Final Edge Question

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Dec 24, 2014
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So I got my forge going and successfully HT'd my first 2 blades. Now establishing the edges is a little more difficult than I assumed. I get my pre HT edge down to approx. .025-.030. Heat treated with no warping.
Now, on the grinder, do I work the edge on both sides to finally meet in the middle, THEN sharpen? Or do I leave a flat to say maybe .005-.01 and then sharpen from there?

Any tips would be great.
 
It depends on what style of knife it is. I think in general that .01 to.015 is good for a final thickness. Then finish your handle, and sharpen as the very last step.
 
It depends on what style of knife it is. I think in general that .01 to.015 is good for a final thickness. Then finish your handle, and sharpen as the very last step.

Ok, thanks. I just was making sure that I could get a knife to cut, and I succeeded. lol. But may have brought the edge a little thin before sharpening.
 
Depending on the use the knife will get, the flat edge after final sanding can be anywhere from .005 to .015. Slicers and fine cutting knives have thinner edges, and camp knives and choppers have thicker ones. As a rule of thumb in the beginning, try for a .010" flat edge at sharpening.

As colu41 said, do all the rest of the knife finishing, including making the sheath, and when the entire knife is finished, sharpen it. There are so many "I sharpened the knife too early" stories that it will curl your hair to hear about how many people got a bad cut when they rushed to make the knife sharp too soon.
 
Depending on the use the knife will get, the flat edge after final sanding can be anywhere from .005 to .015. Slicers and fine cutting knives have thinner edges, and camp knives and choppers have thicker ones. As a rule of thumb in the beginning, try for a .010" flat edge at sharpening.

As colu41 said, do all the rest of the knife finishing, including making the sheath, and when the entire knife is finished, sharpen it. There are so many "I sharpened the knife too early" stories that it will curl your hair to hear about how many people got a bad cut when they rushed to make the knife sharp too soon.

Thanks again Stacy. Colu41 would be me but, I get it. :D I will do that with my next one. But for now, I finally have everything I need to go ahead and finish it. Going to do a little handle shaping and fitting today along with cutting out some more blanks, and hopefully tmrw when the epoxy is set I'll have a finished knife with pics.
 
I'm going to throw something different out. Sharpen the knife before you finish grind and test the edge. I'm not going to hand finish and make a sheath for a knife if I haven't tested the edge. .005 is as good thickness depending on purpose. It all depends on the steel and heat treat and intention.
 
I'm going to throw something different out. Sharpen the knife before you finish grind and test the edge. I'm not going to hand finish and make a sheath for a knife if I haven't tested the edge. .005 is as good thickness depending on purpose. It all depends on the steel and heat treat and intention.

Interesting. I'll have to see what works for me I guess. I'll get it figured out. Theres definitely a lot to learn but, I'm learning fast. Thanks again.
 
I see both sides of it, but I would run the edge across something course to dull it before continuing work as a bad cut can disable you for Life when it comes to your hands. Once you have a verified recipe for heat treat and a way to test the hardness (even the small file set if need be) you shouldn't really need to test every knife's edge before finish work. What would you be testing for? A blade at proper hardness with the proper geometry should perform as intended, albeit small flukes do exist I believe the risk outweighs the benefits personally.

Justin
 
I sharpen the knife and then do the handle and sheath. After sharpening I wrap the blade in printer paper and then a ton of black electrical tape. If I'm doing a kydex sheath then I'll finish the handle, strip all the tape/paper off, and then do the kydex sheath. I use 2 layers of painters tape when doing the kydex sheath. If I'm doing a leather sheath I can leave it taped up, as long as I have the template of the sheath done first.

I'm just real paranoid about the blade finish. I want the blade side done and over with before I start on the handle. I like to have my scratch pattern running vertical on the flats and it's hard to repair(if something was to happen while sharpening, handle forming, sheath making, etc) that if you can't lay the blade flat because there's a handle in the way.
 
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I see both sides of it, but I would run the edge across something course to dull it before continuing work as a bad cut can disable you for Life when it comes to your hands. Once you have a verified recipe for heat treat and a way to test the hardness (even the small file set if need be) you shouldn't really need to test every knife's edge before finish work. What would you be testing for? A blade at proper hardness with the proper geometry should perform as intended, albeit small flukes do exist I believe the risk outweighs the benefits personally.

Justin

Thermocouples have been known to go bad. Depends on what you expect out of your knives I guess. Can't believe anyone wouldn't test the edge.
 
