Alaska Mill Chain Safety

[billstuewe]

My diagnosis is you have the wrong chain/drive sprocket comination and there is nothing wrong with your bar. If new chain slides all the way around and this chain doesn't then there is something wrong with this chain. Look at the back of your drivers. I have tried to blow one up but it is a bit fuzzy. From your picture it appears the backs of each driver is "hammered" or flared out from contact with the sprocket (the very top line of the driver). I got this exact same scenerio when I tried to run Picco chain (.365) on a regular 3/8 (.375) sprocked. I was told I could do it but 10 minutes into milling and the saw could not pull the chain and I almost could not get it out of the bar groove.

The chain was brand new as was the sprocket so I took a dremel and ground the bur off each side of the driver but you may need to replace both the chain and the sprocket and make sure you get them matched up correctly. The drivers should not flare out like that from sprocket contact.

Here is a better one--notice the ridge on the back (left side) of the driver

 

[BobL]

The bar is definitely pinched though. I cleaned the bar up, greased the tip, fitted a new chain in it, and it was so tight I could not move it by hand at all. I fired it up and the motor could not even spin it on the bar! This is the same thing I noted with two different chains right after it happened.

A more complete diagnosis of this usually requires we also get a good look at the sprocket and the bar rails.

Check this out. Does it look familiar?

This was posted last october on the Aussie woodworkers forum.
We also all thought the operator had one or all of the wrong sprocket/chain/bar combo but this turned out not to be the case
After a bit of detective work it was clear the bar was not sufficiently dressed which lead to binding and stretching of the chain - as billstuewe says look at the hammered back of the drivers.

Assuming you have the correct sprocket/chain/bar combo, it appears your chain was pinched which then stretched (as evidence by hammered backs of drivers) the chain and sooner or later a drive link in the region of the stretched ties jumps a sprocket tooth resulting in the sprocket forcing two drivers apart and snapping the chain.

As far as repairing the chain goes, you should replace all the drivers that have hammered backs as they signify overly stretched ties. If they are all hammered then the chain is toast.

 

[Daninvan]

Thanks guys for the ideas.

I believe the chain is "regular" Granberg.

Bill, I was inspired by the direction of your thinking to go take some better pictures. I even washed the chain in Simple Green for the occasion!

I can see clearly the ridges you are talking about, and could feel them with my fingernail. Oddly, many of the drivers have ridges on the front AND back, as you can see in the picture. I wonder if my rookie charges put the chain on backwards??

Also, I note some ridges on the bottoms of the "tie" links as well.

Looks like this chain is beat pretty bad. Which is unlucky, it was my favourite chain.

I am going to run out to the garage and take a picture of the sprocket and the bar rails!

Also, Bill, the problem with the chain not sliding on the bar is with this chain and the other chains too. Sorry my analysis was a bit confusing there. What I was trying to say was that just a couple of drivers can slide easily, but when a whole chain is wrapped on the bar it's frozen/can't move. (The tip is fine, spins easily)

Dan

 

[Daninvan]

OK, I think I'm getting somewhere here now.

First picture is of the bar. I'm thinking we may have our culprit here? And Bobl, I do remember that thread on the Aussie forum, now I am embarrassed to be in the what seems like the same situation! Can I just dress this bar with a file to clean it up?

Also, I took some pictures of a different chain, one that I have not used for quite some time (since last year), although it was used quite a bit up until it hit some metal and was put into retirement. It exhibits similar wear symptoms, but the ridges that were raised up on the rakers look like they have been worn down.

No picture of the sprocket, sorry it looked like something close to actual work to take it out, I have never done that before (take the sprocket off that is!), and at this point I am not sure if I need to?

Thanks Bob and Bill!

Dan

PS I know my raker filing sucks, have a bright and shiny digital angle finder on order from eBay that I am looking forward to using.

 

[mtngun]

No picture of the sprocket, sorry it looked like something close to actual work to take it out, I have never done that before (take the sprocket off that is!), and at this point I am not sure if I need to?

Excellent photography ! ! !

You've never taken the sprocket off ? Are you saying the same drive sprocket has been on there forever and ever ? Ya know, a 3/8 rim sprocket only costs $4 at Baileys.

Your bar looks to need dressing -- a sander works very well, if you have one -- but my milling bar looked 2 - 3 times as bad and it was running just fine. I only recently got around to dressing it. Supposedly the undressed bar is a bad thing because it rubs against the sides of the tie links.

It's your drivers that look like a red flag to me. Something is hammering on those drivers.

Thanks for sharing. We can all learn something from your chain problems.

 

[BobL]

OK, I think I'm getting somewhere here now.

First picture is of the bar. I'm thinking we may have our culprit here? And Bobl, I do remember that thread on the Aussie forum, now I am embarrassed to be in the what seems like the same situation! Can I just dress this bar with a file to clean it up?

That extent to which your bar in undressed is more than enough to break the chain.
Yes you can file it - make sure you keep the file square to the bar.

The burrs on the bottoms of the ties will still allows a couple of drivers to slide easily but when a whole chain is wrapped on the bar the cumulative effect of the burrs will freeze the chain in the recessed self made bar groove. Unfortunately I have seen this too often.

Sprocket should be changed approx every two chains!

 

[BobL]

-- but my milling bar looked 2 - 3 times as bad and it was running just fine.

Bar can be a lot worse and it will indeed still work, but look at his flared tie bases (hey that sounds like somethings from a 1970s wardrobe!).

If the tie bases are OK the chain is far less likely to stick.

A number of combinations are possible
Dressed or Undressed bar, with new/old tight/loose chain and old or new sprocket.

