HD Tactical

What is the correct size drill to drill and tap aluminum for a scope base?

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  • m4a1sof

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    I have an aluminum slide I want to drill and tap for a #6-48 scope base screw. I bought a Williams Gunsight Co. drill and tap set, it comes with a #31 drill but I have read where that is what should be used with a standard steel receiver but you should use a #32 drill for aluminum. Has anyone drilled and tapped an aluminum receiver? If so what size drill should I use. Thanks in advance.
     

    reel_crazy

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    when tapping softer materials like al or brass you would often use a one size smaller drill to achieve 75% versus 50% thread engagement used for steel.. the 32 could potentially give you better results (more holding power) than the 31..

    i think the 31 would work ok..the 32 would as well though it might be harder to tap with out breakage ... note that wd40 works pretty good as a cutting fluid for al..
    rich
     

    m4a1sof

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    Thanks for your reply. I went ahead and used the 32 with no problem, it was still pretty easy to tap. I used WD40 as well. Here is the result:
     

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