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

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....

http://hostmypicture.com/images/bearing.jpg

('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 ?

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.

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

Quote:

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Originally Posted by Lee Roberts

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

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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)

Quote:

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Originally Posted by 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.

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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!

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.

Thanks for the info ...problem is unless it's 100% all the time, then there's gonna be a lot of tool breakages ...and I can't really spin the spindle prior to every session just to warm up the grease (my cnc sessions only last about 5-10 minutes as it is!)

As an aside, this 300W spindle has claimed its first victim - a 0.8mm drill -I forgot to put the grounding croc clip on the *%~+'ing spindle shaft (I never had to do this with my proxxon) ...this is now an emergency issue for me! lol

In the light of your results, it's now looking like bodge 'A' or bodge 'B' (or bodge 'C' which is have some spring steel press down on top of the shaft - which is what some Zen toolworks spindle owners have done)

The answer has to be a slip ring then with carbon contacts. Use something like this mounted on a disc over the top. A little spring to keep in place and your away. You can make the parts on the router easy enough :-)

DEWALT DRILL CARBON BRUSHES DC981 DC984 DC988 DW988 | eBay

or find something like this?

http://www.ebay.co.uk/itm/MILWAUKEE-...item4ac5d5ce05

Something a bit simpler to adapt

DEWALT N012060 CORDLESS DRILL CARBON BRUSHES DCD940 DCD945 DCD980 DCD985 | eBay

Thanks, they're good options - many thanks for the heads up.

In the meantime, I've lashed up a bodge (like I say, bodges I can do!)...

Bodge 'A' ...aka 'spring loaded test probe pushing down on the centre of the spindle shaft'....

http://hostmypicture.com/images/3lvl.jpg

http://hostmypicture.com/images/2lpl.jpg

(there should be 4 screws holding that top piece up....but I only have 3 screws long enough to hand (it'll probably never see a fourth!)

...it works :-)

Nice one! :triumphant: