.01 mm is equivalent to .0004" (4 tenths of a thou). If they expressed it to the next decimal place (.001 mm) they would be tacitly saying their bearing sizes are accurate to .00004" ….. which I doubt.

What I want to know is where did all the extended-race bearings go (commonly inner race but extended outer race bearings were also available)? They used to be quite commonly available (and were arguably more useful than standard bearings) but I rarely see them nowadays. I suspect they are available but to special order which is a pity.

.

"Design updates" maybe … But hopefully not for spares !!

MichaelG.

Vic,

I collect old bearing catalogues. Bearing manufacturers generally show measurements upto 3 decimal places if they show imperial bearings converted to metric dimensions.

Picture from 70s RHP catalogue showing correct imperial measurements:

Similarly imperial measurements converted into metric in an old NACHI catalogue:

I am guessing that the bearing factors web software is just rounding up to two decimal places.

Ketan at ARC.

Hi bandersnatch, are these what you are refering to, **LINK** or maybe these http://www.lutco.com/Products/Radial-Bearing/Flanged-Radial-Extended-Inner-Race-Bearing/

Regards Nick,

Edited By Nicholas Farr on 10/03/2015 11:23:00

Only time I have seen extended inner or outer ring is in special order stuff. Often was used as a surface for oil seal to run on.

If the dimensions are given in imperial there are a bunch of kids now in industry who just wouldn't have a clue and would end up with all manner of non-fitting parts.

Quick test in the office to the two under 25's " what is 1/8 inch in mm". not a clue. Dived for their computers to google it.

I see several people recognise these and have addressed this before I got here today. Just to enlarge a bit, the kind of bearings I meant had the race extended by a small amount … maybe .5 mm in your language …. It was just to stop potential shorting of the inner and outer race in some situations while avoiding the use of shims or shoulders and were routine in the small mechanisms I dealt with in those days. A particular use for extended outer-races that I remember was when the bearing was installed in a blind hole. The end wall of the hole would short the bearing unless it was either stepped (shouldered) or you used an extended outer race.

Tony,

You may be right in so far as it may be a load of cobblers. As I said earlier, I too am guilty for failure to understand imperial measurements, but personally I would disagree that its just about interest, training and aptitude. It may be nothing to do with 'fitting parts' or 'non-fitting parts', as you may see it, from an engineers eye, but mistakes do happen.

Example of non-fitting of parts: I ordered dies and diestocks from one of the biggest and well known Chinese suppliers to the trade. The dies were supposed to be 20mm diameter to fit 20mm diestock.

The diestocks I received were 20mm, but the dies were 20.6375mm in diameter, so they won't fit the diestock. These are split dies, so at first I thought the die had just expanded (lack of understanding on my part perhaps) or that the factory had just used 20mm round bar which was slightly oversized. Now, having never come across imperial in my school life, I would presume that the dies were not made correctly, failing to realise that the round stock from which the die was made was 13/16". Until and unless one talks about this to a person versed in imperial measures, it is reasonably easy to make such a mistake in understanding, as I did. But then, I am not an engineer. May be that is where interest, training and aptitude….and experience could come into it, I suppose.

So please, don't be so harsh on the metric generation

Ketan at ARC

Hi Tony

I don't think that the metric generation is moaning. I am just saying that there may be potential for mistakes when the metric generation has not been exposed to imperial on a daily basis.

As for the dies supplier, I am guessing that something similar happened there. It is just something we will deal with.

Thanks, Ketan.

Edited By Ketan Swali on 10/03/2015 21:08:33

Here in NZ I go to the bearing shop, and if I want imperial bearings that's what I get in inches, and metric in mm, the only thing is that a metric bearing of similar size costs about half that of an imperial one. And if I want cheap, I get 8 mm skate board bearings, they are fine for Stirling Engines