Late August 2008:
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November 29, 2008:
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November 29, 2008 By
November 27, 2008 By
#35. WIA – Scrapers: History, Preparation and Use, Part 3 of 3
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Run time: 23 minutes, 02 seconds
This is Part 3 of 3 of the session on Scrapers: History, Preparation and Use, with Christopher Schwarz. Part3 concludes the series on scrapers.
To get some continuity from Part 2 into Part 3, I included the last 3 minutes from Part 2 as the introduction to this episode. This way you can get back to speed quickly.
In Part 3 Christopher Schwarz actually draws the burr on the scraper. This Part starts with some discussion by The Schwarz on drawing the burr, and continues with the rest of his findings on the study he conducted:
- Best way to get a consistent angle at which to pull the burnisher: Adjust the height of the card scraper in the vise, until you find an angle that gives you the best burr. Use this height setting from now on, and lay down the burnisher on the vise chop (the moving face on the vise). This will give you a constant reference angle as you pull the burnisher.
- Use a lubricant when drawing the burr:
- Use a Japanese hair tonic such as Camellia oil (a Japanese hair tonic)
- Other accounts suggest that the Japanese hair tonic is not the best.
- Rather, one should use oil from behind the ear, or from the nose. - Make several passes with the burnisher, using light pressure. After each pass, “feel” the burr with your fingers.
- Up until today, Chris had always drawn the burr on the pull stroke. After the first pass, someone from the audience asked whether doing it on the push stroke would also work. In the end, it did, and even The Schwarz learned something during this session!
- What pressure to use? “About 12.4 lbs…” <laughter from the audience…>
- Effect of the shape of the burnisher: A tight radius produces a more aggressive burr, i.e., it cuts more at roughly the same pressure; for harder scrapers, use this tight-radius burnisher. But, for softer scrapers he recommends using a wider-radius burnisher. This is the main reason for differences in the shape of the burnishing rod.
- Always buy and use a highly-polished burnisher. He criticizes some commercial burnishers for not being polished enough, which results in jagged edges on the scraper.
- Chris likes to draw the burr while slowly moving the scraper away from the edge. This makes a lot of sense, as it “…keeps the oil moving…”
- Results: Beautiful shavings!
- A huge crowd gathered around Chris and his workbench immediately after the presentation. I am truly sorry I did not leave the camera running to record this!
Approximately the last half portion of Part 3 consists of a Q&A session. Several very good questions originated from attendees to this session, with (what else?) equally good answers from The Schwarz.
I hope you enjoyed this three-part series on scrapers, and hope you will return for more videos from the following sessions I attended:
- Advanced Dovetailing, with Frank Klausz
- Bevel-up vs. bevel-down planes, with Robin Lee, Thomas Lie-Nielsen, and Christopher Schwarz
- Forgotten Workbenches and Workholding, with Christopher Schwarz
- Furniture Design, with Kevin Drake and John Economaki
- My summary and wrap-up, with scenes from the conference.
Not on video, but rather from my own notes, I will have a post on Modern Tools, Tolerances & Myths, with Robin Lee, Thomas Lie-Nielsen, Konrad Sauer, and John Economaki.
I would love to receive your Comments, and any questions or suggestions regarding the Woodworking in America series of videos, and any other content.
November 26, 2008 By
#34. WIA – Scrapers: History, Preparation and Use, Part 2
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Run time: 32 minutes, 37 seconds
Note: I split this session into three parts, for easier downloading of the high-resolution file, and viewing in shorter segments. I apologize for the clumsy tripod movements – for example, at around 50 seconds into the video, the camera came close to hitting the floor. But everything in the session is on video.
Background:
By the end of Part 1, Christopher Schwarz had covered the history of scrapers, using information from “…12 dead guys and 2 living…”, the literature back to the mid-1800s; he was unable to locate earlier references in the literature. He also covered interesting facts about how wood fails, documented with superb photographs of the types of shavings formed. As Part 1 ended, he was filing one edge of the card scraper on the bench.
It is worth repeating here that this work first was published on the PW blog on April 20, 2007; you might want to keep the printed article for future reference. In my opinion, though, it is worth the time to watch Christopher Schwarz go through the entire procedure, in which he fully documents every step, and many misconceptions, about sharpening card scrapers.
Now, Part 2:
In this episode Chris does the prep required to get the edge ready to turn the burr, and covers the following:
- Finishes filing the edge of the scraper, as indicated by complete removal of the marker ink he used for this purpose.
- Stoning the edge: It is essential to keep the scraper at 90° to the stone surface. The best method he found to do this is to use the same block of wood he used to keep the file square to the scraper face. In addition, he moves the block of wood after every stroke.
- Sharpening stones he uses: Shaptons, 1,000 and 4,000 grit. Chris makes the point that a polished edge is more durable, and keeps the sharp edge better than a non-polished edge; thus, stoning with 4,000 grit.
- Polish the side, or face, of the card scraper, using the ruler trick developed by David Charlesworth to prop up a plane iron on a stone to sharpen a very small area on the face of the iron. This drastically reduces the time required to flatten (and polish) the face of the scraper.
- Burnishers: Use a polished burnisher, not a cheap one!
- Use a little oil to burnish the face of the scraper, using rapid movements across the entire face. Doing this creates a specific sound that resulted in burnishers being called “ticketers” in days past.
- This Part ends with some discussion on turning the burr: How? Slide the burnisher? At what angle? Use the Veritas variable burnisher – he set his at 7.2°! How much pressure to use? How many strokes with the burnisher?
It was only earlier this year I finally found myself able to properly sharpen a scraper with any kind of repeatability. But, if you are still struggling to get nice, thin shavings, this session is for you!
To be continued in Part 3…
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