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Posted: 3/30/2010 5:06:24 PM EDT
Since this is the gunsmith and machining forum(?) I'll post this here.  Probably more appreciated here than GD.



I'm pretty good with a stone.  I've hand lapped carbide punch sets, I've sharpened complex compound radius profiled cutting tools, and have been able to apply my profession to sharpening hunting or EDC knives with pretty good results.  Pretty good results.  No matter what I do, or how often I do it however, I'm human and there will always be variations in how I hold the knife to the stone, the stroke pattern I take, the pressure I use, you get the point.  I saw the Edge Pro system in GD, back when the paper wheel idea was stirring up a storm and I thought, that's brilliant.  It's a high priced Lansky, but with better implementation, and more consistency.  I also thought, there's no way I'm paying $350 for such a thing, and then possibly be forced to buy particular stones for the particular system.  







So I set out to manufacture my own sharpening jig, with the restriction of using Gesswein EDM stones that are 1" wide, .250" thick and 6" long.  These are a common stone in industry, they can be purchased through MSC, McMaster, Travers, any number of supply houses, they come in a wide range of grits (I purchased 220, 320, 400, and 600), they are a hard variation of aluminum oxide and tend to hold their shape very well.







My first challenge was to devise a solution of holding these stones in a fashion that would allow them to be held securely, in a repeatable fashion, while still allowing them to be changed without using tools and rather quickly.  I didn't have the capability of making leaf springs, because I didn't have any stock, but what I did have was nylon tipped thrust screws.  These are a hollow set screw, with a spring loaded nylon tip, captured by a smaller set screw.  Captured in the end of the stone holder, they allow a spring set snap in, snap out ability that was as simple to implement as drilling and tapping 2 holes.  

















The holder was a piece of hot rolled 1x.375 steel, milled out .200" deep so the .250" stones would protrude above the surface of the bar.  Add a 5/16-18 hole on the end and a simple fixture handle (available through McMaster).  The guide rod is a piece of centerless ground O1, .3125 in diameter with a 1/4-20 hole on the end.  This attaches with another 1/4-20 set screw used as a threaded stud.









The swivel knuckle was another challenge.  I originally planned to use 2 guide rods, but then quickly realized that this would eliminate the ability to "roll" the stone with the profile of the knifes edge.  So the knuckle is made up of 2 blocks, a dowel pin, a sleeve that captures the dowel pin, and a cap screw used to set the angle by impinging on the swivel rod.  The dowel pin is pressed into the one block, but the other block is reamed .001" over the dowel size to allow for rotation, that is why the sleeve is necessary to capture the assembly.  So rotation in one axis is created here.  Rotation in the second axis is provided by the swivel rod, which is another piece of O1 with a grooved radius cut into it and captured by a .125 dowel pin in the base.  The swivel rod swivels freely.











The back guide is what really makes this system repeatable.  A simple piece of cold rolled milled to fit in the slot of the table, with a tapped hole and thumb screw.  Chamfered for clearance of the stone while working.







Throw it all together and this is what you get.  (Yes I was lazy when attaching a base.  I had built it without a base thinking I would hold it in a vice, or make rubber footed legs, when I said to hell with it, grabbed a piece of drop and zapped it together with the welder.  Quick and dirty.)







To use, you need to establish your angle.  A little sharpie marker on the edge and take a couple passes.  When you're satisfied, stroke the rest of the edge.











I would post drawings, except I don't have any.  I basically built this from seeing the edge pro and coming up with dimensions as I went, based off the size stone I decided to use.  The problem with this, is that it's too large to use for smaller knives.  Anything with less than a 3" blade, and the table interferes with sharpening the tip.  Anything with a blade less than .625" wide, and the edge will not over hang.  I plan to correct this by building a "small knife attachment" that will basically be a set backstop and work surface that extends out past the main table, and replaces the moveable back guide you see here.  This will be 2" wide and only have a 1/2" wide ledge, allowing me to sharpen nearly every knife I own.



Since I don't have drawings to post, here's a picture of my wife's ass to make up for it.




Link Posted: 3/30/2010 5:27:32 PM EDT
Excellent post, I like it.  How are you rolling out to the tip of the blade, can the guide swivel left and right on the post as well as up and down?
Link Posted: 3/30/2010 5:39:43 PM EDT



Originally Posted By ag04blast:


Excellent post, I like it.  How are you rolling out to the tip of the blade, can the guide swivel left and right on the post as well as up and down?


Correct.  The knuckle is tightened against the swivel rod, so the knuckle does not rotate, the entire rod rotates left to right.



 
Link Posted: 4/2/2010 2:09:16 AM EDT
now go post this in the "projects" thread for later reference

Link Posted: 4/2/2010 9:32:46 AM EDT
One tip for the next time you make something like the dowel and retaining collar assembly (cause we all like to learn other ways to do things...) Instead of that, could have just tapped a hole and screwed in a stripper bolt:

Maybe you just didn't have any stripper bolts around either But they can be useful to have
Link Posted: 4/2/2010 10:49:36 AM EDT
[Last Edit: 4/2/2010 10:50:12 AM EDT by Kuraki]
No you're right, a stripper bolt would have been perfect and I had them on hand. The problem was like I mentioned, I originally planned (stupid) to have 2 guide rods, until I realized it would eliminate the ability to index the stone, so that middle block got reamed .001" over with the idea that the pin would be press fit into a block on each side. Since that hole was drilled and reamed before I realized my mistake, it was too large for threads.  It was easier to spin out a collar than to remake a middle block.
Link Posted: 4/2/2010 1:07:02 PM EDT
Originally Posted By Kuraki:
No you're right, a stripper bolt would have been perfect and I had them on hand. The problem was like I mentioned, I originally planned (stupid) to have 2 guide rods, until I realized it would eliminate the ability to index the stone, so that middle block got reamed .001" over with the idea that the pin would be press fit into a block on each side. Since that hole was drilled and reamed before I realized my mistake, it was too large for threads.  It was easier to spin out a collar than to remake a middle block.


Damn you rigid body dynamics!!  Damn you all to hell!  

Still fun to develop stuff
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