[time-nuts] metric / English

J. Forster jfor at quikus.com
Fri Dec 16 18:48:34 UTC 2011


There is no "error" with the change gears. The ratio of inches to
centimeters is exactly 1:2.54 or 100:254 or 50:127. It is often done with
a train of 3 gear pairs to get the center-to-center shaft spacing right.

-John

=================

> Not that hard, actually. My 1984-vintage lathe has an inch lead screw, but
> the quick-change box that drives the leadscrew will do all of the inch and
> most metric threads directly. The few "weird" metric pitches are
> accommodated by changing two gears on the input side of the QC box. I
> suppose that at some very small level, there is some "error" in the metric
> threads produced (and I've never bothered to calculate it for my lathe)
> but
> it's a VERY small error that has never been an issue for me.
>
> 73,
>
> geo - n4ua
>
> On Fri, Dec 16, 2011 at 11:48 AM, Brooke Clarke <brooke at pacific.net>
> wrote:
>
>> Hi Don:
>>
>> Sure converting lengths is easy and I have metric, English and weird
>> taps
>> and dies, but how do you turn metric threads?
>>
>> Have Fun,
>>
>> Brooke Clarke
>> http://www.PRC68.com
>> http://www.**end2partygovernment.com/**Brooke4Congress.html<http://www.end2partygovernment.com/Brooke4Congress.html>
>>
>>
>> Don Couch wrote:
>>
>>> The idea that conversion to metric would require replacing all of the
>>> machine tools (lathes, mills, etc) is a myth. Any U.S. machine shop has
>>> walls and toolboxes covered in conversion charts, converting drill,
>>> screw,
>>> wire, sheet sizes from one crazy measurement to another. One single
>>> additonal conversion chart, inch to metric, and you can keep using your
>>> inch machines on metric projects.
>>>
>>> My mill has inch lead screws. I added a low cost digital readout with a
>>> little button to show inch or millimeter movements, and now I do
>>> everything
>>> in metric. No problem.
>>>
>>> Don Couch
>>>
>>> --- On Thu, 12/15/11, Dan
>>> Kemppainen<dan at irtelemetrics.**com<dan at irtelemetrics.com>>
>>>  wrote:
>>>
>>>  From: Dan Kemppainen<dan at irtelemetrics.**com <dan at irtelemetrics.com>>
>>>> Subject: Re: [time-nuts] time-nuts Digest, Vol 89, Issue 51
>>>> To: time-nuts at febo.com
>>>> Date: Thursday, December 15, 2011, 10:29 AM
>>>>
>>>> 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. I doubt many of the small tool shops
>>>> around here could afford it.It's a great idea to standardize
>>>> in theory, but in practice it becomes difficult. Maybe the
>>>> whole world should standardize our language. We could all
>>>> switch to Spanish or Latin or Chinese to speak with so we
>>>> could all talk with each other. That would probably be more
>>>> helpful to me on a daily basis, than having to switch
>>>> measurement systems.
>>>>
>>>> While we're on the subject, let me throw time back into the
>>>> mix. We use months and days for scheduling projects.
>>>> Meanwhile some of our counterparts use calendar weeks. This
>>>> is much more difficult to convert between than inch and mm.
>>>> When is CW 36???
>>>>
>>>> There I threw some wood on the fire too!
>>>>
>>>> Dan
>>>>
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