Did you regrind your scraper to negative rake?

[John Hicks]

I'm wondering how many of you have reground your traditional scrapers to a negative rake? I have a lucas french curve scraper that is a pleasure to use compared to the three traditional grind scrapers I have. They cut great, but catching is a problem.
Is the angle that is reground very important?

 

[William Rogers]

I have reground all my scrapers to negative rake. I have a couple of Thompsons ground like the Lucas French curve, one on the left and one on the right. I’m not sure on this, however it seemed to be an opinion that you should not exceed 90 degrees total. Most of mine are ground 65/25. I do have a few that are ground to 25/25 and 30/30, but those are for light finish cuts as the burr doesn’t last very long.

 

[Bruce Perry]

Glen Lucas showed me that grinding 22.5 on either side of a negative rake scraper allows a very quick conversion of "handedness". With a fairly fine CBN wheel you get enough burr to work for several seconds, and can turn the tool over and do the same work, while keeping the tool in the center. Mr. Laser might not approve, but his giant skew , freshly ground works really well in this application.

 

[john lucas]

I havent reground all.of the but most. When used as a shear scraper there isnt any advantage of a negative rake so I leave my John Jordan tool alone. There isnt any reason a negative rake wont work as a shear scraper.

 

[Roger Chandler]

Only two of my scrapers are ground to negative rake, they are good only for fine finish cuts, and I still need the regular scrape grind for more use than the Neg/rake.

 

[Clifton C]

I use a couple of my skews as negative rake scrapers on occasion. I also bought a blank and ground it to a negative rake.
I like the finish they leave, but they are not for hogging. Something was wrong with the scrapers I had when I first started turning,
all kinds of catches and dig ins, but, the more I turned the better they got, they hardly catch anymore....

 

[John Torchick]

Interesting thread. I was turning a couple of end grain pieces. I had a round nose scraper but it didn't have enough cutting surface to turn the inside because the tool would hit the other side. I ground the left side of the tool to about one inch down the side and ground a slight negative on the top. Worked better than I anticipated.

 

[Robert Satterfield]

William, Bruce, John L, Roger, Clifton and John T...two critical considerations: Tool rest position and tool angle. Are these the same as a traditional scraper when using a neg-rake scraper?

 

[Clifton C]

I think yes. If you are using the scrapers in the traditional way. If someone were to ask me what that was, I would say, flat on the tool rest, handle up, tip down with the cutting edge above center inside a bowl, below center out, and at center for spindles. This may sound basic, but a lot can be done with basic techniques. Shear scraping, that's a different colored horse...

 

[Rob Price]

All my scrapers are negative rake. I use gouges for shaping and the NRS only for fine tuning a curve here or there.

 

[Doug Freeman]

I use both. Flat top ones usually used at a shear scrape angle, inside and outside, smoothing tool marks, finish shaping. NRS for finish prep mainly - kind of like a fine smoother handplane, reducing lower grit sanding. Cant always get a perfectly smooth cut with shear scraping leaving lite lines/marks. Dont use a flat top flat on the tool rest all that often, likes to create tear out. NRS ground 30/30 with equal bevels, easy to sharpen and flip. Prefer dia hone burr on NRS, honed and burnished burr on flat top. NRS used with handle flat to slightly raised, flat top raised, tool rest as close as feasible,

 

[Bill Boehme]

William, Bruce, John L, Roger, Clifton and John T...two critical considerations: Tool rest position and tool angle. Are these the same as a traditional scraper when using a neg-rake scraper?

No. A NRS is used level on centerline. A standard scraper is normally used with the nose angled down and below center on the outside of a bowl or above center on the inside of a bowl.

 

[Clifton C]

And that's why turning is so much fun, sometimes I use scrapers level, and sometimes I don't. I have no problems using a negative rake scraper canted down a bit. Sometimes, the finish off the tool in the bottom of an end grain box needs no sanding. That's where the YMMV acronym comes into play. When you say "never" someones going to disagree, and that's Ok, but I would say, with traditional scraping, ie. tool flat on the tool rest, never have the handle lower then the cutting end, I think that's just asking for a catch...

