# Set a new CSM record today ! ! !



## mtngun (Sep 12, 2010)

A 17" doug fir blowdown. The pictures never do justice to the terrain, but it was on the side of a steep hill.

The tree yielded four 12' logs.






Pic of the Oly "self-feeding" with the throttle zip tied. Gotta give BobL some competition in the self-feeding department. 





Fast forward to the end of the day and we have 18 not-particularly-large slabs. That's not a record, but ....... the saw logged 4 hours of run time today, and that's a record for me.

By comparison, when I was running lo-pro chain, I'd typically bring home just as much wood with only 2 hours run time. 





Tomorrow I'll post some random speed test data and pics of the rakers. I had experimented with different raker depths and shapes. Two of the chains cut very well, while the third didn't have enough "bite," which is one reason why it took 4 hours to mill that skinny tree.


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## Timberframed (Sep 12, 2010)

Good workout Mtngun! Rafters maybe? You have heavy snow loads there I would suppose. Are you going to do board and batten?


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## mtngun (Sep 13, 2010)

Timberframed said:


> Rafters maybe? You have heavy snow loads there I would suppose.


Very likely rafters.

We have so much wind in the winter that the snow usually gets blown off the roof, but, it's prudent to design for a snow load anyway. So far, I've never had more than 6" on my roof, because it blows away as fast as it falls 



> Are you going to do board and batten?


I'm thinking board and batten ...... next year. There won't be either time or wood enough for siding this year, except perhaps some temporary slab siding.


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## Timberframed (Sep 13, 2010)

When you go to frame your roof, let me know if you need ant technical support. People tell me I'm quite good at it. Ever see one of these?



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Do this?



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1912 Seargent Takedown Square w/Nichols tables Athol Mass.. I think I need some steel wool again!


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## BobL (Sep 13, 2010)

mtngun said:


> Pic of the Oly "self-feeding" with the throttle zip tied. Gotta give BobL some competition in the self-feeding department.



Where's the sawdust?

OK - I see it !

Onya mtngun  
How many RPM was it pulling?


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## gemniii (Sep 13, 2010)

BobL said:


> Where's the sawdust?
> 
> OK - I see it !
> 
> ...


Knowing mntgun from his writings I bet there's no sawdust! Only chips.


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## mtngun (Sep 13, 2010)

BobL said:


> How many RPM was it pulling?


It was only making fine dust, and pulling 10,300 rpm. It was cutting, though -- slowly.


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## mtngun (Sep 13, 2010)

Timberframed said:


> Ever see one of these? Do this?


Now that's pretty fancy. No, I'd never seen one before. What is the advantage -- to be able to carry in a toolbox ?


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## mtngun (Sep 13, 2010)

Chain pics and raker angles.

Lacking a DAF (digital angle finder), I used a machinist's parallel as a straight edge, and a digital caliper as a depth gage, to find the raker depth, and the distance between the cutter and the raker. It's not an easy or highly repeatable method.

Chain #1 (the order in which I used them). Granberg'd 33RP. Raker angle *7.7 degrees*. 

I set the rakers on this by FOPing one raker, then setting the grinder to match the FOP'd raker, then setting the grinder a hair deeper. It wasn't measured, just done by the seat of the pants. Grinder angle was 70 degrees.

This chain was used to make the slabbing cuts, then to cut the smallest (12") log. It worked satisfactorily.






Chain #2, a 33RP. Raker angle *8.7 degrees*. 

Once again, the rakers were set by FOPing one raker, setting the grinder to match the FOP, then dropping the grinder a little more. Grinder angle 70 degrees.

This chain was used on the two intermediate logs, say 13" - 15". It's the chain used in my "self-feeding" picture. I liked it the best.






Chain #3, 33RP, *6.6 degrees*. 

The rakers were set by matching the grinder to the FOP. Grinder angle was 60 degrees, dunno if that matters ?

