[time-nuts] metric / English

[Brooke Clarke]

Hi Chris:

Yes.  In hospitals they are measuring your height in feet and inches, but your weight is in kg (6' 1" 120 kg).  Sort of 
like tire sizes which use inches for the wheel diameter and mm for the section width (P215/65R15 - 215mm section width, 
15" rim diameter).

Even more interesting than the metric/English idea is that my local shop (all CNC) has a no extra cost tolerance that's 
ten times tighter than the no extra charge tolerance (+/-500 Millionths) an experienced machinist can hold (+/-5 mils) 
and they have coordinate measuring equipment to back up the much tighter tolerances you can get for the extra charge.

A related story is that back in the 1960s I was designing microwave parts, many of which were made on a lathe.  There 
was a local shop that had chucker lathes (our company shop also had one) but this local shop would always come in below 
the in house and competitive bids.  These all used "5C" collets.
http://www.prc68.com/I/Lathe.shtml
http://www.prc68.com/I/DrillPress.shtml#5C
It turned out the the low bid shop had a screw machine in the back room that was kept a secret for maybe a year or two.  
The chuckers were really not being used to make parts.  But now screw machines have been replaced by fancier CNC 
machines like the "12 Axis CNC Mill Turn Centers".

-- 
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/Brooke4Congress.html


Chris Albertson wrote:
> On Thu, Dec 15, 2011 at 9:29 AM, Dan Kemppainen<dan at irtelemetrics.com>  wrote:
>> On 12/14/2011 3:59 PM, time-nuts-request at febo.com wrote:
>>> It's not like metric is totally absent.  We drink 2 liter cokes and defend
>>> ourselves with 9mm pistols.   Our cars use mostly metric parts.  Even ham
>>> radio operators, arguably the most jingoistic and set in the past bunch
>>> around, get on the 80, 40, and 20 METER bands.
>>
>> I agree with you, and funnily enough the rest of the NATO world uses 7.62mm
>> and 5.56mm rifles. (Both were originally based on standard inch sized rifle
>> cartridges designed in the US)
>>
>> The problem in converting to metric would require replacing a lot of tools.
>> For example Mills, lathes, and other machining tools and measurement devices
>> are expensive, and last for decades.
> Can you point one even ONE machine shop in the US that can make metric
> parts?  Those guys would have gone out of business years ago.   Also
> how many are still using hand cranks and reading veneer scales?   Even
> small one man ships are using CNC now.
>
> The US is slowly converting.  It will take a long time.  Even now if
> you go to Home Depot and look at plywood you see the better (non
> construction) grades sold in even millimeters with the inches being
> some odd number of 32nds approximation.   This will slowly creep into
> more and more products.
>
> So the debate is silly.  If the US should convert???  No.  the only
> question is how fast are we converting and when will we be fully
> converted.   Not even if this will happen, it will.
>
>
>
>
> Chris Albertson
> Redondo Beach, California
>
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