Miller Electric

Welding Discussion Forums

Home » Resources » Communities » Welding Discussion Forums
 
Miller Welding Discussion Forums - Powered by vBulletin

Results 1 to 8 of 8

Thread: Need Advice

  1. #1
    Join Date
    Dec 2008
    Location
    Arizona
    Posts
    812

    Question Need Advice

    I need to attach a pair of 3/8" aluminum plates (about 3" x 6" ) to some 16ga steel. The plates have a decorative ball mill on them and need to line up in a very close alignment with each other. I was thinking of trying to drill them on the edge and insert a roll pin for the alignment, but I'm open to other ideas. On the back side of the aluminum I need to attach some machine screws (studs) so I can put nuts on them after they pass through the steel. Not sure how to attach anything to the aluminum as it's too thin to drill and tap and if I could find any aluminum screws, welding them might distort the ball mill design on the front and would certainly F up the threads. I was thinking of possibly using some JB weld compound to attach some machine screws to the aluminum.
    Any ideas? Thanks

    EDIT: The AL is only 3/16" not 3/8"......
    Last edited by nocheepgas; 05-25-2009 at 09:44 PM.
    Miller Syncrowave 200
    Homemade Water Cooler
    130XP MIG
    Spectrum 375
    60 year old Logan Lathe
    Select Machine and Tool Mill
    More stuff than I can keep track of..

  2. #2
    Join Date
    Oct 2004
    Location
    Edmonton, Alberta
    Posts
    7,471

    Default

    Well, 3/8" you've got alot of meat there to tap. though bonding it to a mild steel plate without an insulator makes for immediate corriosion between the 2 disimular metals.

  3. #3
    Join Date
    Jan 2006
    Location
    PA
    Posts
    110

    Default

    As cruizer said 3/8 is a decent thickness to work with. I think what I would do is get a couple of #7 drills and grind one off flat. I would drill carefully to a depth of 5/16, then drill again with the ground off bit to the same depth, giving a flat bottomed hole. Tap this with a -20 bottom tap which should make at least of threads. McMaster and probably others sell aluminum studs (example part# 93225A869). I would epoxy these studs in and these would make the mounting bolts.
    You can also get plastic or metal dowel type alignment pins from the same source. (Plastic example part# 98703A740).
    There is still the dissimilar metal problem.

  4. #4
    Join Date
    Dec 2008
    Location
    Arizona
    Posts
    812

    Default

    Not too worried about the interaction of dissimilar metals, The aluminum will be clear anodized and the steel painted. But reading your responses made me realize my mistake, material thickness is 3/16".
    Miller Syncrowave 200
    Homemade Water Cooler
    130XP MIG
    Spectrum 375
    60 year old Logan Lathe
    Select Machine and Tool Mill
    More stuff than I can keep track of..

  5. #5
    Join Date
    Feb 2008
    Posts
    835

    Default

    Quote Originally Posted by nocheepgas View Post
    Not sure how to attach anything to the aluminum as it's too thin to drill and tap
    I did some investigating in Machinery's Handbook (28th Ed.) and found the following on page 1443:

    ...the length of engagement of mating threads should be sufficient to carry the full load necessary to break the screw without the threads stripping.

    If mating internal and external threads are manufactured of material having equal tensile strengths, then to prevent stripping of the external thread, the length of engagement should be no less than that given by Formula (1):

    Le= 2xAt/[3.1416 Knmax[1/2 + .57735n (Esmin-Knmax)] ]...
    So I made a spread sheat and entered all the dimensions of common class 2A threads, fine and coarse, and found the minimum length of engagement Le for all of them. Any screw with a Le less than .1875" (3/16") can be used without stripping (provided it's a similar grade of aluminum). Here's the results:

    screw___thread___Min Engagement__AT_________Kn max _____Es min
    size_____TPI_____inches__________sq. in.______inches______inches
    4_______40_____0.087561624_____0.00604_____0.0939_ ____0.0925
    4_______48_____0.094257374_____0.00661_____0.0968_ ____0.0954
    6_______32_____0.101150431_____0.00909_____0.1140_ ____0.1141
    6_______40_____0.111695325_____0.01015_____0.1190_ ____0.1184
    8_______32_____0.124112652_____0.01400_____0.1390_ ____0.1399
    8_______36_____0.130004293_____0.01474_____0.1420_ ____0.1424
    10______24_____0.133231699_____0.01750_____0.1560_ ____0.1586
    10______32_____0.145589954_____0.02000_____0.1640_ ____0.1658
    12______24_____0.155182487_____0.02420_____0.1810_ ____0.1845
    12______28_____0.162915746_____0.02580_____0.1860_ ____0.1886
    1/4_____20_____0.172846497_____0.03180_____0.2070___ __0.2127
    1/4_____28_____0.194909137_____0.03640_____0.2200___ __0.2225
    5/16____18_____0.223025271_____0.05240_____0.2650___ __0.2712
    5/16____24_____0.242414386_____0.05800_____0.2770___ __0.2806
    So anything up to a 1/4x20 UNC can be used. One thing that suprised me is that I thought for sure a 1/4x28 UNF needed less engagement than a coarse screw. According to the equation, I was wrong.

