Disston KB7-AY + harvester chain?
Close
Login to Your Account
Results 1 to 13 of 13
  1. #1
    Join Date
    Jun 2001
    Location
    downhill from Twain\'s study outside Elmira, NY
    Posts
    11,080
    Post Thanks / Like
    Likes (Given)
    4134
    Likes (Received)
    3913

    Default Disston KB7-AY + harvester chain?

    Might as well ask here, too.

    Anyone conversant with harvester chain?

    We lost some trees over the winter and it has become interesting to possibly rip them for walkboards in our near field (swamp).

    For a gearhead, this provides a great excuse to revisit the idea of trying to put a modern (read "available & productive") saw chain on one of my Disston KB7-AY's.

    Specific chain is Stihl .404H 80 ga.
    .350" kerf appears it should work well with the .250" - .255" thick bar.

    AFAIK, all actual harvesters run center drive/rim support sprockets.
    Center drive sprocket would be easier to machine and probably more stable in heat treat.
    In use, sprocket alignment is critical. (this is not a technical problem. Would it be a problem in use under dynamic conditions?)

    Manual saws generally run spur sprockets.
    Alignment is not much an issue with a spur sprocket, the chain finds its own axial position to align with the bar during break in period.
    Spur drive is somewhat more involved to machine.

    In order to build the new sprocket, final questions are:

    Is there any reason that a spur drive should not be used for my app on a 2 man chainsaw outfitted with same originally (albeit 3/4" pitch original chain)?

    If a center drive sprocket is used, how compliant is is under dynamic conditions? (is there increased risk) with using it on a manual saw with the bar flopped over sideways for ripping/sawmilling?

    Here's a link with pictures & more involved discussion on the chainsaw forums. PM'rs often have a deep and diverse knowlege base. so asking here as well. Scroll back one page for full discussion.

    https://www.arboristsite.com/community/ ... 557/page-2

    smt

    dsc_0110.jpgdsc_0095.jpgdsc_0093.jpg

  2. #2
    Join Date
    Oct 2005
    Country
    UNITED STATES
    State/Province
    Pennsylvania
    Posts
    17,286
    Post Thanks / Like

    Default

    Is this the correct pitch sprocket ?
    Cutter's Choice Online - .404 Pitch

    so you would make an adapter to drive this sprocket (I assume it floats ?)
    That would mate to your crank.

  3. #3
    Join Date
    Jun 2001
    Location
    downhill from Twain\'s study outside Elmira, NY
    Posts
    11,080
    Post Thanks / Like
    Likes (Given)
    4134
    Likes (Received)
    3913

    Default

    Doug -

    Needs to be either 14 or 15 T. I have not committed, but leaning toward 15. 15T puts the soles of the links and straps about where the originals would have been, in relation to the bar.

    Have not decided whether to buy or build. Still have to decided if spur or center drive is best for this app.
    Buying and adapting to the existing clutch is complicated because the parts are hardened, so while all the features can be ground to fit, threading for assembly is not possible.

    There's a suitable hunk of S7 remainder from another project.
    Next few days got keep on the woodworking while cogitating....

    smt

  4. #4
    Join Date
    Jun 2001
    Location
    downhill from Twain\'s study outside Elmira, NY
    Posts
    11,080
    Post Thanks / Like
    Likes (Given)
    4134
    Likes (Received)
    3913

    Default

    Actually, re-calculating -
    Was somewhat off on my backwards adapting.
    Original OD at tips of the original 3/4 pitch spur drive appears to have been 3.125" dia. Subtracting spur projection/cut-out in the straps, about .160 x 2, leaves 2.805 effective dia at the bottom of the straps.

    13T .404 harvester sprocket is listed as "3.0"(76.2 MM)"
    12T is listed as "2-3/4"(70.9mm)" If the metric dimension is correct, that is 2.7913" or very close to the apparent original 2.805".

    Idler, with some wear, is 2.693" at the rim the straps ride on.

    I need to get comfortable about not missing anything before ordering. Preferably handle the actual parts. Saw shop did not have anything bigger than 10 tooth for reference, but the diameters don't seem to correlate with increasing tooth count. Different sources seem to show different diameters for the same pitch & tooth count. Which should not be correct.

    Bar height is about 3.030" at the area the chain enters/exits.



    smt

  5. #5
    Join Date
    Aug 2006
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    617
    Post Thanks / Like
    Likes (Given)
    875
    Likes (Received)
    357

    Default

    I hope you get the rig operating Stephen. but what happens if you find some spectacular grain in the output? Will you just have wet feet?
    Joe

  6. #6
    Join Date
    Jun 2001
    Location
    downhill from Twain\'s study outside Elmira, NY
    Posts
    11,080
    Post Thanks / Like
    Likes (Given)
    4134
    Likes (Received)
    3913

    Default

    Joe - I might save a short section of clear, straight, QS grain. Just in case i ever make any stringed instrument parts.
    The rest is nearly worthless.

    More developments and pix here:
    https://www.arboristsite.com/communi....303557/page-2

    smt

  7. Likes Joe Rogers liked this post
  8. #7
    Join Date
    Jun 2008
    Location
    TN
    Posts
    1,617
    Post Thanks / Like
    Likes (Given)
    377
    Likes (Received)
    304

    Default

    Stephen,
    I have been messing with chainsaw saw milling since 1982. All of it with 100 and 120cc saws with bars up to 42”. Its a tremendous amount of work but kinda fun in a perverse way for some wood workers.

    If you have not already done so, I suggest you do some calculations on your saw to determine chain speed with the various possibilities of sprockets and chain sizes. It might actually be less work and give a better machine to convert to 3/8 chain with its smaller kerf, low cost and ubiquity.

    Or if you have a newer big saw use that instead. Moving that big ol’ saw will get old after an hour or so.

