Page 1 of 3 123 LastLast
Results 1 to 15 of 35
  1. #1
    Join Date
    May 2020
    Location
    australia
    Age
    62
    Posts
    33

    Default Taping a hole metric / whit

    20211002_155216.jpg

    I am lost for understanding what to pick for tapping a hole that is 1/2 inch 20 tpi. My set seems to serve bother system. But then it seems to be only metric. The second tap from the right seems to be the right one 1/2 NF20. But how could a tap serve both metric and whitworth system. I guess that it is M14x 2.0 pitch.

    How to read it correctly?

  2. #2
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,436

    Default

    Hi Dave,

    The lettering on the case seems very confusing ! It might be that the set contains both metric and imperial taps.

    The clue would be to read the size engraved on the tap itself. Often both the tap size and the tapping drill size are engraved.

    1/2" inch by 20 TPI would be a Whitworth or UNF thread, 13 mm would be the closest metric thread but it isn't a standard size.

    HTH.
    Best Regards:
    Baron J.

  3. #3
    Join Date
    Oct 2009
    Location
    Upwey VIC
    Posts
    186

    Default

    I have a metric set and a separate UN set exactly the same (45 piece each from H&F), and they use the same case to carry each set.
    If it's a metric tap set, then the metric tap sizes will be the ones to guide your selection, otherwise use the UN sizes.

    Andrew.

  4. #4
    Join Date
    Jul 2008
    Location
    near Warragul, Victoria
    Posts
    3,718

    Default

    Quote Originally Posted by BaronJ View Post

    1/2" inch by 20 TPI would be a Whitworth or UNF thread,

    HTH.
    hi I think

    1/2" BSW is 12 TPI

    1/2" BSF is 16 TPI

  5. #5
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,436

    Default

    Quote Originally Posted by morrisman View Post
    hi I think

    1/2" BSW is 12 TPI

    1/2" BSF is 16 TPI
    Thanks for your post.

    Yes those are correct ! However 1/2" x 20 is a 55 degree thread angle, the UNF is also 55 degrees with a truncated crest.

    EDIT: I made an error here, the thread angle should be 60 degrees. I misread the table I referenced. Sorry !
    Best Regards:
    Baron J.

  6. #6
    Join Date
    Aug 2007
    Location
    Saskatoon, Saskatchewan, Canada
    Posts
    292

    Default

    Beg to differ Baron. UNF and UNC are 60º as are metric threads.

    Pete

  7. #7
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,436

    Default

    Quote Originally Posted by QC Inspector View Post
    Beg to differ Baron. UNF and UNC are 60º as are metric threads.

    Pete
    Hi Pete,

    Thankyou for your post correcting my error !

    Yes I should have checked that I was looking at the right line of the table I was referencing. The table ran off the right side of the screen and of course when I scrolled it across I read the wrong line.

    I do apologise for my mistake, I consider my wrist slapped.
    Best Regards:
    Baron J.

  8. #8
    Join Date
    Jan 2004
    Location
    Mackay North Qld
    Posts
    6,446

    Default

    Hi davewok

    Its easy to get confused but once you understand how the system works it becomes easier.
    I fancy I spotted an N printed on the shank of the tap at the edge.

    That will probably read NF( National Fine ) - some taps it may read UNF - Unified National Fine. the coarse threads are usually in UNC Unified national Coarse

    https://www.aimsindustrial.com.au/as...Size-Chart.pdf

    The card covers many types of threads - Imperial and Metric. You will find what you seek in there. It also recommends best tapping drill diameters.

    You might like to save the chart as its a very handy. Often the Sutton card card is a giveaway at machine tooling outlets and bolt shops,sometimes bearing shops.


    A thread pitch gauge -if your tap set doesn't have one.- is a handy tool.
    https://www.totaltools.com.au/thread...gauge-set-2-pc


    Grahame

  9. #9
    Join Date
    Aug 2008
    Location
    Charlestown NSW
    Age
    65
    Posts
    1,669

    Default

    Following on from what Grahame said, I'd suggest you print out a thread tapping drill chart. (Unfortunately the Sutton one looks like it would not be very printer friendly with all that blue background but there are heaps out there to chose from) and stick it up in your workshop somewhere. Also a decimal/imperial/metric conversion chart.
    Some metric threads require a tapping drill that will not be a whole or whole + 1/2 size ie the suggested size might be 5.2mm. You can quite often get close with an imperial drill. Which is where the decimal/imperial/metric conversion chart will come in very handy.
    If you have access to a laminator, then laminating the charts will make them more workshop proof.
    regards
    peter

  10. #10
    Join Date
    Nov 2007
    Location
    melbourne australia
    Posts
    3,228

    Default

    Here's a metric tapping drill chart I made because I struggled to read the tiny text in the Black Book.
    The green columns are for the commonly recommended thread engagements and have the same figures you'll find in most tapping charts. But as bollie7 said, you often won't have the exact drill size. So I created columns for other thread engagement percentages. This allows you to see whether a drill bit in your set will give an acceptable thread engagement.

    I can't recall exactly, but I believe the 70% and 60% figures are based upon three threads engaged. If the female thread is deeper than three threads you can use a lower engagement figure (i.e. a larger tapping drill) and still have adequate strength. For tapping difficult materials like SS and titanium I recommend using a lower engagement figure anyway.
    Attached Files Attached Files
    Chris

  11. #11
    Join Date
    Dec 2007
    Location
    Adelaide
    Posts
    574

    Default

    I'm with mahgnia on this one - at the time I purchased a tap and die set I could have had either a metric fine/coarse set or a UNC/UNF set - both sets used the same plastic case marked with both UNC/UNF and Metric fine/coarse, my set has only metric taps and dies.

  12. #12
    Join Date
    Feb 2009
    Location
    moonbi nsw Aus
    Age
    69
    Posts
    364

    Default

    The method I use to find a drill size for tapping is; I use a nut of the thread I want to cut and poke a drill through the hole in the nut. I bought a set of metric drills that are 0.5mm steps apart and choose a drill that way. I never seem to pick a drill that is tight in the hole in the nut so I go for the looser one, drill the hole then cut the thread. I figure that a loose drill in the hole will give me deep threads in the project. I also figure that this method works with any tapping job, WW or UNC, UNF and Metric
    Just do it!

    Kind regards Rod

  13. #13
    Join Date
    May 2020
    Location
    australia
    Age
    62
    Posts
    33

    Default

    my set was from machinery warehouse. I think that the same box is used for Whitworth and metric. The lettering on the taps only say metric. The whole set should be metric. I would not think that I want to deal with imperial systems when located in Australia.

  14. #14
    Join Date
    May 2020
    Location
    australia
    Age
    62
    Posts
    33

    Default

    It is frustrating that I want to tap a hole to fit a nozzle. it seems plumbing fixtures are commonly used with imperial system.

  15. #15
    Join Date
    Nov 2007
    Location
    melbourne australia
    Posts
    3,228

    Default

    Quote Originally Posted by davekwok View Post
    It is frustrating that I want to tap a hole to fit a nozzle. it seems plumbing fixtures are commonly used with imperial system.
    Are you sure you want ½” x 20 tpi? That’s ½” UNF. Most plumbing fittings in Oz are BSP. And I hope I’m not preaching to the choir, but for ½” BSP, the ½” relates to the size of the pipe, not the thread on the fitting. The thread is about 21mm. Apologies if you already knew that.
    Chris

Page 1 of 3 123 LastLast

Similar Threads

  1. 1/16 and 3/32 whit taps
    By kenny_10 in forum METALWORK GENERAL
    Replies: 4
    Last Post: 1st Oct 2018, 10:40 PM
  2. 1/16 and 3/32 whit taps
    By kenny_10 in forum WANTED TO BUY
    Replies: 2
    Last Post: 1st Oct 2018, 05:11 PM
  3. Taping machine /drill press
    By stix012 in forum EBAY, GUMTREE, and other off forum sales sites
    Replies: 1
    Last Post: 1st Mar 2017, 02:51 PM
  4. The hole is too big
    By neksmerj in forum METALWORK GENERAL
    Replies: 15
    Last Post: 21st Jul 2007, 10:29 PM
  5. WTB metric Micrometers
    By sailingamerican in forum METALWORK GENERAL
    Replies: 7
    Last Post: 1st Nov 2005, 02:53 PM

Posting Permissions

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