This chain was used on the butt log (17") and it did not have nearly enough "bite." I had to push it hard and even then, it made fine dust, not chips.


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## BobL (Sep 13, 2010)

Thanks for posting the pics of your chain mtngun.

Unfortunately the images of the cutters are just a bit too small and too compressed to measure the raker angles accurately.

Here's what I mean using chain 1. The edges are a bit too blurry to get a decent reading. When doing this I either go shadow to shadow or hard edge to hard edge.




Anyway - this angle works out to be 6.2 degrees. You might notice my red bars go from the cutter tip to a little way over the raker to what I estimate is the contact point of the wood since the cutter rotates to form that line when it touches wood. Measuring the gullet width approximates this distance as the gullet is a little deeper than the cutter tip and the sider of the raker is a little short of the contact point

Chain 2 is further complicated because the photo does not seem to have been taken fully side on so any measurements will underestimate the raker ange.




The two angles are both around 5º but I could easily be out by a couple of degrees. Either way it doesn't look like an 8.7º angle to me

Chain 3 is 4.2º





I would have thought that cutting softwood would have enabled a slightly greater hook to be used?

One thing I notice is your rakers are quite pointy and I know that this is the profile that FOPs typically generate. Pointier rakers will penetrate wood further during the cutting process than rounded rakers and create an effectively higher cutting angle. This effect will be more evident in softwoods and have little or no effect in Aussie hardwoods. I'm starting to think that the 4.7º FOP generated angle takes that into account and that is why FOPS use a lower than usual angle. By usual I'm referring to the 0.025" for new 3/8 chain which has a gullet of 0.25".

The shape of rakers is not that important but if they are too pointy they will dig too far into the wood and create friction which places a bit more load on the saw. Likewise if the rakers are too flat the leading edge will grab wood and create resistance. Some where in between is probably optimal.


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## BobL (Sep 13, 2010)

mtngun said:


> It was only making fine dust, and pulling 10,300 rpm. It was cutting, though -- slowly.



Chain needs a touch more hook and log needs more slope?


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## mtngun (Sep 13, 2010)

Thanks for your comments, BobL.

However, I have more confidence in my digital calipers than in your photoshopping. It's pretty simple to measure the depth and width and then use trig to calculate the raker angle. 

I had been experimenting with different grinder angle settings on the rakers. I agree that 60 degrees does not "look right." 70 degrees looks better to my eye. I'm not sure what difference it makes, except, as you pointed out, pointy rakers may dig in and act more aggressively.

The pics were not straight on because that would have put the camera's shadow on the chain. Morning sun, lot's of glare.

Not much to be done about hook on a grinder, unless I wanted to try a 50 or 55 degree grinding angle rather than the standard 60 degrees. I imagine that a 50 degree angle would dull faster ? ? ? And no, I don't file, I grind, period. 

This is what I have observed, bearing in mind that the widest I've ever cut was 28" (max capacity of my mill at that time). 










I believe it has to do with the PSI at the kerf. For a given feed force, kerf PSI decreases as width increases. As kerf PSI decreases, the cutters take smaller bites. Above a certain width, they aren't really biting at all, just rubbing and making dust.

To maintain constant kerf PSI as width increases, you would need to either push harder (which isn't feasible for any length of time) or else use a crank.

Alternatively, you could increase the raker angle.

I had been running lo-pro all year until I had to switch to the Oly powerhead. These 3/8 chains had last been run on a defective 066BB that had no guts and bogged like crazy, so I had deliberately avoided experimenting with more aggressive rakers.

Now that I have a powerhead that actually has some guts, I am in a position to try more aggressive rakers. At some point it will start bogging, but I haven't reached that point yet.


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## mtngun (Sep 13, 2010)

BobL said:


> log needs more slope?


The pictures never do justice to the terrain. The slope was about 40 degrees from the horizontal, too much slope for comfort.


