]

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

[Woodturnerjosh]

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

[rtyuiop]

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:

http://rtyuiop.net/workshop/sheerscrapers_IMG_1031.jpeg

http://rtyuiop.net/workshop/sheerscrapers_IMG_1033.jpeg

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

[Skew ChiDAMN!!]

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. :)

[rtyuiop]

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!

[NeilS]

To confuse things a little, IME a good quality HSS ground on a diamond or CBN wheel gets more of a burnish straight off those wheels compared to Alox.

Burnishing is just consolidating the edge with a harder material. A consolidated edge will last longer than a fragile ragged edge.

Hand burnishing with a diamond plate both raises and consolidates the edge at the same time. I tend to do this several times before going back to the grinder.

Sent from my ZTE T84 using Tapatalk

[artful bodger]

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:

http://rtyuiop.net/workshop/sheerscrapers_IMG_1031.jpeg

http://rtyuiop.net/workshop/sheerscrapers_IMG_1033.jpeg

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


Well mate, all I can say is that they have to be the strangest looking scrapers I have ever seen.
Do you use them with the flat side resting on the tool rest?.
Blimey, the one on the right hand side,first pic, looks like a dovetail chisel.
Also the angles people have mentioned are a bit ambiguous. 90 degrees is 90 degrees. However 80 degrees is also 10 degrees and 20 is 70 depending how you read it.
Here is a picture of some of my scrapers.
427378 And hopefully a sort of side on pic of a few of em to show approx grind angles 427379.
I like to use the burr that the grinding wheel makes when you sharpen them. I know how to put a burr on a cabinet scraper with a file then a bit of tool steel but to sharpen my turning tools like that would drive me batty.
When you have a heap of turning to do a quick sharpen is a must and the grinding wheel is where to go. I am sure you could manually put a burr on those turning tools as well but it comes down to time with me.
My long departed step father could not believe that I ground a tool on the grinder each time it needed sharpening when I first got my lathe. He was a product of the depression where nothing was wasted and preferred to somehow hone the scrapers on a stone to prolong their life, until he did the woodturning course that I'd done. He was a grinder after that.
Anyway, you may notice that all my scrapers have a flat bottom (that rests on the tool rest) and top surface. Not saying this is how you "must" do it, but it works well for me.

[rtyuiop]

artful_bodger - yeah, these are specifically only for sheer scraping (with the edge at an angle to the tool rest), I have normal scrapers for non-sheer scraping.

For sharpening - I just grind my normal scrapers (although I must admit I will be trying burnishing them for finishing cuts in the future after what I saw with playing with these!), but for I'd only ever sheer scrape for light finishing cuts, so raising a burr away from the grinder won't take an inordinate amount of time - won't be removing much timber so hopefully won't have to do it all that often...

Danny

[artful bodger]

artful_bodger - yeah, these are specifically only for sheer scraping (with the edge at an angle to the tool rest), I have normal scrapers for non-sheer scraping.

For sharpening - I just grind my normal scrapers (although I must admit I will be trying burnishing them for finishing cuts in the future after what I saw with playing with these!), but for I'd only ever sheer scrape for light finishing cuts, so raising a burr away from the grinder won't take an inordinate amount of time - won't be removing much timber so hopefully won't have to do it all that often...

Danny


Well there you go, you learn something new every day. Once accidentally bought one of those round bottom sheer scrapers off ebay thinking it was flat both sides. Threw it out when it arrived, never seen anything like it before. Ha Ha.
Do sheer scrapers work THAT much better than the regular ones which seem to work fine to me?. What are the advantages of them?.

[NeilS]

When you have a heap of turning to do a quick sharpen is a must and the grinding wheel is where to go.

Looking at your collection of scrapers there, Artful, I guess you could say you are 'scraping' out a living!

Sent from my ZTE T84 using Tapatalk

[NeilS]

Do sheer scrapers work THAT much better than the regular ones which seem to work fine to me?. What are the advantages of them?.

Yes, particularly, when coming up the inside of a bowl through the end grain.

You don't have to use a round bar to shear scrape. Just roll any scraper onto its side and you are shear scraping.

You may need to add a chamfer to the edge that sits on the tool test (the way good skews have that) to avoid it digging into and dinging your tool test.

