I've been milling for a few months now. I recently ran into this bowing effect on 2 large maple logs I milled up. Everything starts out straight as an arrow but as I get close to the heartwood I notice the kerf developing a bow the seems to get progressively worse if I don't take action. To stop the bowing I used a ladder with every cut, but I should not have to do that to maintain a straight cut. I am running a 660 with a 32"bar, Oregon rip chain, and a 30" grandberg. If there are some more experienced CS millers out there who have seen this before I'd love to hear your thoughts and recommendations. Thanks!
Kerf bowing with a CS mill?
- Thread starter Elite64a
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My experience is limited but I think you might find some value in it. What mill are you using?
Start by putting a straight edge across your bar to see if your bar has a cup/belly in it. Some mills like the panther can distort the bar so it's cupped or not parallel to the frame.
Start by putting a straight edge across your bar to see if your bar has a cup/belly in it. Some mills like the panther can distort the bar so it's cupped or not parallel to the frame.
The cut isn't showing a cup. Its more like when looking down the log you can see it is cutting straight then starts to dive.
Most likely internal stress in the log being released as you take off flitches. Are you flipping the log/cant at all or just flat sawing top to bottom?
Sawing is an art. I worked in commercial mill for a while and learned a lot about opening up logs by watching the sawyer as I ran the edger.
Hardwoods that have any lean will have tension wood on the high side of the lean, conifers will have compression wood on the low side. A hint of this is looking at the annular rings on the ends of the log. By that I mean stress. When you remove wood things can bend or twist in the log/cant as stress is relieved.
How you proceed in opening up the log can help prevent this.
If there are any experienced sawyers with portable mills in your area watch them work, or ask to be a stacker for a few days. You will learn a lot.
Sawing is an art. I worked in commercial mill for a while and learned a lot about opening up logs by watching the sawyer as I ran the edger.
Hardwoods that have any lean will have tension wood on the high side of the lean, conifers will have compression wood on the low side. A hint of this is looking at the annular rings on the ends of the log. By that I mean stress. When you remove wood things can bend or twist in the log/cant as stress is relieved.
How you proceed in opening up the log can help prevent this.
If there are any experienced sawyers with portable mills in your area watch them work, or ask to be a stacker for a few days. You will learn a lot.
Is it like this? - see the diving kerfline in between the straight kerf and the dotted red line.
That was caused by the fact that I did not tighten the verticals on the mill enough and the vibe cause the bar to drop.
The most likely cause is however that either your left and right hand cutter -
- lengths are different
- Top plate filing angles are different.
- raker angles are different
BTW if you use progressive raker depth setting then you don't need to worry about cutter lengths being the same provided they are randomised between left and right cutters.
I use log rails or ladder on every cut because it has much friction less that that between mill and log. In between the ladder runs provides a convenient place to put wedges and hammer. And it prevents transference of any twist or bow from the previous cut to the current cut.
I agree with Bob in that it may be a chain issue. I've had a similar problem where one side of the cutters became longer than the other (I found that I was putting slightly more pressure on the file on one side than the other, which eventually made them uneven over time), causing some curve in the cut. As he said, go with his progressive raker style to correct this.
And I also use rails on every cut now. Makes a huge difference, especially when entering and exiting.
And I also use rails on every cut now. Makes a huge difference, especially when entering and exiting.
Exactly like that! I started using the ladder with every cut to keep it straight. Not sure about the length of the cutters it was a brand new chain. I will check them though just to be sure. I haven't heard much about progressive rakers but I will check that out as an option. I do know when I hand file I am much better at filing the left side vs. the right side. Since I am right handed the right side should be easier to file but not the case for me. Thank fellas do the suggestions and advice. How are you attaching the ladder after the first cut. I have had someone hold it down when I had help and I have staked it down on either end when by myself. One other thing my cut doesn't start diving until after I am half way through the cut.
If you aren't doing so already, I found that clamping the bar in a table vise really helps with getting more even pressure on both sides with the file.
Same as for the first cut.
I use Unistrut and all thread rod so I can adjust the width of the log rails.
Progressive rakers can be found at top thread "CS milling 101" Attaching ladder? I use pipe hanging straps for under basement joists w/2 screw holes takes more on first slice, after can use one most of time. Screws tension rung down for stability & no slide. Overhang @ start & finish gives smoother start & end of cut IMHO
Stay safe while you enjoy
Rough hewn
ArboristSite Lurker
Get a professional chain grinder.
When ripping every tooth and every depth gauge need to be perfect.
Absolutely impossible to do with a hand file.
in the field, sharpen by hand, but after put it on the grinder.
Bring it all back to perfect.
Cutting will be faster and leave a cleaner cut board.
Good luck mate
When ripping every tooth and every depth gauge need to be perfect.
Absolutely impossible to do with a hand file.
in the field, sharpen by hand, but after put it on the grinder.
Bring it all back to perfect.
Cutting will be faster and leave a cleaner cut board.
Good luck mate
That's what I did no issues now. Thanks
I have found that if the slab your cutting isn't wedge properly to allow clearance it can cause this, also if pushing to hard on the mill it may not clear the sawdust from the kerf adequately causing a similar thing
BigOakAdot
ArboristSite newb
I had a similar issue that I've been meaning to bring up. I had a cherry cookie that had dried for a few years and was about 5.5" thick.
