# How long you cut between sharpening ripping chain



## Czech_Made (Apr 20, 2016)

I moved from the Eastern Red Cedar to white oak logs I need to rip now. While the ERC was easy - smaller too - and I could cut 100" long, 12" diameter log into 1" slabs using one chain, with the oak (100" long, 14-16" diameter) I feel 2 cuts a chain is about right.

Yeah, I understand, this is a dumb question, but how long do you usually go between swapping ripping chain for sharpenned one? As of now I have two (24", 3/8") and I use them both, clean up and sharpen for the next day operations. Seems like for the oak I should have three chains to keep it at log/afternoon.


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## BobL (Apr 20, 2016)

100" =~8 ft, 15" = 1.25ft so your total cut is 10 sq ft x 2 = 20 sq ft 
Now you have to factor in the bar length - I believe yours is 2ft
So your spec is" 10 sq ft of cut per ft of bar"
More specific than ft of bar is number cutters as this takes into account skip chain.

I generally sharpen about every 32 sq ft but I have a 3ft 6" bar.
So mine comes out to 9.1 sq ft of cut per ft of bar - its actually pretty similar to yours and given how much harder the wood is that I cut I find that surprising.


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## Czech_Made (Apr 20, 2016)

Thank you, sir! Now I know what to look for and I will actually do some measurements. Thats great that there is a single number to represent the performance; I will be back with more accurate data.


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## BobL (Apr 20, 2016)

Czech_Made said:


> Thank you, sir! Now I know what to look for and I will actually do some measurements. Thats greats that there is a single number to represent the performance; I will be back with more accurate data.



Well it's not really that simple and its more of a guide.

I already said wood hardness is significant.

Then there is the side plate filing angle (TPFA) or hook on the cutter, and in conjunction to that the raker angle.
A low TPFA is desirable because in conjunction with raker it will grab a bigger wood chip and produce a more self feeding saw but to also produces a pointier cutter edge which breaks of more easily and will need sharpening more often
A higher TPFA will not go as blunt as quickly. This is what I prefer and lower the raker a bit so it does the work.

And practicalities also come into it.
If our saws have enough grunt we could run really low TPFA and low rakers but wouldn't it be a nuisance if we had to pull the saw out of half completed cut to sharpen it.
A simpler guide is to touch up when you fuel up - that way you are already stopped.
However I wouldn't want to swap chains that often - I touch up the chain direct on the mill.


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## Czech_Made (Apr 20, 2016)

I was doing the fuel stop + touch up when I milled with a chainsaw.

Anyway, thanks for the info, I am not looking for peak performance, just the right combination of time, effort and cost.

Now the next logical question: Do you have chains dedicated to wood type? 

Thank you.


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## Quietfly (Apr 20, 2016)

I'm always amazed at how much knowledge @BobL has to share off the top of his head, as well as the science he backs it up with. 
Personally I sharpen as i feel the saw start cutting differently. I know very subjective, but so far it's worked "ok" .
JMO YMMV


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## BobL (Apr 20, 2016)

Czech_Made said:


> Now the next logical question: Do you have chains dedicated to wood type? .


If I did more CSM'ing I'd probably set up some chains this way. 
However, because 95% of the logs I cut are hard my longer (42 and 60") chains are all set up for hardwood (raker angle ~6.5º). 
I don't even use different raker settings for the longer or shorter chains although I have though about doing this.
Instead for extra hard/wider wood I usually use a 7 pin sprocket instead of the 8pin.
I do have some 9 and 10 pin sprockets but have never used them.
For the times when I do occasionally have a softwood log I usually just swipe the rakers 3-4 times more than usual which increases the raker angle. 

I have a 24" cross cut, full chisel, full comp, 3/8 chain for the 441 with ~9º raker angles for trimming branches off trunks. That's quite aggressive and prone to kick back - not something I let a newbie use. When milling with the 441 I use a 25" bar low pro chain set with rakers set to~ 7.5º. 



Quietfly said:


> Personally I sharpen as i feel the saw start cutting differently. I know very subjective, but so far it's worked "ok" .


Feel is important but by the time the saw feels like it needs an extra load to keep cutting the chain should probably have been sharpened although if you near the end of a cut practicalities indicate you just finish the cut.

