KenV
Member
This discussion is specifically about shear scraping with a burr on the edge of the tool and the removal of material with the burr. Negative rake scrapers involve high angles of approach and are different than the conventional scrapers sold by many.
I have been using a John Jordan Shear Scraper for many years. The blade is 1/4 (nominal 6 mm) rectangular tool steel with a single bevel. John recommends a very fine ceramic hone, but I have use heavy diamond hones (not enough mass in the credit card ones).
Shear Scraper
These have been helpful with finish cuts on challenging acrylic and wood blanks. While John is predominately hollow forms and bowls, the tool fits some pen blanks too.
Had occasion to acquire Stuart Batty negative rake scrapers and give them a try.
Stuart Batty Negative Rake Scraper Blades at Woodworker's Emporium
The tools used a replacable sharpenable steel insert in a heavy steel holder.
Stuart Batty 004107 3/4" Domed/Straight Negative Rake Scraper at Woodworker's Emporium
The insert is double beveled with an included angle of about 40 degrees. The burr is raised on the top side and the top side is not laid onto the tool rest. Again, fine shavings and finished cuts suitable for the final 1/32 or perhaps 1/16 of an inch.
I was using this on acrylics that were chippy and made the buzzzzing sound with a slow feed on a fresh ground skew. I use a skew a lot and am at least of intermediate or better skill level.
I admit to putting on the magnifying head set with this, and was taking very light cuts of 10 to 20 thousands at a time. The pits cleared and the finish was better than 400 grit for polish. Was able to use P400 longitudinally along the pen to smooth out any small ridges and proceed to final finish/polish.
Harder, more dense materials work better. Stabilized wood worked well. Maple was OK, but anything softer was better with the skew. ebony, snakewood, honey mesquite worked well.
Others been using negative rake scrapers??? Experiences???
A good reference on the topic is Doc Green. The Batty NR Scrapers have a fine blade, but appear to be consistent with the discussion, but at lower mass near the edge.
Scrapers Part 2
I have been using a John Jordan Shear Scraper for many years. The blade is 1/4 (nominal 6 mm) rectangular tool steel with a single bevel. John recommends a very fine ceramic hone, but I have use heavy diamond hones (not enough mass in the credit card ones).
Shear Scraper
These have been helpful with finish cuts on challenging acrylic and wood blanks. While John is predominately hollow forms and bowls, the tool fits some pen blanks too.
Had occasion to acquire Stuart Batty negative rake scrapers and give them a try.
Stuart Batty Negative Rake Scraper Blades at Woodworker's Emporium
The tools used a replacable sharpenable steel insert in a heavy steel holder.
Stuart Batty 004107 3/4" Domed/Straight Negative Rake Scraper at Woodworker's Emporium
The insert is double beveled with an included angle of about 40 degrees. The burr is raised on the top side and the top side is not laid onto the tool rest. Again, fine shavings and finished cuts suitable for the final 1/32 or perhaps 1/16 of an inch.
I was using this on acrylics that were chippy and made the buzzzzing sound with a slow feed on a fresh ground skew. I use a skew a lot and am at least of intermediate or better skill level.
I admit to putting on the magnifying head set with this, and was taking very light cuts of 10 to 20 thousands at a time. The pits cleared and the finish was better than 400 grit for polish. Was able to use P400 longitudinally along the pen to smooth out any small ridges and proceed to final finish/polish.
Harder, more dense materials work better. Stabilized wood worked well. Maple was OK, but anything softer was better with the skew. ebony, snakewood, honey mesquite worked well.
Others been using negative rake scrapers??? Experiences???
A good reference on the topic is Doc Green. The Batty NR Scrapers have a fine blade, but appear to be consistent with the discussion, but at lower mass near the edge.
Scrapers Part 2
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