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## BobL (Sep 14, 2010)

mtngun said:


> The pictures never do justice to the terrain. The slope was about 40 degrees from the horizontal, too much slope for comfort.



Wow! - in that case maybe there is not enough hook or raker angle on the cutters. At 40º of log slope my freshly sharpened chains will be very close to bogging down under the weight of the mill.



mtngun said:


> However, I have more confidence in my digital calipers than in your photoshopping. It's pretty simple to measure the depth and width and then use trig to calculate the raker angle.


I agree but I can only work with the images available. When I measure the raker angle direct with a DAF and then photograph it and measure the angle with photoshop they generally agree to within half a degree. Sometimes I'd like to see a good photo of that 8.7º raker angle cutter.



> Not much to be done about hook on a grinder, unless I wanted to try a 50 or 55 degree grinding angle rather than the standard 60 degrees. I imagine that a 50 degree angle would dull faster ? ? ?


Yep - that is highly likely.



> I believe it has to do with the PSI at the kerf. For a given feed force, kerf PSI decreases as width increases. As kerf PSI decreases, the cutters take smaller bites. Above a certain width, they aren't really biting at all, just rubbing and making dust.
> To maintain constant kerf PSI as width increases, you would need to either push harder (which isn't feasible for any length of time) or else use a crank.
> Alternatively, you could increase the raker angle.



I agree that cut width is a key parameter that affects cutting speed and indirectly affects chip size but I don't see it as simple as what I'm interpreting from your response above. 

Inevitably cutters will go blunt especially towards the end of a wider cut and then I agree PSI becomes an issue so an operator often has to push to complete a cut. However no matter how wide a cut, if an operator starts a cut with a freshly sharpened chain and needs to push to get the saw to cut, something is not right. I don't see any difference in chip size between a 20" or 30" wide cut at the start of a cut with a freshly sharpened chain (wider still cuts I discuss below). If the chain is set up right at the start, the need for additional kerf PSI will eventually kick in as the chain starts to go blunt, but when chains go blunt also depends on cutter profile, area of cut, of which width is only one component, and hardness of the wood. of course one can keep everything else constant and just look at width of cut What will always happen with respect to increases in width is whatever the chain setup, eventually the powerhead will run out of puff. This last factor is quite instructive to examine because it ties down one end of what is happening and overlooked by operators moving to wider cuts. 

If the cutters on a chain are set up right once they bite wood they should pull into the wood and generate their own PSI so little or no pushing should be required. Up to some width, more cutters should mean more self generated PSI, so the trick with all cuts is to look to maximize the self generated PSI to keep the saw self feeding. This works up to certain width after which the powerhead simply does not have the power to to drag the cutters into and through the wood, and break off and drag chips through the wider cut. Increasing the PSI or raker angle makes things worse and just bogs the chain even more. Using a freshly sharpened chain with higher raker angles at the start of 36"+ wide cuts I sometimes myself holding the mill back for a ft or two of cut to avoid bogging the saw - this does create smaller chips. Once some of the edge goes off the cutters the saw can cut on it's own and the chips are bigger than before, then as the cutters eventually get blunter, a bit of a lean is needed to finish the cut andat the very end there is always more dust than at the start. 

If one is going to do some really wide cutting on a regular basis, rather than pushing more, this is when going to skip chain might make more sense (but don't forget that skip goes blunter faster although that is less of a problem in softer woods) OR on full comp chain. reducing the raker angle slightly is also possibility because full comp does not go blunt as quickly. Either way, significantly slower cutting speeds are part of the game. Attempting to address this by upping the PSI all the way down the log just wears out the saw, chain and the operator. Alternatively one looks at using a 30HP slabber with 404 chain with 0.06"+ rakers.

I can fully appreciate that few operators are going to run multiple chain types and they will settle on a set up that works for them across a range of conditions.


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## mtngun (Sep 14, 2010)

BobL said:


> At 40º of log slope my freshly sharpened chains will be very close to bogging down under the weight of the mill.


