Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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  #1   Report Post  
Proctologically Violated©®
 
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Default Teflon tape vs. Dope/thread

Awl--

I've been left in the lurch a few times by teflon tape on threaded joints,
where I just couldn't get rid of air/water leaks--proly cuz of chinese
fittings!
I've seen plumbing fittings that go together like a nut on a bolt!

OTOH, pro dope/thread, messy and crappy as it is, has always been
super-reliable, and in fact fixes the teflon problems.

Can you use pro-dope by itself, w/o thread? Ace, I think, makes a teflon
dope--messier than the Hercules trad'l dope.

What do people here use, and when? The bigger the pipe is, the more I lean
toward prodope/thread. Smaller stuff, like 1/4", I'll much prefer teflon.

Anything better than the Hercules pro dope?
What are people paying for teflon? A buck for the 1/2" rolls seems a bit
much.
HD: $1--and up. A local good hardware store (Schalls in Yonkers): 75c!!!

Thanks!
----------------------------
Mr. P.V.'d
formerly Droll Troll


  #2   Report Post  
Ken Finney
 
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Default


"Proctologically Violated©®" wrote in message
...
Awl--

I've been left in the lurch a few times by teflon tape on threaded joints,
where I just couldn't get rid of air/water leaks--proly cuz of chinese
fittings!
I've seen plumbing fittings that go together like a nut on a bolt!

OTOH, pro dope/thread, messy and crappy as it is, has always been
super-reliable, and in fact fixes the teflon problems.

Can you use pro-dope by itself, w/o thread? Ace, I think, makes a teflon
dope--messier than the Hercules trad'l dope.

What do people here use, and when? The bigger the pipe is, the more I

lean
toward prodope/thread. Smaller stuff, like 1/4", I'll much prefer

teflon.

Anything better than the Hercules pro dope?
What are people paying for teflon? A buck for the 1/2" rolls seems a bit
much.
HD: $1--and up. A local good hardware store (Schalls in Yonkers): 75c!!!

Thanks!


There are different grades of teflon tape. Once I started using the thick
pink
stuff (which is hard to find) instead of the thin white stuff, I stopped
having
leaks.



  #3   Report Post  
Grant Erwin
 
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Default

I don't use teflon tape much anymore. I use teflon-bearing pipe dope
instead. Stuff just plain works. - GWE

Kris wrote:

All--

I've been left in the lurch a few times by teflon tape on threaded joints,
where I just couldn't get rid of air/water leaks--proly cuz of chinese
fittings!
I've seen plumbing fittings that go together like a nut on a bolt!

OTOH, pro dope/thread, messy and crappy as it is, has always been
super-reliable, and in fact fixes the teflon problems.

Can you use pro-dope by itself, w/o thread? Ace, I think, makes a teflon
dope--messier than the Hercules trad'l dope.

What do people here use, and when? The bigger the pipe is, the more I lean
toward prodope/thread. Smaller stuff, like 1/4", I'll much prefer teflon.

Anything better than the Hercules pro dope?
What are people paying for teflon? A buck for the 1/2" rolls seems a bit
much.
HD: $1--and up. A local good hardware store (Schalls in Yonkers): 75c!!!


  #4   Report Post  
Lloyd E. Sponenburgh
 
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Default


"Grant Erwin" wrote in message
...
I don't use teflon tape much anymore. I use teflon-bearing pipe dope
instead. Stuff just plain works. - GWE


Oatey makes a teflon-filled dope in a squeeze tube that's not so messy as a
can and swab.

The stuff is the tits for hydraulic work, and any air work with
flow-limiting valves that might get gummed up with a loose hair of teflon
tape.

LLoyd


  #5   Report Post  
Bob May
 
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Default

Dope is the old method while teflon is the new method.
I prefer to first testfit the joint to insure that it is going to seal first
due to the inconsistency of some of the fittings nowdays (chinese crap!) and
then use teflon on them. I do make sure that the joint is tightened to the
point where it really doesn't need tape to do the job right but the tape
makes getting to that point easier.
The pipe joint is actually designed to not need any filler compound but that
takes longer and uses more force than using a lubricant to help in the job.

--
Why isn't there an Ozone Hole at the NORTH Pole?




  #6   Report Post  
carl mciver
 
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Default

"Proctologically Violated©®" wrote in message
...
| Awl--
|
| I've been left in the lurch a few times by teflon tape on threaded joints,
| where I just couldn't get rid of air/water leaks--proly cuz of chinese
| fittings!
| I've seen plumbing fittings that go together like a nut on a bolt!

I've come to understand that the tape is not for sealing. It is to keep
the threads from corroding together and allow for removal. Having recently
taken a steel fitting out of an aluminum casting, still holding the aluminum
threads, it makes perfect sense.
I use hylomar or Indian Head shellac for sealing threads. No leaks yet.

  #7   Report Post  
Grant Erwin
 
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Default

carl mciver wrote:

I've come to understand that the tape is not for sealing. It is to keep
the threads from corroding together and allow for removal. Having recently
taken a steel fitting out of an aluminum casting, still holding the aluminum
threads, it makes perfect sense.


OK, check this out. Take any pipe joint you want, wrap it in teflon tape,
thread the joint together as tightly as it would be in real life, then take
it apart and see ALL the teflon tape gone from the joint. Unless it's wiping
magic invisible teflon oil onto there, it won't prevent squat for corrosion.
Tapered pipe threads seal by crushing together. The teflon tape just helps
it slide in there a little. Teflon pipe dope doesn't really stay in there
either, but it is my opinion (and those of several pro plumbers and pipefitters
I know very well) that it comes much closer than teflon tape.

GWE
  #8   Report Post  
jim rozen
 
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Default

In article , Lloyd E. Sponenburgh
says...

Oatey makes a teflon-filled dope in a squeeze tube that's not so messy as a
can and swab.

The stuff is the tits for hydraulic work, and any air work with
flow-limiting valves that might get gummed up with a loose hair of teflon
tape.


I've known this as "SWAK" which I think is a swagelock trade
name.

This having been said, I use teflon tape nearly exclusively,
never had any leaks. The key to not getting any sealant in the
flow is to keep the tape off of the first thread in the fitting.

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================
  #9   Report Post  
Proctologically Violated©®
 
Posts: n/a
Default

Do any of'em use thread?
----------------------------
Mr. P.V.'d
formerly Droll Troll
"Grant Erwin" wrote in message
...
carl mciver wrote:

I've come to understand that the tape is not for sealing. It is to
keep
the threads from corroding together and allow for removal. Having
recently
taken a steel fitting out of an aluminum casting, still holding the
aluminum
threads, it makes perfect sense.


OK, check this out. Take any pipe joint you want, wrap it in teflon tape,
thread the joint together as tightly as it would be in real life, then
take
it apart and see ALL the teflon tape gone from the joint. Unless it's
wiping
magic invisible teflon oil onto there, it won't prevent squat for
corrosion.
Tapered pipe threads seal by crushing together. The teflon tape just helps
it slide in there a little. Teflon pipe dope doesn't really stay in there
either, but it is my opinion (and those of several pro plumbers and
pipefitters
I know very well) that it comes much closer than teflon tape.

GWE



  #10   Report Post  
Proctologically Violated©®
 
Posts: n/a
Default

Oh yeah, excellent observation on the "disappearing teflon"!! I always
wondered what was up w/ dat!!

Which explains why, when the threads of fittings don't quite "make-up", that
teflon is not so useful, whilst string/dope is.
Ahm thinkin anything over 1", 'n' ahm usin string/dope.
----------------------------
Mr. P.V.'d
formerly Droll Troll
"Grant Erwin" wrote in message
...
carl mciver wrote:

I've come to understand that the tape is not for sealing. It is to
keep
the threads from corroding together and allow for removal. Having
recently
taken a steel fitting out of an aluminum casting, still holding the
aluminum
threads, it makes perfect sense.


OK, check this out. Take any pipe joint you want, wrap it in teflon tape,
thread the joint together as tightly as it would be in real life, then
take
it apart and see ALL the teflon tape gone from the joint. Unless it's
wiping
magic invisible teflon oil onto there, it won't prevent squat for
corrosion.
Tapered pipe threads seal by crushing together. The teflon tape just helps
it slide in there a little. Teflon pipe dope doesn't really stay in there
either, but it is my opinion (and those of several pro plumbers and
pipefitters
I know very well) that it comes much closer than teflon tape.

