Problem with edge thickness

SHOKR

SHOKR

Well-Known Member
Hi all

Im new to knife making and i have trouble sticking to the edge thickness before sharpening
Translation: i mark the edge, but i either go past the lines and end up with thinner edge, or to counter that i end up not reaching the edge and with a thicker edge

How do you guys do it?

Thanks
 
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thanks Warren
its not as simple as that, maybe i didnt ask teh question correctly

what steps do you take?

for example i use anything between 36-80g to establish the bevel, with 36 i need to stop way before the line i scribed, with 80 not so much, but still stop short to give bit of room to finalize with finer grit, etc.
 
I stop at about 0.050" with a 36g belt, then switch to a 60, clean it up, then a 120 and repeat. I am usually at about 0.030 or so at this point, ready for heat treat. Since I grind post heat treat, I stop there, but I do hand sand a bit to make sure there are no gouges I missed. If so I clean them up to prevent stress risers.
 
For flat and scandi: I eyeball it, not very scientifically at all...if it's possible to scientifically eyeball something. My first cuts are at a 45ish degree angle scandi grind (for flat grind also i start with this). I take it down to the center at about a dimes width. I do this evenly on both sides to end up with the final edge thickness before I begin grinding the primary bevels. This also allows me to get it straight and even before doing the brunt of the work. All with a 40 grit belt

I then turn the angle and get what will actually be the bevels. doing this allows me to keep a hairs space between the edge and the belt until it actually get's even with were I stop the grind and becomes flat... because eventually it will take out that convex and be a flat bevel all the way to the edge. I use a 40 grit until about half way up for a close to full flat grind, 80 grit the rest of the way and a 120 just to clean it up. If it looks like I'm goingt o be thining the edge or going past where I've already ground the edge to, I simply don't take the grind up the bevel as far and HT there. After HT, I can always take it as far as I need to go. It takes practice, I don't own a caliper. (man i do need to put that on my Christmas list though :shush: )

After HT, I grind the primarys down a little further to clean up and while doing this makes the edge thin out to the pre-sharpen edge.

I hope that makes sense. see the pic for the 45 angle to start (after this I turn to the "normal" grinding angle and finish the flat grind and it eventually runs into that thinner edge)

10445966_642895955794211_264664126017528194_n.jpg
 
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shokr I leave thick just out side my scribe line, heat treat then do finale grind down to thickness I want. I start with 80 then to 120 then old 220 before heat treat sometimes I hand sand horizontal if its a oil quenched blade so no scratches going vertical but when I do this I go really close to finished edge.
 
As long as you leave yourself .006 min, or .010" to be on the safe side for decarb removal, you are fine. Under .020" at the edge prior to heat treat increases the risk of bacon edge. This is for oil and water quenching steels. Stainless with foil or shielded atmosphere can be pretty much finished dimensions.
 
thanks all

yeah my problem is with the final finishing edge, pre HT its a big deal because i can always remove more material later and i often grind a bit and leave thicker edge then finish up after HT

i will try a new approach soon and see how it goes :)
 
seems to be practice, practice, and more practice. i try to mark the edge of the blank with 3 lines so i end up with an edge about 0.5mm before heat treat. i use a bevel jig so i end with something real close to even.
i have appearance of finished blade as last priority when making a blade. first priority is blade angle for best performance. second is heat treat for hardest possible steel. third is most comfortable handle possible. having the bevels even to a micron is something to work on but not really all that important.
as always, just the opinions of a tired old sailor glad to be home from the sea.
 
Shokr,
Try this,
Remove half what you want to remove with the 36, then half again with the 60 grit then half with the 120 grit and on to your finishing belts. That's what I do, it works for me?
 
like this :les: And in reality what happens is that if you always keep the very edge of what will be the cutting edge off of the belt by a hair, you'll always cut at the top of the what will be the primary until you get it flat with where you end the grind. I might be doing it wrong myself, whooo knows, but it seems to work for me.

Untitled-1 copy.jpg
 
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Thank you all so much

Yesterday i was finishing up a knife (i thought it was almost finished but i had more grinding to do tahn i expwcted) and i took my time getting close to the scribe lines with 80g, then continued with 220g till the lines disappeard.

Thanks a lot for the diagram, thats actually what i did but i ended up leaving that 'hair line', i honestly eont remember if i forgot about it or what, i think it started as over compensation because when i started i used to gouge the edge a lot. And also because i used to only do the breaking of angle first then never touch that partmaybe.
Now the 'hair' is removed near the end while im finishing up and all is good! :D
 
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