I have two people who would like me to make coffee tables with it so I used my chainsaw mill to split it in half. I found that when I made the cut it is cupped in the middle. Like when I put my level on the cookies there's a gap which gets worse in the middle of the round.
There's some rot in the middle so I was thinking maybe it was softer and took more material. If the bar was bowed in the middle the one cut should be raised in the middle while the other one is recessed right? Cause both were cupped in the middle where I made the cut.
Used a ladder FYI so that shouldn't be the issue. I can provide pics later. Any thoughts?
I have two people who would like me to make coffee tables with it so I used my chainsaw mill to split it in half. I found that when I made the cut it is cupped in the middle. Like when I put my level on the cookies there's a gap which gets worse in the middle of the round.
There's some rot in the middle so I was thinking maybe it was softer and took more material. If the bar was bowed in the middle the one cut should be raised in the middle while the other one is recessed right? Cause both were cupped in the middle where I made the cut.
Used a ladder FYI so that shouldn't be the issue. I can provide pics later. Any thoughts?
When I was having the issue the kerf was diving during the last 1/3 of the cut.
Sorry mate, not impossible at all. I hand file all of my milling chains, and it's really hard to get the grinder to work with the saw on the mill. If you don't push the saw to the point it's really dull, it only takes a couple swipes with the file. On Oak and Hickory I touch up the chain about every 3 slabs. On Metasequoia I can get 20 slabs between touch ups, Joe.
Rough hewn
ArboristSite Lurker
Hello rarefish,
I presume you mean a hand held grinder?
I meant a bench grinder, stihl HOS or USG or the Oregon equivalent.
To accurately hand file all teeth and depth gauges to within 0.05mm is quite a feat.
The use of a bench grinder setup is so much quicker and far more accurate.
Yes, I hand file to touch up every few cuts, but at some point it's going on the grinder.
Yes, it does eat the chain a lot quicker,
but more than makes up by the speed of cut and finish of the board.
I presume you mean a hand held grinder?
I meant a bench grinder, stihl HOS or USG or the Oregon equivalent.
To accurately hand file all teeth and depth gauges to within 0.05mm is quite a feat.
The use of a bench grinder setup is so much quicker and far more accurate.
Yes, I hand file to touch up every few cuts, but at some point it's going on the grinder.
Yes, it does eat the chain a lot quicker,
but more than makes up by the speed of cut and finish of the board.
There's no need to file the chain to within 0.05mm or accurately file the cutters and rakers to optimise cutting speed.
The critical settings are raker angle (using progressive raker depth setting) and cutter hook in relation to what size and hardness of what is being cut.
If a basic file holder is used the hook is fixed by a) the file size and b) the file holder size. Chaning the hook then only requires changing one or both of these.
The raker angle just needs to be within a degree.
I used to religiously use a grinder to set the cutter lengths to the same size and the rakers to the same depths but the last time I did that was in 2008 when I switched to progressive raker depth setting.
Progressive raker setting means you can be far less concerned about accuracy especially cutter length.
Longer cutters automatically wear faster so show up as more cutter edge glint so touching up to remove glint will automatically shorten longer cutters and reduce the number of swipes needed by shorter ones.
After a while of doing this they eventually maintain a similar length.
Finish is 90% operator/mill rather than chain dependent.
The critical settings are raker angle (using progressive raker depth setting) and cutter hook in relation to what size and hardness of what is being cut.
If a basic file holder is used the hook is fixed by a) the file size and b) the file holder size. Chaning the hook then only requires changing one or both of these.
The raker angle just needs to be within a degree.
I used to religiously use a grinder to set the cutter lengths to the same size and the rakers to the same depths but the last time I did that was in 2008 when I switched to progressive raker depth setting.
Progressive raker setting means you can be far less concerned about accuracy especially cutter length.
Longer cutters automatically wear faster so show up as more cutter edge glint so touching up to remove glint will automatically shorten longer cutters and reduce the number of swipes needed by shorter ones.
After a while of doing this they eventually maintain a similar length.
Finish is 90% operator/mill rather than chain dependent.
Rough hewn
ArboristSite Lurker
Seriously Bobl?
You hand file 48" chains accurately?
Are you a hobby miller?
Clients don't pay to watch you sharpen your chains.
I Might use 2-4 x 48" chains in a day,
as a professional miller.
What's the finish of your cut like?
Zig zag, lined , or smooth like planed?
What angle for your cutting teeth?
You hand file 48" chains accurately?
Are you a hobby miller?
Clients don't pay to watch you sharpen your chains.
I Might use 2-4 x 48" chains in a day,
as a professional miller.
What's the finish of your cut like?
Zig zag, lined , or smooth like planed?
What angle for your cutting teeth?
No I'm not a pro miller but every pro miller that has seen my accuracy and finish cannot believe I'm not a pro miller.
This is my standard finish on a Eucalypt called Marri
I turn up to paying jobs with 3 chains and only swap them if I break or damage them.
I can touch up a chain for a 42" bar about as fast as I can swap out and I don't have to take the saw off the mill to change the chain.
This is Lemon Scented Gum - It's hard green than Hickory is when it's dry.
This is my standard finish on a Eucalypt called Marri
I turn up to paying jobs with 3 chains and only swap them if I break or damage them.
I can touch up a chain for a 42" bar about as fast as I can swap out and I don't have to take the saw off the mill to change the chain.
This is Lemon Scented Gum - It's hard green than Hickory is when it's dry.
