Excessive spindle run-out

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summat
Posts: 6
Joined: Fri 19 Dec , 2014 22:17 pm
Hardware/Software: StarMill, converted earlier to Mach3

Excessive spindle run-out

Post by summat » Tue 23 Dec , 2014 19:54 pm

I've recently bought a rather modified StarMill, originally with ATC but this was removed prior to me, and converted to Mach3. As part of the modification the previous owner rebuilt the bearings.

I've measured the run-out at the tool-tip and I'm getting 0.2mm( :shock: ), and even at the spindle holder I'm getting 0.05mm. (piccy attached, I hope).


Here's the thing, though - the spindle is quite rigid in the bearings - if I apply force in any axis there's no real play. As I revolve the spindle by hand, the "high" point on the DTI is coincident with the rotational angle of the spindle, and this translates to the offset at the tool-tip.

[Edit]... and for completeness, dialing the spindle above the bearing, the high point is 180 degrees opposed, so it is rotating around the bearing mount. [/Edit]

Now, my brain isn't geared for analysing three dimensions, but it would appear to me that rather than being necessarily a bearing issue, this is more likely an issue with how the spindle is sitting in the bearings (e.g. conceptually - a bit of swarf between two machined surfaces). Is this likely?, or am I relieving myself into the wind? ( :cry: ).

Any suggestions of where to start? (I'm minded to remove the lock-nut on top of the spindle pulley and see where that takes me - is that a silly idea?)

Any advice gratefully received.

Mike
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Martin
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Re: Excessive spindle run-out

Post by Martin » Wed 24 Dec , 2014 21:07 pm

Just tighten the tab nut a couple of tabs

summat
Posts: 6
Joined: Fri 19 Dec , 2014 22:17 pm
Hardware/Software: StarMill, converted earlier to Mach3

Re: Excessive spindle run-out

Post by summat » Thu 25 Dec , 2014 18:08 pm

@Martin, cheers for replying - I've ordered a 58mm C-Spanner to give this a try. Any clue as to how tight this nut should be? 4 white-knuckles?

TDIPower
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Re: Excessive spindle run-out

Post by TDIPower » Thu 25 Dec , 2014 20:05 pm

I think you will find 3 white knuckles and a grunt but you could push it to 4.

Pete

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