Re: [CAD_CAM_EDM_DRO] Re: Stepper cnc retrofit ? For Tape-O-Matic

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


-----Original Message-----
From: JanRwl@... <JanRwl@...>
To: CAD_CAM_EDM_DRO@egroups.com <CAD_CAM_EDM_DRO@egroups.com>
Date: Sunday, December 03, 2000 1:06 PM
Subject: Re: [CAD_CAM_EDM_DRO] Re: Stepper cnc retrofit ? For Tape-O-Matic

>Yes! "Pitch" means how much linear move per turn. TPI (Threads per Inch)
>means how many turns per inch of move.
>
>Metric threads are specified by major-diameter followed by PITCH, not
>"threads per length of measure" as we Americans do it, "threads per inch".
>But often, a metric "thread designation" is for the COARSE version, when
>abbreviated, as "M6" means a 6 mm. dia. bolt, but the 1 mm per thread is
>"understood". If "fine metric thread", "M6" would generally be followed by

a

>pitch-designation, as in "M6-0.75", meaning 6 mm. dia bolt, 0.75 mm per
>thread.
>
>Suggestion: Let's convert to Metric right away, and, nation-wide, throw

out

>$millions in tooling, and buy $ millions more metric taps/dies, and
>lead-screws on our mills and lathes, and learn the new designations

tonight,

>rather than watching TV... Uh, what???
>
>Funny: A standard "M5" bolt will thread-into a 10-32 tapped hole, if kinda
>loosely, but a 10-32 bolt will often not "go into" an M5 tapped hole, or,

if

>it does, quite tightly, if "perfectly" machined. I think this is the ONLY
>thread-size that is "essentially" interchangeable.
>
>
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