Yeah, but your mill weighs twice as much as my mill. 



> When I measure the raker angle direct with a DAF and then photograph it and measure the angle with photoshop they generally agree to within half a degree. Sometimes I'd like to see a good photo of that 8.7º raker angle cutter.


A DAF is on my wish list, though it may have to wait for Santa. I appreciate your various posts on raker angle, which I'd never given any thought until you brought it to my attention.

Meanwhile, you'll just have to take my word that I set it up by filing one raker with the FOP, which you tell me is just shy of 6 degrees, then I adjusted the grinder to take just a bit more off. Thus two of the chains were definitely more aggressive than an FOP, while the 3rd duplicated the FOP raker height, except ground at 60 degrees (which didn't seem to make a difference).



> However no matter how wide a cut, if an operator starts a cut with a freshly sharpened chain and needs to push to get the saw to cut, something is not right.


Yep, and that has been the case on wide (to me) cuts. Lots of push required, and making dust, not chips. And the amazing thing is that the RPMs are 500 - 1000 higher than the same type of chain on a 12" - 14" cut. 



> If the cutters on a chain are set up right once they bite wood they should pull into the wood and generate their own PSI so little or no pushing should be required.


I'm skeptical.  Maybe with gravity pulling 70 something pounds of custom CSM downhill , but I'm not seeing it on a 30 something pound Granberg.


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## BobL (Sep 14, 2010)

> Meanwhile, you'll just have to take my word that I set it up by filing one raker with the FOP, which you tell me is just shy of 6 degrees, then I adjusted the grinder to take just a bit more off. Thus two of the chains were definitely more aggressive than an FOP, while the 3rd duplicated the FOP raker height, except ground at 60 degrees (which didn't seem to make a difference).



Sorry if I sounded overly skeptical - I certainly believe you, over those blurry photoshopped photos any day.



> Yep, and that has been the case on wide (to me) cuts. Lots of push required, and making dust, not chips. And the amazing thing is that the RPMs are 500 - 1000 higher than the same type of chain on a 12" - 14" cut.
> 
> I'm skeptical.  Maybe with gravity pulling 70 something pounds of custom CSM downhill , but I'm not seeing it on a 30 something pound Granberg.



Eureka!
I worked out that on a 40 degree slope a 72 lb CS mill has a down slope force of 46 lb.
This is probably why I don't have to use as much log slope as everyone else seems to need.
Normally I mill at angles of 15º , but even that has a down slope force of 19 lb.
I think you have hit on something very significant - I will have to change my theory about "Life, CS milling and everything" , seriously! How can I criticise winches when I have 20 lbs of forward PSI acting all the time on my mill?

I'm calling it my "Stealth PSI". 

Maybe this is telling us something, forget about winches or pushing, just slope the log and hang a couple of 20 lb weights on your mill! 

Now that I think about it this maybe explains why my mill is so smooth compared to all other CS mills I have run. The weight also acts as a vibe damper. Forget ally, my next mill will be in steel.


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## mtngun (Sep 14, 2010)

BobL said:


> I worked out that on a 40 degree slope a 72 lb CS mill has a down slope force of 46 lb.
> 
> This is probably why I don't have to use as much log slope as everyone else seems to need.
> 
> Normally I mill at angles of 15º , but even that has a down slope force of 19 lb.


That sounds right if you have UHMW on your rails, as I believe you do. Slides like grease unless the mill hangs up on something. 

I would guess that I normally apply somewhere around 10 - 30 pounds of push as I mill small logs. I can apply 10 - 15 pounds all day, but on big (to me) logs I had to push a lot harder -- maybe 50 pounds -- and a crank was starting to sound like a good idea. I can totally understand why people who mill a lot of wide slabs gravitate toward a crank (though maybe they wouldn't need it if they followed BobL's advice on rakers ).

Malloff used a winch. It used to be common for mills to have a helper handle so a second person could help push. Chainsaw milling is still evolving.

Regarding my raker angles, I ordered a DAF, so that you and I will be on the same page when we talk about raker angles.


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## BobL (Sep 14, 2010)

mtngun said:


> That sounds right if you have UHMW on your rails, as I believe you do. Slides like grease unless the mill hangs up on something.


Yep I use the UHWMPE skids - they are really worth using. 



> I would guess that I normally apply somewhere around 10 - 30 pounds of push as I mill small logs. I can apply 10 - 15 pounds all day, but on big (to me) logs I had to push a lot harder -- maybe 50 pounds -- and a crank was starting to sound like a good idea. I can totally understand why people who mill a lot of wide slabs gravitate toward a crank (though maybe they wouldn't need it if they followed BobL's advice on rakers ).



It's funny because I used ally to make my mill to save weight but the swiss army knife part of the brain took over and soon it was much heavier than I first planned. In retrospect that's turned out to be a good thing. So for the 10 seconds it takes for me to lift the mill on and off the log I get a 20 lb PSI advantage all the way through the cut - I think that is a pretty good deal. The down side is possibly getting the mill through the bush to the log. This is not as bad as it seems because I normally wheel the mill around using the add-on pump-up wheels. If the bush is open enough I can wheel the mill through the bush and if not, I remove the powerhead and B&C from the mill and carry all three in separately.



> Malloff used a winch. It used to be common for mills to have a helper handle so a second person could help push. Chainsaw milling is still evolving.


Yes he advocates a winch, but it also seems he never heard about using slope to advantage. I never though the slope would provide such a large advantage to my set up because the main reason I advocate slope is ergonomic. 

The two possibilities now seem to be winch or weight. Weight is "set and forget" but it also needs height/slope, but height helps ergonomically anyway, and you can keep both hands direct on the mill. Winch has the advantage that it works without slope including uphill but only has one hand direct on the mill.

I will now let the swiss army knife part of the brain loose on winches. I figure I can watch the load on my saw via the temp gauge. 



> Regarding my raker angles, I ordered a DAF, so that you and I will be on the same page when we talk about raker angles.


Excellent!


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## mtngun (Sep 15, 2010)

Here's the speed test data:

Chain #1 (GB'd 7.7 deg) 
-- @ 0.6 hours, 12" wide, *0.39 inch/sec*

-- @ 0.7 hours, 12 1/4" wide, *0.39 inch/sec*

Chain #2 (33RP 8.7 deg)
-- @ 0 hours, 13 1/4" wide,* 0.29 inch/sec*

-- @ 0.1 hours, 13 1/2" wide,* 0.28 inch/sec*

Chain #3 (33RP 6.6 deg)
-- @ 0 hours, 12 1/4" wide, *0.38 inch/sec*

It's hard to make direct comparison because the widths were different, but the stale GB'd chain was cutting just as fast as the fresh 6.6 deg chain in similar widths. 

All the speeds are pitifully slow compared to lo-pro.

All the speeds are much slower than the 066 did in a 12 1/4" pine cant, even though the Oly felt strong and had no trouble maintaining 9000+ RPM. I'm puzzled as to how the Oly spins the chain just as fast as the 066, yet the cutting speed is slower ?


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## BobL (Sep 15, 2010)

mtngun said:


> All the speeds are much slower than the 066 did in a 12 1/4" pine cant, even though the Oly felt strong and had no trouble maintaining 9000+ RPM. I'm puzzled as to how the Oly spins the chain just as fast as the 066, yet the cutting speed is slower ?



My guess is you can (maybe even subconsciously) apply a a higher chain forward PSI with the 066?


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## BobL (Sep 15, 2010)

BobL said:


> My guess is you can (maybe even subconsciously) apply a a higher chain forward PSI with the 066?



The chainsaw forum has a "beg for manual" thread.


