Nuzzy
Trail Gnome
No kidding! It only adds to the fun that they've changed and dropped letters in recent years... 
stihl rm vs rs chains---which one and why?
- Thread starter demc570
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No kidding! It only adds to the fun that they've changed and dropped letters in recent years... 
Stlshrk
ArboristSite Member
The extra hump just keeps the cutter from getting as good of a bite, mostly at the nose of the bar on a bore cut or if reaching out for something. Maybe reaching while limbing or something and just a touch on a limb and -- WHAM -- there would be the kickback rotation.
Nuzzy
Trail Gnome
As long as you're cutting on the flat part of the bar, and assuming the extra hump is at or below the level of the raker, it wouldn't really affect anything. However, when the extra hump flexes around the bar tip before the raker on the tooth, it effectively creates a bumper to keep the chain away from the wood. Hence why it's bad for bore cuts.
http://northernwoodlands.org/articles/article/tricks-of-the-trade11
"Some chainsaw chains are designed to minimize the reactive force known as kickback. These chains are found on a wide range of chainsaws made for homeowners, arborists, and loggers and are required to be sold on every new saw with an engine displacement of less than 66 cubic centimeters.
To understand how these chains work, let’s first review how a standard saw chain cuts wood fiber. Each cutter link has a heel, a toe, and, on the bottom half, rivet holes. On the top half, from front to back, you’ll find the depth gauge, the gullet, the cutting corner, the side plate, and the top plate. The depth gauge, which is sometimes erroneously referred to as the raker, does not clean out the chip the way a raker does on a crosscut saw. All the depth gauge does is set the depth or thickness of the chip that will be produced by the cutting corner when it hooks and then severs fiber. Depth gauges function as a safety feature, because by regulating the size of the chip, they also regulate the severity of reactive forces. The thicker the chip, the more severe the potential kickback.
To minimize the possibility of reactive forces, kickback-reducing features on chains limit the amount of fiber that can be hooked by the working corner as it rounds the upper half of the bar tip, which is commonly referred to as the kickback zone.
A common way to do this is to add an extra amount of metal onto the tie straps between the cutting teeth such that the tie strap functions as a higher depth gauge as the chain rounds the upper half of the bar tip. (Tie straps connect the cutting links with the drive links, and so-called bumper tie straps have a higher profile than regular tie straps to prevent the cutting tooth from hooking fiber.) Other anti-kickback approaches include drive links with built-in bumpers and ramped depth gauges so that fiber is somewhat deflected as the chain rounds the kickback zone. Chain must meet ANSI standard B175.1 to be designated as low-kickback.
There are two major drawbacks to low-kickback chain, the first being that it renders the kickback zone nearly useless for bore cutting. If your chainsaw work involves mostly bucking firewood, this is not likely to be a problem. It is, however, a problem if you are felling trees directionally using a bore cut to make your backcut (itself a safety technique intended to minimize “barber chair” and other dangerous felling situations). Because that upper half of the bar tip won’t cut well, bore cuts go very slowly if they go at all with low-kickback chain.
The second drawback to safety chain is that it can be more difficult to sharpen. If you take your saw to the dealer for sharpening anyway, this isn’t a problem, but if you sharpen the saw yourself and end up not keeping the chain suitably sharp, you’ll end up introducing a new risk factor – pressing down too hard on the saw in frustration – which can nullify the advantage of the safety chain in the first place. As with anything else, the key to a safety device is knowing how to use it correctly."
windthrown
361 Junkie
Wow... lots of variable info here. Stihl chain guides are confusing, as are their labels.
RM is rapid micro. It is semi-chisel. The chisel in the edge '7' is filed off for a curved shape '?' cutter. When round filed, the outer edge of the cutter deflects sand, grit and crud and thus stays sharp longer than full chisel. RM comes in safety (green master link) and non-safety (yellow master link). Non-safety comes in full comp and in skip, and full comp was called RM but was replaced with RMC (comfort), which was renamed RM later (confusing?). RM in skip is (and was) RMF. There are and have been several types of safety RM; RM2 had the huge double hump safety rakers that people are talking about here (shown in the photo in the post above), but Stihl no longer makes that stiff. It was the standard loop in all non-pro saws for many years. RMC3 replaced it but was renamed RM3. RM3 is designed so that the safety rakers are next to the cutter rakers on the flat of the bar, but they are flexed when the chain goes around the nose, thus adding more raker area and keeping the bar nose from grabbing as much and causing kickback.
RS is rapid super. It is full chisel. The chisel in the edge '7' is left on the cutters. The outer edge of the full chisel cuts through wood faster, but it also dulls faster, and will dull really fast if it hits any crud, sand or grit. RS also comes in safety and non-safety. Non-safety comes in full comp and in skip, as well as 'L'. Full comp non-safety round file was called RS but was redesigned to RSC (comfort), and then RSC was renamed RS. RS in skip is (and was) RSF. Safety RS was RSC3 but is now called RS3. There is also the round file RSK type chain that is designed for longer bars over 28 inches. Then there are the RSL square file type loops in full comp (RSLK), semi skip (RSLHK), and full skip (RSLFK).
