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Ripping chain sharpening

Discussion in 'Milling & Saw Mills' started by Pcbw69, Feb 10, 2020.

  1. Pcbw69

    Pcbw69 ArboristSite Lurker

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    Hi I have a woodland pro 42 inch ripping chain that needs sharpening. The bench grinder I have available doesn’t seem to tilt enough to get the angles I need, only goes up to 55 degrees. Am I looking at this wrong? PS, This will be my first time sharpening ANY chainsaw chain. Here is a pic of the box with the specs
    Mine is the 3/8 pitch 33rp

    any help would be greatly appreciated
     

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  2. rarefish383

    rarefish383 Addicted to ArboristSite

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    Welcome to the site. I use out of the box Stihl, yellow box, chain. I'm too lazy to swap chains back and forth between milling and cutting firewood. After others posted pics of slabs they milled with ripping chain, and my slabs were better, I never bothered trying it. Sorry I didn't answer your question. I hand file all of my chains. My biggest bar is 45" and I use full comp on all of them.
     
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  3. buzz sawyer

    buzz sawyer Addicted to ArboristSite

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    I also use the same chain as firewood on my sp125c / 36". Finish is fine for me and it cuts well - about 5 mins on a 25" x 8' slab of Ash. Keep the chain tight and rpms up. I like to lead a little with the nose.
     
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  4. rarefish383

    rarefish383 Addicted to ArboristSite

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    I'm with Buzz, but I'm jealous, I want an SP125. My biggest is a Homelite Super 1050.
     
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  5. Pcbw69

    Pcbw69 ArboristSite Lurker

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    the ripping chain works beautifully when sharp but I hit a rock or nail that was embedded on my first pass and that pretty much ruined the day. After the second slab I had to put all of my body weight into the saw to make it through and kind of chewed it up. I’m just confused as to what I set the grinder angle at. The box says top plate cutting angle 60 degrees but is that the tilt of the blade or slide at the base. Also 80 degrees for the side plate angle?? 55 degrees is where the grinder maxes out in any direction. Just doesn’t seem right
     
  6. jnance

    jnance ArboristSite Member

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    On my grinder tip the wheel/motor to 60* The vise turned to 10* then for the 80* my vise tips 10*.


    Sent from my iPad using Tapatalk.
     
  7. Philbert

    Philbert Chainsaw Enthusiast

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    Based on the angles printed on your box, for your chain:

    The grinder head tilt should be set at 60°.

    The grinder vise should be rotated to 10° Right and Left.

    Set the depth gauges (after sharpening) to 0.022".

    Use a 3/16" grinding wheel.

    Some grinders do not adjust to theses angles, or have some angles fixed, or only accept one size wheel. What brand / model grinder are you using?

    Philbert
     
  8. Philbert

    Philbert Chainsaw Enthusiast

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  9. Pcbw69

    Pcbw69 ArboristSite Lurker

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    Thanks for the replies guys
    I’m going to invest in an Oregon sharpener and give it a shot
     
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  10. Mad Professor

    Mad Professor Addicted to ArboristSite

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    I use a file.
     
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  11. BobL

    BobL No longer addicted to AS

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    Definitely agree with the last two, unsure about the first one.
    Have chewed the fat over with a few guys about this many times

    The theory is that on a chain the steel behind the hard chrome coating on a sharp cutter does virtually no cutting.
    The majority of the cutting is done by the hard chrome plate covering the cutter edges which is not affected by grinder heating and this also stays very hard even under red heat, a bit like like HSS
    IN practice filing does not sharpen anything, all it does is remove enough supporting steel under the Cr to generate a new hard chrome edge.
    When a saw goes blunt this means the chrome edges have started to peel off further exposing the raw cutter steel underneath, which rapidly rounds over and makes increasing amounts of what is called cutter edge "glint" , and of course much powder.
    Efficient sharpening effectively removes just enough steel to remove the "cutter glint".
    To maintain a "glint-less" cutter top and side plate requires frequent touch ups.
    GlintEdge.jpg

    Below shows an extreme example - it's a cutter from one of my full comp cross cutting chains after cutting a couple of hardwood slabs.
    The what looks to be two top plate cutting angles is because this chain is mid conversion from 25º to 10º .
    The lower part of the cutter edge with almost no glint has been filed several times at about 10º and the top part is the original angle that has been left at 25º
    Over successive sharpening the 10º segment gets longer while the 25º segment decreases in size until it disappears.
    The 25º segment has severe "glint" because the chrome plate has been peeled right back exposing the cutter steel underneath.
    The 10º segment has about the glint I expect after a cut or two in hardwoods I mill.

    BTW This also suggests that converting a cross cutting chain in this way is not as efficient as converting it by degrees, ie 25 then 20 then 15 etc so that there is always no glint right across the cutter edge.
    Talk about nerdy chain stuff eh! I better stop here.

    Sqgd.jpg

    My mate who always uses a sharpener argues that overheating a cutter enables the Cr plating to peel off easier. Because I rarely use a sharpener I have not be able to assess his argument.
     
  12. Bmac

    Bmac ArboristSite Member

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    Awesome info and awesome post. I've often wondered the best way to convert a cross cutting chain into a ripping chain, I do it the way you are showing with the top plate slowly reshaping into a straight 10 degree edge. I've often wondered if this was the best way to convert a chain. How much do you think the unsharpened section on the top plate affects cutting efficiency?
     
