Re: [CAD_CAM_EDM_DRO] how do I calculate thread pitch or TPI?

In both system (or anything for that matter) pitch is the distance from
one point on the part to the next corresponding identical point. This can be
crest to crest, root to root or pitch line to pitch line. Can be a thread or
a gear (same thing, really).
In the imperial system, it is determined by dividing 1 by the TPI
(1/TPI). In the metric system it's a direct measurement; your leadscrew (if
it's not a multiple-start) is a 2mm pitch.
Most likely your leadscrew is now an acme thread, either. Metric system
(now?) uses the trapezoidal threadform which is 30 deg. included angle, not
the 29 of the acme.
There is an important distinction to be made between lead and pitch.
Pitch is as defined above, while lead is the distance traveled by the nut in
one revolution. On single-start threads, the numbers are the same. On
multi-starts, the lead is the pitch multiplied by the number of starts.
Therefore, if your carriage travels 2mm for each turn of the screw, it is
either 2mm pitch, single start or 1mm pitch 2-start, etc.
Clear?


keith.

----- Original Message -----
From: "Lloyd Leung" <lloyd@...>
To: <Lloyd@...>
Sent: Monday, August 19, 2002 9:14 PM
Subject: [CAD_CAM_EDM_DRO] how do I calculate thread pitch or TPI?


> My lathe is metric, which is not a problem to me as I grew up with
> metric. If someone could show me the math to convert the information
> below, that would be great.
>
>
>
> I don't really know what thread pitch is, but I know threads per inch.
>
>
>
> Here's the information I do know.
>
> - 1 complete turn of the acme screw moves 0.20 cm, or 2 mm. And that's
> about all I know from my lathe.
>
> - So it takes 5 turns of the hand wheel to move 1 cm.
>
> - As there is 2.54 cm in 1 inch, thus somehow I calculate my acme screw
> to be 12.7 TPI. is this correct?
>
>
>
> Also, what is pitch, and how do I calculate it from the TPI?
>
>
>
> Thanks.
>
>
>
> [Non-text portions of this message have been removed]
>
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