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Posted: 11/20/2017 4:12:00 PM EDT
[Last Edit: AeroE]
Link Posted: 1/2/2019 10:38:36 AM EDT
[#1]
I'm reposting this here because I'm sick of typing it out every time someone can't sharpen a knife.

Originally Posted By M1tchell:
I'm glad you guys are entertained

Well I tried the whetstones again with a fresh positive attitude, and I just can't get it sharp.  I went back to the oil stone and I'm shaving hair off my arm again in no time.  I just don't know what I'm doing wrong with the water stones.
View Quote
What's likely happening is the oil stone is creating a thicker serrated burr that is sharp enough to shave.  As soon as you cut something harder, like wood, it'll fold over.  Traditional water stones can finish an edge without a burr, but only when used with the proper amount of pressure and with the creation of an abrasive slurry.

Look, this is what you're trying to accomplish.  The thinner the edge, the better it cuts, the longer it cuts.  Period. "Edge angle had by far the strongest effect on edge retention, much stronger than other effects such as PM vs ingot and the finish it was sharpened to." {1}  Regardless of how hard the knife steel is, sharpening with anything less than the super low pressure, freely cutting abrasive slurry of a water stone is going to result in a burr on the knife edge.  Going from left to right, you have a dull knife.  The second image is your stoned "sharp" knife.  You can see it has a burr.  Steel flexes with geometry more than physical characteristics like hardness.  When you get down to an apex thickness of .001" or less, where paper cutting "sharp" begins, whether it's 50 RC or 70 RC Rex 121, it's going to flex away from your abrasive because the pressure required to cut the steel exceeds the steels ability to withstand it.{2}



The third image is stropping that burr off at a slightly more obtuse angle than you sharpened at.  This is done with various polishing compounds.  You can use anything from 3m cutting compound to .5 micron diamond paste or Flitz or green/red rouge or whatever the fuck.  It doesn't matter in regard to removing the burr, only in how fine of a surface finish you want on the micro edge of your knife.  But you need something, as leather alone will not accomplish anything without abrasive. {3}

This is the only real way to get a truly sharp knife edge like the 4th picture that's not cutting with a floppy burr, outside of water stone slurry.  Free wheeling leather like an old timey barber shop works, but leather glued to a piece of wood works better.  Some people don't even use leather and instead impregnate a piece of basswood or balsa and strop directly on that hard surface.  That requires much more care with pressure, leather is a little more forgiving.

Make a wedge using whatever abrasive technique suits your fancy.  Remove the burr.  Enjoy the sharp.

{1} Maximizing Edge Retention, Larrin Thomas
{2} Burr Removal, Science of Sharp, with SEM edge pictures
{3} Experiments on Knife Sharpening, John Verhoeven
Link Posted: 3/5/2019 7:53:51 PM EDT
[#2]
Investment casting can be found here:

https://www.ar15.com/forums/General/This-is-how-to-do-lost-wax-casting/187-2199746/
Link Posted: 4/17/2020 12:14:08 PM EDT
[#3]
How to make a sterling silver and garnet ring.

Making a ring
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