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why chain requires sharpening?

Started by motif, October 06, 2010, 02:40:53 AM

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motif

I mean why don't they make hard enough chain like from carbon steel or something to
make it not getting blunt. Wood is much softer then steel right? 
Or maybe there are very expensive chains not requiring sharpening?


Ianab

The chains are made from carbon steel, and plated with chrome which forms the actual cutting edge. That's how you can drag those cutters through wood, at about 60mph, for an hour or 2 before you loose the sharp edge.

Wood is of course much softer than steel, but things still wear and loose their edge...  :(

They do make carbide chains, but they don't cut as fast as you can't get the same sharp edge that you can get on a steel/ chrome cutter, and they are almost impossible to sharpen. They sell them for fire brigades where they need to cut through almost anything, or cutting through dirt etc where a normal chain wouldn't lasts 2 seconds.

Ian
Weekend warrior, Peterson JP test pilot, Dolmar 7900 and Stihl MS310 saws and  the usual collection of power tools :)

Cut4fun

Why do you have to sharpen a knife. You only skin deer and whittle wood with it  ::) ::).

motif

Quote from: Cut4fun on October 06, 2010, 06:39:24 AM
Why do you have to sharpen a knife. You only skin deer and whittle wood with it  ::) ::).

right, that's a good question too  :P

Rocky_J

No, it's not really a good question unless you're thirteen years old and your grandpappy has just handed you your very first knife.  :-\

John Mc

Have you ever seen what running water does to rock over time? That water is a DanG sight softer than the rock, but it will still wear it eventually.

It's similar with wood and your chain. It just doesn't take years, since the wood is a lot harder than water. Also, the wood has minerals and other elements in it which are abrasive (some wood, like red cedar - at least the red cedar I've cut - seems to have a whole lot of minerals/dirt in it. It's dulls the chain faster than you'd think, especially for a softwood).

Other factors: it the wood dirty? If you've dragged the logs through the mud before cutting them up, the dirt and bits of rock stuck to the surface will dull your chain pretty quickly. Lastly... sooner or later, you're going to nick a rock or the ground when you are bucking up logs... that will do a real number on your chain, and very quickly.

When I'm cutting clean pine, I can go quite a while without sharpening. When I'm cutting the harder hardwoods, I generally touch up the chain after each tank of gas (assuming I haven't rocked the chain before then). If I stay on top of it, it only takes a couple of strokes per tooth. It really makes a difference. You can "cheat" a bit on bigger saws and get away with not sharpening as often, but I don't recommend it. It's harder on the engine, chain, bar, drive sprocket, not to mention harder on you. On a small saw, frequent touching up is almost a necessity, especially if you are cutting anything of any size.
If the only tool you have is a hammer, you tend to see every problem as a nail.   - Abraham Maslow

Rocky_J

The idea is to keep it sharp, rather than run it until it's dull and then try to resharpen it. This is a very basic fact that every successful sawyer eventually learns. Most casual saw users never get it.

HolmenTree

Yes you learn lots of things the more trees you cut. While falling spruce I find after time the wood hones the chain's cutting edges and gullets which is almost like self sharpening, until I hit the first patch of dirt or a rock. Cutting jack pine which grows in sandy soil and has sand in its course bark near the ground is a negative  :D
File your depth gauges and after continued cutting you'll notice the wood smooths the filed surfaces like glass.
Willard.
Making a living with a saw since age 16.

Tom

Motif,

We sometimes lose track of the hard job our "edges" have to do.   The chainsaw tooth edge is one of them.  Sawmill teeth have some of the same problems.   Our eyes see a 12" log and a bar going through it.  It's easy to get the mindset that we just cut 12", but we didn't. 

The chain scrapes (cuts) out chips that are no thicker than the design of the chain allows(raker/depth gauge) it to cut.  Too much bite and the saw stalls, too little and you get powder instead of chips, or nothing at all.

One of these teeth will only remove a chip of about .025 to .035 inches in thickness. That means that the tooth must pass through the 12" wood (12 x 12)/.025= 5760 times.  Since there are about 6 teeth in the wood at a time, you could divide that number by 6 and then again by the number of 6" increments on the loop of chain to determine the work each tooth must do.   I'm not a mathematician, but I think that would get you in the ball park for a best-case scenario.

That's a lot of work for a little piece of metal that is impacted that many times and scraped that many times, even if it didn't have to deal with the dirt and dust too.  If it were only one tooth on that chain, it would have to pass through a mile of wood to cut that 12" log.

Knives and axes suffer more resistance than just the cutting.  There is the shock and pressure that is applied to make the edge do its work.  Impact transfers a lot of pressure, more than we might realize.  when I was a young boy, quarters and half-dollars were made from silver.  We would take a spoon and rap the edges of the coin, not too hard either, and the edge would spread out.  When we had beaten the edge to the size of a ring, we would drill out the middle and use a rat-tail file to smooth it out.  Voila! We would have a silver ring.  We weren't supposed to do it, but you know how boys are.

So, if a spoon, rapped on the edge of coin, will create that much damage, think of what a 200 lb. man on the handle of an axe, or twenty horse power behind the thin band of a saw might do.

That's why edges require frequent maintenance.  They do a lot of work.

Randy88

Tom and JohnMc have got it covered as far as wear and friction and impact forces, everythiing wears and needs attention including your razor to shave your beard with, lawnmower blades, sickle sections in haybines and combines, it makes no difference at all its just a wear item that needs attention and maintanance.   If you somehow surpass the forces of physics and invent something that needs no attention or touching up remember to patent it and keep us on the forestry forum in mind for all your soon to be aquired wealth, cause your gonna be a rich man.   Until then I guess your gonna have to keep the chain sharp and do the best you can to reduce the drag and friction and forces at work to cut wood.   

RSteiner

Friction is the reason a piece of hard steel can be dulled by a piece of softer wood.  At the thin cutting edge of a chain saw chain or table saw blade or knife blade when it contacts the material it is cutting and dragged through it heat is produced.

Even my wood splitter wedge will get very warm after an hour of splitting just from friction.  I remember reading some where that the very knife edge of a planner blade can see temperatures in the thousands of degrees which is quickly conducted away into the thicker metal of the knife blade and holder. 

A chainsaw cutter works the same, the heat generated at the tip or cutting egde must be conducted away into the metal behind it.  Notice what happens when you try to push a dull chain through a piece of wood, you can see the heat effect on the cutter and you have taken the temper out of the metal.

The chrome edge on the saw chain is hard and a little more heat resistant than the tooth material giving you a tough but yet somewhat ductile cutter.  The harder the metal the more brilttle it becomes and the harder it is to sharpen.  A harder cutter would probably shatter if you hit a rock or hardware when cutting resulting in having to replace the chain because that one tooth is now toast.

Randy
Randy

HolmenTree

Stihl chain I have used tend to sometimes break off a good size chunk of cutter if hard rock is hit.
I have modified sawchain for timbersports where I take the top and side layer of chrome right off the cutters. In competition you're cutting clean debarked logs so edge toughness is not an issue until you hit the 1st big knot, but hitting a big knot usually makes you lose the race anyways.
Chrome gives a poorer edge over unchromed steel. If you have a chance take a look at a sharp chromed cutter's edge under a low power microscope, you'll be amazed how rough that edge is.The chrome breaks up in gouges when filed. Take the chrome off, refile it and take another look.

Willard.
Making a living with a saw since age 16.

tjdub

Quote from: motif on October 06, 2010, 02:40:53 AM
I mean why don't they make hard enough chain like from carbon steel or something to
make it not getting blunt. Wood is much softer then steel right? 
Or maybe there are very expensive chains not requiring sharpening?

http://www.stihllibrary.com/flash/MS460R/main.swf

These rescue chains are carbide.  You know what they say: "If it don't bend, it breaks".

They're not very sharp to start with, can't be sharpened, and they still do wear and are much more likely to snap off cutters.  It's not really what you want for cutting wood.


terrifictimbersllc

Motif, take a magnifying glass (7-10x is good) and look  at a dull edge then look at a sharp edge of a chisel, chain tooth, knife whatever.   You will easily see the difference.  The dull edge is rounded over.  The sharp edge is very thin and pointed.  The reason it gets dull is because the force against the wood or whatever you are cutting easily wears away the very thin sharp edge until it is rounded over again.
DJ Hoover, Terrific Timbers LLC,  Mystic CT Woodmizer Million Board Foot Club member. 2019 LT70 Super Wide 55 Yanmar,  LogRite fetching arch, WM BMS250 sharpener/BMT250 setter.  2001 F350 7.3L PSD 6 spd manual ZF 4x4 Crew Cab Long Bed

JohnG28

You can actually feel the difference between a sharp and dull chain with your finger along the cutter. Nice sharp edge feels sharp and more pointed where the dull cutter feels more blunt.
Stihl MS361, 460 & 200T, Jonsered 490, Jonsereds 90, Husky 350 & 142, Homelite XL and Super XL

Rocky_J

And water is wet and the sky is blue.  ::)

I was about to say that it was beginning to sound like 7th grade shop class in here, except in 7th grade they assumed we had a slight grasp of basic truths. When we bend over so far to cater to the most profoundly unknowing, we tend to lose the interest of those who already grasp the most basic of ideas.

I'm guessing this post may earn me a time out. I doubt I'll miss anything earth shattering. Maybe by the time I get back we will be back up to the "Which two cycle oil do I use?" discussion (again).  :-\

Later 'gators!   8)

Jeff

Just call me the midget doctor.
Forestry Forum Founder and Chief Cook and Bottle Washer.

