Glad to help. I don’t use waterstones, but I did spend years using composite stones that also hollowed badly. There are a couple basic techniques you can use to minimize the hollowing. The first is to use the entire surface of both sides of the stone wherever you can…. not just the center…and the other is to do more on the grinder and less on the stone when completely redoing a bevel.Quote:
Bob,
Could you post a tutorial on how you sharpen? I use waterstones but hate the hassle of trying to keep them flat. I have my grandfather’s oil stones some maybe 50 or 75 years old (just guessing) I …would love to see your thoughts in pictures.
Using the entire stone sometimes means you have to forego some jigs, but it’s always good to develop your ability to sharpen freehand as I can think of dozens of situations in even hobby woodworking where your bench and jig won’t be available. All the grandiose words written in the last couple decades on honing, all the expensive gizmos for sale to help you do it, and all the trouble folks seem to have with it puzzle me some. Grind that blade correctly, and the difference in cutting speeds and technique between oil, water or composite stones is meaningless because there isn’t enough honing to be done to measure a difference.
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So I’ll go you one better on your question. I’ll convert an old abused, 2-dollar half-inch firmer chisel to a small skew for lathe work. Lotsa grinding required here…and on burnable 19th-Century carbon, not burn proof High Speed Steel. Get good enough freehanding on your stones, and it takes no longer to put your best edge on that carbon skew using stones as it does to put an inferior edge on an HSS skew using a grinder.
I mark the bevel I want on the chisel using a bevel gage and carbide scriber…
http://pic3.picturetrail.com/VOL12/1...9/69053176.jpg
…and grind off the old edge square to the line. Looking at the squared-up flat I made, the chisel’s old bevel largely remains on the bottom side in the pic, but the flat penetrates to at least the center of the bevel at the point of the skew to leave enough steel there to grind a perfect bevel and edge next. The objective in all sharpening is razor-sharp…but also consuming minimum steel in the process.
I’m using the coarsest grinding material I have…both my coarsest grinding stone and 26-grit sanding disks for the roughing work. The coarser the abrasive, the cooler it cuts and the faster you can do the job without stopping to cool the steel with every stroke. Remember that if you turn that steel blue with the 600 degrees it takes to do it, you’ve ruined its temper and all that blue must be ground off for that steel to hold an edge. Takes two minutes to grind.
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Next I grind the 20-degree bevel on both sides of the skew. I use the tool rest and the side of the coarse wheel in the 8”, 1750-rpm buffer-grinder. No jigs, no Tormeks, just that angle gage sitting handy on the grinder stand to show me what 20 degrees looks like when grinding either side….working all that out with the wheel stopped, of course. Takes 5 minutes, taking a little bit off at a time then dipping the tool in water and examining the cut for any adjustments in my hold required. The closer I get to forming an edge, the easier it is to burn the edge.
Learn to watch the trail of grinding sparks flying off the steel…. their density and quantity tell you precisely how much steel you are taking off and from where…showing you how uniform your resulting bevel will be.
The stone manufacturers recommend you don't use the side of the stone for grinding, and I don't disagree, although I've been doing it without incident for over 40 years....simply buy top quality stones and don't use much pressure there.
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Here’s the ground edge.
http://pic3.picturetrail.com/VOL12/1...9/69053195.jpg
Now I take the skew to the coarse novaculite stone fresh from the can of kerosene it lives in and measure what 20 degrees looks like for rough honing. I’ll not use a secondary bevel on this edge but hone a flat 20 degrees on both sides. That stone was my uncles, who built boats professionally from 1930 to 1970…no telling how old it is but it’s just as clean and flat as the day it was ground. It may even have belonged to his father, a carriage maker.
You can hollow novaculite stones if you don't spread your sharpening around the stone, especially with narrow chisels, so its a good practice to follow the techniques I discuss above.
Having taught a number of young people to sharpen over the decades, the single biggest factor in ease of honing is the height of the stone. Do what you have to do to get it secure and to the level of your belt buckle…higher than your kitchen counters, let alone most workbenches. This gets your elbows up and free from your torso to aid you keeping a consistent angle without any rocker or rounding.
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I dip the end of the tool in kerosene and make a few strokes on the stone…then I examine it to see what hold adjustments I need to make. See the flat? I need to drop the angle a tad and apply more pressure to the lower edge of the skew to even up that bevel.
http://pic3.picturetrail.com/VOL12/1...9/69053987.jpg
Pressure adjustments are made using the fingers of the left hand while I stroke the tool back and forth using my right. Here I’ve wrapped my fingers around the lower edge side to apply more pressure to that edge than the upper or tip edge.
http://pic3.picturetrail.com/VOL12/1...9/69053979.jpg
Now you can see I have an evenly formed bevel. Its not perfect…but as only a couple thousandths at the edge really matter…it doesn’t have to be. Takes only another 5 minutes, and if this were merely a secondary bevel on an existing chisel, it would have taken one minute or less.
With the bevel honed on both sides, I clean, buff and phosphate blue the skew before final honing. Cold blue or machinist’s layout blue applied to your tool before honing will teach you gobs about the effects you are having, as the camera picks up the small details shown better than the naked eye. Especially a 50+-year-old naked eye, and especially flattening your chisel backs…. do the rough work flattening backs …not on your expensive stones…but on your belt sander using 150 grit…remove the bag and clean out the sawdust first.
Continued…