 

[Bruce Perry]

In answer to the "how do you align the scraper" question: The reason for "trailing" a flat top scraper is to let the "mini' catches, that they constantly produce, push the tool into air rather than dragging it into the wood. Working slightly below center, and with the handle slightly high on outside of your wood means you don't need the death grip that tries to destroy your elbow. On the inside of a bowl, if you stay at or above center the little drags really do become minimal. The nature of the flat scraper is to try to drag itself forward into the wood, and the downward angle makes this worse, if there is wood to drag into.

The negative rake, primarily a fine finishing tool, both gives you that trailing angle for no effort, but keeps the tool from trying to feed, and lets the tool rest absorb all of the energy of cutting.

Most of us find that we can cut wood out of a bowl a lot easier than scraping, done carefully, and with a truly nicely shaped bowl gouge, you can get awfully close to a finished curve really quickly. Trying to get that last 1 % of perfecting the curve with a gouge is worth a try, but it isn't normally worth the extra time compared to making those few passes with a negative rake scraper.

You have to remember that you are cutting with a tiny burr, and that it isn't going to last very long - regardless of how expensive a steel - so keep your grinder platform set, and expect to return after a very short time.

When that doesn't work, step back and think through the toolbox of tricks you've seen, and remember that there are chunks of wood out there that just don't want to be smooth.

I should credit Stuart Batty, he explains this any time he demonstrates, with diagrams, and advise on steels etc. etc.

 

[Bill Boehme]

I should credit Stuart Batty, he explains this any time he demonstrates, with diagrams, and advise on steels etc. etc.

I was about to say that your description reminded me very much of Stu Batty. His explanation of why a NRS is much more controllable than a standard scraper for finishing cuts is a brilliant insight in my opinion.

 

[Bruce Perry]

Sometimes Stu drives me a little nutso, but, try to envision doing the turning in my "avatar" (see next to comment) without a refined use of the negative rake scraper (including the Bowie version)

Stuart was demoing across from my club when I first started working this form, and saved me an amazing number of hours, not to mention s----w ups, just by mentioning that utility.

 

[John Torchick]

When I turned the two end grain pieces, the rest was about center and I presented the tool with the handle raised slightly. Saw one video where end grain was turned with a bowl gouge. I tried but got horrible catches. I figure that it was: different grind angle, presentation, size of the hollowing or something I overlooked.
Edit- Robert, my tool was one of the HF set with the red handles. This was the first time I have used the RN scraper in about 10 years. I'll try to post photos of what I did.

 

[Don Wattenhofer]

I have one round nose scraper ground with the Stuart Batty or who ever defined negative rake and that is the only one that I hold flat on the tool rest. All of the others I have formed a bur on and present them to the work piece at a negative rake angle, which is the original shear scraping method. The original method that I learned about 1990 at demo by Del Stubs involved two cheap skews ground from one side only with the bur formed to the ground side. The subject of the demo was translucent green turned goblet and the skew burred scraper was held at about a 45 degree angle to the tool rest and moved down hill to the grain to shear scrap the outer surface of the cup body. The recent thread "finishing the bark" I included pictures of two cherry goblets made by this method except that all of the scrapers I use now are high speed steel. The burrs are formed by first honing the edge with a 600 grit diamond hone then forming the burr with a polished carbide burnisher that I make my self-using discarded CNC router bits.

 

[Bruce Perry]

One of the details that gets lost in the shuffle: Bagpipes came from Spain, when the remnants of the Spanish Armada wiped out against the shores of Scotland. The Spanish got the blasted noisy things from the Greeks. (And who knows where else, the Turks had them when they irritated Vlad) All of them were turned using negative rake scrapers, hundreds of years ago.

Shear scraping, like Del Stubs used to demo, is still a remarkably useful technique, with separate tools like the Richard Raffin's pointy version, and of course many of us shear scrap with the long and strong, swept back ground. deep fluted gouge.

 

[John Torchick]

I can't turn bagpipes. Wife can't stand them...or accordions. Stick with pens and bowls.

 

[Dean Center]

I can't turn bagpipes. Wife can't stand them...or accordions. Stick with pens and bowls.

I'll give you a dollar if you turn an accordion.

 

[Mark Jundanian]

Accordion, bagpipes and steel drum trio. Now that would be something.

 

[John Torchick]

I'll give you a dollar if you turn an accordion.

Cash only! I would have to use the skew instead of the NRS. I'll keep you posted on the progress.

 

[Don Wattenhofer]

One of the details that gets lost in the shuffle: Bagpipes came from Spain, when the remnants of the Spanish Armada wiped out against the shores of Scotland. The Spanish got the blasted noisy things from the Greeks. (And who knows where else, the Turks had them when they irritated Vlad) All of them were turned using negative rake scrapers, hundreds of years ago.

I would be interested to know where you got your information about the turning method "hundreds of years ago" specifically the point about turning with a negative rake

 

[brian horais]

I purchased a thick scraper for the specific purpose of regrinding it into a two-sided negative rake scraper (NRS). The majority of the grinding was done on an old shop grinder and the finish grinding was done on my lathe tool slow speed grinder. I find having two opposing edges gives me a lot of flexibility. The grind angles were picked so that I sharpen with the same angle as my roughing gouge, which makes the setup easy (I leave a grinding setup in place for this) and I frequently give the NRS a touch-up sharpening on my slow speed grinder. Here's an image of the scraper with a sizing background

 

[Timothy White]

One of the details that gets lost in the shuffle: Bagpipes came from Spain, when the remnants of the Spanish Armada wiped out against the shores of Scotland. The Spanish got the blasted noisy things from the Greeks. (And who knows where else, the Turks had them when they irritated Vlad) All of them were turned using negative rake scrapers, hundreds of years ago
The way I heard it:
The Irish gave the bagpipes to the Scots as a joke.
TheScots still haven’t gotten it.

 

[Bruce Perry]

Don,

There were folks at the Highland Games, in Golden, Colorado, some thirty years back, with examples of Greek and Spanish pipes (and pipers). The half dozen top competitive pipers from those games, some of whom were from Edinburgh, were hanging around the Mercantile (a long time local bar) at around midnight drunk thirty, and both listening to and agreeing with those folk. I'm only 69, so things that happened before Harry Truman was in office I just listen to the experts...

I've seen engravings, allegedly from that era, of Turks leaving the battlefield ahead of Vlad The Impaler, authenticity not something I would guarantee, but some held two drone pipes. I'm really glad I wasn't there to visit with Vlad!

 

[Bill Boehme]

Saw one video where end grain was turned with a bowl gouge. I tried but got horrible catches. I figure that it was: different grind angle, presentation, size of the hollowing or something I overlooked.

I would guess loss of bevel contact as the most likely cause. Type of grind or angle of grind are mostly irrelevant if the gouge is sharp.. A bowl gouge is great for spindle turning especially making pommel cuts on a table leg.

 

[John Torchick]

Bill, I agree. The video had the turner's hand in the way so it was hard to how the tool was presented inside the blank. Will get some wood and try again.

 

[robo hippy]

Well, I have 3 different styles of scrapers I use. The standard scrapers, all at about 70 degree bevels are my primary tool for hogging off massive amounts of waste wood, and I use the burr straight from the grinder. This includes M42 from D Way, V10 from Doug Thompson, and the Big Ugly tools with the Tantung cutting edge.

I have a bunch of different shear scrapers. Again, all at about 70 degree bevels. Some times I will use the burr from the grinder, and this depends more on the wood than the tool. If I have a difficult piece of wood, then I generally go with a honed and burnished burr. I do not consider the NRS to be efficient for shear scraping, and I don't use the swept back gouges for shear scraping either, the scrapers just seem to work better.

