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Posted by Wayne on April 25, 2008, 7:44 pm
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Since I'm going to be tapping into a big buck part and don't
really have any experience tapping cast iron, I figure I'll
just ask a few stupid questions.
I'm tapping a 1/4 NPT hole into the exhaust section of a
turbocharger. An EGT sensor will be put in there. The part
is cast iron, about 1/4 thick. The directions are to remove
the turbocharger, drill a 7/16 hole, then tap. The part
that screws into the hole has a shoulder which is
supposed to rest against the turbocharger.
Alternately they say I can drill and tap the hole
with the engine running. Once the drill bit goes
goes through, the exhaust pressure is supposed to
push any particles out. When drilling cast iron
they say it is supposed to turn to dust. I'd
be drilling from the top down.
I have to get a tap since I don't have one that size.
I assume HSS will be ok?
It's supposed to be a pain to get the turbocharger out.
But if it was out, I could finish the hole with a
7/16 HSS end mill. That I think, would give me a more
round hole than drilling by hand under the hood.
So I would think it would seal better that way.
Any thoughts?
Wayne D.
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Posted by David R Brooks on April 25, 2008, 7:57 pm
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Wayne wrote:
> Since I'm going to be tapping into a big buck part and don't
> really have any experience tapping cast iron, I figure I'll
> just ask a few stupid questions.
>
> I'm tapping a 1/4 NPT hole into the exhaust section of a
> turbocharger. An EGT sensor will be put in there. The part
> is cast iron, about 1/4 thick. The directions are to remove
> the turbocharger, drill a 7/16 hole, then tap. The part
> that screws into the hole has a shoulder which is
> supposed to rest against the turbocharger.
>
> Alternately they say I can drill and tap the hole
> with the engine running. Once the drill bit goes
> goes through, the exhaust pressure is supposed to
> push any particles out. When drilling cast iron
> they say it is supposed to turn to dust. I'd
> be drilling from the top down.
>
> I have to get a tap since I don't have one that size.
> I assume HSS will be ok?
>
> It's supposed to be a pain to get the turbocharger out.
> But if it was out, I could finish the hole with a
> 7/16 HSS end mill. That I think, would give me a more
> round hole than drilling by hand under the hood.
> So I would think it would seal better that way.
>
If the engine is running, I'd expect the turbo to be hot enough to dull
your tools, apart from being most hazardous to work on.
My employer does engine conversions: we left an engine running overnight
on the dynamometer: someone slipped in & took a picture in the dark. The
turbo & exhaust manifold were red hot! I still have a copy of that photo.
Me, I'd bit the bullet & take thing off, work on it at the bench like a
gentleman.
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Posted by Wayne on April 25, 2008, 8:22 pm
Please log in for more thread options wrote:
> Wayne wrote:
>> Since I'm going to be tapping into a big buck part and don't
>> really have any experience tapping cast iron, I figure I'll
>> just ask a few stupid questions.
>> I'm tapping a 1/4 NPT hole into the exhaust section of a
>> turbocharger. An EGT sensor will be put in there. The part
>> is cast iron, about 1/4 thick. The directions are to remove
>> the turbocharger, drill a 7/16 hole, then tap. The part
>> that screws into the hole has a shoulder which is
>> supposed to rest against the turbocharger.
>> Alternately they say I can drill and tap the hole
>> with the engine running. Once the drill bit goes
>> goes through, the exhaust pressure is supposed to
>> push any particles out. When drilling cast iron
>> they say it is supposed to turn to dust. I'd
>> be drilling from the top down.
>> I have to get a tap since I don't have one that size.
>> I assume HSS will be ok?
>> It's supposed to be a pain to get the turbocharger out.
>> But if it was out, I could finish the hole with a
>> 7/16 HSS end mill. That I think, would give me a more
>> round hole than drilling by hand under the hood.
>> So I would think it would seal better that way.
>>
> If the engine is running, I'd expect the turbo to be hot enough to dull
> your tools, apart from being most hazardous to work on.
> My employer does engine conversions: we left an engine running overnight
> on the dynamometer: someone slipped in & took a picture in the dark. The
> turbo & exhaust manifold were red hot! I still have a copy of that photo.
> Me, I'd bit the bullet & take thing off, work on it at the bench like a
> gentleman.
I think I'd feel most comfortable with it removed. I'd just have to work
up the patience (oxymoron) to do it.
Wayne D.
--
Wayne D.
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Posted by Pete C. on April 25, 2008, 8:50 pm
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Wayne wrote:
>
> wrote:
>
> > Wayne wrote:
> >> Since I'm going to be tapping into a big buck part and don't
> >> really have any experience tapping cast iron, I figure I'll
> >> just ask a few stupid questions.
> >> I'm tapping a 1/4 NPT hole into the exhaust section of a
> >> turbocharger. An EGT sensor will be put in there. The part
> >> is cast iron, about 1/4 thick. The directions are to remove
> >> the turbocharger, drill a 7/16 hole, then tap. The part
> >> that screws into the hole has a shoulder which is
> >> supposed to rest against the turbocharger.