In general, full chisel round filed loops cut about 10% faster than semi-chisel round filed loops, and full chisel square filed loops cut about 10-15% faster than full chisel round filed loops. Full chisel round filed loops will dull faster than semi chisel loops, and in any crud, they will dull a LOT faster. Square filed loops will dull way faster as the inside of the chisel is filed to a thin point. Square file chains are also a lot harder to file correctly, and I never got the hang of it. I have one square file loop and I never use it. I keep my RM2 safety semi loops for cutting in any potentially naily wood, like fence posts and yard trees. I use RM non-safety for wood cutting, stump cutting, and for cutting trees like willow that have a lot of grit in the bark (sparks fly!). For noodle/curly fry cutting, I use RS full chisel skip, as the noodles seem to clear better using skip. In clean wood (cross cutting) I use RS or RSF.
RM is rapid micro. It is semi-chisel. The chisel in the edge '7' is filed off for a curved shape '?' cutter. When round filed, the outer edge of the cutter deflects sand, grit and crud and thus stays sharp longer than full chisel. RM comes in safety (green master link) and non-safety (yellow master link). Non-safety comes in full comp and in skip, and full comp was called RM but was replaced with RMC (comfort), which was renamed RM later (confusing?). RM in skip is (and was) RMF. There are and have been several types of safety RM; RM2 had the huge double hump safety rakers that people are talking about here (shown in the photo in the post above), but Stihl no longer makes that stiff. It was the standard loop in all non-pro saws for many years. RMC3 replaced it but was renamed RM3. RM3 is designed so that the safety rakers are next to the cutter rakers on the flat of the bar, but they are flexed when the chain goes around the nose, thus adding more raker area and keeping the bar nose from grabbing as much and causing kickback.
RS is rapid super. It is full chisel. The chisel in the edge '7' is left on the cutters. The outer edge of the full chisel cuts through wood faster, but it also dulls faster, and will dull really fast if it hits any crud, sand or grit. RS also comes in safety and non-safety. Non-safety comes in full comp and in skip, as well as 'L'. Full comp non-safety round file was called RS but was redesigned to RSC (comfort), and then RSC was renamed RS. RS in skip is (and was) RSF. Safety RS was RSC3 but is now called RS3. There is also the round file RSK type chain that is designed for longer bars over 28 inches. Then there are the RSL square file type loops in full comp (RSLK), semi skip (RSLHK), and full skip (RSLFK).
In general, full chisel round filed loops cut about 10% faster than semi-chisel round filed loops, and full chisel square filed loops cut about 10-15% faster than full chisel round filed loops. Full chisel round filed loops will dull faster than semi chisel loops, and in any crud, they will dull a LOT faster. Square filed loops will dull way faster as the inside of the chisel is filed to a thin point. Square file chains are also a lot harder to file correctly, and I never got the hang of it. I have one square file loop and I never use it. I keep my RM2 safety semi loops for cutting in any potentially naily wood, like fence posts and yard trees. I use RM non-safety for wood cutting, stump cutting, and for cutting trees like willow that have a lot of grit in the bark (sparks fly!). For noodle/curly fry cutting, I use RS full chisel skip, as the noodles seem to clear better using skip. In clean wood (cross cutting) I use RS or RSF.
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memory
ArboristSite Guru
I decided to return the chain and get the yellow semi chisel chain. Just to clarify, I want 33 RM 84 to get the yellow semi chisel, right? Is it possible to get the safety chain if you buy the RM series? I just want to make sure that the dealer orders the right part.
Lots of good info in this thread.
Lots of good info in this thread.
Nuzzy
Trail Gnome
That is my understanding, and seems to be corroborated by the chain section of the Stihl site.
RM (RMC) -- http://www.stihlusa.com/products/chain-saws/saw-chains/rm/
"STIHL RAPID™ Micro™ is a taller-profile chain with more mass for larger displacement engines. Featuring a semi-chisel type of cutter, it typically doesn’t get dull as fast as a full-chisel chain during normal use, making it easier to maintain.
Applications: The RM chain is ideal for felling, bucking and limbing. It is a general-purpose chain for the high demands of full-time professionals in agriculture, construction and the forestry industry, but it is also suitable for homeowner users."
RM3 (RMC3) -- http://www.stihlusa.com/products/chain-saws/saw-chains/rmc3/
"STIHL RAPID™ Micro™ 3 is the low-kickback version of STIHL RAPID™ Micro™ saw chain. RM3 retains all the performance of STIHL RM chain, with the added benefit of low kickback to reduce the risk of kickback injury. It is a taller-profile chain with more mass for chain saws with larger displacement engines. Featuring a semi-chisel type of cutter, it typically doesn’t get dull as fast as a full-chisel chain during normal use, making it easier to maintain.
