The scraper burr

[Jon Murphy]

I do most of my work with my gouges and skews, but with some more exotic woods I've found that the touch of the scraper is best. For years I used the Veritas burnishing jig which makes a "forward" burr, but then put is aside and went "purist" and hand burnished a slight "back burr". I've fine scraped with my skews, and made negative bevel scrapers, and they work fine for final smoothing.

I'm working on a 6" slightly enclosed bowl of Indian Rosewood, and the wood is a bit "chippy" so I decided to smooth it out with a scraper rather than my normal way of using David Ellsworth's "finishing cut" that I can do quite well on other woods

That is background, I really do know what I'm doing. My question is this. Should I stay "purist" and hand burnish the burr on my scrapers or remount my Veritas burnishing jig and get a "forward burr" consistently. It seems to me that the angle of the burr to the horizontal shouldn't matter if the presentation to the workpiece is right, but my instinct also tells me the the "forward burr" might be a problem when shear scraping.

I can adjust the angle of my burr when hand burnishing, but I'm also not going to be as consistent as I would if I went back to my Veritas jig (the 10 dg. forward and the 5 dg. forward options). I am aware of the different tool rest levels and the "angle of the dangle". I ask advice as to which is the more versatile for various woods.

Best, Jon

 

[Odie]

I do most of my work with my gouges and skews, but with some more exotic woods I've found that the touch of the scraper is best. For years I used the Veritas burnishing jig which makes a "forward" burr, but then put is aside and went "purist" and hand burnished a slight "back burr". I've fine scraped with my skews, and made negative bevel scrapers, and they work fine for final smoothing.

I'm working on a 6" slightly enclosed bowl of Indian Rosewood, and the wood is a bit "chippy" so I decided to smooth it out with a scraper rather than my normal way of using David Ellsworth's "finishing cut" that I can do quite well on other woods

That is background, I really do know what I'm doing. My question is this. Should I stay "purist" and hand burnish the burr on my scrapers or remount my Veritas burnishing jig and get a "forward burr" consistently. It seems to me that the angle of the burr to the horizontal shouldn't matter if the presentation to the workpiece is right, but my instinct also tells me the the "forward burr" might be a problem when shear scraping.

I can adjust the angle of my burr when hand burnishing, but I'm also not going to be as consistent as I would if I went back to my Veritas jig (the 10 dg. forward and the 5 dg. forward options). I am aware of the different tool rest levels and the "angle of the dangle". I ask advice as to which is the more versatile for various woods.

Best, Jon

Interesting perspective, Jon........so, tell us what you're using to hand burnish a "back bur"?

Personally, I've always considered a back bur, too much curl of the bur itself for finish work......but, it sounds like this is what gives you the best results.

A ground bur straight from the grinding wheel is a back bur, and I use it for rough scraping, and under some conditions, bringing to round. I use it because it's quick and easy to produce. A raised bur is more of a finishing instrument......and, in both cases you speak of, I'm assuming you are discussing raised burs, but different methods of producing them.

-----odie-----

Note: I'm using a Veritas, because that's what is giving me what I consider the best results.

 

[John Torchick]

John, IMHO, whatever it takes to do the job. The goal is to turn a piece that has the best result prior to any sanding and applying a finishing material. I make a lot of pens and feel that I need to learn to use a skew for the quality surface I can get with it. I'm far from an expert at turning but, over the years, learned a lot from working in engineering, R&D, etc.

 

[robo hippy]

I have no idea what 'forward' and 'backward' burrs are. If you are burnishing, and the burnishing rod is at about 10 degrees past the bevel, you will get the same burr. Only difference is how hard you push on the tools to raise the burr. Harder = bigger, softer = smaller. There is some discussion about sharpening right side up compared to up side down, and thus far I can tell no difference, though you will find many who swear by both. The grinder burrs are generally fine for heavy roughing and some shear scraping finish cuts. The burnished burr generally leaves a some what cleaner surface, and you don't need a big burr for this.

