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A Chinese puzzle!

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Cornish Jack29/06/2019 16:16:07
953 forum posts
134 photos

Couple of pics below of some imported components for a drill spindle. Looks to be well made and needs to be assembled. Thereby lies the problem - the tolerances are 'marginal', in that one of the bearings slotted into place with finger pressure., the other is very much an interference fit. The spindle, as is, won't accept either bearing. Not sure what the fit discrepancy is but I've had the spindle in the freezer for a week or so and still not a finger pressure fit in the bearings. I can foresee jamming problems so would greatly appreciate adfvice on best practice assembly routine for spindle to second bearing and then to housing or second bearing to housing THEN spindle through both at the same time.??? Plus any action to the remaining bearing - heating (and how). Ideas very welcome!

rgds

Bill

img_0036a.jpg

img_0035a.jpg

Martin of Wick29/06/2019 16:41:27
93 forum posts
4 photos

You had better luck than I did. In my case the bearings rattled around in the block recess with about .8mm clearance - completely useless.

Had I been fortunate enough to obtain one with a decently tight fit, I would have lubricated thoroughly, pressed the shaft to front bearings then to the block, then tapped the back bearing with tube down over some blocks with something large and heavy (or resorted to the trusty 12 tonne press if all else failed). Other methods would probably work just as well, such as place bearing in block then press shaft in.

If you are of a sensitive disposition, pre fitting, you could polish the spindle up a bit with fine silcarb paper on't lathe to a tight sliding fit , but go easy as easy to overdo.

Martin Hamilton 129/06/2019 16:53:51
145 forum posts

Have a look on Youtube as Steve Jordan done a review recently in these, including assembly. His bearings were both on the tight side & used the vice with a plate to push the bearings in one at a time, his spindle was also tight & sanded/polished it in the lathe. If you have a loose bearing use some Loctite 641 bearing fit.

Tim Stevens29/06/2019 16:55:11
avatar
1101 forum posts

I think you are both victims of a process which seems to be relied on by some (many?) e-bay suppliers. My guess is that decent makers of quality stuff have a rejects section, which accumulates parts which fall outside the standard spec. The firms are (another guess) run by accountants, like many UK firms, and so they see the scrap as a source of income. Along comes an e-bay supplier, and buys up a heap of the scrap, going on to sell it as though it is good to use. And we buy it.

Effective quality control is an expensive process, but not having one is more expensive still.

Regards, Tim

Hollowpoint29/06/2019 17:56:29
240 forum posts
28 photos

Buying from a reputable dealer is no guarantee of quality I'm afraid. You should see the state of the quick change tool holder I bought recently from one of the very well known suppliers.

Cornish Jack29/06/2019 18:41:28
953 forum posts
134 photos

Martin X 2 - many thanks - helpful (and reassuring) It would seem that my overly tight fit is the better bet.

Tim - I quite understand the point you make but for the price paid (including delivery from China,) I could have bought half of the materials (if I was lucky) and then produced an object no more accurate than this. I could well have paid more for the super little chuck than the whole package, so no moans from me on that score.

Hollowpoint - indeed - as noted from time to time in these threads.

rgds

Bill

Neil Wyatt29/06/2019 19:02:42
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Moderator
16740 forum posts
689 photos
76 articles

Perhaps the layer of ice on the spindle is making it oversize

Neil

Phil super729/06/2019 20:21:52
10 forum posts

That looks like a linear bearing

old mart30/06/2019 14:24:31
785 forum posts
77 photos

Even liquid nitrogen will not shrink a small diameter by much, a domestic freezer has little chance of working if the interference is more than 0.0001". You could try heating the bearings to 140C, the lowest most modern fan ovens will go to, which will not damage them. Measuring the bearing bores can be difficult, a set of rocker gauges would be the most economical and quite accurate with care.

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