Blade warping

A

alexmin

Joined
Nov 16, 2005
Messages
513
My blades tend to warp a little when I grind. Yesterday I tried to grind 1/4" and it also warped a little. I am getting an arbor press so it'll be easier to straighten blades. I don't know may be with arbor press you can straighten blades easily but without I find it almost impossible to have a perfectly straight blade. I am using a granite surface plate to check for flatness.
How much of warping is acceptable? For some of my blades I can see any warping by naked eye but if I put it on granite plate it's more obvious(it's less than 1/16" for 12"-15" blade).

Am I been a perfectionist?

Thanks,
Alex
 
I use precision ground O-1 steel. I profile it with band saw then flat grind on both blade sides frequently changing sides. I normally start with 36 or 50 grit.
I grind with bare hands on my KMG and don't let blade to heat too much.
 
Not questioning your abilities, but are you sure it's warped? I had a guy I heat treat for who claimed his blades were warped when I heat treated them, come to find out he had ground more steel off one side than the other and had the optical illusion of being warped. If I do get one that warps, I clamp it to a heavy flat bar that I have while tempering.
Jim
 
I make a pass or two and change sides, keeping it pretty cool. If you're doing that and it's warping then I'd say there's stresses in the bar left over from precision grinding.

Are you using center marking on the blade before grinding, or using parallel edge marks? That will help you keep the grinds even on both sides.

Maybe another supplier. A lot of the guys here that use O1, use a supplier back east and all say it's pretty good and the prices are reasonable. Fast service too.:eek:
http://www.flatground.com/catalog/

I think that's the place. If it's not, somebody please correct me.

Here's a few more places.
http://www.flat-stock.com/

http://www.toolanddie.com/~smgr2/Merchant2/merchant.mv?Screen=CTGY&Store_Code=T&Category_Code=PMGFS

http://www.principalmetals.com/headpages/toolsteels_head.htm
 
sometimes I have been fooled into thinking that my blades have warped but in fact the stock was already slightly curved. I just didnt eyeball untill after and I thought I made it that way...........I stopped worrining about that when I saw some big name guys that had curved blades ;) Just enjoy what your doing and keep making more. Each will have its own unique quality.
 
Weird. Are you SURE its warped, and not just ground unevenly? Many times I though I had a warped piece but upon further investigation, it was simply my having ground one side different that the other.

Also, how much pressure are you putting on the blade while grinding? a 15" blade is a HUGE blade (20+" knife?) and i can see how once some griding is done, an annealed piece of steel that long would not be too hard to warp simply by pressure at the ends while grinding.

Im not even sure you could warp a piece of steel simply be grinding if youre not generating heat...but someoen will i am sure correct you.

If i had to put money on it, i'd bet you are grinding a little deeper and more aggressivly when leading with your good hand, and less with your bad hand, and in the end, it makes it look like a warp.
 
Make sure your steel is not warped before you start. I don't grind large blades so my blades will fit in a mill vice. A trick someone taught me is as follows. I heat treat, then grind. When the steel comes out of heat treat I quench in oil(if a oil hard steel), then throw it in my mill vice and clamp down and let it set until cool. If it is air hard steel, I wait until the red glow is gone, then clamp it in my mill vice. Things tend to be a lot straighter this way. This won't work if you grind then heat treat.
 
Guys,

thank you for all your suggestions.
I just checked my stock against granite surface and found that it's slightly curved!

Alex
 
That pretty much sux for PG O-1. Part of what you're paying for is flat. :mad:
 
fitzo said:
That pretty much sux for PG O-1. Part of what you're paying for is flat. :mad:
Click to expand...

Agreed. I've gotten lots of mill-finished stuff from Admiral that was warped badly. If you get stock like this in longer lengths, it has been sheared so expect it to have at least some curve in it. I have learned to ALWAYS lay my cut blanks on the surface plate to check for flatness.
 
How thick is the steel you are grinding? I've never seen this happen in anything I've ever worked with.
STR
 
Try stress relieving the material before you grind it.
Many times the material that is surface or Blanchard ground will have surface tension on it from the mill.
Also I only grind sub annealed stock.
Standard annealing just don't do it for me.
To much warping.
So if the material you buy is NOT sub annealed I would do that.

I hope this helps.:D
 
What DDR said!

Part of knifemaking is straintening steel and blades at every step in the process.

It ain't really the most fun part of knifemaking... but whadda ya gonna do? :p
 
Darrel Ralph said:
Try stress relieving the material before you grind it.
Many times the material that is surface or Blanchard ground will have surface tension on it from the mill.
Also I only grind sub annealed stock.
Standard annealing just don't do it for me.
To much warping.
So if the material you buy is NOT sub annealed I would do that.

I hope this helps.:D
Click to expand...
this term sub annealing is new to me
is it softer the or harder then a reg annealing
how you do it i have a kiln so i could try it out
 
Subcritical annealing , that is heating below the critical temerature.Also called stress relieving . 1000-1200 F for 2-3 hours.
 
mete said:
Subcritical annealing , that is heating below the critical temerature.Also called stress relieving . 1000-1200 F for 2-3 hours.
Click to expand...
hey thanks mete just a name i had not heard it called before
 
It's that granite surface that's getting you into trouble. Does the blade look straight while you are ginding? When you put it on the granite slab does it lay the same both sides? " If it looks straight it is straight" If you are grinding a long blade, 8 inches or so, you are always checking down the spine and looking at the poiint to make sure the blade looks straight, as you grind. You grind on the heavy side. Even if you are flat grinding, on a 2x72 belt grinder, the blade will not be flat. If you put it on a truely flat surface to check, the surface won't be flat. I use a 4x10 inch diamond stone to" surface" my big blades. I run the diamond surface over both bevels about half way through the rough grind. It will show you every dip, low or high spot the length of the blade. You may believe you are grinding flat. But you are not, even if you have been grinding for years its rare that you would grind a flat surface. If you think about it, thats not an easy thing to do. Jams, Fred :D
 
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