I killed my tip sproket

[Faust M. Ruggiero]

Last week I was cutting up some cherry bowl blanks. My chain was sharp, in fact new, and the saw had plenty of chain oil. I usually have to refill the oil sump at the same time I refill the fuel tank and the chain showed signs of good lubrication. In the middle of a rip cut, the chain slowed and stopped. The tip sprocket was frozen. I don't plunge cut so I assumed the bar had just seen it's time. It was several seasons old but had not seen hard use. I bought a new bar, up sized to 18" from 16" so naturally I replaced the chain also. I set the tension so I could pull the chain without disengaging the drive links from the channel in the bar. With less than 10 minutes use, the new sprocket froze. The store was kind enough to replace it but I am uneasy about firing the saw up tomorrow with the new bar. Any thoughts??
faust

[Leo Van Der Loo]

Some bars are better than others, as with everything, however see if the bar has a little oiling opening, if it has, a bit of oil in there is not a bad idea.
Still it should not seize-up that fast, it has never happened to any of my bars, and some are considered quite cheap.

[Ken Fitzgerald]

The sprocket on my bars require grease and I have a special grease gun for them.

[Fred Perreault]

There are small plunger operated grease guns that can inject a lght grease into the pinhole opening at the tip of most sprocket type bars. These are not expensive devices, and greasing the sprocket is a good idea. Of course, not too many years ago all bars were solid at the "tip", with no sprocket. The sprocket reduces friction and saves engine power, but the downside is that it is much easier to twist the chain off of the sprocket when hacking at branches, slash, and otherwise cutting near the tip.

[Jack Mincey]

I bought my first new chainsaw this summer and was surprised when I read about greasing the sprocket at the end of the bar. It makes great sense and I do it now every third or forth time I use my saw. The thing is I've put hundreds of hours on a forty year old Pro Mac 60 and a 10 plus year old Husky 61 without greasing the sprocket with no problems. The old Mac is old enough that you have to pump a button to oil the chain. Both saws put a lot of oil on the chain and I think that is what helped me out. I can hold the saw in-front of a tree and bring the saw up to speed and it will spray a line of oil on the bark. If you saw does not put out this much oil you may need to adjust the amount that comes out. I have to adjust it on my new saw when I go from a 24" bar to a 32" bar to make sure there is enough oil lubing things up.
Good Luck and be careful,
Jack

[Ken Fitzgerald]

Jack,

Mine is an old Mac sold to me by a saw shop in Bend, OR some 33 years ago. He sold me the grease gun too! Could be the model of the saw. I told him I wanted a professional saw not a homeowner's saw. That why I bought it where the local loggers did. Paid a lot then. It's still functioning.

[Nathan Hawkes]

Like Ken said, most bars require some greasing with regular use. I have two professional-grade saws, a big husky and a Stihl 361, (and a mid-grade stihl), and have never had a tip seize up. I mill with my bigger one, a Husqvarna, and have had a tip sprocket break, but never seize. It's likely that it broke because of the abuse--lots more use than a normal bar would see because of the milling. I'd bet that something was defective. Just for the sake of making sure; you do have the right size sprocket for your type of chain, right? There is .325, 3/8, and .404 "pitch"--the average distance between the riveted links. I haven't ever tried the wrong size, so honestly I don't know what would happen; likely just some undue wear to your drive links, and lots of vibration, but that's a guess.

[Jim Underwood]

I learned about greasing the sprockets at one of the local symposiums, so I went home and got my little grease gun out, pulled the chainsaw out to grease it, and...

...it didn't have a hole for the grease.:confused:

[Ken Hill]

I run my bars upside down and alternate them so the sprockets wear evenly. I also agree with testing the oil spray before you start cutting especially if you are cutting alot of green wood. That sap will clogged alot and it can dry effectivley sealing off the small oil openings. I usually cut through a few dry pieces when im done for the day to help clean some of it off of there.

[Fred Perreault]

The oiler on a saw is very critical to the life of the bar and chain. Take the bar off frequently to clean the bar slot where the chain travels, using a bent coat hanger flattened to a thin pull scraper works well, and clean the oil hole at the power head end of the bar. Inspect the sprocket for wear, take a file and lay the bar on a flat surface and take off the burr that is inevitably created on the edges of the bar down near the power head.You can feel this burr with your fingernail. Rotate the bar as Ken suggested to even out the wear on the sprocket as well as the end of the bar near the operator, where much of the downforce is created by the action of cutting across logs. The quality of the bars we can buy varies widely. Aside from various manufacturing differences, there are 2 basic bar styles.... a solid bar with a machined slot for the chain and oil to run in, and laminated, 3 piece bars. The solid bars are more expensive and usually better made to last longer, but I have had only a few laminated bars start to come apart from use in 40 years. By that time, the rest of the bar had seen better days anyway. I imagine most of us here have learned as we went along, with only a few unfortunate events. But besides the obvious safety aspects, the benefits of saw maintanance are right there with the bandsaw, tablesaw and radial arm saw. Life expectancy and usefulness can both be elevated measurably with additional care and tuning. They sound awful, they are very dirty and heavy, and they can seem ornery. By by cracky, I would rather not return to the days of a 2 man buck saw.