For negative rake scrapers, I have a bunch of them. Most that I use are for boxes and end grain. The problem with them on bowls is that with some woods the NRS works better, and on some you have to use the shear scrape, no clear cut winner. My preferred bevels are about a 60/30. I do not like the grinder burr since it is so weak. I prefer the honed and burnished burr, or some times I just burnish the grinder burr down, and then burnish another burr back up. They can be burnished up and down a couple of times before needing to go back to the grinder. I don't really care for the skew chisel type of NRS. Just too weak. For what it is worth, Stuart coined the phrase 'negative rake scraper'. His dad was using them before Stuart was born, and they were a tool used to refine the shape of ivory billiard balls, which was a couple of years of turning and letting the sphere 'adjust'. The tantung edge on the Big Ugly tool also makes an excellent NRS.

robo hippy

 

[Don Wattenhofer]

Robo I agree with most of what you are saying except the NRS (it would be more accurate the call it a Double Angle Scarper) is not efficient for shear scrapping, but I have found that it is sometimes good when reaching into an end grain piece (turned up at an angle to the tool-rest) for smoothing between the end grain and the side grain. The SAS (Single Angle Scraper) with a burr must be presented to the work at a negative rake in order for it to work and in the case of the skew type SAS it is almost never laid flat on the tool rest. The comment that the "skew chisel type of NRS" is too weak leaves me baffled unless you are using the burr off of the grinder.
The SAS mounted onto 3/4" round of drill rod with and angled mount for a HS tool works well on the inside of bowls since it is the only way I can think of to bring the burr to the proper orientation, note in the picture that the tool should be rotated somewhat counter clockwise to get the best shear action.

 

[Timothy Allen]

@robo hippy, what is the difference between your standard scrapers and your shear scrapers, since they both have about the same grind angle? Obviously there is a difference in how you hold the tool and orient it to the work, but what is the difference in the tool itself? For example, do you grind rounds on the side edges of the bar so that it slide over the tool rest easier while held at an angle?

 

[Mike Adams]

Robo I agree with most of what you are saying except the NRS (it would be more accurate the call it a Double Angle Scarper) ...

Thanks for the picture. I've seen that tool, but couldn't envision how to use it.

 

[robo hippy]

The biggest difference between my shear scrapers and my bowl scrapers is the profile/shape of the tool. My bowl scrapers are 1 inch wide, and have maybe 3/8 inch on the right that is pretty straight, then the rest of it is a 1/4 round profile, which fits perfectly into the inside of a bowl, and the straight edge goes down the outside of a bowl. Most of the time I use the Big Ugly tool for this as the edge lasts a lot longer than standard M42 of V10 metal. For my shear scrapers, I use two general shapes. One is more of a spear point tool, and the first version of that I saw was a Richard Raffen tool, and now Mike Mahoney has a signature one out. This is excellent for shear scraping the outside of a bowl. The other one I use is more of a ) shaped nose rather than a more half round nose profile. I think it just works better on the inside of a bowl. I have 2 videos up, one is 'Scary Scrapers' and the other is 'Shear Scraping' or maybe shear scrapers.... Can't remember. The other difference is that with the shear scrapers, most of the time I use a burnished burr rather than the grinder burr since the burnished burr is sharper and longer lasting.

Don, a NRS can shear scrape on end grain, and I do use them inside boxes some times for a finish cut. If I am shear scraping across the bottom of a box, I still prefer a standard scraper since it is easier to get all the way to a corner than the double bevel on the NRS. Some days that shear scrape is the easiest way for me to get that cut on the dead center in the middle of the box. I am getting better at hitting that dead center with the NRS though... For this type of finish cuts, I always use a burnished burr.

