Thread: Bar problem

lookes like an oregon bar that i have,that bar needs to be dressed badly

This is a good demonstration of why it pays to regularly dress the bar almost if it even looks like it doesn't need it.

As soon as the bottom of the chain ties round over a little they start to put a slight groove into the bar groove and form a thin wire bead on the outside edge of the bar (see left hand side picture below.



If that wire bead is not removed and the bar rails are not flattened on a regular basis the chain will continue to round over more and form a deeper groove. This can get so deep that eventually the sideways pressure on the bar rail becomes so high the steel just cracks as you have seen.I have also seen the groove get so deep the chain jams in the groove that the chain breaks.

The most likely places for this to happen are the major pressure points you describe and the high spot in the middle of the bar is one of these since it sticks out more than the rest of the bar. It woudl be interesting to see how much of a rounded groove you have on the rest of the bar.

It could also just be a dud bar with a soft spot.

Yep it's an Oregon
The total running time of the chain that I just changed (cutters nearly all gone) at a guess might be 2 or 3 hrs, too many incidents with various nails and rocks shortened the chains life, so the bar hasn't done a lot of work since last dress, (last chain change) the bar did need doing as it had formed a small wire edge but not excessive (well I don't think so any way) The non cutting side hardly had any wear at all, what I don't understand is the depth and the short length of the damaged spot and y it is only in a short area compared to the length of what might be the total cutting length of bar and the length of the wire edge that had formed

Pete

The extent of the wire bead on the side opposite the damage in the picture below, is this the same across the rest of the bar?



If so, this is definitely too much and the wire bead should not have been allowed to get to this size. Once the wire bead starts it develops faster and quicker so its best to remove it on a regular basis. I also assume you flip the bar regularly so it wears evenly.

However you also say that the bar has only been used for 2-3 hours

When I see this amount of wire bead develop within such a short time use, the alarms it sets off are
1) Not enough oil - is this a milling saw and do you use an auxilliary oiler?
2) Chain too blunt - unlikely I've see pics of your cutters and they are almost legendary.
3) Pushing way too hard

When I first started milling with my little Mac10-10 I saw a wire bead like yours develop in less than one tank of fuel - what happened was the oiler outlet on the saw had blocked and there was only a tiny dribble of oil coming out.

The way the rail delaminates in short (10 mm) segments is pretty normal and is what I see much more than any longer breaks - the longest break I have seen is about 50 mm long but usually they are between 5 and 10 mm long. My guess is it's a bit like the development of a pot hole in a road. Remember, when it's cutting, the chain rises up of the bar, cuts a short chip and then snaps back down onto the rail. The wear is thus produced by a combo of sliding and pounding under high pressure. As soon as one patch of rail is worn a touch more than the rest of the bar it wears even faster and eventually breaks. On the non-cutting side of the bar, as well as much less pressure there is also no pounding action so there is much less wear.

Like I said before it could be a dud bar but with that amount of wire bead it looks like a normal breakdown to me.

definetly caused by not dressing the bar often enough.

if it wasnt dressed long ago i would suggest checking your oiler is working and turning it up to full if its not already.

Originally Posted by BobL

The extent of the wire bead on the side opposite the damage in the picture below, is this the same across the rest of the bar?..... Wear was pretty much the same



I also assume you flip the bar regularly so it wears evenly..... Yep.

However you also say that the bar has only been used for 2-3 hours.... Yeh That's a bit of a guess, what I was suggesting is that this chain/bar combo hasnt done a lot of work and based on previous bar dressing (new chain time) ( I only have one chain on the go at a time) I haven't seen this before on this same bar with most likely longer periods between dressings

1) Not enough oil - is this a milling saw and do you use an auxilliary oiler?....Could be....Yep, milling saw....aux oiler is one of those on the to do list, however it does spit out a fair amount of oil...sawdust covered oil
Attachment 149821Attachment 149822

2) Chain too blunt - unlikely I've see pics of your cutters and they are almost legendary.
3) Pushing way too hard....I do make it work but if I push too much the clutch slips

.

To me it looks like impact damage, maybe one of those times when the chain is a bit loose and the chain rises up and then snaps back onto the bar moments


Pete

Originally Posted by pjt

To me it looks like impact damage, maybe one of those times when the chain is a bit loose and the chain rises up and then snaps back onto the bar moments

Nah - they fact that you got that much of a wire bead elsewhere in the bar so quickly pretty clearly says not enough oil for that bar - lots of oily sawdust at the nose is precisely why an Aux oiler is used - ideally the oil should stay on the chain as it goes around the nose and come off at the drive sprocket.

I presume the saw is the 3120? That thing puts out a ton of oil (up to 54 mL/min) but it's mostly wasted coming of at the nose. On my mate, Hud's, 3120 I worked out that it needed an Aux oiler.

This is about the amount of excess oil I like to see on the bar from the aux oiler in a 36" cut. Any less than that and the temp gauge on my saw starts to climb.

If you notice on the side view of the bar defect, the paint is worn down further at that point, that may indicate where the bar may could have been pinched once (that can lead to cracking just like in the pic & larger), or thats where last contact is made when cutting, this happens on falling saws just behind the dogs.
regards inter

Have a few posts re oilers, I see an aux oiler taking shape sooner rather than later, gonna go off to the shed and see what I can find, if I can keep the mozzies away


Pete