Metric vs US, (was: Stepper cnc retrofit ? For Tape-O-Matic)

Hi Guys,

I've been sitting here watching NASA TV for the last few hours. It's
live TV of the new chunk getting bolted on to the space station. (Best
thing on TV in weeks.) Keeping in mind that this is the "International
Space Station", I'm amused to hear all the references to 5/8 inch
wrenches and torque measured in foot pounds.

Jeff

On Sun, 3 Dec 2000 13:37:57 -0700, Smoke wrote:

>Metric threads have a greater clearance at the root diameter than US
>standards. Consequently, the larger US threads will not screw into a metric
>hole as easily as you pointed out.
>In addition, the actual pitch dimension (distance between two adjacent
>crests on a screw) between metric and US standards may not be much but it
>DOES make a difference.
>
>As for changing to metric: If you take a long look at all the metric
>"standards" listed in the Machinery Handbook.
>Not only is there an ISO standard, but there is a Britsh standard as well.
>In addition, some standard metric sizes have three or more different pithes
>to choose from whereas most US threads have only two...coarse and fine.
>
>I'll agree that a worldwide standard would be nice but, considering the
>immense cost involved in changing from one system to the other,
>manufacturers are highly resistent to this. What do you do with all the
>millions (maybe billions)of products already made using US standards? Of
>course if the rest of the world would like to PAY us to change....:)
>
>Smoke