One scenario is worn chain on undressed bar (Figure 3). The worn chain eventually wedges itself into the bar wear groove jams and breaks the chain

Another is a new overly tight chain on an undressed bar. The chain gets hammered by the sprocket flaring the tie bases the flared bases jam in the bar wear groove jams and breaks the chain eg Fig 4.

The key to all this is dressing the bar and watching chain tension.
A look at the sprocket will be very revealing.

 

[Daninvan]

Thanks guys, tomorrow will definitely be "bar filing day"! I can make up a little jig to keep the file square.

I've already ordered a couple new loops on line from Granberg.

The pictures are easy to take with any digital camera's macro mode (often accessible via a button with a flower icon on it), then crop them to just the stuff needed, auto adjust the colour (I use Irfanview for these last two - it's free) and upload to Photobucket.

I checked at Bailey's for a sprocket, the only thing they had to fit a 2100 was $15. Not a big deal but the shipping is $18! I think I'll need to order more stuff to average down the shipping costs.

I've never taken a sprocket off, but I've only been doing this for about 5 years, not forever and ever! I did have one changed at a local shop, once. Actually just a few months ago. I can see that it's a good idea so will learn how to do it.

Meanwhile I'll have a go at taking it off tomorrow and post a pic.

Dan

 

[BobL]

Thanks guys, tomorrow will definitely be "bar filing day"! I can make up a little jig to keep the file square.

I've already ordered a couple new loops on line from Granberg.

The pictures are easy to take with any digital camera's macro mode (often accessible via a button with a flower icon on it), then crop them to just the stuff needed, auto adjust the colour (I use Irfanview for these last two - it's free) and upload to Photobucket.

I checked at Bailey's for a sprocket, the only thing they had to fit a 2100 was $15. Not a big deal but the shipping is $18! I think I'll need to order more stuff to average down the shipping costs.

I've never taken a sprocket off, but I've only been doing this for about 5 years, not forever and ever! I did have one changed at a local shop, once. Actually just a few months ago. I can see that it's a good idea so will learn how to do it.

Meanwhile I'll have a go at taking it off tomorrow and post a pic.

Dan

A new sprocket should be used with (a pair of) new chains and dressed bar..

Here was the other guys bar and sprocket - see how worn the drive teeth on the sprocket are.
It's a relatively new sprocket and the chain was also relatively new but his chain was stretched by the undressed bar which mangled his sprocket till it jumped a drive ling and broke the chain.

Here's a new sprocket

Here's a well worn sprocket - but see how the drive teeth are still OK.

 

[Andrew96]

Interesting post. Obviously the wear/lubrication balance requires the number of hours use on the chain/bar/sprocket combo (only quoted in years)...however...is there just a large number of hours on this setup....or is there a lack of lubrication...some of both?

 

[mtngun]

My neglected milling bar & chain looked like #2 and #3, except much, much worse. However, none of my chains were peened on the edge like #4.

I'm not recommending that people neglect their bars like I did, but honestly, it never caused me any problem and the only reason I finally dressed the bar was because I was bored.

I take it Danvan's saw must use a spur sprocket ? Bummer. Rim is the way to go, cheap and versatile.

As for the "change the sprocket every two chains" rule, I think that was intended for people who keep the same chain on their saw until it is worn out. I don't do that. Instead, I have several chains that I swap out when they get dull. Used in that manner, chains may last several years, a lot longer than the drive sprocket.

Since rim sprockets are cheap, I just change them whenever they start to look worn. That works out to about twice a year on my milling saw.

Any way, we look forward to seeing a pic of your drive sprocket, Danivan.

Edit: I went through my milling chain collection and inspected them closely under a magnifying glass. Some of them did have very light peening like #4.

Then I inspected the chains from my Oly which has a nearly new bar with no significant wear. Those chains, which have seen very little use, also have very light peening like #4.

I'm tempted to conclude that light peening along the bottom of the tie straps may be normal and no cause for alarm.

None of my chains had the badly peened drivers like Danivan's chain

 

[stipes]

I never broke one...

Guess the worst thing I had to happen,,I musta got into a rush and didnt tighten my bar nuts up good and I started to notice slack in my chain so bad and after the cut,,my clutch cover was about to fall off....I dont see how I made it tru the cut to this day.....

 

[Daninvan]

OK I finally got the sprocket off and took a picture of it. It looks to me like I abused it for far too long, I guess it should have been replaced a while ago. :blush:

It also looks like it may be the wrong size,I am using 3/8" chain, not .404

As an aside, I broke ANOTHER chain just a couple days ago on my other saw. The bar did have some ridges on it in just one place, cutting edge near the powerhead. The drivers do not look as badly beat up as the ones on the last chain that broke, although I guess that is not saying much. Its sprocket was a mess as well.

Anyways, now I have 3 bars that are all dressed, three powerheads each with new sprockets in them, and three new chains. So I will not let things get so far gone next time!

Cheers, and thank you for all the help with this.

Dan

 

[BobL]

It's generally very useful to read posts like this, especially for newbies, but also to remind us all to check that we have the right setups.

It's not the worst sprocket I have seen but running a 3/8 chain on a 404 I am very surprised you weren't breaking chains sooner. The other thing to note is the battered bottoms of the chain ties. As soon as they look even a little battered that is a sign that there is something wrong. Usually that means that people are not sharpening right or often enough.

Anyway glad for you this problem appears to be sorted and thanks for sharing it with us.

 

[mtngun]

Yep, thanks for posting, even if it is a little embarrassing. We learn from each others mistakes.

3/8" chain on .404 drive sprocket ? And SawTroll thinks it is unthinkable to run 3/8 lo-pro on a 3/8 sprocket.:hmm3grin2orange:

No doubt a new 3/8 sprocket and new chains will put an end to the chain breakage. Some of the chains that have already been battered by the 0.404 sprocket may continue to give you trouble, however.

Now, let's see if I can rep you.