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Re: Dismounting the headstock bearings

 

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Ryan,

I'm not speaking of alignment accuracy that would mainly lead to a machine a taper instead of a cylinder but of runout of the chuck that is currently resulting in an irregular machined surface. And you're right in your rationale, telling that, depending on the location the machining is preformed, the effect is greater when the distance to the chuck is increased. I admit not having checked the conjunction of the bad surface with the distance from the chuck. I take note to do that during the final verification after fixing the trouble.

I don't also remember if I said this : the roughness is drastically improved as well by decoupling the gear train from the 40-teeth drive gear at the end of the spindle. This phenomenon lets me thinking that the two bearings aren't pre-constrained enough. I don't understand yet why the ghost thread it's close to the lead screw pitch (2mm). I gonna change the ratio of the gear train to check it.


On 08.02.25 21:38, Ryan H via groups.io wrote:

1/100mm is about .0003". Over what distance are you trying to maintain that? Just curious as it shouldn't be a problem on shorter lengths with everything properly adjusted and aligned especially the saddle and headstock. I may have missed where you said but if you're saddle travel isn't perfect you're not gonna get .0003" unless you work only in the "good" area of travel. Then the headstock has to be done but anyway...
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The inner race of the inner bearing can be an interference fit on the spindle albeit very slight. Like tap it with a wooden hammer handle only to fully seat it.?
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?The inner race of the outer bearing should be a very snug slip fit on the spindle. That race has to be able to slide just like on a vehicle. ?It's fairly time consuming process. ?Sounds like your spindle wasn't properly fit for the bearing. If it was the race would move so you can set it. I think you're first step is going to be to rectify that and from there you're going to be set on that part.

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