On the BIL mill I can compare the temperature gauge reading with the feel or speed of cut and infer a degree of bluntness - its not rocket science - it is pretty obvious what is going on. 
It's not that easy to see this effect because the temperature always increases as any cut proceeds but is more noticeable in wider/longer cuts).
Initially the temperature always increases rapidly as the powerhead warms up under full load and after about 3-4 ft of cut the temperature starts to increase more slowly.
At some point (hopefully in the second half of the cut!) the temperature starts to increase faster again and sort of steps up to a new level (still increasing) over a distance of about 1-2 ft of cut.
This is clearly the chain going blunt because after this point the mill also needs greater pressure to keep cutting at the same rate and more powder and fewer chips are generated.
At this point I open up the aux oiler a bit more and it sort of helps.
The point in the cut where this happens varies quite a bit probably due to how sharp the chain was to start with, wood hardness, dirt, dryness.
In something like Iron Bark (very hard wood) I have seen this happen around 25 sq ft. 
In silica infused Tuart (this tree is notorious for sucking up silica when water deprived) it can be less. On one Tuart log I had to back the mill out of the cut and touch up the chain for the 2 wider middle slabs of the trunk. The other problem with Tuart is it's pointless pushing the saw too much past this point as the chain heat starts to extract a black resin out of the wood and it gums the chain up something horrible making things even worse. This is where extra aux oil really helps.


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## IyaMan (Apr 20, 2016)

BobL said:


> When milling with the 441 I use a 25" bar low pro chain set with rakers set to~ 7.5º.



Are you using a low-pro bar with that chain, or just a standard bar?


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## BobL (Apr 20, 2016)

IyaMan said:


> Are you using a low-pro bar with that chain, or just a standard bar?



I started by using the standard bar and 3/8 drive sprocket even though I knew there would be difficulties with this and indeed the chain jumped off the bar several times.
I then did what Mtngun did and used a 404 sprocket that has been turned down to the radius to suit the Lopro chain and have had no problems since them 
The nose sprocket teeth are not a perfect fit but they has sort of worn their way into shape.


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## IyaMan (Apr 20, 2016)

BobL, your ingenuity and resourcefulness is impressive. I was wondering how people went about using low-pro chain on a longer bar. I've only been able to find low-pro bars for up to 20" (even though Stihl sells 24" low-pro ripping chain loops). And most low-pro bars are not for large-mount.


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## BobL (Apr 20, 2016)

IyaMan said:


> BobL, your ingenuity and resourcefulness is impressive.


Not my idea Iyaman - I just coped what someone else has done.



> I was wondering how people went about using low-pro chain on a longer bar. I've only been able to find low-pro bars for up to 20" (even though Stihl sells 24" low-pro ripping chain loops). And most low-pro bars are not for large-mount.


The 25" was a GB bar. I've though about using it on even longer bars but I found the 441 stretches the Lopro enough to stop me doing this for example on the 880. If and when I get my 660 restored maybe I'll think about something for that one.


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## Czech_Made (Apr 21, 2016)

Thank you again, Bob.


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## scheffa (Apr 21, 2016)

@BobL what size file and guide do you use for 404 chain to get the desired tpfa, I currently just use the standard Stihl file guide and their 404 files and it cuts pretty good, just curious for your input for cutting our hardwoods


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## BobL (Apr 21, 2016)

scheffa said:


> @BobL what size file and guide do you use for 404 chain to get the desired tpfa, I currently just use the standard Stihl file guide and their 404 files and it cuts pretty good, just curious for your input for cutting our hardwoods



Blimey its so long since I used 404 I can't remember what sharpening gear I used. 
All except a couple of my mill loops are is 3/8. 
I think I last used 404 in 2007 and it wasn't for milling.
I know it was an Oregon file guide and I think it was a 7/32" file


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## Mad Professor (Apr 21, 2016)

066 and stihl PMX usually hardwoods and just enough bar for the logs. Important to have clean logs, I wash them or use a stiff brush. Be careful with a pressure washer as you can drive the crud into the bark.

I sharpen as soon as the cut slows down, if not you heat up the bar and chain. Sometimes I get many cuts, but others I wonder what junk I missed?


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## BigOakAdot (Apr 21, 2016)

This may sound stupid but when talking about raker angles, what is this angle you're recommending? Is it a slight angle down away from the corresponding tooth? Not sure how to explain this correctly but I always thought the rakers depth was the important part.


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## scheffa (Apr 21, 2016)

Is there a reason you no longer use 404? I use 3/8 up to 42" then jump up to 404 for longer bars


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## Quietfly (Apr 21, 2016)

BigOakAdot said:


> This may sound stupid but when talking about raker angles, what is this angle you're recommending? Is it a slight angle down away from the corresponding tooth? Not sure how to explain this correctly but I always thought the rakers depth was the important part.





BobL said:


> FOP's are semi-progressive but ay least they work (sort of) for longer through a chain life than regular gauges do. FOPs are also not very aggressive and they do not allow the operator to optimise their cutting speed. BUT if you can't be bothered with full progressive raker setting then FOPs are a worth getting
> 
> 
> That is one way of doing it and the raker depth can be measure using feeler gauges. I would not suggest starting on 1/9 or 1/8. Start at 1/10 and see how this goes.
> ...




here's a post of @BobL explaining it


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## BigOakAdot (Apr 21, 2016)

Thanks!


