Adjusting Challenge 305 Knife Gibs

Wondering if anybody has any tips on adjusting the knife gibs on a Challenge 305 hydraulic cutter. A classic mustard yellow one, looks like this:

The manual states how important it is to adjust them, but gives no direction. Prior to this I had a smaller table-top Challenge and with that, you could adjust the gibs and feel how much tension there was or wasn’t when pulling the knife down.

With this cutter, I don’t have that option. I know to adjust the top gib while the blade is in the up position, and I assume the middle and bottom gibs while it is in the down position. But how tight should it be? I don’t want to tighten it so much the knife has trouble lowering or causes wear, but not so loose as to have difficulty cutting straight and consistent.

Any thoughts?

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I had a 305mc for 17 years and never had to adjust the jibs. I would strongly advise that you get a paper cutter machinist/repairman to make this adjustment and look the cutter over. these are great machines but very unforgiving if you don’t know what you’re doing. The money will be well spent.
-Ted Lavin

We found a description in a similar Challenge manual stating to make them “snug”. The left one wasn’t moving at all, the right one was loose. The top right gib had a different bolt than the rest, and that part of the blade carrier was badly scored, so it clearly had already seen some damage. We made the adjustment and it seems to be moving freely and cutting straight and consistent.