Results 1 to 7 of 7

Thread: Specific question on tapping aluminum what pitch tap to use?

  1. #1
    Registered
    Join Date
    Jan 2011
    Location
    USA
    Posts
    33
    Downloads
    0
    Uploads
    0

    Arrow Specific question on tapping aluminum what pitch tap to use?

    Ok I am going to hand tap some 1/4" diameter holes into 6061 aluminum they will also be about 1/4" to at most 5/16" deep .. I will be using 1/4" steel set screws in them to hold some plastic parts.


    Now my question is what thread pitch is the strongest for this ... coarse, medium or fine?

    Oh yeah and if you could explain why, it may make it easier for me to decide in the future for other projects when tapping aluminum, so I won't have to bug people lol.


    Thanks for any replies they will be really appreciated

    Similar Threads:


  2. #2
    Registered
    Join Date
    Oct 2005
    Location
    US
    Posts
    1237
    Downloads
    0
    Uploads
    0

    Default

    There is no medium. You get two flavors. Coarse and fine. Course threads 1/4-20 are strongest in aluminum and for aluminum, you want at least 3/8" of full thread engagement. Why is course better than fine? I don't know the physics/engineering answer, it just is.



  3. #3
    Registered
    Join Date
    Jan 2007
    Location
    USA
    Posts
    355
    Downloads
    0
    Uploads
    0

    Default

    A course pitch thread is a bad choice in this application. Use a fine pitch for tapping thin material. You'll have more thread engagement.

    Use a 1/4-28 uncoated spiral flute tap, and some cutting oil.

    btw, fine pitch threads actually have greater holding force than the same diameter course thread.

    Fine Threads vs Course Threads

    Diplomacy is the art of saying "Nice doggie" until you can find a rock. - Will Rogers


  4. #4
    Gold Member
    Join Date
    Jul 2005
    Location
    Canada
    Posts
    12146
    Downloads
    0
    Uploads
    0

    Default

    1/4" to 5/16" length of thread for 1/4" does not qualify as thin material, at least not the way I look at 'thin'.

    I have been making my own product line of aluminum parts for over twenty years and have fooled around extensively with different threads. My experience is that coarse is definitely the best in all sizes up to 1/2". You get a higher strip-out strength and a longer life under frequent loosen and re-tighten with coarse.

    You can get a higher holding force, at the same torque with fine compared to coarse, but it is my experience that you can take coarse threads to a higher torque and a higher holding force, before failure.

    An open mind is a virtue...so long as all the common sense has not leaked out.


  5. #5
    Registered
    Join Date
    Jan 2011
    Location
    USA
    Posts
    33
    Downloads
    0
    Uploads
    0

    Default

    Thanks for the replies, see I looked for this over the internet and as you can see above this is what I found, people really have differing opinions on this ... its hard for me to find a fine thread in exactly what I want so i'll try the coarse first and if thats not working I will try the other, thanks for the replies they are really interesting ... too me anyway ... i'll report back in case anyone else searches something like this.



  6. #6
    Registered
    Join Date
    Jan 2011
    Location
    usa
    Posts
    7
    Downloads
    0
    Uploads
    0

    Cool

    another way to get stronger threads, if that is important, is to use a heli-coil. you tap the hole larger (with the helicoil kit), and install the insert. now you have the strength of around a 3/8 dia thread and still use the 1/4-20 bolt. also, if you can't helicoil, then form threading is stronger than cut threading, with a form tap you are displacing the metal in the hole which makes it much harder to pull the threads out with the bolt. great for aluminum, it takes a larger tap drill for a form tap than a cut tap, be sure to get the correct size.



  7. #7
    Registered
    Join Date
    Mar 2008
    Location
    USA
    Posts
    236
    Downloads
    0
    Uploads
    0

    Default

    What ever tap you use follow up with a bottom going (flat bottom) tap to get the most depth. You can make one yourselves by grinding an old tap flat and backing off the first thread. You can also ask any toolmaker to do it for you. That way your set screws will go all the way to the bottom.



Tags for this Thread

Posting Permissions

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


About CNCzone.com

    We are the largest and most active discussion forum from DIY CNC Machines to the Cad/Cam software to run them. The site is 100% free to join and use, so join today!

Follow us on

Facebook Dribbble RSS Feed