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## DaltonPaull (Sep 17, 2010)

Thanks for posting all the comparison info on the chains. I'm glad someone is taking some scientific data. Most of the comparison I notice is between my usual free hand file before and after hitting a nail in a yard tree. Hitting all these nails prompted me to buy one of the Oregon grinder rip-offs from Northern Tool. For now I'm just getting the hang of getting consistent results but later maybe I'll start experimenting.



BobL said:


> Yes he advocates a winch, but it also seems he never heard about using slope to advantage.



Seams like the cool thing about a winch is that it can get you away from the exhaust and dust. I built one but decided it was too much hassle to use. 
Slope is nice too but I don't find that it pays back enough to go to too much trouble to create it. I've never thought that leaning on the mill to push it through was all that tiring but then again I just turned 30 so maybe I'll change my mind.


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## BobL (Sep 17, 2010)

DaltonPaull said:


> Seams like the cool thing about a winch is that it can get you away from the exhaust and dust.


My 076 and 880 setups blows the exhaust away from the operator so that's not a problem for me and I'd rather be in physical contact with the mill than on the end of a rope or a long handle but other operators don't seem to mind that.



> I built one but decided it was too much hassle to use.
> Slope is nice too but I don't find that it pays back enough to go to too much trouble to create it.


I guess if you don't mind pushing you don't mind bending over either.
Like I said, without knowing it the 72 lb 880 in the BIL mill = 20 lbs of forward force on a 15º slope so no wonder I don't need to push.



> I've never thought that leaning on the mill to push it through was all that tiring but then again I just turned 30 so maybe I'll change my mind.


Maybe you don't mind milling on your knees either but somewhere between now and double your current age maybe you will say why did I do it that way?


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## DaltonPaull (Sep 17, 2010)

BobL said:


> My 076 and 880 setups blows the exhaust away from the operator



I'd like to see how you did this with the 076. Is there a post you can send me to were you describe it?

I don't like bending over to pick something up but bending to push on something doesn't seem to cause me trouble. I do try to keep my back straight during the milling procecs but dropping into a crouch or getting on my knees if I have to doesn't bother me either. If I can't get the log off the ground the dust and exhaust tend to be the killer.

I've been on summer vacation from school so I've done quite a bit of milling and my back feels great. I'm about 2/3 of the way through a masters of electrical engineering and what kills my back is studying if I'm not careful. I like to study by working design problems that take an hour or so each. My tendency to slouch over the paper feels comfortable until I try to stand up again afterward and find myself walking with a limp. School starts on Monday so I'll be working on my posture.

Today I was milling some old growth larch in the forest behind my parents house in Idaho. The tree I was milling was cut by loggers and just left laying next to the stump. I don't know why they just left it but the last logging here was done in 1943 so it's been cut a long time but I wanted to see if i could still salvage some wood from it if possible. I got some nice slabs but at times the progress was really slow going. When I looked at the chain the gullets were filled part way in with dust and the 'sharp' part of the cutters was so caked that I'm not sure how it cut at all. Although there were some punky areas in the log it was mostly sound. Could it have been the punky spots that caused the chain to cake up? This was with standard skip tooth on the 066 because I only brought milling chain for the 075 but had to order a part for that saw. I'm not sure what I did with my camera so no pictures


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## BobL (Sep 18, 2010)

DaltonPaull said:


> I'd like to see how you did this with the 076. Is there a post you can send me to were you describe it?


sorry if you thought I'd done something to the 076, the standard exhaust blows away from the operator if they stand in the usual milling position.



> Could it have been the punky spots that caused the chain to cake up? This was with standard skip tooth on the 066 because I only brought milling chain for the 075 but had to order a part for that saw. I'm not sure what I did with my camera so no pictures


Most chains will mow thru punky wood, unless its got some grit in it from say termites or other bugs and then even though it might be soft it will slow you down quickly.