GWE





  #11   Report Post  
 
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Default

I use teflon tape on everything but gas pipes, and I've never had a
leak. Are you putting on enough layers of teflon tape on the threads?

For gas lines, I use conventional pipe dope, because the contained in
the distributed natural gas seems to bond better with black iron gas
pipe and pipe dope than with teflon tape. Also, this was the advice
that I received from a friend who works for the local gas company.

Harry C.

  #12   Report Post  
jim rozen
 
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Default

In article , Grant Erwin says...

OK, check this out. Take any pipe joint you want, wrap it in teflon tape,
thread the joint together as tightly as it would be in real life, then take
it apart and see ALL the teflon tape gone from the joint. Unless it's wiping
magic invisible teflon oil onto there, it won't prevent squat for corrosion.
Tapered pipe threads seal by crushing together. The teflon tape just helps
it slide in there a little. Teflon pipe dope doesn't really stay in there
either, but it is my opinion (and those of several pro plumbers and pipefitters
I know very well) that it comes much closer than teflon tape.


The sealant (tape or dope) seals the helical gap that remains
above the crest of the male threads. If one sufficiently overpressures
an NPT fitting, the helix of teflon (or other sealant) will
extrude out of the fitting. I've seen this happen.

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================
  #13   Report Post  
 
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Default

RectorSeal Works well for me. Compatble with almost everything, except
oxygen. --Doozer in Buffalo

  #15   Report Post  
Eric R Snow
 
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Default

On 29 Apr 2005 12:08:18 -0700, jim rozen
wrote:

In article , Lloyd E. Sponenburgh
says...

Oatey makes a teflon-filled dope in a squeeze tube that's not so messy as a
can and swab.

The stuff is the tits for hydraulic work, and any air work with
flow-limiting valves that might get gummed up with a loose hair of teflon
tape.


I've known this as "SWAK" which I think is a swagelock trade
name.

This having been said, I use teflon tape nearly exclusively,
never had any leaks. The key to not getting any sealant in the
flow is to keep the tape off of the first thread in the fitting.

Jim

Jim,
The first time I did gas piping using black iron pipe I was told to
use teflon tape. EVERY joint leaked, even though all were tightened
correctly. And none could be made leak free with further tightening.
After speaking to some who knew, I bought the teflon pipe dope. It
always works with black iron gas piping. Never had a leak since. But
on all the brass fittings it's teflon tape. Never had any clogs or
pieces of tape get into the inside.
Eric


  #16   Report Post  
Jeff Wisnia
 
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Default

Grant Erwin wrote:
carl mciver wrote:

I've come to understand that the tape is not for sealing. It is
to keep
the threads from corroding together and allow for removal. Having
recently
taken a steel fitting out of an aluminum casting, still holding the
aluminum
threads, it makes perfect sense.



OK, check this out. Take any pipe joint you want, wrap it in teflon tape,
thread the joint together as tightly as it would be in real life, then take
it apart and see ALL the teflon tape gone from the joint. Unless it's
wiping
magic invisible teflon oil onto there, it won't prevent squat for
corrosion.
Tapered pipe threads seal by crushing together.


No they don't, not NPT threads at least, if they are made to spec.

Check the thread form drawings in Machinery's Handbook and you'll see
that the crests of male NPT threads are truncated, which creates the
well known "spiral leak path" requiring some kind of "pipe dope" to plug it.

NFTF ("Dryseal") threads, available on some small sized brass fittings,
have a form which provides the slight crushing action you refer to and
are intended to provide a tight seal without dope.

The "F" in NPTF stands for "fuel" as those threads were originally
designed to be used on fuel fittings long before Teflon or other fuel
resistant pipe dopes were a twinkle in some chemist's eye.

The teflon tape just helps
it slide in there a little. Teflon pipe dope doesn't really stay in there
either, but it is my opinion (and those of several pro plumbers and
pipefitters
I know very well) that it comes much closer than teflon tape.

GWE


Jeff (Who remembers using cotton string to seal pipe threads in his
earlier days.)

