When is 9mm not 9mm?

I'm not ashamed to admit I often buy small consumable items from eBay, although I find that in practice anything costing more than a few pounds is often cheaper elsewhere.

I was surprised to receive a pack of ten 9mm stainless ball bearings very quickly between Christmas and New Year.

I just measured them... and my vernier says they are 9.53 - in other words 3/8"

Probably usable, but very annoying when I want to fit something into as small a space as possible.

Neil

Probably the same as the 300mm length of 1" brass bar I bought recently, to match some other items already turned out of 1" bar......that turned out to be 25 mm

.

I seem to recall that you had a similar experience with some control knobs ... which supposedly fit 6mm shafts, but were about 0.175mm eccentric when mounted.

MichaelG.

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Well, I've just demonstrated that the forum search facility works 

http://www.model-engineer.co.uk/forums/postings.asp?th=84424

Edited By Michael Gilligan on 03/01/2018 22:33:47

" David Standing 1

Probably the same as the 300mm length of 1" brass bar I bought recently, to match some other items already turned out of 1" bar......that turned out to be 25 mm "

At least it was dimensionally the right way round so could be used in a pinch. But that is very annoying indeed.

regards

Gets really bad when it's a reamer you bought - kind of the whole point of reamers that they are a very specific size.

Just as well you remembered that, I didn't!

Neil

Neil that was just the manufacturer allowing for the bedding in process , if they are from the far east i would also check to see if they are actually round and hard !

Bazyle, i have had the same experience - ordered a 9/16 reamer and a 14mm turned up in the mail !

Ian.

Edited By jason udall on 04/01/2018 07:23:19

Er no, the last time I checked, 25 mm is 0.4 mm undersized for 1" (or, if you prefer, 16/000"  ).

I wanted 1", they sent me 25 mm.

Edited By David Standing 1 on 04/01/2018 07:40:58

Poor s*** rang me up this morning after getting feedback. Young fellow who sounded shellshocked!

He doesn't even understand imperial measurements, but they've measured all their stock and all but the 9mm seem to be OK. He claims he's sending them back to his supplier.

My guess is that it's not worth ordering 9mm ball bearings from any small supplier on ebay for the forseeable future...

Neil

This thread reminded me of purchasing a piece of wood years ago. I asked for a 3 ft. length. Sorry came the reply, we're metric now. OK says I, One metre please. Sorry came the reply, we measure in 300mm units!

Absolutely true.

Yes but the standard lengths of wood were in 300mm units, if you really needed 1 Metre you had to buy 1.2M ! I had the opposite experience, asked for a 3 metre length of timber, Oh you mean 10 feet

Same here in Oz, which went metric in the 70s. Steel is still sold in inch-sized cross sections. Resulting in my asking for a piece of 25mm round bar, only to be told they only have one inch. Okay, give me three feet of that, then. Oh, we only sell it by the metre. Other places sell threaded rod in conveniently pre-cut lenghts -- of 920mm (exactly three foot of course!) And houses are all built on 60cm (24 inch) grid patterns, eg distance between wall studs etc. So all plywood and wall board etc comes in convenient 2.4m x 1.2m sheets. Metric, making life easier for us all by using round numbers divisible by 10. Yeah, right. So much easier than working with 8 foot by 4 foot sheets.

Wood's been a dimensional nonsense since Noah's cubits. Length is the easy part. Height and Width are often nominal in wood; for instance unplaned 2 by 4" isn't the same size as planed 2 by 4", and planed 2 by 4" is erratically smaller than rule inches. I reckon it's done deliberately to stuff up amateurs - only the trade know what to ask for!

Where I worked in the 70's wood was accounted for by the 'foot-run'. Although important, no-one seemed to know what the difference between a 'foot-run' and a 'foot' was!

Accounting complications make wood a tempting target for various types of thievery. My woody experience comes from supporting a suspected fraud investigation with a computer. I used it to analyse 5 years worth of transactions. Although individual naughtiness was difficult to detect and prove, criminal behaviour stood out like a lighthouse on a moonless night as soon as the data was taken as a whole. The police investigation that followed resulted in several fines and sackings, two prison sentences and a suicide. I don't believe the miscreants ever understood how the police knew quite so precisely where to look for hard evidence, or why the awkward questions were so horribly well-informed.

Dave

I think the wood spoilers are a bit special with their wood sizes, if it is planed it is the size before it was planed that was quoted.

Mike

Cloth is often 90mm wide because they just had to go metric but the 36in loom doesn't stretch to a metre.

Cloth is often 90mm wide because they just had to go metric but the 36in loom doesn't stretch to a metre.

No way would 90mm stretch to any where near a yard!! Unless it was a rubber band!

But I know what you meant.

Oldiron

Lol, don't worry about it, wouldn't be the first time I had misread a post!

Oh, and a little tip - if you want to quote a post and don't want to get your reply mixed up with the quoted text, start your reply BELOW the vertical line on the left of the posted text

I have resisted commenting until now but it is driving me mad, does anyone else find the seemingly increasing practice of repeating the question in an answer really irritating?

Bill D