Had to look up what FOP was, file -o- plate. Never used them as I think I have too many different sizes and types of chain.
The guide should be positioned in relation to the top of cutting edge instead of the back of the next cutter. That way the angle stays more constant.
Cool Bob!
I understand the importance of cutting angle...that's why I put back-bevels on my block plane blades. Didn't occur to me that it would vary with a constant distance between cutter and raker.
I do have one question though...cutting efficiency also should vary as a function of the thickness of the shaving. It certainly does with my hand planes. At some point, would it be better to lose a little cutting angle (not as drastic as what you demonstrated) to reduce the thickness of the cut, or do you run out of cutter before that would become a problem.
If both have an effect, there should be some optimum reduction of cutting angle and corresponding increase in what is removed from the raker.
It sounds like you might be confusing cutting angle with blade angle - these are not the same.
Sorry for the rambling response.
Husky combi gauge is better I think, its more progressive. The pivot point is a little farther back then the FOP gauge.
I had a bit of brain fade one day and used the combi gauge for .325" on a 3/8" chain it made it really aggresive just the raker part BTW.
Thanks Philbert - I guess it makes a change from just yelling Husky - Stihl at random folk?Fun thread BobL - tired to rep you, but the rep Gods said I have to wait.
The change in cutting angle across the cutter varies with the top plate cutting angle and the width of the gullet.I think that the FOP argument is interesting, but as you point out, the relationship between the depth gauge and the cutter (top plate edge) still varies, only it varies differently that with a constant depth gauge setting tool (standard Oregon, STIHL type).
SureI keep thinking of the wood plane analogy. On my block plane, the cutting angle is fixed by the angle ground into the blade. I can adjust the depth that the blade sticks through the plane sole (analogous to the depth gauge height on a chain?) and I can adjust the length of the throat opening (analogous to the length of the gullet as the chain is sharpened?). Both of these adjustments make a big difference in how the plane cuts.
A longer gullet is unlikely to change the chip length. The chip length is determined by the cutting angle and the degree of hook and the type of wood. From this point of view cutters are more like a chisel (cutting cross grain) than a plane cutting with the grain. The chip length is determined by how high or how shallow an angle the chisel makes with the wood - this is the combo of hook plus angle of chisel.As the cutter is ground back, it takes a longer chip, so maybe a change in the angle you describe is OK?
The cutter sort of rocks its way into the wood. Cutter bites, rocker resists, cutter bites more rocker resists more , cutter bites a touch more, rakers resists and then some sort of equilibrium is reached. The raker actually digs into the wood depending on its profile.In Carlton's book ( http://www.sawchain.com/images/complete book.pdf ), around page 19, they justify the FOP based on the way the cutter pivots when it hits the wood, and as the edge gets filed back. If the cutter only heeled back, letting the depth gauge rise up to the wood that would make sense. But if the top plate of the cutter then rises up into the wood, you would still end up with a longer, shallower. chip.
Sure that's what all the old timers did and I do that myself in the field. I only do the digital caliper raker checking at home in the evenings.In practice, if the chain isn't cutting after being ground back, I would just take the depth gauges down a few more file strokes.
this is the threadhttp://www.arboristsite.com/showthread.php?t=69081***I would like to see a photo of how you use your vernier caliper to set depth gauges and a mention of how you determine the settings***
That'll do it !
BTW just based on a scaling factor, going from a .375" (3/8) chain to .325" should only increase teh cutting angle by ~1º which most saws should be able to cope with , what sort of saw was it?
Justsaws said:The guide should be positioned in relation to the top of cutting edge instead of the back of the next cutter. That way the angle stays more constant.
It seems like we are talking about 2 different things in this thread: 1) a 'progressive' raker guide, where raker height varies with the width of the gullet / height of the top plate; and 2) maintaining a constant 'cutting angle' (BobL's term) - not necessarily the same.
This (red line) would be a simpler way to maintain a constant angle. A slight modification of the standard Oregon constant depth gauge - a constant angle depth gauge.
This makes more sense to me.
It seems like we are talking about 2 different things in this thread: 1) a 'progressive' raker guide, where raker height varies with the width of the gullet / height of the top plate; and 2) maintaining a constant 'cutting angle' (BobL's term) - not necessarily the same.
This (red line) would be a simpler way to maintain a constant angle. A slight modification of the standard Oregon constant depth gauge - a constant angle depth gauge. Similar to some of the comments on that other thread that BobL referenced. Would work on full comp, semi-skip, skip tooth, and even (shudder) low-kickback chain.
I have fiddled with making this device but I just don't like to put a hardened steel plate (raker guide) directly on top of my freshly formed cutter edges.
Do you have access to Teflon sheeting? The stuff I am refering to is similar to wax paper but but extremely cut resistant except from the outside edge in. It is handy stuff for protecting cutting edges from the uglies.
As long as it wears down evenly it would be OK. I just realize I have a nice piece in my shed I will experiment when I get chance.You could always mill yourself one out of impregnated block. Might be a bit bulky but some sides to keep it squared and a handle would be nice. Face the file area HSP because the files wear it down fast despite what the manufacture says.
Yep I am familar with this stuff.
Excellent, it is good stuff to have around. Lots of woodworking shops out there with food grade guides and jigs.
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