Negative Rake Scrapers

[Birdhunter]

I’ve been researching Negative Rake Scrapers. Their advantage seems to be leaving a very fine surface and less probability of a catch.

Anyone tried them? I’m looking at DWay’s tool.

 

[Michael Kellough]

That’s new to me but Here is a good discussion.

I’ve never had a catch with a scraper but I can see how you could get a catch with a regular scraper on the inside of a turning. I don’t get how the thin edge of the negative hook scraper would produce a finer finish but this is a new topic for me too.

For a fine finish on the outside I like a skew but I’d never try that on the inside.  [scared]

 

[Dick Mahany]

I've made my own by regrinding various lathe tools to obtain the profile.  I don't have a lot of experience with them however they can leave a very fine finish and aren't prone to catches.  The trick is to get a properly obtained burr for the cutting edge.  Those burrs don't last very long and need to be reformed frequently.  I bought some very inexpensive lathe tools from Penn State and used those for re grinding as the HSS material is actually quite good.

 

[Michael Kellough]

So up close it’s more like a card scraper on the end of a steel stick?

 

[Birdhunter]

There is a similarity in that both use a burr to do the cutting. The major difference is that the negative rake scrapers have a bevel on top and on the bottom. The tool I am looking at has a 20 degree top bevel and a 70 degree bevel on the underside. The burr is created by lightly grinding the bottom bevel. There appears to be a number of preferred bevel angles, but there is always a top bevel.

 

[Birdhunter]

I just used a negative rake scraper for the first time. I was cutting the inside of a cherry bowl and hit an area where the wood grain was doing some weird stuff. The negative rake scraper left a very smooth surface where my regular scraper was leaving some tear out. I don’t think the negative rake scraper will replace my regular scrapers, but it will become my finish scraper.

Mine came from Boxmaster Tools which has become D Way. Extremely well finished tool and very sharp out of the box.

 

[Michael Kellough]

Thanks for the report. Also, didn’t know things had changed at D-Way.