Help with primary grind

greentrout

greentrout

Joined
Apr 20, 2016
Messages
663
I have read a thread on here about regrinding a primary grind to thin out a blade and correct poor factory grinds. For the life of me I can't find it now that I need it. I have a knife that came with an awful factory grind. Uneven primary and secondary grinds. I wasn't surprised as it was a cheap knife that I intended to mod anyway. Having said that, I've done my mods I wanted. I was scared to mess with the primary grind so I just sharpened the knife. I'm not satisfied with it so I'm looking to try thinning, and hopefully correcting the primary grind.
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The tip isn't bent, it's​ just the angle of the picture. But if you look close you can see how uneven the grind is.
I'm​ fairly new to freehand sharpening. I have a Norton combo Crystolon stone. Can I do the thinning by sharpening the knife like I normally would, just on the primary grind? Also, is the coarse side of my Norton the best bet or would I be better off with sandpaper on glass or a file even? I hope I have explained this clearly!

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I'd do a convex scandi grind. Bark river does some really nice ones.
 
I'm fairly new and I'm not really sure what that is.

To clear up a little more, this knife is 1095 and sort of a small bird and trout or EDC fixed blade.
 
What are your primary goals, aesthetics or cutting performance?

Yes, can be done freehand, but consider how much more metal will be removed from primary bevels (compared to only working the secondary bevels) when you did the sharpening. I would investigate options for powered grinding (belt sanders can be found on the cheap).

I believe the Crystalize stone is Silicone Carbide (SiC), so should cut 1095 fine. Do you know what grit your stone(s) is/are?

If I am not mistaken 120/180/320 Coarse/Medium/Fine would be the typical options. I would not attack a primary with the 320 option.

Regards,
 
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Primary goal is cutting performance. I think a full flat grind would be ideal for what I want out of this knife. I would lose the original maker's mark, but that isn't important.
I do have a 1x30 belt grinder as well.
 
You want to go from a very low Saber grind to a full flat grind ..., WOW.

First thing that comes to mind is start with a different knife. I would assume the low Saber is because the maker began with a thin spine, that may not support such drastic structural removal.

Then I think, go ahead and do the mod's how you want. This is the best way to learn ;-)

Perhaps begin with a mid Saber and if that still works for your cutting purposes (no too weak), progress up to a 3/4 or 7/8 Saber en-route to full flat grind.

Along the way, adjust the TBE (Thickness Behind the Edge - transition shoulder between Primary & Secondary), and the Secondary bevel angles to the point if failure under use, then thicken them slightly to achieve best overall performance.

Along the way, you should find great pleasure (unless an issue related to the metalurgly arises - heat treatment and/or tempering), and considerable first hand knowledge about yourself and your goal (a great evolution will transfer).

Regards,
 
You can do some of this on the coarse side of a combination stone but will take a long time and dish the stone if you aren't careful to move all around on the stone.

I'd get Norton Blaze 60 and 120 grit belts for your HF and do it that way. Dip the knife often in cold water and only run for a 3-4 count at a time. The 60 will pull off steel very quickly and the 120 will civilize the scratch pattern a bit. You can take it up a notch to a 320 grit SiC belt from there or finish it on the fine side of your combination stone.

I'd also recommend you get two of each belts and experiment on an Old Hickory unmodded blade so you have a real good idea what you're doing before resetting a blade you've got time in on.

It should turn out a lot better cutter than the factory grinds.
 
Spey - Again, I'm new. In knives I definitely prefer a flat grind. This knife is 1/16" stock. I know I've seen paring knives of similar stock with a full height flat grind, but again their could be a reason these blades don't come that way. My original post was asking about doing more of what you said. Keeping the saber grind and just thinning the secondary bevel.

HeavyHanded- you answered my concerns with my stone, dishing. I think if I go the route of the belt sander, another knife will definitely be sacrificed first.
 
Thank you Greentrout.
I book marked that one.
I have done, very successfully, what you are looking to do . . . I used :

A cool cutting grinding wheel on a bench grinder (first just a white wheel then bought a better (faster, more coarse and cooler blue wheel) then used a quality 120 water bench stone to smooth out and blend the surface.

Totally worth doing. I do it to many brand new medium dollar (expensive to me) production knives.

The alternative is to just use a $9 paring knife but that's the easy way . . . not the Cowboy Way. I enjoy the Cowboy Way.

Not saying don't use the belt sander.
Go man go !

Be careful though belts can throw knives across the room or back at yah.
KEEP THAT STEEL COOL BY CONSTANTLY DUNKING AND KEEP YOUR BARE FINGERS ON IT. Too hot to hold = too hot to keep on the belt / grinder.
 
Actually wowbagger, it started as a $9 paring knife. It's a modded Old Hickory 3 1\4" paring knife.

I'm going to be thinning the cheeks on this. I won't be going for a flat grind, but we'll see what happens.
 
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