Now, as for using a scraper for a finishing tool on bowls, I don't. Main reason is that in bowl/side grain orientation, you still run against the grain 2 times each revolution and this will produce tear out. I prefer the shear scrape as being, most of the time, a better finishing cut. Since the cutting edge is at a high angle, you get much less 'pull' as you cut. Scrapers can do a fair job of sweeping across the bottom of a bowl since you are not cutting down through the grain, but as soon as you hit the transition, you start getting some tear out.

Scrapers can do an excellent job of finish cutting on end grain, like boxes. For this type of finish cut, most of the time I will use a NRS (negative rake scraper) as it is less grabby. With the harder exotic woods, some prefer to use a scraper where the burr has been honed off, again because it is less grabby.

I have a video up 'Scary Scrapers' which is one of my more recent ones, and talk about most of this.

robo hippy

 

[john lucas]

Jon Have you considered a Hunter carbide tool for those cuts. I use either the #5 Badger or one of the back cutting bent tools to cut areas where other tools won't reach successfully.

 

[John Torchick]

"I have a video up 'Scary Scrapers' which is one of my more recent ones, and talk about most of this."
I'll have nightmares after watching it. OK, need to watch it. Always something new to learn. Thanks, robo hippy.

 

[Bobby Smith]

John, IMHO, whatever it takes to do the job. The goal is to turn a piece that has the best result prior to any sanding and applying a finishing material. I make a lot of pens and feel that I need to learn to use a skew for the quality surface I can get with it. I'm far from an expert at turning but, over the years, learned a lot from working in engineering, R&D, etc.

Don't want to take away from the original OP's thread, but John, I use a skew on all my pens. Once you get use to it, you'll really like the finish that it leaves. I also like that you can get better uniformity and don't always have to jump back and forth with calipers.

 

[John Torchick]

Thanks, Bobby. I notice that some of the turning videos show a sackful of tools in the rack. It is my understanding that experience turners will take a tool and modify it to do one thing as turning a certain species of wood that is hard or soft, hollowing, scraping, etc. This thread on the scraper has been interesting.

 

[Odie]

I used the Veritas burnishing jig which makes a "forward" burr, but then put is aside and went "purist" and hand burnished a slight "back burr".

I see Jon hasn't checked back in.......but, I want to clarify what I believe is the difference between a "forward" or "back" bur, as Jon is describing it. Matter of fact, I don't believe I've considered any terminology to define the differences prior to this thread.....but, they probably exist somewhere. How much angle the scraper is ground, along with how much pressure used will be the variables. (It is possible to get the "back bur" if the angle is acute, and the pressure is great, using the Veritas.) To my thinking if the tip of the bur faces backwards from 90°, or straight up, it is a "back bur". If the bur leans forward from 90°, the bur would be considered a "forward" bur.

My scrapers are ground to about 75-80° +/-, so it'd be pretty tough to get a back bur on my scrapers. Of course, with a lot of pressure, it could be done. I know some turners have more acute angles on their scrapers, so for them, curling the bur backwards would be more within the realm of possibilities for them to do so.

I feel the best, cleanest cut, using a scraper (shear cut mode, and regardless of how the bur is formed) is just slightly below the centerline of the turning. So, depending on the thickness and width of the scraper, and where along the cutting edge it makes contact with the wood, the tool rest height must be adjusted to compensate for these variables.

Jon, please provide some input to make more clear your intentions on this thread.....

-----odie-----

 

[Don Wattenhofer]

I do most of my work with my gouges and skews, but with some more exotic woods I've found that the touch of the scraper is best. For years I used the Veritas burnishing jig which makes a "forward" burr, but then put is aside and went "purist" and hand burnished a slight "back burr". I've fine scraped with my skews, and made negative bevel scrapers, and they work fine for final smoothing.

I'm working on a 6" slightly enclosed bowl of Indian Rosewood, and the wood is a bit "chippy" so I decided to smooth it out with a scraper rather than my normal way of using David Ellsworth's "finishing cut" that I can do quite well on other woods

That is background, I really do know what I'm doing. My question is this. Should I stay "purist" and hand burnish the burr on my scrapers or remount my Veritas burnishing jig and get a "forward burr" consistently. It seems to me that the angle of the burr to the horizontal shouldn't matter if the presentation to the workpiece is right, but my instinct also tells me the the "forward burr" might be a problem when shear scraping.