If you don't have a round bar scraper, a bowl gouge rolled over with the second edge close to but not touching is also good for shear scraping, particularly on the outside of bowls, but also works for some areas on the inside like the end grain.

Start with a 45deg angle to the horizontal and use very light cuts.

Sent from my ZTE T84 using Tapatalk

[rtyuiop]

Yeah, it really does make a difference on timber that’s prone to tear out!

I find myself sheer scraping (before these dedicated tools I’d use either a normal scraper on edge or a bowl gouge, as NeilS mentions) for finishing cuts on things like aust cedar or even US walnut.

Cheers,

Danny

[artful bodger]

Yeah, it really does make a difference on timber that’s prone to tear out!

I find myself sheer scraping (before these dedicated tools I’d use either a normal scraper on edge or a bowl gouge, as NeilS mentions) for finishing cuts on things like aust cedar or even US walnut.

Cheers,

Danny



Well, best I go an peruse youtube to find out more about these "sheer scraper" things.

[tony_A]

AB. You might like to have a look at thus clip by Reed Gray. Its the one that got me interested in shear scraping.
https://www.youtube.com/watch?v=xeOhPqOsORs&lc=z23febrpiuz5yp5ubacdp43ak4fruiuom1zzk2tkj0hw03c010c

Like a lot of other techniques related to wood turning its never quite as easy as a pro makes it appear.
Funny how I have been turning for nearly a year now and had never heard of shear scraping until I saw this vid then hear that a whole heap of other turners are using it. Make me wonder how many other tricks that the more experienced turners have up their sleeves that they aren't telling me about.

Tony

[rtyuiop]

Minor update on this topic...

Out of the tools pictured earlier in the thread, I don't often use either the round shaft with a straight grind, or the one with a square shaft - I think they'll be reshaped to something else when I need the something else.

The round shaft with a rounded tip has become one of my go-to tools (always hitting it with the burnisher after sharpening), so much so I added something similar to the tool set recently - wanted something bigger, so got a 5/8 spindle gouge blank with a shallow flute, and reground it so the flute is irrelevant (if I could have gotten a plain round 5/8 blank I would have!):

http://rtyuiop.net/workshop/IMG_1459.jpg
http://rtyuiop.net/workshop/IMG_1460.jpg
http://rtyuiop.net/workshop/IMG_1461.jpg

Gave it it's first run this week, working very nicely - the bigger blank gives more edge to use before it needs resharpening. Still haven't decided if I'll leave the top ground flat or will round it like the bottom...

Cheers,

Danny

[Skew ChiDAMN!!]

I tend to grind mine so that the plane the cutting edge lies in is parallel to the tool axis. (ie. the same as a profile on a bit of flat steel stock) This usually means a curved grind on both top and bottom.

That way, no matter which part of the cutting edge I'm using (I like to "use all the sharp bits" before heading back to grinder ;)) it's still cutting at around the same angle so long as I don't make a major changer to the tool presentation.

Looking at the side pic of your tool, this plane is angled nose down, so there'd be quite a difference between cutting in the centre and cutting on either wing..

Not so important when you can keep eyes on the job, but when you're working blind in hollow forms or undercuts this sort of thing makes life sooo much easier.

[rtyuiop]

Yeah, I think I am going to regrind to that shape - was using it yesterday and having to track the angle of the cutting edge as you change the section you're using is a pain!

[rtyuiop]

Discovered another great use for the sheer scraper above - finishing cuts in corners of boxes. Because of the shape you can get really deep into a corner... Being super careful to cut with the tip, so that the upper edge of the tool doesn't touch the 'other' surface (the one you're not cutting) and catch!

[NeilS]

Discovered another great use for the sheer scraper above - finishing cuts in corners of boxes. Because of the shape you can get really deep into a corner... Being super careful to cut with the tip, so that the upper edge of the tool doesn't touch the 'other' surface (the one you're not cutting) and catch!

That is how Richard Raffan and Benoit Averly do the inside of their boxes. First they do the inside out hollowing cut that Richard perfected with the gouge, viz.


450453

They are cutting in both in and out directions. That video clip is not sped up! Then they clean up the bottom corners with a scraper. The outside is completed with a skew. They complete the whole box and lid with a perfect suck fit in less than 10 mins. Benoir is faster than Richard now, but he learnt the technique from Richard.

[rtyuiop]

If only I were that good with a gouge!