My comment about the skew chisel type NRS being weak is mostly about there not being much metal under the burr to support it, so it breaks off almost instantly. I have a couple of 25 and 30 degree skews that I some times use for finish cuts on the lip of a box where the lid and body meet, and for threaded boxes to properly time the fit so the grain lines up. The skew chisel is excellent for this. Now, as for the burr on the skew chisel type, from the grinder, that one is gone instantly. I have had bad luck with trying to burnish a burr on the skew chisel types. I may be 'armstronging' it too much as I can hear the edge fracturing as I draw the burnisher across the edge. I try to be very light with it, and keep the rod at maybe 5 degrees off of the bevel angle, but still can hear that crinkling sound as I draw the burr. The 60/30 leaves more metal under the burnished burr and it outlasts by far, the grinder burr.

robo hippy

 

[robo hippy]

My shear scraping video:

View: https://www.youtube.com/watch?v=xeOhPqOsORs


robo hippy

 

[robo hippy]

Scary Scrapers:

View: https://www.youtube.com/watch?v=T4MKTOutZ3w


I will get a NRS video together some time later this year...

robo hippy

 

[Doug Freeman]

Robo, for a 30/30 nrs you say you hear crinkling when burnishing. Are you burnishing off the grinder or honing the edge 1st then burnishing? Same question for 60/30 nrs. Just curious.

 

[Don Wattenhofer]

My comment about the skew chisel type NRS being weak is mostly about there not being much metal under the burr to support it, so it breaks off almost instantly. I have a couple of 25 and 30 degree skews that I some times use for finish cuts on the lip of a box where the lid and body meet, and for threaded boxes to properly time the fit so the grain lines up. The skew chisel is excellent for this. Now, as for the burr on the skew chisel type, from the grinder, that one is gone instantly. I have had bad luck with trying to burnish a burr on the skew chisel types. I may be 'armstronging' it too much as I can hear the edge fracturing as I draw the burnisher across the edge. I try to be very light with it, and keep the rod at maybe 5 degrees off of the bevel angle, but still can hear that crinkling sound as I draw the burr. The 60/30 leaves more metal under the burnished burr and it outlasts by far, the grinder burr.
robo hippy[/QUOTE]
The skew type single angle shear scarpers that I use are about 30 degrees but I have never broken the burr in use. At one time I would clamp the honed scraper in a vice and draw the burr with the carbide burnisher, but I found that it was to easy to put too much pressure on it and either roll it to much or fracture the edge. The simple and best way I have come up with is to hold the honed scarper in the left hand and make one pass with the burnisher held in the right hand. There is another thing that may come into play is the finish on the carbide burnisher, which if it is not highly polished may be abrasive as it passes over the edge. The bench mounted carbide burnisher or the carbide blanks sold appear to me to be rough surfaced so I purchased scrap CNC combo up cut / down cut bits that had been sharpened to many times so there was a gap between the up/dwn but the shank is highly polished and the hardest steel will not mar them.

 

[robo hippy]

Doug, I have tried it both ways with the 30/30 and get the same results. I may have to experiment with it some more, but may not do that. It doesn't happen at all with the 60/30 grind, and again I have tried it both ways, honed and straight off the grinder. I think there is a certain point in angles where too acute of an angle does not support the scraping edge, and too blunt of an angle makes it difficult to form a burnished burr. Sorby has a 'hardwood NRS' which is about an 80/20, and I find it almost impossible to burnish a burr on it. I have tried pretty much all angles from 30/30 to 70/30, and settled on the 60/30 as the one that works best for me. I don't have one of the bench top burnishing things from Veritas, I think, mostly because it is limited to set scraper angles, and don't really know how coarse the burnishing rods are. I did get a bunch of micro grained carbide burnishing rods, which seem to be very slick.

robo hippy

 

[John Torchick]

Scary Scrapers:

View: https://www.youtube.com/watch?v=T4MKTOutZ3w


I will get a NRS video together some time later this year...

robo hippy

Looking forward to it. This thread has been very interesting. Like to go back and start reading from the original thread and read all the way through.