    Anyway, if you can carefully drill it without breaking through (say with a drill press and a 2 flute end mill, you could tap it to, say, 10x24. And keep in mind that the Le calculated gives the depth required for the full breaking strength of the screw. Depending on how many screws you use, you may not need anywhere close to the breaking strength. So you might even drill 75% depth and tap to 60% depth.
    Last edited by Bodybagger; 05-26-2009 at 04:01 AM.
    Equipped with red and blue... and red and green!
    80% of failures are from 20% of causes
    Never compromise your principles today in the name of furthering them in the future.
    "All I ever wanted was an honest week's pay for an honest day's work." -Sgt. Bilko
    "We are generally better persuaded by reasons we discover ourselves than by those given to us by others." -Pascal
    "Since we cannot know all that there is to be known about anything, we ought to know a little about everything." -Pascal

  6. #6
    Join Date
    Jul 2006
    Posts
    1,508

    Default

    Quote Originally Posted by nocheepgas View Post
    Not too worried about the interaction of dissimilar metals
    If you find your self in a situation where you are, swab on a layer of this to each side to be bonded. Clamp them together according to time limit.
    Attached Images Attached Images

  7. #7
    Join Date
    Oct 2004
    Location
    Edmonton, Alberta
    Posts
    7,471

    Default

    Besides you could always use rivets, or aircraft riv nuts

  8. #8
    Join Date
    Dec 2008
    Location
    Arizona
    Posts
    812

    Default

    Quote Originally Posted by Sonora Iron View Post
    If you find your self in a situation where you are, swab on a layer of this to each side to be bonded. Clamp them together according to time limit.
    Quote Originally Posted by cruizer View Post
    Besides you could always use rivets, or aircraft riv nuts
    The assembly needs to be removeable, and I didn't want anything showing on the face of the AL otherwise I'd just use a machine screw through both pieces of metal.

    Bodybagger: Thanks for the info. the problem I see is the hole depth would be 1/8", and that does not seem to be enough room to get a tap started. Thinking of seeing if I can find a T-slot mill that's only 1/16" and sliding screws in from the ends???
    Miller Syncrowave 200
    Homemade Water Cooler
    130XP MIG
    Spectrum 375
    60 year old Logan Lathe
    Select Machine and Tool Mill
    More stuff than I can keep track of..

Posting Permissions

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

Warning: Non-static method PhpQuickProfiler::getMicroTime() should not be called statically in /mnt/stor3-wc1-dfw1/357822/357839/www.millerwelds.com/web/content/lib/pqp/classes/Console.php on line 77

Warning: Non-static method PhpQuickProfiler::getMicroTime() should not be called statically in /mnt/stor3-wc1-dfw1/357822/357839/www.millerwelds.com/web/content/lib/pqp/classes/Console.php on line 77

Warning: Non-static method PhpQuickProfiler::getMicroTime() should not be called statically in /mnt/stor3-wc1-dfw1/357822/357839/www.millerwelds.com/web/content/lib/pqp/classes/Console.php on line 77

Warning: Non-static method PhpQuickProfiler::getMicroTime() should not be called statically in /mnt/stor3-wc1-dfw1/357822/357839/www.millerwelds.com/web/content/lib/pqp/classes/Console.php on line 77

Warning: Non-static method PhpQuickProfiler::getMicroTime() should not be called statically in /mnt/stor3-wc1-dfw1/357822/357839/www.millerwelds.com/web/content/lib/pqp/classes/Console.php on line 77

Warning: Non-static method PhpQuickProfiler::getMicroTime() should not be called statically in /mnt/stor3-wc1-dfw1/357822/357839/www.millerwelds.com/web/content/lib/pqp/classes/Console.php on line 77

Warning: Non-static method PhpQuickProfiler::getMicroTime() should not be called statically in /mnt/stor3-wc1-dfw1/357822/357839/www.millerwelds.com/web/content/lib/pqp/classes/Console.php on line 77

Warning: Non-static method PhpQuickProfiler::getMicroTime() should not be called statically in /mnt/stor3-wc1-dfw1/357822/357839/www.millerwelds.com/web/content/lib/pqp/classes/Console.php on line 77

Warning: Function split() is deprecated in /mnt/stor3-wc1-dfw1/357822/357839/www.millerwelds.com/web/content/lib/footer.inc.php on line 62

Welding Projects

Special Offers: See the latest Miller deals and promotions.

Warning: Function split() is deprecated in /mnt/stor3-wc1-dfw1/357822/357839/www.millerwelds.com/web/content/lib/footer.inc.php on line 137