Date: Fri, 29 Aug 2008 11:39:26 -0400
Reply-To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject: Re: Header bolts broken
In-Reply-To: <4d1b79350808280505h5ee3b2b2h29ecd01335dfdf27@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-2"
Taps are available in three tapers, starting, plug, and bottoming. Most
store taps are plug which is OK for most re working. Starting taps really
help with those distorted bolt holes and when doing new work. For Standard
tap drill sizes, you will often need letter or number drills for the sizes
needed between available fractional drills. For example 1/4-20 needs a #7
and 5/16 uses an "F" drill. Use a tap-drill chart to determine the drill
size really needed.
If you want to get really technical, there are also classes of thread fit
and different thread forms. MSC Direct and McMaster-Carr offer more
drills, taps, and dies then you can imagine.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Jim Felder
Sent: Thursday, August 28, 2008 8:05 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Header bolts broken
Chris,
A fine point but maybe worth something to those who need to cut
threads now and again: tapered and "square" (bottoming) taps are made
to be used in pairs. The tapered tap should be used to cut the thread,
with lubricant, going in about an eight of a turn at a time and then
turning back to break the chip with each turn. If the hole is blind,
as is a stud hole, and especially if you want usable thread to the
bottom of the hole, you want to follow with a bottoming tap using the
same turn-and-cut-back procedure.
Also, most people don't know that you can choose the correct drill
size for a tap by subtracting the pitch from the diameter (in SAE or
metric) to get the correct drill diameter for a 75% thread.
Jim
On Wed, Aug 27, 2008 at 8:47 PM, Chris S <szpejankowski@gmail.com> wrote:
> An alternative to helicoils are "step-up" studs - half is 8mm and the
other
> is 10mm. You drill out the old stud, tap the hole out to 10mm, and
install
> the new stud. Make sure you use the proper tap with a square not taper
> end. The square-taper taps will cut a thread to the bottom of the hole.
> Theoretically the 10mm end will be stronger than 8mm as there's more
> thread. You local hardware store such as Ace, believe it or not,
carries
> these magical studs. I had to do this to a couple of exhaust studs on
my
> old 1.9L engine.
>
> On Mon, Aug 25, 2008 at 10:33 PM, Cullen Stewart
<cullberly@vermontel.net>wrote:
>
>> The worst has happened. After very patiently removing the nuts and
bolts on
>> my wbx I twisted 2 off and still have 1 to go. They are flush with the
head
>> and have nothing to grab onto. What are my options with out removing
the
>> head. They are obviously not grade 5 or 8, but good old garbage grade 2
>> considering they twisted off with a minimum amount off force. Is it
possible
>> to helicoil these while in the van?
>>
>
>
>
> --
> Chris S.
> "Jeszcze Polska Nie Zginęła"
>
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