[Faust M. Ruggiero]

Thanks for all the input. Mine saw is a Stihl saw that is surely not a professional use machine. I believe it only cost me about $300 or so in 2001. The bar is laminated and has no grease hole at the tip. I will increase the oil flow and try to manually get a bit of grease into the tip sprocket. My saw has always been fine for homeowner cleanup and a bit of firewood. Preparing turning blanks is new to me and taxes the saw more than simple yard cleanup. I assume there are techniques to be learned that will also help. Thanks for the reply.
faust

[Jake Helmboldt]

I set the tension so I could pull the chain without disengaging the drive links from the channel in the bar. With less than 10 minutes use, the new sprocket froze.

Faust, when you say you can't disengage the drive links, how far down can you pull the chain?

1. The bar tip needs to be lifted up when you tighten the bar after tensioning the chain.

2. You should be able to pull the chain down to expose the drive links but it should not sag (and should snap back up into the bar channel.

3. The chain should move freely by hand and not be overly tight.

Am I understanding that two sprockets seized on you? If it was only one, I'd chalk it up to a bad sprocket. I have a GB bar that arrived with metal filings in the sprocket, causing it to bind. I had to flush it out and lube it to get it freed up.

But if you had two seize then I'd suspect the chain is too tight and/or the oiler is not putting out enough.

[Faust M. Ruggiero]

Jake,
I explained myself poorly. I tension as you described. I will increase the oil flow because I also don't believe two in a row is just bad luck.
faust

[Ryan Baker]

Fred pretty well covered it already. The question is whether the sprocket actually seized up or was just jammed up. If you don't regularly clean out the bar groove carefully, you can build up an amazing amount of crud in the groove and it will eventually jam the tip sprocket up tight -- especially in certain woods. The build-up also stops the oil flow. If that's the case, you can take off the bar and clean it out well and the sprocket will free up again. You should be going through a tank of bar oil in the same time as a tank of gas if you oiler is putting out enough. Rip cutting with the tip buried can be a good way to clog the tip fast in stringy woods that don't clear out of the kerf well.

[Jeff Nicol]

Faust, I see a couple of things that could be happening. If the pump on the saw is not working correctly you will not get enough oil. Leave the bar off and either run the engine or pull the recoil to see if oil is being pumped out to the chain. The first sprocket could be from just wearing out, but I do believe that the tension you are setting it at is too tight. What I have noticed over 35 years of chainsaw use is that when a new chain is put on and you first run the machine without putting any extra oil in the bar groove or on the chain before running it up to max rpm and start cutting (Even when tensioned correctly) the chain will dry out and all the links will bind and the bar and chain will heat up and bind thus shortening the length of the chain and putting undo pressure on the sprocket. Each time I put on a brand new chain I make sure there is oil on the chain and in the bar, because the chain looks oily from the box but it will burn off in a heart beat and the heat will build up quickly. So with the oil in place and the chain on I tension it just a little loose so when and if it heats up this won't happen. Then after a few minutes of cutting and making sure that the oiler is working and the chain is "Broke in and stretched out" I will re-tighten and be on my merry way. I have never had a sprocket on a stihl or any saw that I have owned ever freeze up. A little pre chain lube goes a long way in keeping things running for a long time.

One other thing I just thought of, if for some reason you got the wrong drive link that went on and you did not notice it that would have caused the problem too, as it would have been binding and not running true. Someone could have put the wrong chain in the package or sols you the wrong one at the store. I had it happen to me and when I tried to put the chain on it was close but the chain was to proud on the tip and I knew something was wrong. Mistakes happen in the best planned scenarios.

Hope we all give you some helpful insight,

Jeff

[Harvey Schneider]

Another possible cause of over-tensioning occurs when the chain is re-tensioned while hot.
As everything cools down, the chain tension increases. This can happen when you go from heavy cutting to lighter trimming. Or, in the extreme if you don't release the chain tension when you finish a work session (coffee break).
I think that there had to be inadequate lubrication in the case of your second failed sprocket, but likely an over tensioned chain added to the stress.

[Faust M. Ruggiero]

Thanks for the further replies. Jeff, I will run the saw minus the bar to check oil flow. I didn't know you could do that. I will also pre-oil the chain. I suspect you are all correct about chain tension and the dynamics of heating and stretching and shrinking and cooling. I re-tensioned the chain after running it a few minutes to take up any stretch caused by heat. I probably overdid it.
The good news is the Ace store that sold me the bar took it back and ordered me a replacement. It will arrive tomorrow. I will take all necessary precautions this time. Thanks for the help.
faust

[Kyle Iwamoto]

When I was a mechanic, I seen a couple "frozen" tips. They turned out to be just some rubbish in the tip. Spray some light oil, WD-xx works, and try rocking the sprocket back and forth, If it can move, keep doing that. Spray WD to flush out the junk. It always worked, so in reality, I have seen NO truly frozen sprockets either. Oh yeah, you should not tighten the chain when hot....

A word about "sizing up". If the saw is designed for a 16" bar, it is generally not a good idea to put more bar on. If you saw can not drag the full length of bar through the log, adding more is just a waste of money... Some of the chainsaw makers just put a 20" bar on a small saw, just to attract the buyers. Bigger must be better. Sometimes this is not true. Since it's a Stihl, they are pretty good about stating what bar lengths are reccommended for your saw. You can look up what you saw can handle.

Just my $0.02.

[Faust M. Ruggiero]

Kyle,
I have the old bar and will try to flush it out again this evening. It turns all the way around but gets really tight at one point. I sprayed Boshield and worked it but it will not spin freely. The second bar froze completely and wouldn't move at all but the store took it back.
My saw is sold with either 14, 16 or 18" bars. I stayed within the manufacturers instructions.
faust