Lots of ways to sharpen chains - if you find something that works for you, stick with it.
There are really 4 basic settings when sharpening chain, whether filing or grinding (aside from the size of the file 'x' or grinding wheel used):
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A' -
the top plate angle (typically 30°) determines the angle of top plate entry into the wood (like the angle a skew chisel when woodworking), *but also, the bevel angle of the side plate cutting edge*;
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C' - called the
side plate angle (typically 60°), but really the bevel of the top plate cutting edge (again, think of the cutting bevel of a wood working chisel). This is a function of the file diameter and the height that the file is held (or the angle of the grinder). Oregon says that this should be 1/5 (20%) of the file diameter - some file guides position this for you;
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B' -
the down angle (since the handle of the file is held level or dropped down 10°) makes this into a more complex, compound angle. I have been told that under controlled test conditions, this absolutely makes a difference in some chains. Some file guides, however, are not designed to be used in this position, and some grinders do not accommodate the down angle. Up to you, but going back-and-forth between 0° and 10° will waste a lot of time and cutter life, so pick one;
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D' -
depth gauge offset - some people say that this should be a fixed measurement (like 0.025") - others say that it should be 'progressive' (change as the top plate wears back), and use an angular relationship. The Carlton File-O-Plates and Husqvarna guides can help you with a progressive setting.
BUT (and it's a big 'But'), these are all starting points. Chain companies make chain for millions of users, in dozens of countries, cutting hundreds of species of wood, under different conditions, with different saws. Their opinion about what is 'best' for 'general use' changes, as have their recommendations. You may find that different angles or settings work for you. You may want different settings for different cutting conditions (you might want different chains filed / ground at different angles for different wood). Just do this intentionally - in other words, if you want a chain filed to 35/55/10 or 25/65/0 go ahead, but don't do this mistakenly thinking that you are filing at 30/60/0.
Understand that chain from different manufacturers is also not exactly the same - the height or angles on a STIHL cutter may vary slightly from that on an Oregon or Carlton cutter, even though they look similar and all fit the same saw. And manufacturers may disagree on what is 'best'. So recommended angles and settings may vary. *One advantage of sharpening your own chains is that you get to decide what is 'best' for you.*
No.
If each cutter is properly sharpened on both bevels (top plate and side plate), and the depth gauge offset is properly set, the chain will probably cut and throw chips. But the
length of the cutter is directly related to the
height of the cutter and the
width (
kerf) of the cutter. No tooth cuts alone in a loop. If all the cutters are not the same height, the chain will bounce more (at a chain speed of 60 mph this will translate into vibration), and higher cutters may participate more in the cut, preventing lower cutters from taking as thick of a chip. Getting all of the cutting teeth the same same height on a saw is generally referred to as
jointing.
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Similarly, as the cutter is worn / filed / ground back, it becomes
narrower, affecting the kerf. A narrower tooth may not fully clear the side wall of the kerf, making the next tooth scrape it a second time. Getting all of the cutting teeth to extend the same distance sideways on a saw is generally referred to as
setting.
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A saw that is not properly jointed and set may still cut, but it will not be as efficient or as smooth.
The OP (remember the OP?) asked about rounding over depth gauges. Note the illustration below *but note that position '3' continues as long as the tooth is in the cut - it does not 'porpoise' continuously along the guide bar*. If the depth gauge is filed off flat, it will leave a sharp corner that 1) can dig into the wood, causing drag, and 2) act as a fulcrum point to push the cutting edges farther from the wood. Since we cannot know the exact angle that a cutter will always rock to (depends on tension, sharpness, wood, etc.), we use a rounded profile that will essentially maintain the same offset, regardless of the cutter angle / position.
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- A decent grinder is an investment, for those who use them, and especially those who sharpen or restore a lot of chains. Good ones keep much of their value.
- Dressing the wheel takes seconds. Less time than tapping out a file over the course of sharpening a loop.
- Don't buy a diamond wheel (I don't have one - they are only for carbide chains). I don't own a CBN wheel (for standard chains) either.
- The grinder does not chew up chains - the operator chews up chains using the grinder. (Just for fun, mail me a new chain and file, and let me show you how badly I can chew it up by filing incorrectly!).
Philbert
