Internal thread minor diameter
Largest Manufacturing Technology
Community On The Web
Close
Login to Your Account

Results 1 to 9 of 9
  1. #1
    Join Date
    Jul 2008
    Location
    Alpine, TX
    Posts
    168
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    2

    Default Internal thread minor diameter

    I have a one-only job to make a female threaded adapter for a guitar stand. The male thread I have to match is a odd size (near 7/8th's) and is 26tpi. My question is how to determine hole size for single point threading? My idea was to measure major diameter of the male threaded piece and subtract the double depth of 26tpi (.050) extrapolated from the figures found on a Starrett center gage. Is this the way to figure this or is there a better way?

    Thnx - John C

  2. #2
    Join Date
    Nov 2005
    Location
    SC
    Posts
    132
    Post Thanks / Like
    Likes (Given)
    9
    Likes (Received)
    28

    Default

    You sure it's not metric? As in 22-1.0 mm thread?

  3. #3
    Join Date
    Jul 2008
    Location
    Alpine, TX
    Posts
    168
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    2

    Default Internal thread

    Sorry, I made a typo, the male thread is near "5/8ths" (.607 is the major dia.). I tried a 1.0mm thread gage and it fits fair but not as good as a 26tpi gage to the best of my vision. It measures 15.44mm and I can't find a 16 X 1.0 tap in any of the catalogs I have.

    Am I in the ballpark on figuring the minor dia. hole size for any oddball size female thread with the double depth of the thread pitch subtracted from the major dia. of the male thread I want to fit?

    Thnx - John C

  4. #4
    Join Date
    Oct 2006
    Location
    Adams,MA USA
    Posts
    16
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    1

    Default

    Subtract one thread pitch ( .0384 ) from the major dia. and you get tap drill size.

  5. #5
    Join Date
    Jul 2005
    Location
    central Illinois
    Posts
    141
    Post Thanks / Like
    Likes (Given)
    845
    Likes (Received)
    31

    Default

    I think you'll find the actual TPI is 27.

    Gus

  6. #6
    Join Date
    Sep 2004
    Location
    North Olmsted, Ohio
    Posts
    91
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    12

    Default

    Quote Originally Posted by johncollins View Post
    I have a one-only job to make a female threaded adapter for a guitar stand. The male thread I have to match is a odd size (near 7/8th's) and is 26tpi. My question is how to determine hole size for single point threading? My idea was to measure major diameter of the male threaded piece and subtract the double depth of 26tpi (.050) extrapolated from the figures found on a Starrett center gage. Is this the way to figure this or is there a better way?

    Thnx - John C
    Take a look here. They show a fine metric thread 16 x 1 with a 15 mm tap drill

    http://www.kramerusa.com/DrillTapChart.htm

  7. #7
    Join Date
    Jan 2007
    Location
    Florida
    Posts
    1,014
    Post Thanks / Like
    Likes (Given)
    3
    Likes (Received)
    63

  8. #8
    Join Date
    Jul 2008
    Location
    Alpine, TX
    Posts
    168
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    2

    Default Internal thread

    Thanks guys for the info. I bored the hole based on the formula (major dia - one thread advance, .615 - .038 = .575 and 26TPI) and it fit the external thread I had to match perfectly. I think it was originally 5/8" x 26 but I cant imagine a mfg using such an odd size.

    John C

  9. #9
    Join Date
    Jul 2007
    Location
    Laidley, SE Queensland
    Posts
    206
    Post Thanks / Like
    Likes (Given)
    8
    Likes (Received)
    54


Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •