Primary bevel..to jig or not to jig

T

TJ88

Joined
Apr 28, 2016
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Ok so im starting my second knife. The first that i will temper. Its .15 inches thick and the maximum blade length from spine to cutting edge is 1 inch. Im going to go for a flat grind and would like suggestions on a bevel angle. I want a sturdy slicer so i imagine it will need to be a low angle. I have a jig to hold an angle but if i set it for 10 degrees wouldnt that give me a 20 degree overall bevel angle?
 
Throw the jig away and grind buddy! Just grind from the center line of the edge almost the entire way to the spine. Leave some room on the edge if you're grinding before heat treat. .30 thou or so. Think the thickness of a dime. Every blade is different depending on its expected usage, material thickness and size. Look at the pics posted all over this forum. You'll notice how similar the grinds are. Remember, thin is in!!
 
see... now i would argue to jig. to each their own, but i know if i'm going for accuracy i still use a jig a lot of the time, it's just one less thing to have to be as good at, lol
 
So for a .15 thick knofe and a bevel that would be .8-.9 id be looking at at a 5-8 degree bevel per side by that chart right?
 
TJ88 said:
So for a .15 thick knofe and a bevel that would be .8-.9 id be looking at at a 5-8 degree bevel per side by that chart right?
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Not quite, for a 1" bevel height with 1/8" stock you grind each side at a 3.6 degree angle. Your stock is a little bigger so you would have a slightly larger angle. You have to interpolate between the two nearest sizes. These angles are just to get you started. Set the angle then grind to either .015 of your marked center line or to the height of the grind you want, whichever comes first. Then you will need to adjust your angle so as to get the final grind height and edge thickness that you want by eye.
 
Ok when you say .015 of center you are reffering to a line that would be drawn exactly in the middle of the .15 stock on the opposite end of the spine? That is to say what will become the cutting edge?
 
TJ88 said:
Ok when you say .015 of center you are reffering to a line that would be drawn exactly in the middle of the .15 stock on the opposite end of the spine? That is to say what will become the cutting edge?
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Yes, I draw a line down the center of what will become the edge. I say to grind to within 15 thousands of this line as you want to keep the edge at 30 thousands so your blade won't warp during heat treat. by keeping .015 on each side of the line you come up with a .030 edge.
 
Ok i understand perfectly now. And when you say adjust for the final angle i assume you are meabing the second bevel angle that will become the acual edge. 20-25 degreesor whatever i end up deciding on?
 
TJ88 said:
Ok i understand perfectly now. And when you say adjust for the final angle i assume you are meabing the second bevel angle that will become the acual edge. 20-25 degreesor whatever i end up deciding on?
Click to expand...

No, what I'm saying is that it's just about impossible to set your jig to the exact angle you need. The chart will get you close, but you will need to adjust slightly to get your bevels exactly as you want them. You won't know what this adjustment is going to be until you have ground 90% of your bevel. If your initial angle is to steep your grind will hit the center line first. If it was too shallow, you will get to the bevel height first. Once you hit either of these desired dimensions stop and adjust your angle, so that your grind meets both the edge and bevel height at the same time.
 
TJ88 said:
Ok i understand perfectly now. And when you say adjust for the final angle i assume you are meabing the second bevel angle that will become the acual edge. 20-25 degreesor whatever i end up deciding on?
Click to expand...
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Sorry , I just realize that you ask about jig for belt grinder , not for file jig :thumbup:
 
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I thought about various jigs and things when I started as well. I ended up not having the patience to make jigs and just ground and mangled some steel. I'm glad I learned how to freehand grind at this point. My .02.
 
Here is a comparison drawing between an 1/8" thick blade and a 1/4" thick blade with a 1" bevel leaving .030 for the heat treat.

 
Any one have suggestions on how to get the edge center line marked? I think i saw a youtuber use a twist drill bit the same diameter as the stock and use the point to scribe a line down the length?
 
