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Thread: Fixture to rough bowl blanks with a chainsaw

  1. #1
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    Fixture to rough bowl blanks with a chainsaw

    Iím looking for safe ways to rough cut bowl blanks, mostly from large rounds (think 20-40 inches in diameter), for mounting on my lathe. Ideally using a chainsaw.

    Iíve tried roughing out bowl blanks with my bandsaw and thatís fine when I start with logs under a certain size (say 18 inches round), but my bandsaw isnít big enough (nor does it feel safe) with larger rounds.

    Iím thinking about building a cradle to hold log blanks vertically (grain oriented vertically), but looking for inspiration. I know I need to hold the logs up off the ground to avoid running my saw into the pavement underneath.

  2. #2
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    Quote Originally Posted by Ben Grefe View Post
    Iím looking for safe ways to rough cut bowl blanks, mostly from large rounds (think 20-40 inches in diameter), for mounting on my lathe. Ideally using a chainsaw.

    Iíve tried roughing out bowl blanks with my bandsaw and thatís fine when I start with logs under a certain size (say 18 inches round), but my bandsaw isnít big enough (nor does it feel safe) with larger rounds.

    Iím thinking about building a cradle to hold log blanks vertically (grain oriented vertically), but looking for inspiration. I know I need to hold the logs up off the ground to avoid running my saw into the pavement underneath.
    Someone, it may have been Reed Gray, made a chainsaw "chop saw" with, if I remember, a pivoting bracket attached to the chainsaw and the wood held securely. It's been a LONG time since i saw the pictures. It seems to me a rig could hold the blank, say by a faceplate, and let you turn it a little at at time, chopping off smaller and smaller corners until the blank was almost round.

    JKJ

  3. #3
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    Chainsaw chains are not ground for ripping. You'll have really slow going if you cut vertically through a 40" log. You must have a chainsaw like mine. I have a Husky 3120 with a 36" bar. Cut a lot of urban logs for a while there. Darned thing sounds like a dirt bike when it's really eatin'

  4. #4
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  5. #5
    With straight-grained material you can save time and effort on the initial roughing by splitting with wedges. Start with a chainsaw kerf and go from there. For better precision use ripping chain and a powerful saw.

  6. #6
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    I have seen a video showing Johannes Michelson (the hat guy) cutting large blanks with a chain saw. It was all free-hand. First he cuts down the middle along the pith. I am pretty sure the next step was to make a parallel cut on the bark side so the piece can sit flat on either side. For these two cuts, there are several cradle-shaped sawbuck designs that you can find on forums like this one. I use a simple sawbuck made with two parallel 2X4's attached to a base of other 2X4's. A log standing upright with a V-shaped cut can also hold a log easily. The bigger the blank, the lower to the ground you want the sawbuck, to avoid the need for heavy lifting. Mine is just 4 -6 inches off the ground. Then he drew a circle with a template, and cut the corners off, first making an octagon and then continuing to cut off smaller corners. All this with the blank sitting on another chunk of log that is acting as the sawbuck. I have tried this on medium to large size blanks, I am happy with the method.

  7. #7
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    I built a version of Robohippy's chopsaw and it works great for cutting up the blanks with removing the pith section. Because you are cutting lengthwise you don't need or want a ripping blade. You still have to knock the corners off or make them rounds on the bandsaw. I have mine on an elevated stand so I don't have to bend over and can bring the bucket of the tractor up level so no lifting is required. It doesn't get any easier. Reed's design is a good one.

  8. #8
    I do a fair amount of log milling for bowl blanks and while a chop saw may be nice to get parallel surfaces, I think it's just as easy to do it with a conventional 'saw buck'. The trick to slabbing is not cutting all the way through until all the slabs are mostly formed.

    If you are referring to a jig to ROUND the blanks, then the issue is that the chain on a chainsaw grabs very aggressively. So, any kind of circle cutting jig analogous to a bandsaw circle jig will be very dangerous. When the blanks are too large to heave onto my bandsaw, I cut the blank into an octagon with the chainsaw. I seat the blank on the ground end grain up, then cut off the corners so the blank is to the right of the blade. This will pull the blank into the pawls and prevent it from spinning. I cut almost all the way through on the four corners. You can then go back and trim each of the octagonal corners the same way. The lathe is then the most efficient way (for me) to remove the residual.