Commercial circle sawmill sawyer in a past life for 25yrs.
Ezekiel 22:30

HolmenTree

Quote from: JohnG28 on October 08, 2010, 08:07:31 PM
You can actually feel the difference between a sharp and dull chain with your finger along the cutter. Nice sharp edge feels sharp and more pointed where the dull cutter feels more blunt.
A quick look at a dull rounded edge is also easily seen by the light reflecting off its surface. A sharp edge shows no light.
Probably why I can't file my dull chains in direct sunlight.... I get blinded by the light :D
Willard.  
Making a living with a saw since age 16.

Dan_Shade

a saw this yesterday:  http://powersharp.com/ 

I think it's designed for smaller saws.

Woodmizer LT40HDG25 / Stihl 066 alaskan
lots of dull bands and chains

There's a fine line between turning firewood into beautiful things and beautiful things into firewood.

Okrafarmer

Quote from: Rocky_J on October 08, 2010, 08:47:45 PMand the sky is blue.  ::)

Where?  :o

My boss only has to sharpen the chain on his MS 192 every few months. He uses it only for climbing, and way up in the trees the occasion to hit sand, dirt, and rocks is very slight. Even when he uses it heavily, he doesn't have to sharpen it very often. Only when one of us grabs it and starts doing something on the ground with it.  ::)

Just wondering though, what if they made diamond toothed chainsaws?
He that dwelleth in the secret place of the most High shall abide under the shadow of the Almighty. Psalm 91:1

Operating a 2020 Woodmizer LT35 hydraulic for Upcountry Sawmill, Dacusville, SC

Now selling Logrite tools!

Writing fiction and nonfiction! Check my website.

beenthere

Quote from: Okrafarmer on October 09, 2010, 10:02:20 AM..........
My boss only has to sharpen the chain on his MS 192 every few months. He uses it only for climbing, and way up in the trees the occasion to hit sand, dirt, and rocks is very slight. Even when he uses it heavily, he doesn't have to sharpen it very often. Only when one of us grabs it and starts doing something on the ground with it.  ::)
.............

If the saw isn't used, then there is no need to sharpen the chain.  ;D
But I file mine before it "has to be" sharpened and that is at least every tankful of fuel.
And if I was climbing, the last thing I'd want high in a tree would be a chain that has to be sharpened.

A bit like eating....I eat to keep from getting hungry, not as a result of being hungry.  ;D
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

HolmenTree

Quote from: beenthere on October 09, 2010, 10:41:26 AM


A bit like eating....I eat to keep from getting hungry, not as a result of being hungry.  ;D
:D No offense beenthere, but most times its better to eat when hungry then to eat when you're not.  ;)
Willard.
Making a living with a saw since age 16.

Okrafarmer

Quote from: HolmenTree on October 09, 2010, 08:20:17 PM
Quote from: beenthere on October 09, 2010, 10:41:26 AM


A bit like eating....I eat to keep from getting hungry, not as a result of being hungry.  ;D
:D No offense beenthere, but most times its better to eat when hungry then to eat when you're not.  ;)
Willard.

I'd agree there. There are at least two (2) very different metabolism types. One works more like Beenthere says and one works more like Holmen says.

We do not EVER sharpen our saws in the field. We keep multiple chains around. When we feel that one is getting dull, we grab a newly sharpened chain and put it on. The chains are sharpened off the saw back at the shop. we try to keep at least 4 chains for each saw sharp, except for the two identical climbing saws-- it suffices to keep on chain available for them.

And yes, sometimes boss does go through many days or even weeks worth of days of hard climbing and cutting, all with the same chain without sharpening, and using it in hardwoods, especially oak, more often than not. And no I'm neither lying nor making it up.  :-*
He that dwelleth in the secret place of the most High shall abide under the shadow of the Almighty. Psalm 91:1

Operating a 2020 Woodmizer LT35 hydraulic for Upcountry Sawmill, Dacusville, SC

Now selling Logrite tools!

Writing fiction and nonfiction! Check my website.

bill m

When I had 2 crews working for me the climbing saws ( 020T ) were never used on the ground and only needed sharpening about every 2 weeks. All other saws were sharpened every morning. Filing every tankfull sounds like a waste of chain to me unless your in the dirt all the time.
NH tc55da Metavic 4x4 trailer Stihl and Husky saws

rockman

How many cutting tools can you name that NEVER need sharpening ? I guess when and how you sharpen your saw is a personal thing. When I was a logger in the late 70,s early 80,s I sharpened when needed, sometimes after each cut( depending on mud, dirt etc.)but always at each gas and oil fill. When cutting for a living(payed by the cord ) speed is king, although now most cutting is done with machines rather than chainsaws. I am still the same way, if the saw is dull I sharpen it( I hate having to force a dull saw through wood)it only takes a second to keep it sharp. Something I have observed over the years is the more novice the saw operator the more often it needs to be sharpened. Sharpening a saw chain is a skill most novices do not take the time to learn, I know alot of people who throw chains away and replace them instead because they don't know how to sharpen them, I don't have that kind of money.
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