Haas VF-2 worth upgrading to AC ball screw bearings
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  1. #1
    Join Date
    Apr 2012
    Ocoee, Florida
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    Default Haas VF-2 worth upgrading to AC ball screw bearings

    I'm refurbing my old '92 VF-2 and while reassembling and checking the axial play on the x and y ball screws I'm noticing about +- 1 or 2 tenths with 50-75lbs of force applied to the bed/carriage (indicating at the end of the screw). Total backlash is about twice that so half in the ball nut and half, in what I assume is the needle thrust bearings. I did replace these bearings with new Koyo 35x20 and although i dont know how much preload I have on them its enough to create noticeable drag and I wouldnt want to run them much tighter.
    My question is if I were to fit 60deg NSK 20TAC47BDDGSUC10PN7BP4 ABEC-7 AC bearings (same OD/ID)to the cartridges would this play be eliminated? Haas says to physically push and pull on the axis and +- a tenth is good. I'm probably getting a bit more than that and although the old girl has been retired to hobby use the anal machinist in me wants it to be the best I can make it. What you say? is it worth a few hundred $ and some machining if it will eliminate half of the backlash?

  2. #2
    Join Date
    Jul 2006
    Hillsboro, New Hampshire
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    If it's that little work and money, do it. Needle thrust bearing always have lower performance than properly installed AC bearings, it's inevitable due to the extra friction and scrub of the needle as it rolls at different surface speeds along its thrust washer.

    Emphasis on properly installed - if you don't get it right it may not last acceptably long.

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