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## BobL (Apr 21, 2016)

scheffa said:


> Is there a reason you no longer use 404? I use 3/8 up to 42" then jump up to 404 for longer bars


When I bought my 076 it came with a 30" bar and a loop of 404. I used this combo it on my small mill for a while and it seemed to work fine but when I bought my first 42" bar I bought a roll of 3/8 and Ive never used anything else since. 

The 3/8 does stretch a fair bit when new and there is not a lot of kerf advantaged of 3/8 over 404 so I am interested in giving 404 a go with the longer bar especially in harder wood. The 60" Stihl sprocket bar I got with the 880 came with a loop of 404 for milling. It has never been used because I already had a 60" bar that is in good condition. I have since modified the at bar to run a roller nose and in doing so it is now 3" longer. 


I could return this bar to the 404 sprocket nose and try the 404 chain out instead I'prefer to lengthen the chain by 6 drive links so I could use it on the roller nose bar.
If anyone in Oz has 6 spare 404 links I would be happy to pay for it and postage.


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## BigOakAdot (Apr 22, 2016)

So Bob in that video you're measuring the angle from the cutter to the raker? Which is essentially a different way of figuring out what depth to set your rakers so they are even?


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## BobL (Apr 22, 2016)

BigOakAdot said:


> So Bob in that video you're measuring the angle from the cutter to the raker? Which is essentially a different way of figuring out what depth to set your rakers so they are even?



Sort of correct but it translates to a difference raker depth depending on the extent of the cutter wear.
OR
The rakers can be at different depths because the depth depends on the cutter length.

For new chain a 6º raker angle translates to a 0.025" for a gullet length of 0.25" i.e. approx a 10:1 ratio.
When cutter wears and needs sharpening and eventually the gullet reaches 0.5" , the raker should be 0.050" (not 0.025")
When gullet = 0.3" raker should be 0.030". gullet = 0.4" raker should be 0.04" etc

You can get raker depth gauges in 0.005" increments i.e. 0.025. 0.030. 0.035, 0.040. 0.045 etc but if you measure the raker angle with a DAF
a) cutter length is irrelevant as long as the angel stays constant.
b) you can set the angle to any setting in-between the 0.005" increments
Remember the cutters don't sit on the bar rails and act like little planes shaving the wood out of the kerf, instead the jump up off the bar and take a bite/chip out the wood. What determines the size of the chip is the raker angle - so it doesn't matter if the cutters are not even lengths provided the rakers are filed to a compensatory depth to generate the same raker angle.

And remember this is for a given drive sprocket pin count, saw power, cut width, log hardness, dryness of log etc
Of narrow softwoods with a large saw rakers angles as high as 9.5º can be sustained with resulting cutting speeds of a drunken monkey
On wide hardwoods with a small saw you might have to use 5º

The only person who can work out their optimum angles is the operator but I recommend starting with 6º and work it up (or down from there).

The easiest way to make an assessment is to make a test cut and then swipe the rakers 2/3 times, repeat the cut, swipe the rakers 2/3 more etc until the saw starts to grab - then you know you have gone too far and you make have to take 5/6 swipes off the cutters to back the angle off a bit, then measure the angle then you know you have optimised the chain.


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## Quietfly (Apr 22, 2016)

It's a pain in the but to do this way but the results are definitely there. 
@BobL has totally made a believer out of me.


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## BobL (Apr 22, 2016)

It is painful to set up if you can maintain the rakers regularly 2/3 swipes every 3-4 touchups so but after while you get to work our chat keeps the whole chain in the zone. The old timers were not that far away from this. My dad only used raker gauges for the first half dozen or so sharpening then he would touch them up depending on how much powder the saw was generating.


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## Quietfly (Apr 22, 2016)

BobL said:


> It is painful to set up if you can maintain the rakers regularly 2/3 swipes every 3-4 touchups so but after while you get to work our chat keeps the whole chain in the zone. The old timers were not that far away from this. My dad only used raker gauges for the first half dozen or so sharpening then he would touch them up depending on how much powder the saw was generating.


So i've moved over to using the Grandberg file n Joint for sharpening and still using the DAF for the rakers and its made a HUGE difference in milling. i'm just waiting to get my big saw back.....


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## wombler (May 17, 2016)

BobL said:


> If anyone in Oz has 6 spare 404 links I would be happy to pay for it and postage.



If you're still in need of a few DLs, I've got a length of about 10 404 .063 sitting around doing nothing. Happy to drop 'em in a padded bag, just PM me your address.


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