    You can do any of your long grain rips with a hatchet and mallet on most woods. So, on a flat or quartersawn bowl, that means you can slab with the hatchet. On an end grain bowl, you can 'clip the corners into round with the hatchet. For spindles, you can skip the chainsaw altogether once you get the log sized to length.

  9. #9
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    Cutting blanks the easy way

    Quote Originally Posted by Mike Nathal View Post
    I have seen a video showing Johannes Michelson (the hat guy) cutting large blanks with a chain saw. It was all free-hand. First he cuts down the middle along the pith. I am pretty sure the next step was to make a parallel cut on the bark side so the piece can sit flat on either side. ...The bigger the blank, the lower to the ground you want the sawbuck, to avoid the need for heavy lifting. ...
    For ease of ripping a big log down the pith nothing beats a bandsaw mill! I have a small manual woodmizer behind the barn and have cut truck loads of blanks for people who like to turn bowls and for club wood auctions. Since the woodmizer normally needs a log about 4' long to support and clamp it sufficiently, I build a sacrificial fence by fastening two 2x12s together with lag screws in to an L shape, set than on the bed, and clamp the short sections to that for cutting. This also lets me easily cut a perfectly parallel flat spot on the top if desired. I often take the opportunity to cut a few 8/4 or 16/4 short pieces to cut up further and air dry for smaller bowls, platters, vessels, spindles.

    It's a lot quicker and easier to get the logs in longer sections then cut them up with the chainsaw later but more often people bring shorter pieces since they load them by hand.

    sawmill_blanks.jpg P2253156s2.jpg sawmill_gordon_jake_2_3_18.jpg blocks_from_sawmill.jpg

    I used to use forks or skidding tongs on the tractor bucket on the tractor to load even long logs on the mill. These days I use a new machine that will easily unload and carry a 2500lb log and either set it gently on the mill or hold it off the ground for chainsawing. (BTW, chains last longer if you hold the log off the ground and hose the dirt and rocks off the bark.)

    trackhoe_20190916_190256.jpg

    And BTW, I have no trouble cutting a log section down the pith with a chainsaw with a normal blade (not ground for ripping). I hold it an an angle rather than straight across the end grain, or parallel with the grain if the blank is short enough. I get long shavings. Most of what I cut up by one means or another I section into slabs/planks or turning squares from 1x1 up to 12x12 and put them up for drying. I have no interest in turning a bunch of big bowls. Enough people do that. The first picture is of a few blanks cut from a large stash of ambrosia maple. The tree was over 3' in diameter.

    ambrosia_maple_IMG_20171202_175649_933.jpg auction_wood_2018.jpg spalted_Suggs.jpg

    One other thing about chainsaws. After many years of using typical Stihl chains I finally bought a carbide toothed Stilh chain. So far I've used it to cut up a LOT of logs, some with dirt embedded in the bark, and it does not yet show signs of getting dull. A friend used his for years before sharpening. The cost for carbide chains has dropped a lot over the last decade or so. I think I paid $60 from Baileys On Line.

    JKJ
    Last edited by John K Jordan; 05-28-2020 at 9:31 AM.

  10. #10
    I do plan to 'new and improve' my chainsaw chopsaw. I will use a longer blade with a 'handle' on the nose end that will go into a guide so I don't have to mark both sides. Over the years, I have found that just having wedges under a log helps, but if you cut a flat on one side and then lay out your blanks that is a lot more stable. I do use plywood strips, 1/2 inch increments from 1 to 8 inches, to lay out cutting lines, on both sides of the log, though I generally only notch the back side of the log blank. Chainsaw kerf is 1/2 inch, minimum. I do have another video about rough cutting blanks with the chainsaw as well, maybe I can find it...

    I am curious why a couple of people have said chainsaw are not designed to rip. I do use a skip tooth chain, and find that the chainsaw rips much better than it cuts through end grain. I would guess that the standard tooth cuts through end grain better.

