Leading edge, stet or tilt on chainsaw chain cutters

[Crispin Rogers]

Perhaps somebody knows why Stihl chain is supposed to be sharpened at 90 degress whilst Oregon chain is generally 10 degrees down from the vertical. What is the theory behind this? I assume that Stihl chain has a rectangular cut whilst Oregon has a triangular cut. As Stihl chains tend to have a wider guage for the same class of chainsaw than Oregon could this be anything to do with it? e.g. the Stihl 362 has a guage of 1.60 mm whilst the Echo 600 has a guage of 1.47 mm i.e. does a narrower guage need a 10 degrees down leading edge or tilt?

[RichardKing]

I was taught that as the chain tilts over as you cut anyway (unless its over tight), just ignore the ten degree drop.
Mind you I have never met two people who agree on the subject of sharpening.

[carlight]

hi .
Bit of a tricky one to discuss via keyboard .
(ie - when you say "10 degrees down from the vertical" , presume you mean horizontal ?)
Would say that when you talk of gauge of 1,6mm etc ,that is surely referring to the width of the drive link lower spur/the width of the slot in the bar . Different gauges(amongst chains of the same pitch) were introduced specifically to wind up parts depts. And/or to ensure that r&d depts could justify themselves . And to allow folk to believe that their brand is better . No doubt ,also ,if one sells a bar at a low profit margin ,but that has a brand-specific gauge ,profits on suitable chains could be advantageously set .
As for that crucial top edge of the cutter , i was taught that the outside corner is the most important part , especially with full chisel chain ,and would always want to sharpen with the 10 degree drop .
As i'm now old , i also use those canny little sharpening guides ,which are somewhat new ,and consist of a pair of rollers , total size=would fit in a matchbox. ( I don't see stihl making their own at 0 degrees yet ,?)

[Crispin Rogers]

Opps! Please read horizontal. What I was thinking off was 90 degrees to the bar. Question remains why typically does Oregon specify 10 degrees down on some but not all their chains whist Stihl is horizontal?

Stihl now does a roller guide for each of their sizes of file, new this spring the FG4 filing tool. Also they do their version of the Grandberg holder filing guide the FF1. Page 50 of their 2012 catalogue.

[carlight]

Could it be the different profiles that bring this on - say between semi chisel and full chisel ?
PS am sure there's a definitive answer to be had on 'arbtalk' , but where's the fun in that !

[Crispin Rogers]

Here is the explanation that I received from Oregon,

The 10 degree down angle is suggested for Oregon chisel cutters, This angle positions the grinding wheel So that is sharpens the underside of the cutter this has a twofold benefit. The first being is that it shapes the “hook” angle to allow for the debris or chip to leave the cutter so not to clog up the saw so much. The next is that it puts a nice sharp knifing edge on the forward edge, this makes the cutter cut faster. A good analogy is the difference between and ax and a hatchet.

The downside to this very sharp edge is that if you are cutting in abrasive conditions it is harder to maintain, and you may have to sharpen your chains more often. The Grind angles have been tested. The angles including the 10 down were tested against chains sharpened without the 10 down. Testing showed the Chain with the 10 down degree cut faster.

What do you make of it?

[carlight]

hmmm , bit of a confusing reply ,but good on them for replying .
I mean , the underside of the cutter is being sharpened whatever the angle ,10 deg down , or horizontal .
And yet , the reply does seem to substantiate the theory re full chisel cutters .
With a 10 deg down sharpen , that top outside corner is the first point of contact , and with a sharp full chisel chain is very efficient .
With a semi chisel chain ,(that doesn't have that top outside corner) one is never going to get that same magnificent cutting , but , sharpened at 0 deg ,will sort of last longer between sharpenings .
That top outside corner on the full chisel is crucial . Once it is slightly damaged (often on one side ) ,sharpening is required .
The semi chisel ,especially at 0 deg (?) , will share the wear all along its leading edge .
As far as st*hl 's 0 deg goes , i believe that if one is not using proper ( ie husqvarna ) equipment ,then what do you expect !

[Crispin Rogers]

I seem to have started something! Here is the latest reply from Oregon.

All saw chain sharpening of “standard” hooded chisel cutter chain involves sharpening the underside of the cutter. (PowerSharp chain sharpens from the top down in 5 sec BTW http://www.powersharp.com ) The 10 deg file or grinder down angle we recommend for Chisel and semi chisel cutters is due to the fact that the round file having 20% of its diameter above the cutter top plate at the cutting corner, there is a compound angle created with the 10 deg down angle that requires you to increase the top plate filing angle to about 27 deg to end up with a resultant 25 deg actual top plate angle. The result of that action is that the included sharpness angle under the cutter top plate becomes sharper and therefore wood chip flow through the cutter becomes slightly more efficient. This can increase the cutting speed of any brand cutter by 3-5% which would be noticeable to a skilled user. A casual user may not have the experience to notice the difference. The downside of putting in down angle in abrasive conditions is that cutter stay sharp can be reduced due to the sharper angle on the top plate. Also if too much down angle is used, the area under the top plate can be thinned out to where it flexes more and causes the chrome plating on the top plate to fracture and thereby reduce stay sharp as well. Please note that when using the Oregon filing guide we do not recommend putting in down angle since the file then exceeds 20% of its diameter above the top plate at the cutting corner and the side plate cutting angle will be reduced. This data is anecdotal information we observed from our own testing as part of our chain development. Please go to http://www.oregonchain.com and click on the application icon at the bottom of the professional US site. On pages 96-97 you will see Oregon chain filing and grinding information.

Stihl seems to have got into the act, their new F4 sharpening guide files at 5 degrees down!

[Crispin Rogers]

I must admit to being a little puzzled by the last email I received from Oregon so I requested further clarification and here it is.

The side plate filing angle of 60 deg on a 3/8 pro pitch chisel cutter is a result of the 7/32” diameter being positioned so that 20% of its diameter is above the top plate of the cutter. With the file held perpendicular to the center of the chain, a 25 deg angle on the top plate will produce a 25 deg result on the top plate. When you lower the file by 10 deg from the perpendicular however the resultant top plate becomes about 22 deg even with the file held to 25 deg. A compensation of 3 deg will correct that and create a sharper included angle under the top plate and more efficient cutting. The side plate and top plate of a cutter have each an angle and the file position determines what they will be.