I can adjust the angle of my burr when hand burnishing, but I'm also not going to be as consistent as I would if I went back to my Veritas jig (the 10 dg. forward and the 5 dg. forward options). I am aware of the different tool rest levels and the "angle of the dangle". I ask advice as to which is the more versatile for various woods.

Best, Jon

First let me mention one important point burred scrappers must be presented at a negative rake if not you will just be pushing a rounded edge against the work. I have been using burred scrappers since I attended a Del Stubbs demo in about 1990. Del had 2 skews that he formed the bur (using a slip tone) opposite what the vertas would accomplish so if you laid the back side against the tool rest it would present the burr at a negative rake but it was never used flat on the tool rest. I have tried the Vertas but I felt it had too much torque and the finish on the carbide to rough and would roll the burr it to far. I have made my own burnishing tool using scrape carbide CNC router bits mounted with the polished shank end exposed. To get the best cut I hone the edge to raiser sharp then roll the bur. The amount of pressure necessary to produce a sharp bur takes practice and when you get it right you will know.

 

[robo hippy]

So, a back burr would be one, that to me is over burnished and you have a big burr that actually rolls over like a breaking wave???? That type is uselss to me. Hard to do on a 70 or so degree bevel unless you really 'armstrong' it, easier to do on a 50 to 60 degree bevel or a skew chisel. Just a light brush with a carbide burnishing tool on a 30/30 NRS or skew, and you can hear the edge breaking....

robo hippy

 

[Odie]

To get the best cut I hone the edge to raiser sharp then roll the bur. The amount of pressure necessary to produce a sharp bur takes practice and when you get it right you will know.

This, I agree with this wholeheartedly, Don......I don't agree with your contention that the Veritas will not produce the best possible bur, though. Nevertheless, what you said about pressure in this statement is the real key to success. the Veritas does provide a leverage point, and using that to it's best advantage doesn't mean using as much pressure as is possible. As you say, it does take some practice.....and, the only way to experience success, is by the results you get. There is a combination of things to analyze here, and it excludes the the visual......in other words, a blind man can determine the success better than a seeing person. Those who have crossed that bridge, will know fully well what I mean.....

-----odie-----

 

[Don Wattenhofer]

So, a back burr would be one, that to me is over burnished and you have a big burr that actually rolls over like a breaking wave???? That type is uselss to me. Hard to do on a 70 or so degree bevel unless you really 'armstrong' it, easier to do on a 50 to 60 degree bevel or a skew chisel. Just a light brush with a carbide burnishing tool on a 30/30 NRS or skew, and you can hear the edge breaking....

robo hippy

I thought it was evident that the breaking wave as you described it is useless and and should be avoided.

 

[Don Wattenhofer]

This, I agree with this wholeheartedly, Don......I don't agree with your contention that the Veritas will not produce the best possible bur, though. Nevertheless, what you said about pressure in this statement is the real key to success. the Veritas does provide a leverage point, and using that to it's best advantage doesn't mean using as much pressure as is possible. As you say, it does take some practice.....and, the only way to experience success, is by the results you get. There is a combination of things to analyze here, and it excludes the the visual......in other words, a blind man can determine the success better than a seeing person. Those who have crossed that bridge, will know fully well what I mean.....

-----odie-----

I did not mean to say that you could not get a good burr with the Vertas it's just that I feel that the free hand method is easier to judge the right amount of pressure.

 

[Odie]

I did not mean to say that you could not get a good burr with the Vertas it's just that I feel that the free hand method is easier to judge the right amount of pressure.

Oh.....pardon me.

As well, individual perceptions can vary.....and, I understand how my experience can, or won't apply to others, even though they are very real and applicable to me in my own turning.....

