Math question fom Dec"Done finely"

[prarieboy]

Hey Folks I have a file that is 3/8" thick I would like my primary bevels to end 7/8" from the edge of the blade. I need to know the angle to make that happen!
Better yet to know how to figure out that angle!!!!
Thanks for Your help.
Hope this ain't so simple as to make someone spray coffe on their screen in a fit of laughter!!!!

Ok this knife is a family linage I rekon!It is for freinds Grandson.The file it is made from I located in The childs Great Great Grandads
Farm Smithy!The antler is a drop from the Family property.The black leather I used for the inlay were a pair of airforce issue gloves that
belonged to his great granddad.The rattle snake skin inlay is a snake that I killed while deer hunting their property.The brand of course
is the family brand.

     
   
   


C-Ya Bob

[robtattoo]

Here's a very cool website that is an immense help for stuff like this.....

    http://ostermiller.org/calc/triangle.html    

If you think of the grind as a triangle. The blade width is 3/8" (Base of the triangle)
The grind height you want to be 7/8" (sides of the triangle)

So enter the values 0.375 (base) & 0.875 (sides) & it'll calculate you an angle of 24.7º

If you then halve that angle, you'll be grinding each bevel at 12.35º Call it 12½ & you'll be near as makes no difference    

I love this program!

Nice knife too! Lotta family history in that one    

[kbaknife]

Rob is a genius.
I'm not, so bear with me.
Don't over-think this.
Even if you knew exactly what angle you were looking for - would you be able to duplicate it on a grinder?
Not unless it was a CNC machine.
And by hand/eye, even knowing the exact angle will not stop you from either grinding too much or too little.
Now don't think me a smarty-pants for saying this, but if you want your grind height to only go so high - stop before you get there.
Adjust your cutting edge accordingly.

Reminds me of the joke about the guy who walks into a Doctor's office, raises his arm up over his head and says, "Doc, it hurts when I do this!".
Doctor says, "Then don't do that."

[prarieboy]

Hey thanks Guys I did finely just do it the way that I had been doinit for a while.I have a homemade jig that rests on the grinder table then finish by hand.
 I was just very scared of messin that file up there ain't another in captivity That belonged to Great Great Grandad.
 Rob I did use that method to get close with my redneck jig but as for da norm Karl is correct  in that it ain't perfect.
That Makes it just like the Guy that made the knife!LOL!
 C-Ya Bob

[Roughcountry]

Nice knife. I also like that snake inlay. I've got several rattler hides I plan to tan and try a few inlays. It's on my never done list and needs crosed off.

[MTArrowLauncher]

Nice knife and the rattler skin is awesome on that sheath