Talk:Jewel bearing

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Comment

I think the article should mention explicitly what sorts of jewels are used, which varieties are better for the task, and also how the jewels are used - I believe the bearing is just a jewel with a hole carved in it for the shaft, but the article doesn't say. Bryan 15:09, 17 Apr 2005 (UTC)

Non-jewel jewel bearings?

Is it still called a jewel bearing if it's not a jewel? For example, a salad spinner often has a basket with a conical dimple in the bottom that mates with a conical spike in its tub. It's plastic-on-plastic. Similarly model train wheels are typically steel axels with conical tips that mate with ABS plastic conical holes. In both cases, the principal is the same as for a typical V jewel bearing: by moving the contact radius down to nearly zero, if you have Coulomb friction, the rotational friction goes to zero. —Ben FrantzDale (talk) 02:16, 21 July 2015 (UTC)[reply]

No, a jewel bearing is not necessarily (and in fact is not usually) a needle bearing, with a conical shaft end supported on bearing material. That is only found in a capstone bearing (see lower drawing in article). Most jewel bearings are plain journal bearings, consisting of a shaft rotating in a hole lined with bearing material (upper drawing). The distinguishing feature of a jewel bearing is the use of an ultrahard bearing material like sapphire, so your examples would not be called jewel bearings. --Chetvorno^TALK 02:35, 21 July 2015 (UTC)[reply]

As far as I can tell from Wikipedia, a sharp-cone-in-cup bearing is not a needle bearing. To the contrary, needle bearings have many slender rollers that add up to produce "high radial load carrying capacity". This is in contrast with a sharp-cone-in-cup bearing, which has extremely high contact stress and so relatively low radial load-carrying capacity. And again, it seems like the notion of making a bearing with extremely low radius is half of what makes jewel bearings good (the other half being using ultrahard bearing materials. —Ben FrantzDale (talk) 14:00, 21 July 2015 (UTC)[reply]