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First Turning with the new lathe
Well.... finally got everything in place and set up and gave it a test with a platter. The turning went great...love the lathe... this is nothing spectacular but I'm pleased with how it came out.... it's about 12 1/2" X 2 1/2".....
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what is a negative rake scraper?
Quote:
Originally Posted by
Barry McFadden
I have to admit that I don't really know what a negative rake scraper is or what advantage it has over a regular scraper..
Barry, I posted these pictures recently in another thread. The first one is of some small scrapers I made mostly for detail, the second is of some larger scrapers ground to work on the inside and outside of bowls, platters, and such. You can see how each edge has two bevels and how much they vary. The angles of the bevels do change how the tool works but are not very critical for most use.
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I didn't read all the responses yet but in case no one has answered - a negative rake scraper (NRS) is just a scraper with a bevel cut on the top side as well as the bottom. The shape and the amount of the bevel depends on what you want to do. The curved edge scrapers are perfect for smoothing away tool marks on a bowl.
There are several differences between the standard scraper and the negative rake. The biggest is the NRS are more controllable. A standard scraper is usually used with the handle raised so the flat on the top of the tool and therefore the cutting edge is angled downward. This lets the scraper move easily away from the wood in the event that it bite too hard into the wood. The NRS has this angle built into it so it is usually held horizontally on the rest and presented straight into the wood. A catch with a normal scraper can be spectacular! It is actually difficult to get a catch with a negative rake scraper. Holding it flat on the rest makes it easier to hold and control too since you don't have to hold the handle high.
Just like a regular scraper you do have to have a "burr" the edge of an NRS. It doesn't need to be much but you should be able to feel it with your finger when you touch the upper bevel. "Traditionally", woodturning scrapers were used with the burr you get from a grinder. When you grind a bevel a burr of deformed metal sticks up from the bevel. Simply leave that bevel on the scraper and use it. This burr is rough, works very well, but doesn't last too long until it's knocked off or worn away - then back to the grinder.
Instead of the grinder burr, I use a burnishing tool exactly like one that fine furniture makers use on a hand-held cabinet scraper. I first remove any burr from the grinder with a hone or by stropping. Then I press a round or oval burnishing rod into and draw it along the tool edge from the bottom at a slight angle which deforms the sharpest part of the edge and raises a smooth burr up from the bottom bevel. It usually doesn't take a lot of pressure. You can easily feel this sharp burnished burr with your finger or catch it with your finger nail. You can use any hardened rod as a burnishing tool, even a lathe tool like a spindle or bowl gouge. The smaller diameter the rod the less force it takes.
Here are some burnishing tools I use, made by epoxying a rod into a handle. The first is one I've used for years, shown with an extra rod - the second is one I made recently from some small rods I got from Reed Grey.
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The third is a burnishing tool from Veritas. I've had it the longest but I don't use it any more. It is easy to be too aggressive with it and raise TOO much of a burr which can make the tool too aggressive in use. It is better for really big scrapers for big work.
I use the first two burnishers on cabinet scrapers and similar smaller hand-held scrapers as shown below. I have used some of these on a variety of turnings for almost as long as I've been playing with lathes.
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Hope this helped! I am certainly no expert on these but this is what works for me.
JKJ