Sprocket on bar tip shattered

[Treeaddict]

Ran my 54” Forester B/C and heard a rattle halfway through the cut. I actually stopped cutting and didn’t try to finish because I’m not 20 years old anymore.😁 Found the sprocket cracked into several pieces. The bar has seen about 40 hrs of cutting and is frequently greased. I know the saw oils the whole length was well. I suppose it’ll go to a saw shop and get a new nose. It was more of a value brand so maybe a get what you pay for?

Anyone have a sprocket bust?

 

[lxskllr]

Never broken a sprocket, but I've had a nose come apart. I either threw a chain, and it blew the nose apart, or the nose came apart and threw the chain. Probably the former, but I dunno.

 

[Treeaddict]

Did you put a new nose on?

 

[lxskllr]

No, it was a laminated bar. Stock echo homeowner type bar, so pretty cheap. I would have if it had a replaceable tip. It was very low hour when it came apart.

 

[cory]

Sprocket failure is common with enough use and abuse but I'm not sure of typical hour meter reading for it. 40 hours sounds far too soon.

 

[Nutball]

Long bar takes a lot more tension to get the chain normal tight, so maybe normal tight shouldn't be attempted. Ideally long bars have a wide middle, so you don't need as much tension to keep the chain from sagging.

Also, for some reason (why I don't know), greasing the sprocket frequently or at all can shorten it's life. Maybe do it before the first run on a new bar, but never again.

 

[lxskllr]

I've heard grease it or not, but not halfway. If you grease, you have to daily grease or it'll fail sooner. I don't grease tips.

 

[Altissimus]

They break ... rear sprockets too (not everyday but happens)

 

[cory]

I've never seen that

 

[Treeaddict]

True that they need to be pretty darn tight to make the normal “snap” test copacetic. Maybe the next one will be run a little looser and not greased.

I’ve heard the same things about greasing/not greasing. I don’t understand greasing causing failure but more than one reputable source proclaims such.

 

[lxskllr]

My guess is partial greasing leaves it tacky around the bearings and attracts dirt, whereas daily greasing pushes the dirt out, and keeps a higher grease to crud ratio so it won't grind the bearings as readily. Oil just flows and keeps it washed out. Stihl bars don't come with a grease hole. I just pretend all my bars are Stihl :^P

 

[Trains]

What brand was it.
ive seen high hr brand name bars with worn sprockets, which have been replaced.
But ive also seen the cheap chinga ones fail rather regularly.

dont think lack of lube is the issue, more of quality, or lack there of.

If there is a hole, grease it, if there isnt, hit it with a good dose of bar oil, you can feel once its working its way into those roller bearings, you need lube to both lubricate it and protect it from moisture between uses.

 

[flushcut]

Sprocket failure is common with enough use and abuse but I'm not sure of typical hour meter reading for it. 40 hours sounds far too soon.

400 hours is a more reasonable number for sprocket life. IMO

 

[Treeaddict]

@Trains

It is a Forester brand bar.

Not too cheap but no Sugihara or high end bar. Heck, I don’t think there’s knock off chinga bars in that size class. Those Holtzforma bars stop at 36” last I looked.

Gonna look for a replacement nose

 

[Trains]

It looks like a laminated bar, and not the pro version which has the removable nose sprocket assy.

still, if you can get a replacement nose sprocket, then press out those 4 rivets, remove the remaining bits and pieces, clean, lube and fit new sprocket, and pein over the rivets and call it good.

 

[Gypo]

Blown tips are common.

If you put another tip on it, be sure to make sure the rails are clear. Sometimes a bearing will lodge between the rails.

 

[Bart]

If you think your nose sprocket is gummed up, submerge it in varsol and keep spinning it (no chain) until crud stops coming out. This will also remove hardened grease if you're patient. Then either regrease or oil the cleaned nose bearing. I've seen dirt come out once, definitely not good for bearings.

 

[SkwerI]

I quit trying to grease bar tips 25 years ago. Bar oil does a fine job.
When cleaning my bars, I use compressed air to blast out the rails and to spin the sprocket tip as fast as it will go and throw out any debris. If it won't spin I work it back and forth until I can make it sing with the air nozzle. In the last 25 years the only sprocket tips I've lost were the very small carving tip on the MS150T, mostly from plunge cutting too often but I think Stihl had a run of bad bars as well.

 

[Bermy]

^^^ Ditto, except I just spin the nose with air enough to see that it's spinning freely, not enough to take off for Mars.
The hooked wire picks I have drag a lot of gunk out of the area between the end of the bar and the nose sprocket before I blast it with the comp.air.

 

[friedrich]

interesting, i was taught to not spin the tip sprocket with compressed air.

 

[Treeaddict]

interesting, i was taught to not spin the tip sprocket with compressed air.

Why is that? Possibly blow debris into it?

 

[Trains]

Why is that? Possibly blow debris into it?

spooling up a bearing with compressed air can result in very high rpm, and combined with comp air often being used to clean out a just cleaned bearing, there is little lubrication, so its basically dry.

high rpm and dry bearing = not that good.

just because you can, dosent mean you should .

Have seen apprentices spool up bearings with comp air, and the cage failed and sent needle rollers into every corner of the workshop.
And they needed a change of overalls and undies and a trip to the hospital.

Have heard, but not wittnessed it, of people holding a bearing with their fingers, or slid onto a finger, spooling it up, and the bearing locking up and taking out a finger or two in the process.

So, personally I strongly advise against it, a little to move it and clean it, yes, but not seeing how high pitched you can get it into crazy rpm figures and it fails spectacularly.

 

[Nutball]

I often have a hard time getting them going with compressed air, and have to soak them with WD40 and work at it a bit, but then it really flings the gunk out. I had a video of one spooling up to like 68,400rpm, on a cheap chinese laminated 3/8 bar too.

 

[Bart]

Machinist/engine guys are all about the wear from revving with no lube on a precision bearing, which is the essence of a good bearing. Tip bearings are big imprecise grit tolerant fat needle bearings, if you've ever seen one apart. Going back and forth between solvent and air spin can speed up the grit clean out process without too much wear as the solvent is a partial lube for most of the spin. Air spin also preps for the oil not instantly running out because it mixed with the solvent.

 

[Ed L]

I have a older Forrester bar on a 254xp, no issues, it was made by Windsor.
Those days are gone, everything they market now is pure Chineeseium...

They get none of my money.

Ed