Thread: Bar rail closer

These Bar Rail Closers (BRC) cost $20 in the USA but I need to use this particular bar tomorrow so I knocked this BRC up this afternoon. I've been meaning to have a go at making make one for a while anyway and a quick check showed I had all the parts except the longer 10 mm bolts.

I've been using my 441 with the 050" grooved bar and the lopro chain to prep logs and also to do some prelim chainsaw carving. Both of these activities involved using the saw like a knife to shave bits of the sides of logs during which the chain gets forced over on its side which tends to force open the bar rails/groove. On Wednesday when I was cutting I noticed the chain was very sloppy in the groove and at first I thought it was just a worn chain but checking with a micrometer showed that none of the supposed 050" drivers are no less than 0.049" thin.
Then I measured the groove with a feeler gauge and the top of the bar groove was as wide as 0.058" !

Here what the BRC looks like sitting on the bar rails -




This is what it looks like underneath.
The lower bearing is fixed while the bolt hole for the other is slotted so that its position can be adjusted radially so that the gap between the bearings is narrower than the bar rails. Pushing the BRC along the bar then forces the bar rails to close up.
The numbers 1 and 2 on the picture below refer to two height adjustable stops that make the BRC ride about 5 - 7 mm above the bar so that only the lower half of the bearings are in contact withe the sides of the rails and the bearings are not just trying to compress the solid bar itself
Stop 2 rides on top of the bar rails while stop 1 rides inside on the bottom of the groove. It's a 6mm machine screw that has been ground/filed down to 0.050" thick so that if the groove is closed down too far you will feel resistance from this stop.
Stop 2 can be easily replaced with other thickness screws to suit other size grooved bars.


Below you can see the adjustments from on top. A and B are the height adjustment screws - same as 1 and 2 above.
To adjust the pressure on the bar rails, D is loosened and C is tightened pushing that bearing closer to the other, and then D is retightened.
After applying some light machine oil to the groove and rails, the BRC is run back and forth until it becomes easy to do this and then D and C are (re)adjusted and the BRC run repeated over the rails until Depth stop A (= 1 in the above photo) starts to tighten up.
It only took about 4 adjustments to get the rails back to where I wanted them to be.