Steel flatness and bevels

J

JBC69

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Feb 22, 2015
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I bought some 1080 from Kelly Cupples a couple weeks back and have been grinding on it a bit with my KMG and after burning up nearly 4 feet I have yet to to produce a blade that is anywhere near straight... The steel was a little wavy when I received it, so I've been carefully straightening it as best as I could as I cut each blank out. However, there is also a slight cup in the bar stock width wise... It is convex on one side and concave on the other and is quite noticeable when a straight edge is put on it. I'm assuming this is part of my problem? Is there any way to remove the cup before I start my bevel?
 
I would have contacted the seller and made arrangements to send it back, when you pay for blade steel you pay for flat steel
 
Hold your profiled blank on the flat platen vertically with a 50 grit belt or so. Use a push stick to apply pressure. If it's already been heat treated then don't overheat it. I do mine pre ht.
 
John Katt said:
when you pay for blade steel you pay for flat steel
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I don't agree. I think when you pay for blade steel, you pay for REASONABLY flat steel. PG steel exists for a reason; not only dimensional accuracy but also straightness.

It helps to quantify what "flat" means. I consider "reasonably" flat to mean a warp of 0.030" over 12" or better. Meaning if I sit the steel on a flat reference surface with the crown up, I should not be able to fit a shim thicker than 0.030" in the gap.
 
P.Brewster said:
I don't agree. I think when you pay for blade steel, you pay for REASONABLY flat steel. PG steel exists for a reason; not only dimensional accuracy but also straightness.

It helps to quantify what "flat" means. I consider "reasonably" flat to mean a warp of 0.030" over 12" or better. Meaning if I sit the steel on a flat reference surface with the crown up, I should not be able to fit a shim thicker than 0.030" in the gap.
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Patric we are talking about a cup that runs across the length, not down the length, as far as I am concerned steel cupped like that is junk and should be sent back
 
John Katt said:
Patric we are talking about a cup that runs across the length, not down the length
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I know; that is why I expressed my flatness as a ratio. With precise enough measuring equipment, you will find a cup on any piece of steel. The question is: how much of a cup is acceptable?

Back to OP's question: The cup can be remedied by either grinding, hammer and anvil, or forming. Forming would require a powerful press with relatively special tooling, so it is not a practical solution unless you have access to a nice press brake or something similar.
 
theres no way you should be able to see a cup across the width of blade steel unless maybe its 4'' wide. if it was dished in .030 on one side ans the same dish out on the other you would have to order 3/16 to end up with an 1/8.
 
P.Brewster said:
I know; that is why I expressed my flatness as a ratio. With precise enough measuring equipment, you will find a cup on any piece of steel. The question is: how much of a cup is acceptable?

Back to OP's question: The cup can be remedied by either grinding, hammer and anvil, or forming. Forming would require a powerful press with relatively special tooling, so it is not a practical solution unless you have access to a nice press brake or something similar.
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0.003 across the width of 1 1/2 stock would be unacceptable for me, little alone 0.030, that crack would be big enough to throw a cat through, and so you know I'm not just speculating here, over the last 2 years a rather large quantity of annealed 1095 has passed through my hands, 3 pieces were sent back because they were wavy, no questions were asked by the seller

also why would I spend my time and money fixing something that shouldn't be broke
 
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John Katt said:
0.003 across the width of 1 1/2 stock would be unacceptable for me, little alone 0.030, that crack would be big enough to throw a cat through, and so you know I'm not just speculating here, over the last 2 years a rather large quantity of annealed 1095 has passed through my hands, 3 pieces were sent back because they were wavy, no questions were asked by the seller

also why would I spend my time and money fixing something that shouldn't be broke
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I understand your stance. What I don't understand is the basis for your stance. Flatness is something that requires considerable resources and/or care to achieve in steel manufacturing. If I assume correctly, your seller makes no claim as to the flatness of the product you're buying. Do you also expect a mirror finish? Precise dimensional accuracy?

In the "real world" (the manufacturing and steel distribution world); flatness, or any quality, is not provided unless stated by the seller. Willingness of a vendor to accept a return is not evidence that your stance is universally valid; it is simply evidence that your vendor values your business and would rather process your return than disappoint you.
 