If that's the best you have it'll work. Take a sharpie and color the edge then scribe. Dykem and dividers set to the exact measurement leaving the .015 for each side and scribing from both sides is better but a drill but the same size as the thickness will work. Just leave some room from the line for the ht so it doesn't warp.
 
pleasanthill said:
If that's the best you have it'll work. Take a sharpie and color the edge then scribe. Dykem and dividers set to the exact measurement leaving the .015 for each side and scribing from both sides is better but a drill but the same size as the thickness will work. Just leave some room from the line for the ht so it doesn't warp.
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You can do that with drill to :) If steel is 3.5mm thick use 3mm drill , scribe one side then flip blade and scribe again ..end you have 0.5mm edge center line . At least i do that way :thumbup:

2md3vjl.jpg
 
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TJ88 said:
Any one have suggestions on how to get the edge center line marked? I think i saw a youtuber use a twist drill bit the same diameter as the stock and use the point to scribe a line down the length?
Click to expand...

For the best looking bevel with the least amount of corrections, start grinding the edge at a 5 degree per side setting. With a blade height of 1 inch you may grind the entire bevel using the five degree setting without changing to a more acute angle such as 4 degrees.
I begin grinding most blades whatever the height using the 5 degree setting. Doing this gives you options but without adding to the work. Once the edge is at .035--.045, pre heat treat thickness, you can then adjust the angle to 4 degrees and continue to grind towards the spine. As long as the grind lines at the same height the edge will end up in the center of the blade, there is no need to scribe the edge.
Keep grinding at the 4 degree setting and keep the grind lines matched, watch the grind line move towards the spine. At the 4 degree setting the bevel will move towards the previously ground edge and towards the spine at the same angle.
When the bevel intersects the ground edge at the 4 degree setting and the grind lines match side to side; check and see if the grind is at the height you want, if it is the bevels will match, the edge will be in the center of the blade and there is no "blending" of different grinds on each side to make them look good.
When the blade comes out of heat treat you will already know what angle to use to clean up the bevels and continue the grind to bring the edge to zero pitch.
You will get the sharpest edge if its taken to zero. On a zero edge the sharpening angle can be "less" acute to produce an extremely sharp edge.
The thicker the edge is left, the more acute the sharpening angle must be to produce an identically sharp edge as on an identical blade.

I'm using a Bubble Jig to grind with and what is described above is easily accomplished with a jig that offers a broad range of grinding angles. If your jig can produce angles through a range of 2 degrees to 7 degrees, there is no blade you cannot grind using these settings.

Good luck, Fred
 
THANK YOU everyone for the tips. My jig can adjust through to about 20 degrees. I may take some cold rolled steel i have from lowes and practice first. Ill have to drop some pictures of the actual knife. Unless i botch the hell out of it.
 
Fred.Rowe said:
For the best looking bevel with the least amount of corrections, start grinding the edge at a 5 degree per side setting. With a blade height of 1 inch you may grind the entire bevel using the five degree setting without changing to a more acute angle such as 4 degrees.
I begin grinding most blades whatever the height using the 5 degree setting. Doing this gives you options but without adding to the work. Once the edge is at .035--.045, pre heat treat thickness, you can then adjust the angle to 4 degrees and continue to grind towards the spine. As long as the grind lines at the same height the edge will end up in the center of the blade, there is no need to scribe the edge.
Keep grinding at the 4 degree setting and keep the grind lines matched, watch the grind line move towards the spine. At the 4 degree setting the bevel will move towards the previously ground edge and towards the spine at the same angle.
When the bevel intersects the ground edge at the 4 degree setting and the grind lines match side to side; check and see if the grind is at the height you want, if it is the bevels will match, the edge will be in the center of the blade and there is no "blending" of different grinds on each side to make them look good.
When the blade comes out of heat treat you will already know what angle to use to clean up the bevels and continue the grind to bring the edge to zero pitch.
You will get the sharpest edge if its taken to zero. On a zero edge the sharpening angle can be "less" acute to produce an extremely sharp edge.
The thicker the edge is left, the more acute the sharpening angle must be to produce an identically sharp edge as on an identical blade.

I'm using a Bubble Jig to grind with and what is described above is easily accomplished with a jig that offers a broad range of grinding angles. If your jig can produce angles through a range of 2 degrees to 7 degrees, there is no blade you cannot grind using these settings.

Good luck, Fred
Click to expand...


I'm going to try this with your bubble jig... it is just top notch by the way.
 
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