    I mentioned to Ken Rizza if he had any idea about CBN grinding wheels for chainsaw sharpeners. He hadn't heard of them. I googled them and found them for about $100 each. I know Ken will have a better price, if we harass him enough to let him know there is a market for them.....

    robo hippy

  11. #11
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    No fair John! You have all the fun toys..



    Quote Originally Posted by John K Jordan View Post
    That spalted ?maple? is gorgeous!
    Brian

    "Any intelligent fool can make things bigger or more complicated...it takes a touch of genius and a lot of courage to move in the opposite direction." - E.F. Schumacher

  12. #12
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    Quote Originally Posted by Prashun Patel View Post
    ...
    If you are referring to a jig to ROUND the blanks, then the issue is that the chain on a chainsaw grabs very aggressively. So, any kind of circle cutting jig analogous to a bandsaw circle jig will be very dangerous. ...

    What I envisioned was a jig to hold the blank horizontally on a axis (faceplate) and hold it very tight, perhaps with clamps or something like a big vise. Then use the restrained chop-chainsaw to cut of the corners. Loosen the clamps and rotate a bit, tighten and cut off smaller corners. Repeat for as round as desired.

    BTW, did you ever see the late Lissi Oland prepare big blanks? Not only cuts them almost round but she CORES with a chainsaw. (4:42 in this clip)

    https://www.youtube.com/watch?v=1PMEJ7rirso

    I visited her several times in Brasstown NC before she moved back to Denmark - what an impressive lathe she has and what an impressive and kind person! I have a complete set of her big-bowl turning tools still in the box, made by her husband Knud. Maybe a piece of history.

  13. #13
    That video is fantastic. The size of the blank relative to the size of her chainsaw works to her advantage to keep it stable while truncating the corners straight down. I was referring to some kind of jig to cut a circle similar to the way it's done on a bandsaw: with a pivot point.

    The coring was very cool.

  14. #14
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    Quote Originally Posted by Prashun Patel View Post
    That video is fantastic. The size of the blank relative to the size of her chainsaw works to her advantage to keep it stable while truncating the corners straight down. I was referring to some kind of jig to cut a circle similar to the way it's done on a bandsaw: with a pivot point.

    The coring was very cool.
    She had a little octagonal building attached to the shop that was used as a showroom. It was full of big bowls, some you could probably take a bath in.

    I thought I had a lot of wood. Lissi loaded up my vehicle when I visited. Some was box elder was from the root "ball" below the ground and had more red in it than I'd seen before.

    boxelder_root.jpg

    JKJ

  15. #15
    I guess I can add to my ideas about new and improving my chainsaw chopsaw... Perhaps others can chime in with feedback... Anyway, I want the cuts to be as parallel as possible. Best way I can think of to 'stabilize' the log so it won't roll as I am cutting is to first cut a flat on one side of the log, the part which is normally turned off, unless I want natural edge bowls. Then roll the log 90 degrees so it rests on the flats. I need to come up with a way to have some sort of 'dogs' to screw into towards sides of the log to keep it in place as well. Very coarse/bit all thread rod maybe. Or like one of the bar clamps with a big vertical face. The set up does not need to be rigid, but shall we say 'sturdy'. Then for the bracket that bolts onto the chainsaw bar, instead of the wide bracket that is designed to go onto a 2 by 4 or 2 by 6, I put a closed eye type bolt on it, and then that goes over/around a piece of black pipe that screws into a floor flange that is bolted to the platform the whole thing sits on. This would be easier than the 2 by set up. On the far side of the log, and on the end of the chainsaw bar, another eye bolt that is on a bracket that again bolts to the bar. You can't just clamp them on because every thing on a chainsaw vibrates loose eventually. There would again be black pipe screwed into a floor flange. This set up would keep the saw in line and surfaces could be pretty much dead on parallel. I will keep the lazy susan set up so I can pivot the log for square to the grain and pith, then clamp it down... Just thinking out loud. I will make the angle iron be longer than what I started with, since it comes in 10 foot lengths, have the track be 2 sections 5 feet long. This won't be a set up that every turner will have, but every club should have one. No, I will never make them to sell, even parts and pieces. I am sure there are some genius types out there who can make the brackets from nothing, and more efficiently than I can...

    robo hippy

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