threading formula

[skipper]

Hi All,

Well I've asked this question before and got links to the efunda site that has a table that is really confusing. I am trying to cut threads on my lathe, I am looking for what size of diameter to machine down to so I can thread on a rod. Like I mentioned, I've seen some tables but it is rather confusing with all the different choices. Can someone give me a easy to read table or better yet let me know what they use for these standard sizes. Whats the magic formula for figuring this out?

Thanks,
skipper

6-32
8-32
10-32/24
1/4-20
5/16
3/8
1/2-13

[chucker]

Try out this link
http://www.engineersedge.com/screw_threads_chart.htm

[tauntdesigns]

IIRC: back a long time ago, an old hand told me #0 was .06" and they got bigger by .013" as they stepped up in numbers.

To find the other number sizes you can use this equation.
major dia. = ( # size times .013" ) plus .06"


I never found that info in any book.... just off the top of the Old Hand's head.
EDIT: oops.... Just found it in Machinery's Handbook

Jack
P.S. for 00, 000, and 0000 #sizes subtract .013" for each extra 0 from #0=.06"
00=.047", 000=.034", and 0000=.021"

[tauntdesigns]

6-32............ .1380-.1329"
8-32............ .1640-.1585"
10-32/24...... .1900-.1840"
1/4-20......... .2500-.2435"
5/16............ .3125-.3053"
3/8.............. .3750-3688"
1/2-13......... .5000-.4919"

The chart from the Handbook I got those numbers from didn't show number of threads. Just the screw sizes major max to min

Hope this helps some,
Jack

[tauntdesigns]

Here's an online site with a chart showing thread per and such
http://www.engineershandbook.com/Tab...readlimits.htm

[skipper]

Thanks guys,
this helps a whole lot.

skipper