[Public-List] Manifold petcock Atomic 4

[Kris Coward]

A bottoming tap is intended to be used _after_ a regular tapered tap;
going straight to a bottoming tap can lead to uneven threads (because
the bottoming tap doesn't have enough of a thread to bite on at the
beginning of the hole), or even shards of broken tap left in the hole
(taps are hard and therefore brittle; if one has to cut too much
thread at once, the stress can crack it, and then it'll need to be
ground out). It may be less of a concern when cutting a softer metal
like brass out of an existing thread, but I've damaged enough threaded
holes (and ground out enough tool shards) that I wouldn't hesitate to
get and use both taps just to be on the safe side.

Cheers,
Kris

On Sat, May 19, 2012 at 09:40:37AM -0400, Don Campbell wrote:
> If you can find a bottoming tap of the correct size, it has far less
> taper than the normal tapered tap. You might want to compare it with
> a plug tap to see which might suit you best. I imagine you will have
> to go to an industrial supplier who carries an open line of tools to
> find them.
> Don #528
> 
> On 5/19/2012 8:27 AM, Ronald Walker wrote:
> >The engine is the old Atomic-4.Its my understanding that all Albergs were originally powered by them.I believe the petcock is brass and the manifold is some type of steel. As I said the threads are there, just flattened out. I'm going to try some J.B.Weld. Don't know what else to do.
> >
> >--- On Sat, 5/19/12, Glennb<brooks.glenn at comcast.net>  wrote:
> >
> >>From: Glennb<brooks.glenn at comcast.net>
> >>Subject: Re: [Public-List] Manifold petcock Atomic 4
> >>To: "Alberg 30 Public List -- open to all"<public-list at lists.alberg30.org>
> >>Date: Saturday, May 19, 2012, 1:18 AM
> >>What kind of engine/manifold do you
> >>have, and what material is the petcock made of?  sounds
> >>like the petcock corroded off, leaving part of the threaded
> >>portion in the manifold.
> >>
> >>If so, try going in with a very small drill bit, maybe
> >>slightly larger than the ID of the hole, then run a series
> >>of increasingly larger taps to ream out the old material to
> >>match the original ID and thread.
> >>
> >>just did this on my steam engine, took about an hour to
> >>replace the broken nipple. But it was brass and the boiler
> >>is steel.
> >>
> >>Glenn p
> >>dolce 318
> >>
> >>
> >>Sent from my iPad
> >>
> >>On May 18, 2012, at 12:47 PM, Ronald Walker<rwpsw at sbcglobal.net>
> >>wrote:
> >>
> >>>Maybe someone can help me with a small problem I
> >>discovered during the spring start-up procedure.On the aft
> >>part of the manifold there is a petcock. Its is for draining
> >>the manifold water jacket. As I began to close the petcock I
> >>noticed it was loose. I tried to tighten it but it ended up
> >>falling off in my hand. After a good close look I saw that
> >>the threads were all buggered up.On the petcock as well as
> >>the hole. I thought about running a tap in to maybe sweeten
> >>up the threads but the recess is way to shallow. Any advise
> >>would be appreciated.
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-- 
Kris Coward					http://unripe.melon.org/
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