-----odie-----

 

[Lamar Wright]

but, I want to clarify what I believe is the difference between a "forward" or "back" bur,

Thanks,......Odie for explaining that. I didn't understand what the difference was between a "forward" or "back" burr. All I know is that when I sharpen my round nose scraper that there is small burr on the top side. I sharpen mine on a diamond wheel at a 60 degree angle.

 

[Emiliano Achaval]

I have no idea what 'forward' and 'backward' burrs are. If you are burnishing, and the burnishing rod is at about 10 degrees past the bevel, you will get the same burr. Only difference is how hard you push on the tools to raise the burr. Harder = bigger, softer = smaller. There is some discussion about sharpening right side up compared to up side down, and thus far I can tell no difference, though you will find many who swear by both. The grinder burrs are generally fine for heavy roughing and some shear scraping finish cuts. The burnished burr generally leaves a some what cleaner surface, and you don't need a big burr for this.

Now, as for using a scraper for a finishing tool on bowls, I don't. Main reason is that in bowl/side grain orientation, you still run against the grain 2 times each revolution and this will produce tear out. I prefer the shear scrape as being, most of the time, a better finishing cut. Since the cutting edge is at a high angle, you get much less 'pull' as you cut. Scrapers can do a fair job of sweeping across the bottom of a bowl since you are not cutting down through the grain, but as soon as you hit the transition, you start getting some tear out.

Scrapers can do an excellent job of finish cutting on end grain, like boxes. For this type of finish cut, most of the time I will use a NRS (negative rake scraper) as it is less grabby. With the harder exotic woods, some prefer to use a scraper where the burr has been honed off, again because it is less grabby.

I have a video up 'Scary Scrapers' which is one of my more recent ones, and talk about most of this.

robo hippy

Glad to hear I'm not alone in not knowing what a forward or backward burrs are... I have never bothered to check them for orientation, I just feel them with my thumb to see if they are there. Now I'm curious, what do I have?

 

[Odie]

Thanks,......Odie for explaining that. I didn't understand what the difference was between a "forward" or "back" bur. All I know is that when I sharpen my round nose scraper that there is small bur on the top side. I sharpen mine on a diamond wheel at a 60 degree angle.

Glad to hear I'm not alone in not knowing what a forward or backward burrs are... I have never bothered to check them for orientation, I just feel them with my thumb to see if they are there. Now I'm curious, what do I have?

Gentlemen......I'm not sure how well my own definition applies universally. As I said, I've never really used terminology to define the differences between types of burs until this thread. Although I have been well aware of those differences for my own purposes......I was surmising.

Lamar.......I'm using an SG Norton 80gt wheel for all my tools, along with hand honing both top and bottom intersecting edges......except for a "ground bur". Here, I'm getting a "back bur". The back bur is very effective for roughing purposes, and is quick and easy to produce......very useful. My ground bur is mostly used flat to the tool rest, and only occasionally used in a shear scrape mode.....while the raised bur is almost exclusively used in the shear scrape mode. Since, technically, you are getting a ground bur from your diamond wheel, it must be a finer bur than I get straight from the wheel. Do you consider your bur produced in this manner as a back bur?

Emiliano......your ability to definitively feel for the bur is a component of the point I was attempting to make regarding not using visual indicators to evaluate the effectiveness of one's own bur. Since the wood is spinning, it's impossible to see how well your bur and tool handling is performing in real time......so, one must use other means. Sight is certainly useful after the fact.....but, during turning, we are left with using our sense of feel and hearing to make small adjustments to the cut. Being a more experienced turner, I'm sure you've been using your other senses for some time. I especially like your boxes with threaded lids......very exceptional work, Emiliano.

-----odie-----

 

[Lamar Wright]

it must be a finer burr than I get straight from the wheel. Do you consider your bur produced in this manner as a back bur?

Yes Odie....the burr is very fine off the diamond wheel and I do consider it as a back burr. I have a Norton 80g wheel on another grinder and I'll try it and see what the difference the bur is between the two wheels. Let you know.

