Is it acceptable to have blades scratched?

Hengelo_77

Hengelo_77

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Mar 2, 2006
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I have a problem at the moment.
I've send five blades away to be hardened professionaly.
They were hand finishes from gritt 240 up to 2500

When I've recieved them back they were all scratched.
I've been E-mailing ever since with the hardener.
He now claims it to be normal to return scratched blades.

I expected them to be returned scrach free.
Is it normal for something like this to happen?

Hi Bart,
I showed your blades to some guys at Olching. (a knife show)
I talked with "NAME" and "NAME".
All of them wouldn`t expect that a heat treatment comes out without some work afterwards.
At the heat treat company they said that the small impacts might happened while handling into the soft annealing. I don`t know.
But they didn`t wanted to do something.
So I?ve send you back your blades today.
In my opinion they are OK
 
I can only speak of my excellent experience with Rob Ridley, Alberta, Canada, and stainless steel (more than 20 blades). I receive my blades in the exact condition I sent them, except with a yellowish coat that is easily removed while performing the final hand sanding. I know Rob uses SS tin foil. I don't know what to expect for carbon steel though. Hope this helps.
 
While it is not uncommon to see some scuffing I usually finish my blades to 240 grit before heat treating and do my final finish after heat treating so it is not a real problem.

George
 
I've never considered it before - I guess it depends on the scratches/damage. Dimples in the steel may simply be hardness testing, which is a good thing in my opinion. I've never had a blade completely finished and ready to handle before heat treating, so I wouldn't know the difference in most cases.
 
Yeah, even when heat treating myself, I get minor surface scratches. Especially with stainless steels as you are wraping the blade in a stainless steel foil pack and often just snipping the pack and pulling the blade out. Now if these were terrible gouges, I'd be more concerned.

In my opinion, there is no reason to finish so high before heat treating. I just finish up to about 250 to 400 depending on my mood, but always refinish after heat treating.

--nathan
 
Most times heat treating is done in batches with blades rubbing against one another. I would expect the heat treater to use reasonable care in handling the blades, but to be realistic, I would expect to see some handling marks.
 
It is hard to capture something like this on camera well, but this is what it is like:
GroteFoto-WWNGY8PV.jpg

GroteFoto-PYSWY6VN.jpg


They admitted this:
"At the heat treat company they said that the small impacts might happened while handling into the soft annealing."

The way I see it is that I've trusted my work to there care and they let small impacts happen.
Is it naive to find this unacceptable?
 
Sometimes the maker benefits from finishing a blade to a higher polish prior to heat treating a steel that is very resistant to being hand polished like 3V or M4. Even then 400 grit would probably be our max prior to hardening, and you always expect to do the final polish after the blade has been heat treated.
 
to me personally, it doesn't look like a scratch, but more of little dents caused by the heat treater possibly having to straighten your blades out in possibly a vise of some sort. Even if the jaws are made of aluminum or something like that, can cause little dents in the soft plastic state of steel.

Just my $.02
 
Leu could be exactly right. First off I just finished asking this question more or less and pretty much everyone said dont over finish a blade because during heat treat things happen. I was buffing and really spending alot of time prior to heat treat but sanding up to 500 is now the MAX for me. Why waste you time redoing a blade twice . Ive never had a problem with Rob at Ranger they do a great job and are reasonably priced. If your still not happy with the end result buy a oven and cryo tank and do it yourself then youll see its not as easy as you think. kellyw
 
In my years of experience those marks are pit marks which didn't get completely removed before heat treating. They were probably filled by cuttings from your fine sanding and you didn't see them before.

One of the tricks to avoid this sort of problem is to sand across the previous grit each time you change grits. This shows up any pits or scratches at an earlier point so you can go back and remove them before you go on.

I wouldn't blame your heat treater.

George
 
I'm with George. There are often pits and flaws, especially on forged blades, that don't really show up until the steel is hardened. That is one reason that sanding to 2500 pre-HT is a bit foolish. 400 grit is plenty, as the real finish sanding is done post-HT.
Stacy
 
On stainless I rairly finish past 320, on forged blades about the same. On small stainless a lot of times I won't even grind till after heat treat.
 
Im with George I ground 4 blades out today and every time you switch grits change direction slightly to see the pit marks.
 
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