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What hole size for 1/4" screw?

asopasop Member Posts: 9,004 ✭✭✭✭
edited November 2016 in General Discussion
I want to tap some skinny alum. to take a 1/4"-28 screw. Bit size 15/64" or maybe 7/32"?? Thanks
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Comments

  • discusdaddiscusdad Member Posts: 11,427 ✭✭✭✭
    edited November -1
    wd40 makes a great thread cutting lubricant on aluminum
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  • iceracerxiceracerx Member Posts: 8,860 ✭✭✭
    edited November -1
    You posted 'skinny' aluminum. The MINIMUM thread engagement for non cast aluminum alloys is 1 1/2 to 2 times the fastener diameter.

    So, you need at least 3/8" PLUS material for a counter sink as a MINIMUM thickness. 1/2" PLUS would be better.

    I've had better results with paraffin as a lube for thread cutting in alloys.

    Edit: apparently too many years working in metric has made my old inch mind mush.

    Thanks again Bob.
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  • AlpineAlpine Member Posts: 15,092 ✭✭✭✭
    edited November -1
    If it's sheet metal: machine screw and nut. Nothing else will last.

    Pop rivet is next best option.
    ?The problem with socialism is that you eventually run out of other people's money.?
    Margaret Thatcher

    "There are three kinds of lies: lies, damned lies and statistics."
    Mark Twain
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  • cbxjeffcbxjeff Member Posts: 17,624 ✭✭✭✭
    edited November -1
    Right Alpine. If you don't have a 4-5 thread engagement (depending on load) go with plan B.
    It's too late for me, save yourself.
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  • Mr. PerfectMr. Perfect Member, Moderator Posts: 66,404 ******
    edited November -1
    While a 7/32" drill will work fine, the proper tap drill for a 1/4-28 is a Number 3 drill, which is 0.2130 dia.

    As others have said, drill a clearance hole and use a nut, in sheet metal. Or use a sheet-metal insert, such as a PEM.

    Gun oil or 30wt. is my preference for lube, if you don't have tapping fluid.
    Some will die in hot pursuit
    And fiery auto crashes
    Some will die in hot pursuit
    While sifting through my ashes
    Some will fall in love with life
    And drink it from a fountain
    That is pouring like an avalanche
    Coming down the mountain
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  • OakieOakie Member Posts: 40,521 ✭✭✭✭
    edited November -1
    7/8". It will drop right in for ya all[;)]Don
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  • CaptFunCaptFun Member Posts: 16,678 ✭✭✭
    edited November -1
    quote:Originally posted by Oakie
    7/8". It will drop right in for ya all[;)]Don


    You can always machine it smaller to make a worls class presentation....
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  • woodshed87woodshed87 Member Posts: 23,478 ✭✭✭
    edited November -1
    quote:Originally posted by CaptFun
    quote:Originally posted by Oakie
    7/8". It will drop right in for ya all[;)]Don


    You can always machine it smaller to make a worls class presentation....

    HEY HEY HEY Thats Enough Now [:o)]
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  • cbxjeffcbxjeff Member Posts: 17,624 ✭✭✭✭
    edited November -1
    Sometime I miss that guy, 87!
    It's too late for me, save yourself.
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  • Tailgunner1954Tailgunner1954 Member Posts: 7,734 ✭✭
    edited November -1
    quote:Originally posted by iceracerx
    You posted 'skinny' aluminum. The MINIMUM thread engagement for non cast aluminum alloys is 1 1/2 to 2 times the fastener diameter.

    So, you need at least 5/8" PLUS material for a counter sink as a MINIMUM thickness. 1/2" PLUS would be better.

    I've had better results with paraffin as a lube for thread cutting in alloys.



    I think you mean 3/8" (.375) minimum [:D]
    PS:
    You good with a media mail delivery? Been reading the Phil Sharpe I'm planning to loan you, veeery interesting (but NOT stupid)
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  • 35 Whelen35 Whelen Member Posts: 14,307 ✭✭✭
    edited November -1
    quote:Originally posted by CaptFun
    quote:Originally posted by Oakie
    7/8". It will drop right in for ya all[;)]Don


    You can always machine it smaller to make a worls class presentation....



    Pretty sure the neighbors four doors down just heard me laugh.[:D]
    An unarmed man can only flee from evil, and evil is not overcome by fleeing from it.
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  • pulsarncpulsarnc Member Posts: 6,509 ✭✭✭✭
    edited November -1
    if it strips out a little JB weld will fix it right up
    cry Havoc and let slip  the dogs of war..... 
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  • Horse Plains DrifterHorse Plains Drifter Forums Admins, Member, Moderator Posts: 40,164 ***** Forums Admin
    edited November -1
    quote:Originally posted by CaptFun
    quote:Originally posted by Oakie
    7/8". It will drop right in for ya all[;)]Don


    You can always machine it smaller to make a worls class presentation....
    You bet, and while you're at it, take your screw gun and put some record book antlers on that puppy!!
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  • asphalt cowboyasphalt cowboy Member Posts: 8,904 ✭✭✭✭
    edited November -1
    quote:Originally posted by Oakie
    7/8". It will drop right in for ya all[;)]Don


    No, No, No! 3/16ths and tap it with a BFH.[:p]
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  • groundhog244groundhog244 Member Posts: 55 ✭✭
    edited November -1
    Why don't you try a 1/4x32 tap if more thread is needed
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  • Mr. PerfectMr. Perfect Member, Moderator Posts: 66,404 ******
    edited November -1
    quote:Originally posted by CaptFun
    quote:Originally posted by Oakie
    7/8". It will drop right in for ya all[;)]Don


    You can always machine it smaller to make a worls class presentation....
    Joe? Is that you?
    Some will die in hot pursuit
    And fiery auto crashes
    Some will die in hot pursuit
    While sifting through my ashes
    Some will fall in love with life
    And drink it from a fountain
    That is pouring like an avalanche
    Coming down the mountain
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  • FrancFFrancF Member Posts: 35,279 ✭✭✭
    edited November -1
    Self Taping fine thread sheet metal screws. If they don't start. use a #20 drill bit as a pilot hole. For Alum around 16ga to 1/8' 10-32 will be a safe bet to tap (That's what I would do).
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  • grumpygygrumpygy Member Posts: 48,464 ✭✭✭
    edited November -1
    quote:Originally posted by discusdad
    wd40 makes a great thread cutting lubricant on aluminum


    Wax is much better. or this stuff if you can find it..

    79045-2.jpg
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  • asopasop Member Posts: 9,004 ✭✭✭✭
    edited November -1
    Just simply a wonderful site we have here. Full of informed data & a lot of humor to boot[:0]
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  • rongrong Member Posts: 8,459
    edited November -1
    Pem Nut
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