Tap n' Die Questions - longish

[haygood@aemail4u.com (Haygood)]

PS:  I find that for a 8mmx1.25 thread, your drill size should be 6.80mm, or 6.9mm as a second choice.  Converting those gives you

0.2677157" and 0.2716527"

(don't gripe about sig. figs, I'm cutting and pasting)

You could go as high as 7.4mm, apparently (0.2913377")

The fractional size in that range is 9/32" (=7.142mm).  The better size, if you have access to Letter sized bits, is size I (=.2720" =6.909").

If you want to be cool like me and have all the bits, order Harbor Freight's 112 piece Titanium coated bit set, which has 1/16" or so to 1/2", Letters A-Z, and numbers 1-60.  

--- T Berk <tberk@mindspring.com> wrote:
>(btw- pls edit out the top text when replying to this, I think the
>Digest folks will certainly appreciate it.)
>
>I picked up a Hydro GTI head some time back, had the mating surface
>flattened and found some time in it's past it had (at least once
>before been a replacement. 
>
>Trouble was it had an exhaust stud broken off just beneath flush and I
>wanted to get the old steel out of the aluminum head before putting my
>motor back together.
>
>I have had poor success (if you can call it that) with those reverse
>thread screw extractor, after all the two different metals have galled
>to each other, what with the heat and all, it's better I think to just
>drill it out and re-thread.
>
>A friend loaned me a Helicoil tap but I realize it doesn't leave
>thread ready for the stud, and I'd rather tap directly, besides I have
>no coils at the moment anyway.
>
>Lucky for me I was able to locate an ala carte M8x1.25 metric tap
>today at Orchard Supply.  :])
>
>So, I know you probably want to go over the basics with me (if you
>would) and fill n the glaring blanks in my knowledge.
>
>- You want to go slow, maybe advancing only 1/4 turn each time. 
>
>- You want to use some lubricating oil, somewhat like cutting oil.
>
>- You want to drill the pilot hole to xxxxx size for a metric 8 by
>1.25 hole.
>
>
>Thx and Keep a Rocc'n.
>TBerk
>Getting back to life, without Meds.
>
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>Scirocco-l@scirocco.org
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