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Thread: Z axis crank fix

  1. #1
    Toolmaker51's Avatar
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    Feb 2016
    Midwest USA
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    Toolmaker51's Tools

    Z axis crank fix

    Apparently, some import machine builders have gauging issues, no 5/8" reamers, or combination of the two. Why else would a .625 shaft be matched with a .632 crank bore?
    I'm constantly repositioning the knee. Lowering is faster taking a grip right at the hub and swiveling the crank just with wrist action. Ergonomics keep the handle in place, usually.
    Raising it, handle constantly leaps off the shaft, due to shoulder and elbow getting the act. But fit of shaft and bore are the cause; clearance makes angularity, which disengages the teeth, then handle is out of it's arc of control. If it drops to concrete, loss of drive teeth is next.
    After figuring how to clamp and indicate everything, I bushed it with a common bronze sleeve. A simple mod, and 100% effective.
    The setup took work.
    After checking teeth and front side for parallel [weren't];
    1] strap clamp face directly on table. They're only dependable FAO surface [Finished All Over]. Hopefully related to establishing hole position.
    2] skimmed half of exposed area with end mill, moved clamp and milled remainder.
    3] set handle with teeth up on a spacer, two straps and a large washer over the teeth.
    4] indicated existing bore AND inner side of teeth. Not perfectly concentric, reasoned teeth position as correct X .000 Y .000.
    5] a light boring cut re-centered the two.
    6] reamed 3/4".
    7] pressed in bushing.
    Z axis crank fix-z-axis.jpg Click the pic.
    Note worn paint. I do that Z swivel motion a lot.
    ...we'll learn more by wandering than searching...

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    Frank S (04-01-2018), Jon (04-02-2018), PJs (04-04-2018), Seedtick (04-02-2018)

  3. #2
    Frank S's Avatar
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    Aug 2015
    Peacock TX
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    Frank S's Tools
    I have encountered very similar issues with various types of machines poor casting grade lack of concentricy of machined parts or being sold as cast without proper clean up or even passing through a final inspection prior to packaging and shipment. Since in the Middle East sending something back to the factory for warranty was essentially a non existent option. Our service department took care of all the warranty claims on everything we sold.or manufactured. We had this 1 American made air compressor I won't mention the brand we sold several brands of air compressors made in the USA as well as a dozen other countries. But this one kept sucking the parts of an intake valve. The first time my mechanic just replaced it with new spares. the 2nd time a week later I had him pull the head and bring it to me. As it turned out the location was bored too close to part of the casting's side at a slight angle and when the compressor was running after it got hot the edge of the valve keeper could hit the side of the casting over boring the pressed seat area then pressing in a cast iron insert and re-boring straight and a few dozen thou away from the side 2 years later no additional problems But when it came to lathes drills or mills the fiddly-diddly spin knob gear change selectors and plastic hand wheels on machines made in the Ukraine could drive a man to drinking boiled camel snot.

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