GB Bar pintched at clutch end

[firebrick43]

I bought a GB pro-top and some carlton chisel chain for the 450 homelite and finally was able to do so cutting this weekend. It cut so fast I could hardly pick it back up and put it into a cut fast enough. Well anyway I used a tank of fuel to cut a truck load of cherry wood. Cutters didnt look dull but I have read many of your post on how to maintain full chisel chain so I very litely touched them up. I took that chain off and was going to put my other chain on and flip the bar when I noticed that the very bottom edge of the drive links had worn to a very sharp point in only one tank? Checked alignment, looked good, the oiler was working well. I turned the bar and put the new chain on and felt a little bit of bind about the distance of every cutter. Removed the bar and noticed that the very end (clutch end) of the bar groves apeared pinched and could see were the tips of the drive links were wearing. What is up, I thought these were supposed to be really good bars? I spread the grove just slightly and it allowed the chain to travel very smothly so I dont think there will be any more problems.


Removed the bar and

 

[galde]

Was the clutch-end of the bar really pinched or was it peened form the drive links crashing onto the rails? If excess slack is permitted to accumulate, then the chain can arc away from the bar when it comes off the sprocket and miss the groove. The opening at the rear of the bar should be tapered open with a file or Dremel-type grinder to help the chain enter the groove. The drive links can also be battered by the drive sprocket if the chain is too loose. In a heavy cut, the chain is pushed out to the outer tips of the sprocket, and all the force is applied to the tips of the sprocket and the drive links, with accelerated wear and tear on both.

 

[firebrick43]

The chain was keep tight, tightened three times in the first tank while it stretched. The bar grove wasnt pinched at the top but at the mid way point and down, maybe not pinched but machined wrong? The place on the chain that is was wearing is at the very tip of the drive link into a V shape looking head on, not up where the drive link first enters the grove.

 

[begleytree]

I've always thought GB bars were a little tight to begin with, just haven't thought enough about opening the bar rails a little.
-Ralph