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## mtngun (Sep 20, 2010)

Haven't had a chance to go milling again yet, but my DAF showed up and I've been learning to use it on chains.

The first thing I learned is that it would be handy to have a "real" chain vise. I have been using an old bar to hold chains for measuring and filing, but the slight curvature of the bar throws off the DAF measurements. For now, I just put a mark on the bar, leveled the bar at the mark, and did all my measurements at the mark.






In case anyone wants to check the DAF with photoshop, here's the same chain/link without the DAF in the way.





To measure a chain that is installed on a saw, I clamped the bar, saw and all, in a vise, marked a spot, laid a straight edge over the cutters at that spot, and zeroed the DAF on the straight edge. 





In general, I had a hard time getting consistent results with the DAF, plus there was a surprisingly large variation from one cutter to the next, even though my chains are done on a grinder and the grinder does a far more consistent job than I could ever do by hand (a virgin factory chain also showed quite a bit of variation from one cutter to the next). I suspect it is just inherently difficult to measure the angle over such a short distance, especially when the surfaces are pointy and non-flat.

Then I tried a different way of measuring the raker angle using calipers. The last time I used calipers to measure rakers, I had laid a straight edge across the top of the cutters, and measured down from the straight edge. It was tough to get consistent measurements that way, and a certain Aussie questioned my results. 

This time I measured from the top of the cutter (or raker) to the bottom of the link. Even though the bottom of the link was slightly rounded and peened, I was still able to get pretty consistent measurements this way.





Some DAF results, bearing in mind that this was my first outing with the DAF and I'm still getting the hang of it:

Virgin 33RC -- *5.5 degree* raker angle

FOP'd 0.325 -- *5 to 5.5 degree* raker angle (it has been my experience that the 325 FOP is not aggressive enough).

FOP'd lo-pro -- *4.5 degree raker angle* -- and yet the lo-pro FOP is a little* too *aggressive. Maybe it has more kerf PSI due to the narrow kerf ?

Experimental GB'd 3/8 milling chain -- *5 to 6 degree raker angle on regular cutters, 5 degrees on scoring cutters*, _even though I had ground more off the scoring cutter rakers._ Doesn't make sense, but that's what the DAF said.

Experimental 33RP #1 -- *6 degree*, even though this had been dressed much, much more aggressively than an FOP.

Experimental 33RP #2 -- *7.5 degree*, (I deliberately ground this more aggressively, just to see what will happen).

Here's the GB'd chain as measured with the calipers. I measured 3 of the scoring cutters and 3 of the regular cutters and took an average for each.

regular cutters -- *6.03 degree *

scoring cutters -- *7.2 degree*

The caliper results are just the opposite of the DAF results -- the DAF said the regular cutters were more aggressive, while the calipers said the scoring cutters are more aggressive. The DAF is wrong and the calipers are right, because I intentionally ground more off the scoring rakers.

I can only guess that the narrow shape of the scoring cutters throws off the DAF somehow. 

Even though the calipers are more reliable, the DAF is faster and easier to use, so I'll stick with the DAF most of the time.


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## BobL (Sep 20, 2010)

mtngun said:


> The first thing I learned is that it would be handy to have a "real" chain vise. I have been using an old bar to hold chains for measuring and filing, but the slight curvature of the bar throws off the DAF measurements. For now, I just put a mark on the bar, leveled the bar at the mark, and did all my measurements at the mark.


Yep I agree chain stability is a problem, but I found an even worse problem is not holding the DAF truly vertical, and such that the chain does not drop into the little magnetic dimples some DAFs have on their sides. 

To get around this I use this.