A couple of thoughts. If the OP (colu41) believes he may have ground the edge too thin for the intended use of the knife he can sand the edge back to an appropriate thickness. Next, a lot of people sharpen last and for good reason. Hand sanding a sharpened blade takes a lot of concentration (and up to date medical insurance). I fall into that group because I don't like a visible sharpened edge bevel on my blades. I sharpen then hand blend the bevels into a smooth convex edge. Then I apply the final lengthwise pulled sanding strokes. This I do before constructing the handle because I want that nice finish to run up to and underneath the handle. But some testing can be done in the shop without putting a super sharp edge on the blade. A brass rod test will give you a decent indication whether or not the heat treatment was successful.
 
A couple of thoughts. If the OP (colu41) believes he may have ground the edge too thin for the intended use of the knife he can sand the edge back to an appropriate thickness. Next, a lot of people sharpen last and for good reason. Hand sanding a sharpened blade takes a lot of concentration (and up to date medical insurance). I fall into that group because I don't like a visible sharpened edge bevel on my blades. I sharpen then hand blend the bevels into a smooth convex edge. Then I apply the final lengthwise pulled sanding strokes. This I do before constructing the handle because I want that nice finish to run up to and underneath the handle. But some testing can be done in the shop without putting a super sharp edge on the blade. A brass rod test will give you a decent indication whether or not the heat treatment was successful.

Brass rod? How does that work?
 
A quick search will turn up lots of explanations but this is basically how it works. Secure a 1/4" diameter brass rod in a vise. The length isn't important. A 4" length is plenty. Set it horizontally in the vise with half the round sitting above the vise jaws. After your blade is ground to it's final thickness (sharpened or just slightly softened from sharp) lay the blade over on it's side and run the cutting edge over the brass rod. Use just enough pressure against the rod to cause some deflection of the steel. If properly heat treated the steel at the edge should deform as it passes over the rod then return to true. If the edge chips out the blade is too hard and can be tempered back further and tested again. If the edge curls or deforms but does not return to true the blade didn't get hard enough or was tempered too soft. In that case, I suppose you can anneal the blade and re heat treat the blade. That is one reason to test your blade before adding the handle.
 
A quick search will turn up lots of explanations but this is basically how it works. Secure a 1/4" diameter brass rod in a vise. The length isn't important. A 4" length is plenty. Set it horizontally in the vise with half the round sitting above the vise jaws. After your blade is ground to it's final thickness (sharpened or just slightly softened from sharp) lay the blade over on it's side and run the cutting edge over the brass rod. Use just enough pressure against the rod to cause some deflection of the steel. If properly heat treated the steel at the edge should deform as it passes over the rod then return to true. If the edge chips out the blade is too hard and can be tempered back further and tested again. If the edge curls or deforms but does not return to true the blade didn't get hard enough or was tempered too soft. In that case, I suppose you can anneal the blade and re heat treat the blade. That is one reason to test your blade before adding the handle.


Interesting. Thanks
 
Thermocouples have been known to go bad. Depends on what you expect out of your knives I guess. Can't believe anyone wouldn't test the edge.

As I said, small flukes do exist, and that includes cases that thermocouples fail. I didn't mean to say that one should go about it blindly, which is why I recommend getting at least a hardness file set. I use a set on every blade to ensure I'm within a given range and every couple months I send a coupon with my buddy who works at detroit deisel, and their metal lab tests the hardness for me. So far the deviation has been more than acceptable.

A bad edge will be discovered at some point before it leaves my hands regardless. I personally don't like to take the risk and would rather peel a pair of scales off in the case of it not performing as intended. Doing due diligence and spot checks periodically leaves me with the utmost confidence in my blades. Many makers do it this way, so it seems odd to me that this surprises anyone.

A cut on the hand can me more than superficial. Tendons and nerves are extremely exposed in the hands and damage in some cases means permanent disability. This could not only effect your hobby but your career, your livelihood, you marital situation, or all of the above. I'm a bit of a safety nazi, but I have seen first hand what complacency can do and have personally witnessed how bad the damage can be because of it. It only takes one slip up in the wrong way and you've lost the use of most of your hand, or worse.

I was working with my brother on a concrete crusher and he operated the plant. It was a long day and we worked into the dark. During the end of day inspections my brother made a mistake and slipped doing something he did every day for almost a year. The massive rotor sliced his hand severely and crushed/broke 3 metatarsals along with severe tendon, muscle and nerve damage. The only thing that saved him from losing his hand was his index metatarsal, the only bone that did not break. Obviously this is a worst case scenario in a very different circumstance, but my point is it only takes one instance of complacency to make a mistake that will influence the rest of your life decisions.

Sorry to be so long winded, but I hate having to explain why I do things in the safest possible fashion. Accidents don't "just happen" and most are avoidable. I try to do my best to avoid them.

Justin
 
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