John Katt said:
Patric we are talking about a cup that runs across the length, not down the length, as far as I am concerned steel cupped like that is junk and should be sent back
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Naw man, I gotta disagree with this. Junk steel is out of spec, dirty, inclusions etc. Exterior dimensions aren't always explicitly controlled. When you're paying a few dollars a pound for minimally processed material you have to expect some work will be needed. A person making Damascus with it wouldn't care. But if you're doing stock removal with HRPO you're going to need to flatten it. Sometimes more than others.

What I hate is when the material was straight to start with and some knuckle head puts a big kink in it with a dull shear. That's something to get mad at...
 
Tell you what I hate. I've been buying precision ground A2 flat bars from Flatground.com for some crimpers I make. I don't use this for cutlery, but it's fine for a simple machine I build.

What pisses me off is I by this precision ground bar of steel, that I have reasonable expectations will be straight, flat, accurate and clean and 9 times out of 10, there are dents, dings, gouges and other mess that weren't there when they ground it, but some dumbass beat the piss out of it before wrapping it up. I'm not talking about shipping damage, it's under the wrapping, some useless POS should get flogged for that.
 
Give Kelly a call and tell him the condition of the steel you received. Blade steel is not in the same realm as mild steel you pick up at the local hardware. I've never had to straighten blade steel especially cupped flat stock. Blade steel that is warped length ways is a pain to work as well.
The reason we pay the prices we do for blade steel is because it is produced differently the quality control is different. Your not so much paying for the atoms of iron and carbon as you are paying for the condition of the product.
 
Just to add a little meat to my stand, this is what I have come to expect, Just a quick estimate over 3000' of this 1095 in 1 1/2" and 2" has passed through my hands, and because I'm kind of a nit-picker on quality, every single piece looks like this one, or it doesnt get out of my shop, you can see a very small gap at one edge from the plate sheer that is less then 0.003, but other then that its dead flat across the width, now there is a bit barrel roll in the picture because I have a cheap camera don't let that fool you

IMG_2401_zpsv7zij6iu.jpg
 
Nathan the Machinist said:
Tell you what I hate. I've been buying precision ground A2 flat bars from Flatground.com for some crimpers I make. I don't use this for cutlery, but it's fine for a simple machine I build.

What pisses me off is I by this precision ground bar of steel, that I have reasonable expectations will be straight, flat, accurate and clean and 9 times out of 10, there are dents, dings, gouges and other mess that weren't there when they ground it, but some dumbass beat the piss out of it before wrapping it up. I'm not talking about shipping damage, it's under the wrapping, some useless POS should get flogged for that.
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I got an 01 bar from them with my last shipment that had a gash all the way down it like it was drug across some sharp jagged edge and that particular piece had waves in it like none I've ever seen. I mean it's not a big deal to me but it sure can be a pain sometimes.
 
John Katt said:
Just to add a little meat to my stand, this is what I have come to expect, Just a quick estimate over 3000' of this 1095 in 1 1/2" and 2" has passed through my hands, and because I'm kind of a nit-picker on quality, every single piece looks like this one, or it doesnt get out of my shop, you can see a very small gap at one edge from the plate sheer that is less then 0.003, but other then that its dead flat across the width, now there is a bit barrel roll in the picture because I have a cheap camera don't let that fool you
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That is excellent; you have found a consistent high-quality product. Instead of telling other people to expect this level of quality from every vendor, perhaps the wisest action is to direct people to the good product/vendor.

In other words, the fact that you are buying a consistently flat product is not a reason to expect flatness from all vendors for all steel products.
 
P.Brewster said:
In other words, the fact that you are buying a consistently flat product is not a reason to expect flatness from all vendors for all steel products.
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Its a little more black and white for me, if you are selling a product at the maximum market value, your quality control should also be at maximum

On a side note, I have read in more then one place that cutting plate steel in strips across the grain instead of with the grain is a bad idea ( I may have that reversed) plate steel comes in 4 x 8-10-12 Kelly seems to sell his steel in 4' lengths
 
Does the seller have flatness standards ? Was the steel within that ? Some flatness problems can be fixed [though a pita ] with a stress relieve treatment of 1200 F for 2 hours , then straighten.
 
I think this is why most suppliers offer milled finish and precision ground. If I'm paying the extra for precision ground, then it expect it to be precision.
 
It's sheared from a sheet, or hot rolled. Not cold rolled annealed or precision ground. Buy a different product, or grind it flat.
 
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