> >> Alternately they say I can drill and tap the hole
> >> with the engine running. Once the drill bit goes
> >> goes through, the exhaust pressure is supposed to
> >> push any particles out. When drilling cast iron
> >> they say it is supposed to turn to dust. I'd
> >> be drilling from the top down.
> >> I have to get a tap since I don't have one that size.
> >> I assume HSS will be ok?
> >> It's supposed to be a pain to get the turbocharger out.
> >> But if it was out, I could finish the hole with a
> >> 7/16 HSS end mill. That I think, would give me a more
> >> round hole than drilling by hand under the hood.
> >> So I would think it would seal better that way.
> >>
> > If the engine is running, I'd expect the turbo to be hot enough to dull
> > your tools, apart from being most hazardous to work on.
> > My employer does engine conversions: we left an engine running overnight
> > on the dynamometer: someone slipped in & took a picture in the dark. The
> > turbo & exhaust manifold were red hot! I still have a copy of that photo.
> > Me, I'd bit the bullet & take thing off, work on it at the bench like a
> > gentleman.
>
> I think I'd feel most comfortable with it removed. I'd just have to work
> up the patience (oxymoron) to do it.
I would presume you immediately do the drilling after starting from a
cold start. The turbo should take a lot longer than the few minutes
drilling would take to get hot enough to be an issue, particularly
sitting at idle.
I would personally be more comfortable working up to the tap drill size
in a few steps than drilling that relatively large hole in one shot. At
least starting with a center drill for a pilot hole and starting taper
would be good.
I would get the tap and tap drill as a quality set if possible. For
sealing I'd think a light coat of a suitable high temp gasket maker
would be good.
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Posted by Steve W. on April 25, 2008, 9:40 pm
Please log in for more thread options Wayne wrote:
> On Fri, 25 Apr 2008 18:57:13 -0500, David R Brooks
>
>> Wayne wrote:
>>> Since I'm going to be tapping into a big buck part and don't
>>> really have any experience tapping cast iron, I figure I'll
>>> just ask a few stupid questions.
>>> I'm tapping a 1/4 NPT hole into the exhaust section of a
>>> turbocharger. An EGT sensor will be put in there. The part
>>> is cast iron, about 1/4 thick. The directions are to remove
>>> the turbocharger, drill a 7/16 hole, then tap. The part
>>> that screws into the hole has a shoulder which is
>>> supposed to rest against the turbocharger.
>>> Alternately they say I can drill and tap the hole
>>> with the engine running. Once the drill bit goes
>>> goes through, the exhaust pressure is supposed to
>>> push any particles out. When drilling cast iron
>>> they say it is supposed to turn to dust. I'd
>>> be drilling from the top down.
>>> I have to get a tap since I don't have one that size.
>>> I assume HSS will be ok?
>>> It's supposed to be a pain to get the turbocharger out.
>>> But if it was out, I could finish the hole with a
>>> 7/16 HSS end mill. That I think, would give me a more
>>> round hole than drilling by hand under the hood.
>>> So I would think it would seal better that way.
>
> I think I'd feel most comfortable with it removed. I'd just have to work
> up the patience (oxymoron) to do it.
>
> Wayne D.
>
>
This is downstream from the turbine housing correct? If so just coat the
bit with heavy grease to catch most of the chips. Then do the same with
the tap. Step drill it so you get a nice hole. Any swarf you lose into
the hole will just get blown downstream into the catalytic converter and
not be a problem. This is a common thing to do when you add EGT sensors
or do an EFI conversion and need to drill the manifold or the head pipe.
I wold make VERY sure of the turbines position before you drill, some
of them extend down a bit into the outer end of the scroll.
--
Steve W.
Near Cooperstown, New York
Life is not like a box of chocolates
it's more like a jar of jalapenos-
what you do today could burn your ass tomorrow!
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> really have any experience tapping cast iron, I figure I'll
> just ask a few stupid questions.
>
> I'm tapping a 1/4 NPT hole into the exhaust section of a
> turbocharger. An EGT sensor will be put in there. The part
> is cast iron, about 1/4 thick. The directions are to remove
> the turbocharger, drill a 7/16 hole, then tap. The part
> that screws into the hole has a shoulder which is
> supposed to rest against the turbocharger.
>
> Alternately they say I can drill and tap the hole
> with the engine running. Once the drill bit goes
> goes through, the exhaust pressure is supposed to
> push any particles out. When drilling cast iron
> they say it is supposed to turn to dust. I'd
> be drilling from the top down.
>
> I have to get a tap since I don't have one that size.
> I assume HSS will be ok?
>
> It's supposed to be a pain to get the turbocharger out.
> But if it was out, I could finish the hole with a
> 7/16 HSS end mill. That I think, would give me a more
> round hole than drilling by hand under the hood.
> So I would think it would seal better that way.
>