Author Topic: TAP & DRILL SIZE  (Read 10822 times)

0 Members and 1 Guest are viewing this topic.

askimball (Doc)

  • Active Members
  • ***
  • Posts: 471
  • Cell - 318-518-0829 Central Time
    • View Profile
TAP & DRILL SIZE
« on: August 09, 2011, 11:30:12 pm »
QUESTION.. :D

For the Star Die/s Thread Size >  11/16 x 24 TPI  :-[

Is the Drill Size for the 11/16x24 Tap  >  21/32.. ::) ???
« Last Edit: August 11, 2011, 09:40:50 pm by askimball (Doc) »
Doc - I.Y.A.A.Y.A.S.
Retired Police Captain

maurilew

  • Active Members
  • ***
  • Posts: 33
    • View Profile
Re: TAP & DRILL SIZE
« Reply #1 on: August 10, 2011, 12:59:27 am »
my book says 41/64 alum    21/32 steel
« Last Edit: August 11, 2011, 09:41:17 pm by askimball (Doc) »
maurilew

askimball (Doc)

  • Active Members
  • ***
  • Posts: 471
  • Cell - 318-518-0829 Central Time
    • View Profile
Re: TAP & DRILL SIZE
« Reply #2 on: August 10, 2011, 01:46:04 am »
10-4 ;D
« Last Edit: August 11, 2011, 09:41:39 pm by askimball (Doc) »
Doc - I.Y.A.A.Y.A.S.
Retired Police Captain

rbwillnj

  • Global Moderator
  • ****
  • Posts: 1216
    • View Profile
    • Star Machine Works
Re: TAP & DRILL SIZE
« Reply #3 on: August 10, 2011, 09:23:16 am »
I use 41/64 even for Steel (Cast Iron?).  According to the book, that yields a 90% thread.
« Last Edit: August 11, 2011, 09:42:03 pm by askimball (Doc) »
Star Machine Works
Star, the original blue Press.  Made by machinist, not machines.
www.StarMachineWorks.com

askimball (Doc)

  • Active Members
  • ***
  • Posts: 471
  • Cell - 318-518-0829 Central Time
    • View Profile
Re: TAP & DRILL SIZE
« Reply #4 on: August 10, 2011, 01:13:08 pm »
Bruce
The Chart I have Shows 75% Thread  :-\

http://www.shender4.com/thread_chart.htm
« Last Edit: August 11, 2011, 09:42:26 pm by askimball (Doc) »
Doc - I.Y.A.A.Y.A.S.
Retired Police Captain

fc60

  • Active Members
  • ***
  • Posts: 480
    • View Profile
Re: TAP & DRILL SIZE
« Reply #5 on: August 10, 2011, 01:23:39 pm »
Greetings,

The 11/16-24 tapped hole in the tool head is precisely located. Simply drilling may not leave the hole in the correct location. To be done properly, it should be drilled undersize then bored to 0.650".

The 0.650" is also a 16.5mm drill.

You need a 0.650" hole minimum to clear the 9/16" lock nut on the die. Otherwise, you will not be able to insert the seating die assembly with the nut attached.

Cheers,

Dave
« Last Edit: August 11, 2011, 09:42:49 pm by askimball (Doc) »

askimball (Doc)

  • Active Members
  • ***
  • Posts: 471
  • Cell - 318-518-0829 Central Time
    • View Profile
Re: TAP & DRILL SIZE
« Reply #6 on: August 10, 2011, 01:54:41 pm »
Thanks to rbwillnj  &  fc60   :)
« Last Edit: August 11, 2011, 09:43:17 pm by askimball (Doc) »
Doc - I.Y.A.A.Y.A.S.
Retired Police Captain

rbwillnj

  • Global Moderator
  • ****
  • Posts: 1216
    • View Profile
    • Star Machine Works
Re: TAP & DRILL SIZE
« Reply #7 on: August 10, 2011, 03:22:31 pm »
Dave is correct about making sure the hole is located correctly.  It should be fully indexed to determine the center of the hole.   Holding the tool head in the proper position during drilling to assure the hole is perpendicular to the flange of the tool head is also important.  You can't just clamp the tool head in a vice and drill away.  I have a jig to hold the tool head and mount it in the milling machine.  Then you have to find the exact center of the 3/8" hole before drilling and tapping.  This is not a job that can be done properly in a drill press.

« Last Edit: August 11, 2011, 09:43:41 pm by askimball (Doc) »
Star Machine Works
Star, the original blue Press.  Made by machinist, not machines.
www.StarMachineWorks.com

askimball (Doc)

  • Active Members
  • ***
  • Posts: 471
  • Cell - 318-518-0829 Central Time
    • View Profile
Re: TAP & DRILL SIZE
« Reply #8 on: August 10, 2011, 06:18:09 pm »
Thanks Guys for all the 'Heads Up'

I have a Friend that has a HUGE Bridgeport Mill.. His vise is large enough to set the head down flat... He first lined up the hole with
a 3/8 drill bit, then drilled it, not sure what size drill he used...Measeured it with a inside type mike thing, checked it and took a
reamer & took off a little more, tapped it.....Perfect fit.....Charged me $10.00.
« Last Edit: August 11, 2011, 09:44:03 pm by askimball (Doc) »
Doc - I.Y.A.A.Y.A.S.
Retired Police Captain

LeupoldMRK4

  • Active Members
  • ***
  • Posts: 99
    • View Profile
Re: TAP & DRILL SIZE
« Reply #9 on: August 10, 2011, 09:26:17 pm »
D-1/N=Tap drill size
diameter minus.........1 divided by the number of threads.(pitch)
This is the formula I use in the shop.

« Last Edit: August 11, 2011, 09:44:29 pm by askimball (Doc) »