Author Topic: "Hard" chain link problem?  (Read 771 times)

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Offline John Mc

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"Hard" chain link problem?
« on: April 18, 2013, 09:49:43 am »
Several years ago, I ran into a problem with some Total chain (made by Carlton, I believe) where a couple of the teeth on a loop were so hard I couldn't do much with a hand file.  The rest of the teeth filed normally.  I had a similar problem with a couple of depth gauges that would ruin my flat files.  I chalked it up to bad heat treating of the chain, and when it happened again, I stopped buying the Total/Carlton brand chain. (It was only a couple teeth each on two loops of chain, out of maybe a dozen chains, but it was a pain in the neck.)

I didn't think much more about it until it happened with an Oregon chain recently.  There are a couple of teeth on the loop that the file just slides past, without doing much.  Switching to a brand new Pferd file makes no difference.  It's very noticeable, since the rest of the teeth on the chain sharpen so easily.  What was odd was that this chain was already filed halfway back to the witness marks.  It had been a while since I used this chain (still mounted on the saw from the last time I used it), but I'm sure I would have noticed when I last used it.

I have a theory on this:  I almost always hand-sharpen my chains, but occasionally if they get rocked, I'll take them to a shop with a very good reputation in my area and have they owner sharpen them for me on his grinder.  This last Oregon chain had been sharpened at the shop.  I'm wondering if he might have hardened the tooth by getting it too hot with the grinder.  (It's been too long ago for me to remember whether the Total chain was grinder sharpened.)

I worked for a good bit of my life for a company that makes and heat treats high carbon steel wire, and some chrome alloys.  All of the steel alloys with which we work need to be heated, then quenched to harden them (we then heat the wire back up to "temper" it, otherwise it's too hard and brittle to do much of anything with it.)  This shop does not quench the chain, or do anything to cool it other than let it sit.  Ordinarily, I would expect heating the steel and letting it cool in air to soften it (annealing the steel). However, I do know there are such things as "air hardening" steel alloys that basically quench in air (and small parts such as a chain tooth will tend to cool rather quickly anyway).  You'd have to get the metal a good bit hotter than the minimum needed for annealing to have even a chance at hardening it, but I suppose it's possible to get that contact point with the grinding wheel hot enough.  Does anyone know what type of steel these chains are made of?  If I knew that, I could figure out if "air hardening" after grinding is a possibility.

The guy at the shop is very experienced. Has been in the business for decades.  He's one of the ones the pro's in the area bring their saws to when they need repairs.  He is getting older, though (he's well past "normal" retirement age), and I suppose it's possible he occasionally hits a tooth too hard, overheating it.

Have any of you guys run across a hard tooth in the middle of an otherwise normal loop?

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Offline Cut4fun .

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Re: "Hard" chain link problem?
« Reply #1 on: April 18, 2013, 12:44:51 pm »
I have only seen this on a hardened tooth that has been over heated on a grinder. Never by hand or factory that way.
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Offline John Mc

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Re: "Hard" chain link problem?
« Reply #2 on: April 18, 2013, 02:46:53 pm »
I'm thinking that this was form a grinder.  This most recent chain was grinder sharpened before I put it away last time I used it.  The previous Total/Carlton Chain was so long ago, I don't remember.

I'm so used to dealing with steel that requires a water or oil quench to harden, that it never crossed my mind that this could have been "air hardened" until now.  I just assumed that over heating during grinding would have softened it (softening is still possible if it's not overheated beyond a certain critical temperature).

I'm still curious what the alloy is in a chain... but not curious enough to pay to send a piece out for chemical analysis...

Online 660magnum

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Re: "Hard" chain link problem?
« Reply #3 on: April 18, 2013, 03:34:16 pm »
If you worked in a metal heat treating plant, they should have several people that can grind a stream of sparks from a tooth and tell you exactly what metal alloy it is.

I used to work in a steel mill and metal identification was a critical factor as we worked mostly with alloyed steels. I would take parts from the machine shop down there for alloy I.D.
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Offline John Mc

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Re: "Hard" chain link problem?
« Reply #4 on: April 18, 2013, 05:50:11 pm »
I've seen plenty of folks who can get get pretty close guessing the carbon content of the steel (I used to be half decent at that myself, but far from an expert, and I've been away from it for long enough that I wouldn't even hazard a guess now). I've seen a few who can make a decent stab at some of the other alloying elements. 

I've never met anyone who could get the actual grade of steel with any real reliability (i.e. that's a 1050 grade, or that's 4140 grade, 9254 etc.)  If you've got access to folks who can do that you're lucky.  It seems to be a vanishing art.  With all the liability concerns around these days, we always have to do an analysis if there is any doubt, or if a customer comes in with a question or claim.

Offline Al Smith

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Re: "Hard" chain link problem?
« Reply #5 on: April 18, 2013, 09:01:16 pm »
I can get pretty close to the classification by the chips a lathe makes but certainly not to the true alloy .

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Re: "Hard" chain link problem?
« Reply #6 on: April 18, 2013, 09:11:48 pm »
When I would get one sparked, he would spark it against know samples.

One thing about it, I know D2 tool steel at a glance.

I also know AMPCO Bronze when I see it and when I try to drill or torch steel, I know of it is manganese plate.

Armor plate is a new one for me. It came along after I left.
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Offline Al Smith

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Re: "Hard" chain link problem?
« Reply #7 on: April 19, 2013, 04:44:38 am »
I'm real close to AMPCO 18 as I have a sliver buried in my thumb .

Offline brokenbudget

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Re: "Hard" chain link problem?
« Reply #8 on: April 19, 2013, 07:33:08 am »
at what point does the hardness have to be where that piece of metal is so small that you almost can't see it, hurts like you just lopped off the tip of your finger and jammed it into a salt shaker >:(
i did tires for almost 5 years at the local popular tire shop and can tell you from accute experience that the little steel belts hurt worse than a nail or piece of glass much larger in size.
hell. it didn't hurt near as much when i nearly cut my left thimb off.
well. the needle in the cut for the freezing hurt like hell. but again. it's a little tiny steel needle :-[
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Offline Magnus

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Re: "Hard" chain link problem?
« Reply #9 on: April 19, 2013, 07:58:35 am »
I had some Carlton chains here that I sold them come back hard as glass.
I found they had run hot.

It is likly just surface. If it is one or two teeth it is easy to do by hand, but if it is a hole chain I grind it first, then file.

To get this harder surface of it is not easy, but a stroke with another filr might crack it enough to get correct cutting again.
Vibration doing this kills/dulls files so try to make sure file doesn't vibrate, instead cut as it should.

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