Doesn't matter if the rub is 'friendly'. All that matters is that the needles bring up the twine from the spools and the twine gets into the twine disk notches. When the disks rotate, they grab the twine and the needles retract. That's it. Roll the knotting operation thru by hand without twine threaded and watch the action. The needles lift up thru each knotter frame and run by the billhooks. You can set the needle bolts while they are in this position because thats all that matters. Then run it thru a knotting operation under power at idle rpm. There will be some clacking as the tucker finger cam pulls the fingers over in preparation for a billhook twist. If the needles survive this test you are in business. Remember they were designed from mallable iron so they could be 'adjusted' in the field, literally. Whats really important is why they got hamered. Check the plunger stop. Sometime its floating action is bound up with old hay chaff or the springs are all rusted and shot. If the needle brake is not tight enough, they will bounce back into no-man's land and get clobbered. While you are watching in slow motion, check the twine cutter action to make sure the wiper arms scrape the billhooks. If they are worn, the completed knot won't come off the billhooks correctly and the knot can break or worse: be left on the hooks. The needles aren't sewing leather, just pulling the twine up thru the knotter frames. They don't punch thru anything.
