Author Topic: Negative Rake Scrapers  (Read 748 times)

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Offline Birdhunter

  • Posts: 2689
  • Woodworker, Sportsman, Retired
Negative Rake Scrapers
« on: September 11, 2019, 08:53 PM »
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.
Birdhunter

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Offline Michael Kellough

  • Posts: 4229
Re: Negative Rake Scrapers
« Reply #1 on: September 11, 2019, 11:27 PM »
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]

Offline Dick Mahany

  • Posts: 516
Re: Negative Rake Scrapers
« Reply #2 on: September 12, 2019, 08:39 AM »
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.

Offline Michael Kellough

  • Posts: 4229
Re: Negative Rake Scrapers
« Reply #3 on: September 12, 2019, 10:32 AM »
So up close it’s more like a card scraper on the end of a steel stick?

Offline Birdhunter

  • Posts: 2689
  • Woodworker, Sportsman, Retired
Re: Negative Rake Scrapers
« Reply #4 on: September 12, 2019, 01:00 PM »
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

Offline Birdhunter

  • Posts: 2689
  • Woodworker, Sportsman, Retired
Re: Negative Rake Scrapers
« Reply #5 on: September 24, 2019, 02:01 PM »
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.
Birdhunter

Offline Michael Kellough

  • Posts: 4229
Re: Negative Rake Scrapers
« Reply #6 on: September 24, 2019, 02:28 PM »
Thanks for the report. Also, didn’t know things had changed at D-Way.