Chinese 300W DC spindle - is the spindle shaft grounded?

[HankMcSpank]

My digital calipers are playing up (pah, that's LIDL for you ....must get a new one asap!), but I reckon the shaft protuding out the top is about 8mm dia. (eg I have an oldham coupler that's got an 8mm bore & that fitted onto the top shaft very snugly).

So how does this normally work? .....presumably a bog standard 8mm ID bearing will fit over the shaft, but it won't be a press fit (whereas the original fan that came fitted was a press fit & actually took some prizing off!)...& presumably I'll need a press fit here? (at this point, I'm hoping 'press fit' is the right term......ie were the bearing doesn't just slide on, but needs to be coaxed on with some pressure) ...I therefore probably need a bearing a tad less than 8mm?!!!

[Swarfing]

A couple of grubbed screw collars would hold it in place (8mm drill bit stops)

[HankMcSpank]

So I had a look in my bearing drawer, which was totally empty bar one 8mm ID bearing - result......except there's no electrical continuity between this particular bearing's inner & the bearing's outer casing....



('scuse the crud - it's been a drawer for a couple of years!)


....and it ain't a ceramic type either! (i dunno you just can't get the bearings nowadays!).

Therefore I guess we can consider this case closed....clearly some bearings (even non ceramic ones) are open circuit whereas others seem fine (which could make sourcing ones that do have electrical continuity a bit of a lottery!)

Edit: Oh, BTW (as suspected) whilst 'neat', an 8mm ID bearing isn't a tight push fit....do you reckon a 5/16" (7.94mm) ID bearing fit ?

[WandrinAndy]

How about bodging some electric carbon brushes around the shaft, like those used in electric motors, to give you the electrical continuity ?

Off eBay a pair of these costs about £1.50.

[Lee Roberts]

For anyone intrested the new spindle Hank has ordered is for sale on ebay: ER11 Spindle for Sable-2015 / SPD-ER11 / ENGRAVER-mill,PCB's,engraving

Thanks for the updates Hank, look forward to seeing how the new spindle dose.

.Me

[HankMcSpank]

For anyone intrested the new spindle Hank has ordered is for sale on ebay

The advert doesn't show the P&P to the UK...it's $23 & is a 10 day postal service.

(for all the spindle's back bracket is an exact fit for the sable 2015 - which I have - I'm sure it's an easy enough job to either change the backplate or knock up some form of adapter plate....the sable 2015 Z axis has M5 holes 71mm between centres & two rows spaced 27mm between centres)

How about bodging some electric carbon brushes around the shaft, like those used in electric motors, to give you the electrical continuity ?

Off eBay a pair of these costs about £1.50.

Bodge 'A' is my present attack (a spring loaded test probe, pressing down in the middle if the top shaft)

Bodge 'B' ...could be what you've suggested

...fortunately, I excel at bodging.

A better option would be to either source some bearings that are electrically conductive between inner & outer casing or buy a spindle that has these fitted!

[Swarfing]

Hank i just did a little experiment. It appears that mine is not kosher in the continuity stakes. What it looks like it is intermittent. So checked my mill and that is, the 2.2kw on the router is also. It could be a question of the grease breaking that connection? So i fired the 300w spindle up and let it run for 10 mins to get the grease going, guess what....connection all the way.