Entry Level Negative Rake Scrapers

[Dean Center]

Since seeing Tom Wirsing make platters at the Rocky Mountain Symposium last Fall, I've been periodically trying negative rake scraping and am pretty impressed with the method for a variety of tasks. I've been using my skew held flat as a negative rake scraper with fair results but, as Tom showed, variable shapes are desirable and I don't want to screw up my skews. Since the bank account won't allow a full quiver of SB negative rake scrapers, I've wondered if I could take some standard scrapers, or inexpensive skews, and convert them into negative rake scrapers. Scrapers appear to be a little thicker than skews at the same width. What would those of you who use a negative rake scraper think about this approach? What did you use when you started and how did that work out?

thanks.

 

[Bill Boehme]

There is no rule against repurposing a tool. Any thickness fron 1/4" to 3/8" should be fine. A NRS is for taking very light shavings so you do not need a thick tool. Why isn't just one sufficient? I have one (made from a P&N blank) and think that perhaps they are overrated.

 

[robo hippy]

Negative rake scrapers work fairly well on harder woods. I find them especially useful on end grain clean up, and less useful on bowls. Most of my bowls are madrone and myrtle. The last batch of logs I got had some big leaf maple. The NRS work on the myrtle some what, and on the madrone (just about everything works on madrone), but weren't good on the big leaf maple. A shear scrape works better on all 3. I have one made from a converted Raffen spear point scraper, 40 degree bevel on each side. I have one 3/4 by 1/4 Thompson scraper that I converted with a 70 degree bevel on the bottom side, and a 15 or 20 on the top side. Excellent for box sides, and tops and bottoms to clean up any small tool marks. Most of the time lately, I have seen Stuart Batty using them on honey locust. That stuff is generally pretty hard.

robo hippy

 

[billooms]

I bought a number of 1/2" Benjamins Best skews from Penn State Industries and re-shaped them to my needs. At $13.95 each it won't break the bank (their part #LX010).

 

[john lucas]

I made a negative rake scraper from a 3/8" thick wide scraper. I like it but it took forever to grind the negative rake on something that thick. I would use a thinner piece next time. I'm with the others. Just repurpose a tool that you can get at a reasonable cost. The downside is it may not hold that burr very long. Something like a Thompson scraper re ground to a negative rake would hold the burr longer.

 

[Hy Tran]

I bought the least expensive scraper from Craft Supplies when they were having a sale--I think it was a Henry Taylor round-nosed scraper. Then, I just reground a bit of the top edge to give the negative angle. I regrind the bottom to put the burr on. I didn't grind it to be symmetric so you can flip top/bottom; it's not as radical as a full-on negative scraper as demonstrated by Tom Wirsing, but it works, and isn't that expensive.

The suggestion to buy a Benjamin's Best and repurpose is also a good one.

Hy

 

[Steve Worcester]

Ignoring factor like thickness, the major difference between good steel and lesser here is how long it will hold the edge. With a NR scraper, don't push it too long, resharpen. On a lower grade steel, maybe 10 seconds, higher grade, 45-60ish. Granted pure conjecture based on wood and steel.

 

[Fred Belknap]

I like it but it took forever to grind the negative rake on something that thick.

John is the size of the negative rake important? I just use a very small bevel on the top of a scraper and use for finish cuts. I use gouges to do most of the turning and finish with the NRS. The only negative (no pun intended) is some vibration near the edge of the bowl. Very lite cuts and when I can use a finger or three on the outside eliminates most of this. A NRS can be used above the center or below without the danger of a catch, it also cuts pushing or pulling. I find a burr on the scraper helps a lot on the inside sides of bow.

 

[Bill Boehme]

... is the size of the negative rake important?

Are you asking about size or angle? If a small size is what you are referring to then it won't be long before the upper bevel is ground away and, in essence it is not much different from a regular scraper. If asking about the angle, I prefer the lower angle to be rather blunt ... 80° or even more. I believe that it also helps if the included angle is greater than 90°. If you put a 20° angle on top and 80° on the bottom, that results in an included angle of 100°. With those settings, it is hard to get a catch. The downside is that the tiny bur won't last long.

 

[john lucas]

I'm pretty new at negative rake scraping so take this with a grain of salt. I don't think the size of the tool (thickness) matters much because it is a tool designed for extremely light cuts. From my experiments the negative rake scraper puts less forward pressure against the wood which helps prevent chatter on things like thin natural edge or winged vessels. Consequently you need a good sharp burr. I said what I said about thickness because I had a very thick scraper that I use often hanging over the rest a good ways and it seems to work well. However it's thickness made it take forever to establish the initial grind. Now that it's there it's pretty quick to get a burr since I'm using the flip over method that Stuart uses. The ideal thing is stewarts tool which is a thin cutter mounted in a thick stock. That's pretty hard for most of us to build so it's easier to just take an existing scraper or skew and convert it.

 

[john lucas]

A wide scraper like Stewarts is good because you can move the tool to cut with a fresh edge which should make trips to the grinder a little less frequent. After all it's well established that a fresh burr doesn't last long