help with blade thicknes for edge centering

B

bartblade

Joined
Nov 4, 2002
Messages
344
i just got my knife markning gauge yesterday i mounted it on my table in the shop took out my micrometer for my first truly centered edge the blade is .144 thick how do i figure what to set the scribe to mark my center lines and what do i use to set the scribe to heighth to do it. i too the heighth gauge and mounted the cast metal holder for the heighth bar and scribe under the tables bottom and drilled a hole in the table to take the height gauce os i can set it as low as i need it. its a very genious set up but for the life of me i cant figure out what the thickness formula is to use it.
 
If I wanted my edge to end up 20 mil thick: subtract 20 from 144, divide by two = 62 mil (0.062 inch). Two lines are scribed leaving a 20 mil space between lines. Set your device to 62 thousanths for 20 thousanths edge after grinding bevels. Scribe a line, flip the blade blank over and scribe the other.

RL
 
thanks r linger so the formula is to take the thickness you want and subtract it from the blade thickness and then devide by 2 thats so easy thanks a lot i was deviding by 2 first and was getting fusterated because i kept comming up with paper thin measurements i dont know what i was thinking overly excited about my new toy i guess.
 
You can easily do it that way too. Divide by two = 0.072 inch. Then divide your space between lines by two (in this case 0.020 / 2 = 0.010 inch) and subtract from 0.072 = 0.062 inch. Set your scribe for 0.062 inch.

Later you can use your ginding experience and scribe only one dead center line like Nick does. I do that for my Scandi grinds; those that have no edge thickness to speak of.

RL
 
rlinger said:
You can easily do it that way too. Divide by two = 0.072 inch. Then divide your space between lines by two (in this case 0.020 / 2 = 0.010 inch) and subtract from 0.072 = 0.062 inch. Set your scribe for 0.062 inch.

Later you can use your ginding experience and scribe only one dead center line like Nick does. I do that for my Scandi grinds; those that have no edge thickness to speak of.
RL
Click to expand...

I do it the way rlinger does it except I add the .010" to the center line (to make it .082") so that I scribe the opposite side and then flip over. That way, when I slip (like I tend to do from time to time) the bad line is made inside the lines and I can still get a nice clean scribe line on a second pass.
 
NickWheeler said:
I only scribe one line, in dead center. :)

-Nick-
Click to expand...
To make sure you're in the center, scribe it once, flip over the blade and scribe it again.
 
I still like my height gauge and surface plate.I use RL's formula too, The land you want left after rough grinding minus blade thickness divided by 2.Lay the blade on the surface plate ;scribe;flip over blade;scribe.
 
I use a height gauge (about 70 or 80 bucks - www.use-enco.com) and granite block too. I had bought the height gauge before making knives and it took me about a year to figure out its value in scribing edge lines!!! (da)

Many well experienced makers scribe no lines at all.

RL
 
Sounds like we might have similar units RL.In response to not using any lines at all--How do they do that :confused: I know;practice,practice,practice.
I'm back out to the shop men !! see ya
 
wats with scribing lines is that so you can see when you go too far and have to grind more of the other side off to equilibriate...lol i have never scribed a centre line nor have i seen the need to even when making tantos... but maybe thats cause i forge most of my edges to a point where they just need a finish grind.
 
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