slightly ot

Red: What they are referring to is the "Scary Sharp" method. You can google search it and come up with various techniques, etc!

"Reyd Dorakeen" skrev i melding news:BC237667.364C% snipped-for-privacy@shaw.ca...

Sharpening is not a straight science.

To explain your problem you should think of a knife-edge as a micro-sawblade. With 4000 stone you simply get a too smooth edge. The cutting is assisted by having the edge micro-serrated, like a sawblade. The 1000 sandpaper gives the edge enough "edge" to cut what you want and at the same time gives the edge the fine teeth.

Therefore the finishing touches of sharpening should always be made in an angle of near 90 degrees to the edge, and not along the edge.

Any good edge will need a slight sawing motion to give an effective cut, unless you use more power.

Bjarte

The measurment scale of "grit" size is not the same for sandpaper and sharpening stones. I don't have a conversion chart handy, but 2000 grit sandpaper is roughly equivolent to a stone between 4000 and 6000 grit.

This is true of some things like rope, but it is not true in woodworking. A smooth edge is sharper.

David

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But - as it is presented differently in turning than in flat woodworking, his assertion is correct.

thats what I was reading:P I was wondering whether it gives a better edge then a 4000x waterstone.

then how come razors-blades are so good for cutting things, they have a very smooth edge?

No, they aren't particularly smooth, as the old photomicrographs in FWW's sharpening article demonstrated. Thin fibers respond best to shear angles - note the discussion of shear versus non shear scraping. The same edge, presented differently makes a radically different surface. One of the reasons for this is the microsharp effect of an interrupted edge as mentioned. Try pushing the razor edge straight ahead in a piece of paper versus shearing, and you'll notice how this works.

Your beard doesn't have a "grain" to make selection of shear angle worthwhile, but there is a lesson in the greater ease of cutting wet versus dry hair. Some folks will even spritz with water prior to a final pass, or soak with solvent or wax to soften the fibers.

Smooth, until you put it under a microscope. Razorblades also cut better when it is presented to the stubble with an angle.

Bjarte

(Top-posting is bad for you and us:)

"Reyd Dorakeen" skrev i melding news:BC240F0D.36A8% snipped-for-privacy@shaw.ca...

I don't think all grits are created equal. I think the standards for sand paper and sharpening stones are different. ( the particle size equaling grit size)

Bruce

I disagree. I get the best finish off of the tools when I have them as sharp and smooth as possible. I want them to be shaving the wood, not sawing it.

David

remove the key to email me.

Damnit i'm feeling really dumb, but could somebody post/or send me a .mpg/.avi, or picture of the difference between shear scraping, and normal scraping(I still don't get it)

This has been discussed before to some degree. A comparison was made to wood carvers (myself, one) honing their cutting tools for the really sharp edge and wood turners who will give their gouge a pass with an 80 grit (or less) wheel and feel that leaves a truly sharp edge. I have a tendency to go along with them. For wood carvers, you are the power to move the tool and for wood turners the tool is held steady and the wood comes at you with great velocity. Honing gouges is sort of a waste of time as the terrific speed of the wood and its natural grit causes it to lose its honed edge pretty quickly. I will hone a gouge or other tool if it is being used to make very light cuts in the final shaping. I have never noticed any particular difference between honed or wheel ground edges for a sheer cut.

Do yourself a great favor by trying to get ahold of a copy of Leonard Lee's book, "The Complete Guide to Sharpening". He shows micrographs and discusses all the minute details of the process - it's sorta the "bible" for the science of sharpening. (I've borrowed it from my local library - yours may have it or be able to inter-library loan it.)

To address your 4000vs2000 question; unfortunately there are a number of grit grading systems in use around the world. The Japanese waterstones are graded on a different system than the natural Arkansas stones than are the silicon carbide (SiC) papers and so on - there's American grading, European grading and Japanese grading systems which all differ. That's OK, but they use similar methods of stating a "grit" which is where the confusion sets in.

Your 1000x waterstone is roughly equivalent to: a US 700 grit SiC paper; Hard White Arkansas stone; Fine Diamond; and Medium Ceramic. The 2000x waterstone is roughly equivalent to: a US 1200 grit SiC paper; Hard Black Arkansas; and X-Fine Diamond. Your 4000x is roughly equivalent to: a US 1500 grit SiC; X-Fine White Ceramic; green rouge. You would need to go to an 8000x waterstone to get the equivalent of a 2000 grit SiC paper for abrasive particle size.

Here's a link showing a "grit" chart:

_____ American Association of Woodturners Cascade Woodturners Assoc., Portland, Oregon Northwest Woodturners, Tigard, Oregon _____

Your disagreement in no way alters reality. The analogy of the ryoba, which, if viewed broadside, is rough and makes visible scratches, yet, if viewed and used along its length, produces smooth surfaces either side, is one I have often given.

Presentation of the tool so that the final depth is a cut versus a peel is obtained by tool position. When you follow with other aspects of the process like fiber compression, heating and bevel burnishing, the "sawing" diminishes to null.

Sorry, but I don't follow your logic. I agree that serations help when the cut is made in line with the blade, ie: sawing. However, turning tools do not cut directly in line with the edge. Instead, they make a skewed cut, similar to puching a handplane or chisel on a skew for flatwork.

So are you saying that you are relying upon the tool to burnish the wood to provide the smooth surface?

OK, not to be argumentative, but what are you basing your assertions on. We can argue based upon theory all day, but practise is another thing. I freely admit I have not done any qualitative testing. Have you? If so, I'd be interested in the detials.

David

remove the key to email me.

Yes they do, or almost so, if you present them properly. Look at this ASCII representation \ ( .

The slash is the inside of your bowl, the parenthesis the leading edge of your gouge. Slide the nose of your gouge left until you start a curl, then follow from edge to bottom. The slash is always in the same position, representing as it does one piece of the greater rotating item. Not surprisingly, the smoothest cut is produced when the combination of angle of attack and position on the curve of the gouge most closely matches the curve of the piece, since the fibers are dragged by to be cut nearly at right angles.

Now I use forged pattern gouges, because they can be sharpened with nearly the same bevel angle all around, allowing me to hold a shaving from edge to bottom, allowing a quicker route to fair curve than step cutting. I personally guide versus ride the bevel, because my technique of fixing the toolrest below centerline and gouge selection doesn't require me to reference the cut to the bevel for support, though some like to exert the outward pressure it takes to ride the bevel, making the surface _apparently_ smoother as it compresses, heats, and hardens the surface.

There is no "empirical" test for smoothness of surface, but the place to put your time and effort is in tool presentation, not shining edges. Save those for your carving tools, where your ability to skew (saw) is more limited than on the lathe, where the electric motor does it continuously.

This just appeared on my server. Your case is well made. Now if only wood were made of fibers like the others you mentioned ... oh, it is, isn't it?