 

[robo hippy]

I used to only use my 80 grit CBN wheel to raise the burr on my scrapers. Now I use the 180 grit wheel. I have used a 320, 600, and 1000 grit wheel. They each make a finer burr. The 180 does make a good burr for heavy roughing. The finer wheels make a better burr for shear scraping. I can't tell if they go dull more quickly when roughing, or just that the burr isn't heavy duty enough for that job. For shear scraping, I prefer the raised burr, but the 180 burr will work for most shear scraping...

I have found that with shear scraping, I get much less run out in the bowls than I do with a gouge cut. If I ease a pencil into a spinning bowl, with the shear scrape, I can get an almost complete pencil line all the way around the bowl. With the bowl gouge, there seems to be 2 gaps that correspond to the end grain, there is always a little bounce with a gouge since you are rubbing the surface, and the end and side grains cut differently....

robo hippy

 

[Lamar Wright]

Gentlemen......I'm not sure how well my own definition applies universally. As I said, I've never really used terminology to define the differences between types of burs until this thread. Although I have been well aware of those differences for my own purposes......I was surmising.

Lamar.......I'm using an SG Norton 80gt wheel for all my tools, along with hand honing both top and bottom intersecting edges......except for a "ground bur". Here, I'm getting a "back bur". The back bur is very effective for roughing purposes, and is quick and easy to produce......very useful. My ground bur is mostly used flat to the tool rest, and only occasionally used in a shear scrape mode.....while the raised bur is almost exclusively used in the shear scrape mode. Since, technically, you are getting a ground bur from your diamond wheel, it must be a finer bur than I get straight from the wheel. Do you consider your bur produced in this manner as a back bur?

Emiliano......your ability to definitively feel for the bur is a component of the point I was attempting to make regarding not using visual indicators to evaluate the effectiveness of one's own bur. Since the wood is spinning, it's impossible to see how well your bur and tool handling is performing in real time......so, one must use other means. Sight is certainly useful after the fact.....but, during turning, we are left with using our sense of feel and hearing to make small adjustments to the cut. Being a more experienced turner, I'm sure you've been using your other senses for some time. I especially like your boxes with threaded lids......very exceptional work, Emiliano.

-----odie-----

Odie..... The ground burr is raised for sure sharpened with the 80g Norton wheel at the same 60 degree bevel that I use....A raised burr on the scraper is much superior I would think for roughing. Doesn't take much burr or it is too aggressive at least for me. ! If I can feel the burr with my finger nail I go with that.

 

[Don Wattenhofer]

Glad to hear I'm not alone in not knowing what a forward or backward burrs are... I have never bothered to check them for orientation, I just feel them with my thumb to see if they are there. Now I'm curious, what do I have?

Thanks for pointing that out, I have to say this is the first time I Have heard the terms used used and I could not figure out what it means.

 

[Fred Belknap]

This may be bit off topic but still relevant. I have been experimenting with NRS (negative rake scrapers) and find that I like them. I had been putting the burr on with the Veritas and it worked very well. I watched a video where one of the turners was grinding his NRS upside down on the grinding platform. This lets the grinding wheel turn in the direction that the burr is. It seems to work great on my system which is a well used 180 grit CBN. The tool seems to cut better and longer till it needed sharpening. A quick run through the grinder upside down and it was ready to go again. My scrapers are about 80/25 degrees with the 25 the top angle. It gives a good quality of cut but may be a little slower than a gouge. I normally use both when turning a bowl, use the NRS for all of the finish cuts.

 

[Bill Boehme]

The terms are new to me also. I think that the terms forward and backward bur were coined by Jon. Maybe he will fess up. I just raise a bur with a burnishing tool and don't think about naming it anything besides "sharp".

I have the burnisher tilted a few degrees from the bevel which is somewhere between 70° and 80° so I suppose that makes it a "forward" bur. My thought is that a "backwards" bur also will cut and that either one can be ruined by overworking the edge until it rolls over and becomes brittle from work hardening.

When putting a bur on a NRS I hold the burnisher almost perpendicular to the tool, but tilted forward just a hair.

 

[Jon Murphy]

Sorry guys, I was temporarily out of action. I seem to have started quite a thread. I haven't read all the answers yet but I have a sense of them.