This consistently sets the horizontal depth at which the measurements are made and holds the DAF upright making it much easier to make the measurement. Here's a video of my setup and how I do it. http://www.youtube.com/watch?v=FSr9j2EDoqk

When holding the DAF like this the main holding force is against the wooden back and the DAF is bought down firmly to push the chain onto the bar so it much less likely to push the chain sideways

BTW zeroing the DAF to the bar is not really right since tzero line should be the line between two adjacent cutter tips. If one wants accurate results then one needs to rezero for every pair of cutters but then who cares about about having rakers set to +/- 0.001"?



> The DAF is wrong and the calipers are right, because I intentionally ground more off the scoring rakers.
> I can only guess that the narrow shape of the scoring cutters throws off the DAF somehow.
> Even though the calipers are more reliable, the DAF is faster and easier to use, so I'll stick with the DAF most of the time.



I used calipers to measure the cutting angles on all my chains in a similar way you show for about 6 months so I have done thousands of measurements with calipers (and DAFs) and while they can be less precise I disagree that the DAF is less accurate. On examining the actual contact points involved with both setups, what I found was that it's using calipers that will give the incorrect angle.

Provided the DAF is held still vertically and the chain is held consistently, the DAF measures the angle directly onto the actual raker wood contact point like this blue line. 





The Caliper measures the raker height as per the red line which is not correct. To measure the distance between the cutter tip and and the contact point using a caliper is basically impossible. Cutters that have slightly differing hook or raker shape means that the required distance is not being measured right. Measuring the gullet is just an approximation - so while using a caliper will give very precise results but they are not necessarily measuring the real cutting angle. 

In reality precision is what matters for an individual chain, ie being able to reproduce the angles that work for you on that one chain. If I can get the angle to between ~6 and 6.5º I consider that close enough for regular cutting (and a DAF is only good to about 0.2º anyway). However, accuracy is important if we want to be able to compare angles between different types of chains and to discuss angles on this forum. The best way to do this is using the most accurate method available.


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## mtngun (Sep 20, 2010)

BobL said:


> an even worse problem is not holding the DAF truly vertical


I deliberately tried rocking the DAF side to side, to see how sensitive it was, and it only changed the output a tenth or two.

Nonetheless, I admire your DAF jig, and will try to borrow some of your good ideas if I ever find time to make a chain vise.





> The Caliper measures the raker height as per the red line which is not correct.








That may be true if the raker is rounded, but my rakers are all ground (or filed, if I'm using an FOP) with a straight slope. 

I set the grinder depth 1/8 turn deeper on the scoring rakers, so there is no doubt whatsoever that they are ground deeper. The calipers got it right, the DAF did not. 

This is the GB'd chain. You can see that the rakers are not rounded. All cutters on this chain were all ground at the same angle and length. The only difference in cutters is the width, which you can't see from this angle.

I don't have an explanation at this point, just reporting what I observed. 





Here's the raw caliper data for the GB'd chain. It shows that all the cutters were all the same approximate height, but the scoring rakers were lower than the regular rakers.

type/# ... cutter height ....raker height....raker depth
score 1 .... 0.487" .... 0.446" .... 0.041"
score 2 .... 0.493" .... 0.437" .... 0.056"
score 3 .... 0.485" .... 0.444" .... 0.041"

cutter 1 .... 0.493" .... 0.451" .... 0.042"
cutter 2 .... 0.489" .... 0.454" .... 0.035"
cutter 3 .... 0.489" .... 0.454" .... 0.035"

The biggest source of error for the caliper technique is measuring the gullet width, because the caliper points are too skinny to contact the curves surfaces correctly. Some "eyeballing" was required.

No doubt my DAF accuracy will improve as I hone my technique. Thanks for your suggestions.


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## BobL (Sep 21, 2010)

Have you checked the DAF direct against the caliper?
ie measure the slope of a edge of wood and then measure rise over run etc?


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## mtngun (Sep 21, 2010)

I just checked the DAF on a drafting triangle and the output was spot on. 

I'm sure the error I'm seeing on chains is due to the uneven surfaces and short distances involved. Perhaps your suggested jig will help -- if I can ever find time to make it.


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