Curved left-side negative rake scraper

I have a set of 3 rounded-end scrapers from Hurricane Tools (large, medium, small). I have modified all of them to create a negative rake on the cutting edges, which I've found to be very helpful. They're pretty nice tools.

I am thinking about modifying one of them, probably the medium size, to extend the cutting edge around the left side, for use in finishing the inside wall of objects where it is hard to get the front edge of the scraper to work. For example, a natural edge bowl that has a wall that curves in some as it comes up from the base to the top edge. Often it is difficult or impossible to get the front edge of the scraper positioned to work on that inside wall, because the angle needed is too extreme and you'd end up hitting the natural edge of the work with the right side of the tool, destroying the bark you're trying to preserve.

Is there any reason NOT to modify the tool I have, and instead to purchase a tool specifically designed and sold for that purpose? I don't mind doing the grinding required, and I DO like to hold onto a dollar if I can.

Your thoughts appreciated.

Robert

Modify it and see how it works, don't give it a second thought.
It's your tool, make it work for you.

Most of my NRS are sharpened that way. I like them sharpened that way for that very reason you mention.
You can get to the sides of virtually any bowl unless it's very closed at the top and should be called a hollow form.
I can't see any reason you would not want to sharpen a NRS that way. At least one of them anyways. You have 3. My $0.02 is to take the biggest of them and turn that into a NRS not the smallest. My favorite NRS is an 1.25" Sorby. It seems to take the vibrations out better than the smaller ones, especially on those NE wings.
Good luck in your choice.

Robert, i have two of D-ways large NR Scrapers, one with the right side sweep grind and one with the left. I use these at least one of these tools on everything i make. I love the heft of them and the finish they provide.

https://d-waytools.com/curved-neg-ra...-3-8-5-8-tang/

Depends on how you value your labor. Buy a new one if you don't have the time.

I think your best option is to experiment on an inexpensive tool. If the shape really suites you then perhaps you'd want to make another with a higher-end steel.

Robert,

I think you'll be happy with either modifying an existing scraper or buying one just to modify.

I've been grinding NRS like this for a while, at least 5 years:

Attachment 477593 Attachment 477594

I grind the top and bottom bevels the same with the included angle about 60-deg I think. One reason to make symmetrical bevels is I can put the burr on either side to make them left- or right-handed as needed.
I remove the grinder burr and use a burnishing tool to add a smooth and longer-lasting burr.

Most I've seen with a curved side have the end rounded over. I made some like that for special situation but in general grinding a narrow (nearly) flat end is much more useful for me. You might try it both ways.
I ground several from Thompson scraper stock and one from a Thompson skew chisel. To shape I use a 60 grit CBN wheel - it takes a lot of grinding! To sharpen I use a 600 grit CBN wheel - extremely quick.

Pictures of one in use on the curved bottom of a "small squarish platter" and using the flat on the end to smooth the wings when turning "air":

Attachment 477595 Attachment 477596

I use these inside bowls and dished platters as well as the outsides. Following with hand scrapers gives a surface smooth enough that coarse sandpaper and power sanding is not needed.

BTW, I never put these scrapers in handles. There is not enough force on the tool to make a handle necessary.
I've made a bunch of NRS and rarely use a standard scraper now. Here are a few of my smaller NRS. One of these is ground from Thompson round stock and one from a Thompson shallow detail spindle gouge.

Attachment 477597

JKJ

Quote:

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Originally Posted by Robert Marshall

I have a set of 3 rounded-end scrapers from Hurricane Tools (large, medium, small). I have modified all of them to create a negative rake on the cutting edges, which I've found to be very helpful. They're pretty nice tools.

I am thinking about modifying one of them, probably the medium size, to extend the cutting edge around the left side, for use in finishing the inside wall of objects where it is hard to get the front edge of the scraper to work. For example, a natural edge bowl that has a wall that curves in some as it comes up from the base to the top edge. Often it is difficult or impossible to get the front edge of the scraper positioned to work on that inside wall, because the angle needed is too extreme and you'd end up hitting the natural edge of the work with the right side of the tool, destroying the bark you're trying to preserve.

Is there any reason NOT to modify the tool I have, and instead to purchase a tool specifically designed and sold for that purpose? I don't mind doing the grinding required, and I DO like to hold onto a dollar if I can.

Your thoughts appreciated.

Robert

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One thing that none of those otherwise excellent NS scarpers can do is present the scraper to the wood at a shear angle inside a hollow form or under the shoulder of an undercut bowl. The only one I know that can do that is this one...

https://www.cwsonline.com.au/shop/it...me-scraper-kit
'
The shaft end is round and the tip can be rotated to whatever shear angle you choose. This makes it very versatile when mounted in a swan's neck bar.