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"As long as there are final exams, there will be prayer in public
schools"
  #17   Report Post  
Gunner
 
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Default

On Fri, 29 Apr 2005 17:14:57 -0700, Eric R Snow
wrote:

On 29 Apr 2005 12:08:18 -0700, jim rozen
wrote:

In article , Lloyd E. Sponenburgh
says...

Oatey makes a teflon-filled dope in a squeeze tube that's not so messy as a
can and swab.

The stuff is the tits for hydraulic work, and any air work with
flow-limiting valves that might get gummed up with a loose hair of teflon
tape.


I've known this as "SWAK" which I think is a swagelock trade
name.

This having been said, I use teflon tape nearly exclusively,
never had any leaks. The key to not getting any sealant in the
flow is to keep the tape off of the first thread in the fitting.

Jim

Jim,
The first time I did gas piping using black iron pipe I was told to
use teflon tape. EVERY joint leaked, even though all were tightened
correctly. And none could be made leak free with further tightening.
After speaking to some who knew, I bought the teflon pipe dope. It
always works with black iron gas piping. Never had a leak since. But
on all the brass fittings it's teflon tape. Never had any clogs or
pieces of tape get into the inside.
Eric


Same here, but I use dope on ALL fittings, brass or not, since the
several times I pulled a chunk of tape out of the locked up or leaking
air soleniode on a machine tool

Gunner

"At the core of liberalism is the spoiled child -
miserable, as all spoiled children are, unsatisfied,
demanding, ill-disciplined, despotic and useless.
Liberalism is a philosphy of sniveling brats." -- P.J. O'Rourke
  #18   Report Post  
jim rozen
 
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Default

In article , Jeff Wisnia says...

Check the thread form drawings in Machinery's Handbook and you'll see
that the crests of male NPT threads are truncated, which creates the
well known "spiral leak path" requiring some kind of "pipe dope" to plug it.


Yep. And I saw a parker representative demonstrate that yes,
the goop in the spiral leak path does indeed extrude out at
extreme pressures - *before* a swagelock fitting will let loose.

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================
  #19   Report Post  
ATP*
 
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Default


"Jeff Wisnia" wrote in message
...
Grant Erwin wrote:
carl mciver wrote:

I've come to understand that the tape is not for sealing. It is to
keep
the threads from corroding together and allow for removal. Having
recently
taken a steel fitting out of an aluminum casting, still holding the
aluminum
threads, it makes perfect sense.



OK, check this out. Take any pipe joint you want, wrap it in teflon tape,
thread the joint together as tightly as it would be in real life, then
take
it apart and see ALL the teflon tape gone from the joint. Unless it's
wiping
magic invisible teflon oil onto there, it won't prevent squat for
corrosion.
Tapered pipe threads seal by crushing together.


No they don't, not NPT threads at least, if they are made to spec.

Check the thread form drawings in Machinery's Handbook and you'll see that
the crests of male NPT threads are truncated, which creates the well known
"spiral leak path" requiring some kind of "pipe dope" to plug it.

NFTF ("Dryseal") threads, available on some small sized brass fittings,
have a form which provides the slight crushing action you refer to and are
intended to provide a tight seal without dope.

The "F" in NPTF stands for "fuel" as those threads were originally
designed to be used on fuel fittings long before Teflon or other fuel
resistant pipe dopes were a twinkle in some chemist's eye.

The teflon tape just helps
it slide in there a little. Teflon pipe dope doesn't really stay in there
either, but it is my opinion (and those of several pro plumbers and
pipefitters
I know very well) that it comes much closer than teflon tape.

GWE


Jeff (Who remembers using cotton string to seal pipe threads in his
earlier days.)

Still the way to go if the pipe holds water. Lampwick and dope if it's a
fitting that would be hard to redo, e.g. in a boiler manifold.


  #20   Report Post  
Cydrome Leader
 
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Lloyd E. Sponenburgh wrote:

"Grant Erwin" wrote in message
...
I don't use teflon tape much anymore. I use teflon-bearing pipe dope
instead. Stuff just plain works. - GWE


Oatey makes a teflon-filled dope in a squeeze tube that's not so messy as a
can and swab.


I tried this stuff for oil at under 150PSI and all it did was leak. Teflon pipe thread worked fine.


The stuff is the tits for hydraulic work, and any air work with
flow-limiting valves that might get gummed up with a loose hair of teflon
tape.

LLoyd


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