One of my favorite gurus is Alan Lacer - we correspond on email now and then as I'm a "home bound" wood turner and learn from my own experience and from web sites. My use of forward and back burr was coined by me, Bill, but with a certain logic. Alan, in his articles on his web site, suggests burnishing a scraper at about 5 dgs. off the vertical when the plane of the top of the scraper is horizontal. The 5 dgs. is "inward", i.e. it is a "back curl" in relation to the plane of the top surface. He also recommends a bevel of around 60 dgs. That would make the angle of the bevel about 35 dgs from the bevel and angled a bit inward. So what I called a backward burr is one that has an acute angle to the plane of the top of the scraper.

In contrast, the burr made by the Veritas device, where the bottom of the scraper is flat on the device, can be five or ten degrees "forward" of the vertical (or is it 10 and 15?). No matter the bevel angle the burr will have an angle away from the plane of the tool.

Oops, it gets more complicated. If one is using a negative rake scraper (which basically is a scraper with the top surface ground to a bevel downward to some extent) then you could get a "back burr" with the Veritas burnishing device using the 10 dg. post if your negative rake was 20 dgs.

When you really come down to it the question is the "angle of the dangle" of the burr to the bevel and the presentation to the work piece. When I look at it logically rather than by experience I see the angle of the burr to the bevel as being important for retention of the burr. It is a matter of the metal and the support of the burr. The bevel angle for a scraper is more a matter of clearance than "sharpness" (as the burr is the cutting edge). I see no value to the negative rake scraper except the convenience of lying the tool flat on the rest. But that is a good convenience and I use it. I've done fine scraping with my skews and no burr, it works for fine smoothing.

I think I opened a tempest in a teapot, but I still want to get the various views. The angle of the burr to the bevel must affect the life of the burr. The angle of the bevel affects the use of the scraper on different shaped and sized bowls for the internal cuts due to clearance. I think I may disagree with Alan and the inward 5 dgs. and perhaps remount my Veritas device. If I want a 'back burr" I can get it by grinding the scraper to a negative rake. A philosopher once called consistency the measure of fools, but consistency in the shape of tools allows us to use our skills to change the presentation to the wood to get the results we want.

Enough - that was a big Murph Says.

Best, Jon

 

[Emiliano Achaval]

Gentlemen......I'm not sure how well my own definition applies universally. As I said, I've never really used terminology to define the differences between types of burs until this thread. Although I have been well aware of those differences for my own purposes......I was surmising.

Lamar.......I'm using an SG Norton 80gt wheel for all my tools, along with hand honing both top and bottom intersecting edges......except for a "ground bur". Here, I'm getting a "back bur". The back bur is very effective for roughing purposes, and is quick and easy to produce......very useful. My ground bur is mostly used flat to the tool rest, and only occasionally used in a shear scrape mode.....while the raised bur is almost exclusively used in the shear scrape mode. Since, technically, you are getting a ground bur from your diamond wheel, it must be a finer bur than I get straight from the wheel. Do you consider your bur produced in this manner as a back bur?

Emiliano......your ability to definitively feel for the bur is a component of the point I was attempting to make regarding not using visual indicators to evaluate the effectiveness of one's own bur. Since the wood is spinning, it's impossible to see how well your bur and tool handling is performing in real time......so, one must use other means. Sight is certainly useful after the fact.....but, during turning, we are left with using our sense of feel and hearing to make small adjustments to the cut. Being a more experienced turner, I'm sure you've been using your other senses for some time. I especially like your boxes with threaded lids......very exceptional work, Emiliano.

-----odie-----

Thank you Odie! Yes, I do not know what burr I have, I just know what works for me, you need to know how long the burr lasts with different woods. When I chase threads, I take off my noise canceling Bose headphones to listen to the chasers, I can tell how the thread is going by the sound of it...

 

[robo hippy]

One reason I never went with the Veritas burnishing tool is that you can't vary the angle like you can with hand held. I always keep it at about 5 or so degrees off of the bottom bevel...

robo hippy