That little tip is one of the most valuable tools I have when I'm doing hollow forms and inside the shoulder on an undercut bowl.

They are a bit hard to come by now but they would be easy enough to make for a DIYer.

Well, for shear scraping, I prefer a burnished burr on my scrapers. You could do that for hollow forms. Not sure how shear scraping would work. I don't do many hollow forms, but would think that since most hollow forms are end grain, it would not be necessary. Side grain HFs would benefit from the shear scraping though. The burr on a NRS would not last for long enough to make it worth the time spent, at least to me.

robo hippy

Quote:

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Originally Posted by Neil Strong

One thing that none of those otherwise excellent NS scarpers can do is present the scraper to the wood at a shear angle inside a hollow form or under the shoulder of an undercut bowl. The only one I know that can do that is this one...

https://www.cwsonline.com.au/shop/it...me-scraper-kit
'
The shaft end is round and the tip can be rotated to whatever shear angle you choose. This makes it very versatile when mounted in a swan's neck bar.

That little tip is one of the most valuable tools I have when I'm doing hollow forms and inside the shoulder on an undercut bowl.

They are a bit hard to come by now but they would be easy enough to make for a DIYer.

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I use those, made by Sorby. I often use them for under the rim, the sides and bottom.
You can buy that tip or a variety of others.
https://www.rockler.com/high-speed-s...nmaster-system
I don't know the difference between the teardrop they call a cutter and what they call a sheer scraper, maybe the hole size? I use them only for scraping to smooth the inside after hollowing.
https://www.rockler.com/robert-sorby...t-blade-rs200c

I have both the straight and gooseneck Multitip shafts, large and mini. I also grind my own shapes from cabinet scrapers, cut a hole, and mount in the same handles.

Attachment 477919 Attachment 477917 Attachment 477918

These are great for smoothing since, as mentioned, they can be rotated to match almost any profile.

JKJ

Looking back at my previous post I wasn't clear enough...

Yes, JKJ, scraper tips are available from many outlets and Robert Sorby has a number of tools that use such scraper tips, like their Ultima, Multi Tip Hollowing Tool, Hollowmaster and their Internal Shear Scraper. But, none of those can provide a shear scrape up under the shoulder of a narrow necked hollow form.

For that you need both a swan's neck and a tip that can be rotated to the required shear angle.

As far as I know, the only tool that can do that is the Pro-Scraper Head mounted in a swan's neck bar.

Although the area under the shoulder cannot be seen it can be felt down to finger length, so it is important to get that smooth to the touch.

Of course, a traditional scrape can be done in that area with a standard swan's neck tool bar, but as we know you don't get quite as good a finish in that orientation as you do with a shear scrape.

And, if the opening in the hollow form is wide enough, a satisfactory shear scrape can be done under the shoulder of a hollow form with a reversed bowl gouge that has a a swept back grind.

Quote:

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Originally Posted by Neil Strong

Looking back at my previous post I wasn't clear enough...

... But, none of those can provide a shear scrape up under the shoulder of a narrow necked hollow form.
...

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Oddly, I generally don't have trouble smoothing the underside of a necked piece. If I do, I use a small, curved cabinet scraper with a good burnished burr mounted on a handle to reach inside. It's not in the orientation generally understood to provide "shear" scraping as with the wing as a gouge or with a conventional scraper held at a significant angle, but it works extremely well. I can understand an angled tip on a handle might be useful and would make one if I needed it.

I use one similar to this or one of the small scrapers shown at the left of the second picture, but different shape, and cut a hole in the middle to fasten it to a handle.
Attachment 477941 Attachment 477942
If the opening is big enough I scrape by hand with the piece off the lathe, holding a small scraper with my fingers without a handle. This way I can use it at any angle. The surface is baby cheek soft after some 400 grit paper (again, by hand, with piece off the lathe).

JKJ

Quote:

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Originally Posted by John K Jordan

I use one similar to this or one of the small scrapers shown at the left of the second picture, but different shape, and cut a hole in the middle to fasten it to a handle.
Attachment 477941 Attachment 477942
If the opening is big enough I scrape by hand with the piece off the lathe, holding a small scraper with my fingers without a handle. This way I can use it at any angle. The surface is baby cheek soft after some 400 grit paper (again, by hand, with piece off the lathe).

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JKJ

Thanks for that exposé of your method.