Applications: The RM3 chain is ideal for felling, bucking and limbing. It is a general-purpose chain for the high demands of full-time professionals in agriculture, construction and the forestry industry, but it is also suitable for occasional users."
Nuzzy
Trail Gnome
Also (and since we're dissecting Stihl chain), the first 3 designates a 3/8" pitch, the second 3 designates .050" gauge for the bar, and 84 is the drive link count.
http://www.stihlusa.com/WebContent/.../STIHL-Saw-Chain-Selection-Identification.pdf
windthrown
361 Junkie
Yes, RM comes in safety which is RM3 (or older RMC3, or discontinued RM2). RM non-safety is RM (or RMC, or older RM non-C). For a 25 inch bar, you would order 33RM-84 for 0.050 gauge, or 36RM-84 for a 0.063 gauge bar. I have found RM loops to be harder to get.
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Nuzzy
Trail Gnome
If the box says RM or RMC, you will get yellow.
If it says RM3 or RMC3, kindly offer to move it to the womens' lingerie section of the store.opcorn:
If it says RM3 or RMC3, kindly offer to move it to the womens' lingerie section of the store.
opcorn:
memory
ArboristSite Guru
I told him to order the right chain, 33RM-84. I just wanted to make sure it wasn't possible to get safety chain in the RM version which it looks like it isn't possible.
windthrown
361 Junkie
Well, I went into the Stihl shop in Cottage Grove, OR some years ago and ordered up a few loops of RM, and they made them out of RM2~!~! They apologized, and made the real RM loops up for me and tossed the others into the little grey boxes ad put them on the shelf.
Say what??
There's several posts in this thread explaining it... YES, both the RM and RS chains come in both configurations.
If the part number contains the "3"... as in RM3 (older designation was RMC3), rather than plain RM (older designation was RMC)... it is what you're calling "safety chain" (humped tie straps, green label, reduced kick-back).
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memory
ArboristSite Guru
That isn't what I meant. What I meant was if I ordered let's say 33RM-84, is it possible I could be getting a safety chain? From what I understand, if I specifically ask for an RM chain, not RM3 or RMC3, there is no chance of getting a safety chain. Sorry for the confusion.
KenJax Tree
Terraphobic
Not unless they screw up and ship RMC3 instead.
Sent from my Autotune Carb
Sent from my Autotune Carb
Yeah, I've asked for both RM and RS before and have the dealer hand me RM3 or RS3, and at more than one dealer.
Stihl recommends low kick-back ("3") for nearly all their saws... and I've had several "not-so-full-service" dealers tell me they only carry and sell what is recommended.
I've gone to specifying "yellow" label when asking for or ordering chain, as in I will say "26RM-67 Yellow Label"... and I'll still get handed the "green" on occasion.
The dealer I use most often has pre-cut, packaged chains hanging on a rack... all of the PICCO and .325 are "RM3", all of 3/8 are "RS3". He has others, or can make them up, but you have to ask. I asked him why he did it that way and he told me most of the guys don't have a clue, and he'd rather they error on the "safest" side or at least per manufacturer recommendation... so he just displays what is "recommended". But the guys that do have a clue will ask... and he'll sell 'em what they ask for.
I can see his point... half the guys I know think a chain-is-a-chain, and half of them are likely to put the damn thing on backwards‼
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Stihl recommends low kick-back ("3") for nearly all their saws... and I've had several "not-so-full-service" dealers tell me they only carry and sell what is recommended.
I've gone to specifying "yellow" label when asking for or ordering chain, as in I will say "26RM-67 Yellow Label"... and I'll still get handed the "green" on occasion.
The dealer I use most often has pre-cut, packaged chains hanging on a rack... all of the PICCO and .325 are "RM3", all of 3/8 are "RS3". He has others, or can make them up, but you have to ask. I asked him why he did it that way and he told me most of the guys don't have a clue, and he'd rather they error on the "safest" side or at least per manufacturer recommendation... so he just displays what is "recommended". But the guys that do have a clue will ask... and he'll sell 'em what they ask for.
I can see his point... half the guys I know think a chain-is-a-chain, and half of them are likely to put the damn thing on backwards‼
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D
Deleted member 116684
Guest
i use rs, but then, i love to sharpen chains...
Glockem45
ArboristSite Member
This is the best thread about chains I have found on this website. Thanks for all the quality discussion here.
cre73
Always Lurking, never posting
That darn yellow and green I cannot tell apart, being color blind. Just have to remember my part number.
Rs cuts fast ..also chips and goes to crap much faster too the rm is your big name overpriced basic chain . Oregon lgx is my favorite .its cheaper it Cuts faster and lasts longer between sharpenings . Used the Stihl chain for years but got tired of running to the Stihl stealer ship and blowing 27$ On one. I found the Stihl chains to be too brittle . I order lgx on eBay shipped to my door for 19$ now
sunfish
Fish Head
Same here, used Stihl chain for years! But not much anymore.
Use LPX & BPX also and pay less than ebay prices.
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