  13. Philbert

    Philbert Chainsaw Enthusiast

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    A lot of stuff covered in your post Bob; as always I appreciate and respect the perspectives you bring. But I am sticking with 'avoid overheating the cutters' as a general rule for grinding chains.

    1. If you want to intentionally overheat and harden the cutting edges, for some reason, that might be something else. Certainly, the teeth on many inexpensive, hardware store saws are induction hardened (which makes them next-to-impossible to hand sharpen). And most laminated guide bars have induction hardened rails. But most chain manufacturers do not do this with their cutters. So, if you are over-heating and hardening cutter edges due to lack of skill or knowledge, that would be carelessness, not intent.

    2. Cutter edges are very fine; a harder edge will be more brittle and more prone to chipping.

    3. 'Grinder hardened' edges are impossible to file, so not a good option if you file in the field and grind at home (like me), or if you are 'evening up' a chain for someone else who will be filing in-between machine sharpenings.

    5. I have been told by chain engineers that the hard chrome plating on a cutter is just for protection against abrasion. That it cannot be 'sharpened' and does not contribute to the cutting. Some guys remove the chrome from their 'race chains' for this reason, when removing every gram of weight. The questions came up when discussing the Oregon 'MultiCut' / 'DuraCut' chains with the thicker chrome plating.
    https://www.oregonproducts.com/en/p...racut-saw-chain-and-guide-bars/c/duracut-sc-p

    6. I have seen the chrome curl up and flake off on grinder 'burned' cutters; so I you want to keep it on, overheating is not a good idea.

    I like the idea of incrementally converting a cross cut chain to a ripping profile to get more usable life out of it.

    That's what these forums are all about!

    Philbert
     
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  14. BobL

    BobL No longer addicted to AS

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    Some good points there especially about the hardened cutters being near impossible to file. Thanks
     
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  15. frank_

    frank_ ArboristSite Member

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    my understanding is that steel is hardened by heating it red hot then quenching.
    then it can be tempered/softened by heating it blue and then leaving it to cool naturally.
    so getting it blue hot by grinding it too aggressively will actually SOFTEN the tip
     
  16. Philbert

    Philbert Chainsaw Enthusiast

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    A common misunderstanding. What happens is that, unlike a large piece of steel which retains a large thermal mass, the very thin metal at the cutter edges cools very quickly; an engineer referred to this an 'air quench'. https://www.sst.net/air-quenching-steel/

    Theory aside, try filing a cutter that has been overheated by a grinder; even a new file slides over it like a knife on buttered glass. It is usually possible to grind through / past this hardened area, making the cutter edges fileable once more. It can be prevented by taking lots of small taps with the grinder, and dressing the grinding wheel frequently to maintain fresh abrasive that cuts/scrapes/abrades the steel, instead of rubbing dull abrasive against it, which causes friction.

    Philbert
     
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  17. frank_

    frank_ ArboristSite Member

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    that link ^ describes compressed air being "forced over the piece to cool it down " tho
    my experience of burning out drills by getting them too hot always makes the tip of the drill go soft
    and you have to grind loads off the end of the drill to get back down to the hard part
     
  18. Philbert

    Philbert Chainsaw Enthusiast

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    Again, I was trying to explain the theory, as explained to me by a saw chain engineer, since it seemed contradictory to me too.

    But try it. Heat a saw chain cutter blue or black with a dull grinding wheel and then try to file it. It will 'speak for itself'.

    Perhaps the alloys used, or the mass of the drill bit, cause it to act differently when overheated in a drilling operation, versus the thin saw cutter edge in a grinding operation. My friends who are metallurgists always talk about the 'art' as well as the 'science' of metal.

    Philbert
     
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  19. sweepleader

    sweepleader Chainsaws and Fire Trucks, perfect.

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    Philbert, you are right on as usual, even if you are not certain this time.

    The alloys used for cutting tools, whether for saw chains or drill bits or excavator teeth, are wildly different. They each require their own heat treatments to obtain the best results.

    Air hardening tool steels are common along with oil and water hardening types. The mass and geometry are critical to proper results and tool failures can often be traced to the wrong alloy or heat treat.

    Saw chain cutters have several conflicting requirements for good service. They need to retain a very fragile cutting edge while withstanding impacts and temperature changes as well as abrasive conditions. Material selection and processing steps for this use is not for the faint of heart.
     
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  20. rarefish383

    rarefish383 Addicted to ArboristSite

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    A couple years ago a friend, and daughter of one of my Dad's competitors, gave me 7-8 of her dad's old saws, and an old chain grinder. It was top of the line for the time. I tried to find new discs for it and couldn't, but I didn't look all that hard. I tried it out on an old chain on my bench. I tried to take a very small bite and still turned a few teeth purple/blue. When you say take lots of small taps, do you mean take like 1/10 of the bite, then 2/10, 3/10, until you have the full stroke completed? You DO NOT mean take a very shallow, but, full stroke, do you? I was going to sell the grinder at my spring Man Cave Yard Sale. But I may hold on to it and try to learn how to use it properly.
     

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