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MH300 - Z (vertical) axis handwheel drive shaft mystery bolt


Feb 11, 2024

On my MH300 Z axis handwheel shaft extension I have something that looks like a sheared bolt somebody tried to drill out (and failed).
Do you have any ideas what could have been there?



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One clue I've found in MH400 manual and This Old Tony's video was that there might be a sprag clutch bearing here keeping the table from creeping down from vibrations on it's own.

His machine is very different though (MH400P vs my MH300M).

MH400M manual also seems to indicate that there might be some clutch braking mechanism here

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My assembly is significantly different thought. Seems like there is a subassembly (red) in MH400 that should be bolted from the front (green) but I don't see anything like that in my machine.


But it indeed feels like the handle turns ever so slightly easier table down that up (when disassembled). MH400 is slightly different, but that's the best guess I have for now.


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So can't see the bolt/screw well enough to tell. Is it an Allen style set screw, or a slotted head screw?
Since it has no head on the surface its only function would be retaining/locating something inside that casting, most likely a bushing, or its like Bruce surmises as being a lube point.

Remove it, if it is bottomed out on something inside, then its a retaining screw, if it passes through to a shaft of ? then its for lube....
My vote is a lube point just based on the fact that its placed on top of the casting.
Cheers Ross
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I can't tell either - it was already drilled out to ~5mm below the casting surface. I'm trying to understand what it was originally - since there are definitive signs of some failed past repair or modification.