  9. #8
    Join Date
    Apr 2015
    Country
    AUSTRALIA
    Posts
    712
    Post Thanks / Like
    Likes (Given)
    37
    Likes (Received)
    157

    Default

    I had a 3120 xp husqvarna 119cc saw it was awesome, but even still i would look at this lucas mill for doing milling, a chainsaw is a hard way to do it.

    Lucas Mill > Home

    Maybe get a group together to buy one or find out if you can hire one...i suppose it depends on how much you want to do, there is a agent in the USA for them its australian made.
    I even made parts for them as a external supplier way back in 1992 when they first got going.

  10. #9
    Join Date
    Jun 2001
    Location
    downhill from Twain\'s study outside Elmira, NY
    Posts
    11,080
    Post Thanks / Like
    Likes (Given)
    4134
    Likes (Received)
    3913

    Default

    convert to 3/8 chain with its smaller kerf, low cost and ubiquity.
    Saw shop mentioned that option, but the problem is that 80 ga is required, and the kerf has to be at least 5/16" to clear the bar (.250" - .255" thick). Though at one time i considered thinning the bar on my larger surface grinder.

    As described above and in the posts on linked sites, .404 is still a lot smaller chain than original Disston chisel chain. A LOT smaller.

    I've owned the saw since about 1965 when i bought it at a fire hall auction with the nefarious intent of converting the 2 cylinder motor and in-out clutch to go-kart use. After acquiring it, it was too beautiful a machine to ever take apart. I'm the oldest of nine, so there was usually some brother or other who could be compelled by bribery or threat to take the other end. This is around age 12 - 14, we were sawing logs, and then started ripping them at that age for me, younger for the others. With the poor old scratcher chain.

    In our 20's, we used it for bucking while doing commercial felling around the DC area on forests being cleared for development.

    A few years from age 70, so this is for play. Not going out in our woods and making much lumber with any intent anymore. I just prefer to have machines around that run the way they were intended, and work nicely and efficiently.

    Motor is 245cc twin.

    photos show original Disston 3/4" pitch scratcher & chisel chain compared with modern .404 80 ga harvester chain.

    dsc_0090.jpg

    dsc_0084.jpg

    dsc_0087.jpg

    smt

  11. Likes Joe Rogers liked this post
  12. #10
    Join Date
    Aug 2006
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    617
    Post Thanks / Like
    Likes (Given)
    875
    Likes (Received)
    357

    Default

    That go cart would have wrinkled pavement had you built it. Had a friend in 1969 with a Mac powered cart and it would go sideways on an uneven patch of blacktop. And no where near 245 ccs!
    Joe

  13. Likes stephen thomas liked this post
  14. #11
    Join Date
    Aug 2012
    Location
    Pittsburg, KS
    Posts
    1,275
    Post Thanks / Like
    Likes (Given)
    140
    Likes (Received)
    566

    Default

    My experience with chainsaws is minimal compared to most people, where I grew up no one that I knew had one, if we had a tree, we weren't about to cut it down. Now I live in an area where many people heat their homes with wood so lots of saws running around here.

    Anyway, that chain is awful big, is there some commercial logging or processing machinery that would use a chain closer to that size? Any idea as to what those buncher feller processors use? (those cool excavator looking ones with the tree grabber and saw on the end)

    Or instead of modifying the bar for thickness, could you update to a newer bar that uses the available chain?

  15. #12
    Join Date
    Jun 2001
    Location
    downhill from Twain\'s study outside Elmira, NY
    Posts
    11,080
    Post Thanks / Like
    Likes (Given)
    4134
    Likes (Received)
    3913

    Default

    Jason-

    "Harvester" chain is the name of the chain run on the machines you describe.
    IOW, the type i am using.
    3/4" pitch harvester chain is very close to the original Disston chisel chain that ran on this bar in size. tooth form, straps, etc. However, it is .122 ga. The bar takes .80 ga. Hence my choice of the .404 size harvester chain. I'm also happy to have smaller chain on it for less prying force on the bar.

    Open question is whether the saw will pull it, without changing the sharpening specs.
    Depth gages on it are factory cut to 1-1/2mmm I think the original Disston was around 1mm. But the Disston teeth are twice the size. (see previous pics above). OTOH, there are 180% more teeth on the .404 per given length.
    Then yet again, original bars could be had up to 84".

    Chain only runs around 1,222 fpm. Harvesters run the same chain per Stihl spec at 8,000.

    I never rolled the bar, but about 10 years ago did completely re-dressed it. It probably does not have 2 hrs of show time on it since.
    It had been turned at least once. Disston points out in the manual that it is symmetrical, hence offers 4 surfaces that can be turned to the greatest wear area at the bottom just in front of the snubber in front of the transmission.

    I tested the sprocket cutter, but have not started on the S-7/real blank yet due to needing to finish a woodwork job.

    dsc_0031-copy.jpg

    dsc_0034.jpg

    dsc_0033.jpg

    smt

  16. #13
    Join Date
    Jun 2001
    Location
    downhill from Twain\'s study outside Elmira, NY
    Posts
    11,080
    Post Thanks / Like
    Likes (Given)
    4134
    Likes (Received)
    3913

    Default

    Having an awful time with finish on the furniture, so decided to let it cure a couple days.

    Leading to time for the chainsaw project again.

    dsc_0031-copy.jpg

    dsc_0001.jpg

    dsc_0005.jpg

    dsc_0006.jpg

    finished too late to put in furnace tonight.
    Hoping for trouble free heat treat tommorrow.
    There's grinding allowance "all over" though hope is to not have to profile teeth or hard bore for pins.
    Photos can be revealing - need to polish out that boring bar withdrawal scratch.

    smt

  17. Likes henrya, duckfarmer27 liked this post

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •