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  
Karl Townsend
 
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Default cut pipes to weld a "T"

I need a "T" made out of two six inch 1/8" wall thickness pipes.

I need a way to mark a chalk line on each pipe so I can cut it with a torch
and then fit the two together and weld.

I did a layout like this in drafting class thirty years ago. Made each piece
out of paper. Cut them out and wrapped around the pipe to mark the lines. I
don't remember much else about it.

Anyone know how this is done?

Karl



  #2   Report Post  
Ben
 
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Default cut pipes to weld a "T"

Look up tube mitering on google or go to these links and see the tube
mitering download links
ftp://ftp.ihpva.org/pub/software/index.html
http://www.ihpva.org/people/tstrike/...ng/tubemit.htm


Ben



"Karl Townsend" wrote in message
ink.net...
I need a "T" made out of two six inch 1/8" wall thickness pipes.

I need a way to mark a chalk line on each pipe so I can cut it with a

torch
and then fit the two together and weld.

I did a layout like this in drafting class thirty years ago. Made each

piece
out of paper. Cut them out and wrapped around the pipe to mark the lines.

I
don't remember much else about it.

Anyone know how this is done?

Karl





  #3   Report Post  
Karl Townsend
 
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Default cut pipes to weld a "T"


"Ben" wrote in message
news:Z8wpb.115238$EO3.30463@clgrps13...
Look up tube mitering on google or go to these links and see the tube
mitering download links
ftp://ftp.ihpva.org/pub/software/index.html
http://www.ihpva.org/people/tstrike/...ng/tubemit.htm



I've just ****ed away 1 1/2 hours trying to get something to work here. The
first link needs a postscript printer - ain't got it.

The second link, tubemiter.exe prints out the paper copy of the tube miter
fit to an 8 1/2 x 11 paper, not to scale.

Another link on down the page, winmiter.exe has the same problem. Maybe
there's something I don't know about printer setup here????

The link talking about an excel spreadsheet feeding AutoCAD would be just
GREAT, but the link don't point to it. Points to some page about building
bicycles.


Anybody know of something else, or the old fashioned way with paper and a
drafting machine?

Karl





  #4   Report Post  
Grant Erwin
 
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Default cut pipes to weld a "T"

The real old-fashioned way, Karl, is to clamp the pipes in a T and
use a long piece of soapstone to scribe one off the other, then
cut it, clean up the cut, reclamp, and scribe the other off the
first, then make that cut, clean up, fit and weld. I've seen
shipyard pipefitters do that hundreds of times.

Grant

Karl Townsend wrote:

"Ben" wrote in message
news:Z8wpb.115238$EO3.30463@clgrps13...

Look up tube mitering on google or go to these links and see the tube
mitering download links
ftp://ftp.ihpva.org/pub/software/index.html
http://www.ihpva.org/people/tstrike/...ng/tubemit.htm




I've just ****ed away 1 1/2 hours trying to get something to work here. The
first link needs a postscript printer - ain't got it.

The second link, tubemiter.exe prints out the paper copy of the tube miter
fit to an 8 1/2 x 11 paper, not to scale.

Another link on down the page, winmiter.exe has the same problem. Maybe
there's something I don't know about printer setup here????

The link talking about an excel spreadsheet feeding AutoCAD would be just
GREAT, but the link don't point to it. Points to some page about building
bicycles.


Anybody know of something else, or the old fashioned way with paper and a
drafting machine?

Karl






  #5   Report Post  
Tom Kendrick
 
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Default cut pipes to weld a "T"

Does this joint need to be capable of passing liquid or air?
How much mechanical load should the joint support?
It would appear that the pipe approaching the side of the other pipe
requires a fishmouth cut. If no connection is required, the other pipe
can be left as is.
If liquid must flow, the other pipe will require a matching joint to
receive the fishmouthed end.


"Karl Townsend" wrote in message link.net...
I need a "T" made out of two six inch 1/8" wall thickness pipes.

I need a way to mark a chalk line on each pipe so I can cut it with a torch
and then fit the two together and weld.

I did a layout like this in drafting class thirty years ago. Made each piece
out of paper. Cut them out and wrapped around the pipe to mark the lines. I
don't remember much else about it.

Anyone know how this is done?

Karl



  #6   Report Post  
woodsy
 
Posts: n/a
Default cut pipes to weld a "T"

Using paper, I'd imagine a compass would be involved to draw a half circle.
Thats about all I can come up with for now. Too lazy to do much thinking at
the moment.
"Karl Townsend" wrote in message
ink.net...
I need a "T" made out of two six inch 1/8" wall thickness pipes.

I need a way to mark a chalk line on each pipe so I can cut it with a

torch
and then fit the two together and weld.

I did a layout like this in drafting class thirty years ago. Made each

piece
out of paper. Cut them out and wrapped around the pipe to mark the lines.

I
don't remember much else about it.

Anyone know how this is done?

Karl





  #7   Report Post  
JTMcC
 
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Default cut pipes to weld a "T"


"Karl Townsend" wrote in message
ink.net...
I need a "T" made out of two six inch 1/8" wall thickness pipes.

I need a way to mark a chalk line on each pipe so I can cut it with a

torch
and then fit the two together and weld.

I did a layout like this in drafting class thirty years ago. Made each

piece
out of paper. Cut them out and wrapped around the pipe to mark the lines.

I
don't remember much else about it.

Anyone know how this is done?

Karl


I know how it's done and have to do it regularly as part of the 12 on 12
inverted branch test, which is a common welding test in the pipe field. But,
it's pretty hard to describe, at least for me, your best bet is to buy one
of two small books, "Blue Book of Fitters...Welders Pattern and Layout
Manual" by H.G. Thorsness or "The Pipe Fitters and Pipe Welders Handbook" by
Thomas W. Frankland. Both show the steps to lay out a branch as well as many
other things. Or, you can buy store bought patterns, or, you can try one of
the online sources mentioned tho you seem to not have had any luck there.
Another alternative if you have time on your hands, is to just start
whittling away until it fits.

regards,
JTMcC.







  #8   Report Post  
Ken Moffett
 
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Default cut pipes to weld a "T"

Karl Townsend wrote:

"Ben" wrote in message
news:Z8wpb.115238$EO3.30463@clgrps13..
Look up tube mitering on google or go to these links and see the tube
mitering download links
ftp://ftp.ihpva.org/pub/software/index.html
http://www.ihpva.org/people/tstrike/...ng/tubemit.htm


I've just ****ed away 1 1/2 hours trying to get something to work here. The
first link needs a postscript printer - ain't got it.

The second link, tubemiter.exe prints out the paper copy of the tube miter
fit to an 8 1/2 x 11 paper, not to scale.

Another link on down the page, winmiter.exe has the same problem. Maybe
there's something I don't know about printer setup here????

The link talking about an excel spreadsheet feeding AutoCAD would be just
GREAT, but the link don't point to it. Points to some page about building
bicycles.

Anybody know of something else, or the old fashioned way with paper and a
drafting machine?

Karl


I just ran your dimensions on Tubemiter. The units are mm, so you have
to convert from inches to mm. The printout was only 1/2 the template, so
you need to run it twice and paste them together. I didn't try it, but
it looks about right.

I also ran your dimensions on Winmiter. Again, the printout was only 1/2
(in landscape mode) the template. But print and paste two copies and you
have a whole template.

I did overlay the printouts from both programs, and they match very
closely.
  #9   Report Post  
Dan Caster
 
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Default cut pipes to weld a "T"

Another old fashioned way is to use something fairly stiff as some
heavy gasket material to hold on the pipe in what you think is the
right shape and mark it with soapstone. Cut with oxy/acet, see how
much you missed it by and mark again using the guide. A piece of four
or six inch wide flat belt a couple of feet long would work real well.

With six inch dia pipe, the deepest part ought to be 3 inches in from
a straight cut end.

Dan


Grant Erwin wrote in message ...
The real old-fashioned way, Karl, is to clamp the pipes in a T and
use a long piece of soapstone to scribe one off the other, then
cut it, clean up the cut, reclamp, and scribe the other off the
first, then make that cut, clean up, fit and weld. I've seen
shipyard pipefitters do that hundreds of times.

Grant

  #10   Report Post  
Dan Caster
 
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Default cut pipes to weld a "T"

I would also suggest you ask at Sci.engr.joining.welding. There are a
lot of pipe welders there.

Dan


"Karl Townsend" wrote in message Anyone know how this is done?

Karl



  #11   Report Post  
Larry Jaques
 
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Default cut pipes to weld a "T"

On Mon, 03 Nov 2003 21:24:21 GMT, "Karl Townsend"
brought forth from the murky depths:

Anybody know of something else, or the old fashioned way with paper and a
drafting machine?


Hold the end of one pipe on a piece of paper (or use a coin the same
size if possible, and draw a circle. Fold the paper in half so the
arcs line up and cut out the circle. Wrap that around the pipe, mark,
cut, and grind to suit. Flop the cut piece over and weld it.
Easy enough?

  #12   Report Post  
SteveB
 
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Default cut pipes to weld a "T"


"Karl Townsend" wrote in message
ink.net...
I need a "T" made out of two six inch 1/8" wall thickness pipes.

I need a way to mark a chalk line on each pipe so I can cut it with a

torch
and then fit the two together and weld.

I did a layout like this in drafting class thirty years ago. Made each

piece
out of paper. Cut them out and wrapped around the pipe to mark the lines.

I
don't remember much else about it.

Anyone know how this is done?

Karl




Go to a welding store and buy a "Wrap Around". There are different sizes.
There are instructions and marks on it that allow you to cut out the desired
shape you need to get a repeatable pattern. I believe you can even order
one specific to your use from them.

Steve


  #13   Report Post  
JMartin957
 
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Default cut pipes to weld a "T"


Hold the end of one pipe on a piece of paper (or use a coin the same
size if possible, and draw a circle. Fold the paper in half so the
arcs line up and cut out the circle. Wrap that around the pipe, mark,
cut, and grind to suit. Flop the cut piece over and weld it.
Easy enough?



Easy enough, but it won't work.

Your way, you'll get an arc (a half-circle, actually) with a chord length equal
to the pipe diameter, and with the arcs tangent at 90 degrees to the chord.

The correct pattern will be an arc with a chord length of pi divided by twice
the diameter, and with the arcs tangent at 45 degrees.

Instead, I'd make the 45 degree cuts on the end of the vertical piece first,
and make a pattern from that. Or, butt the pieces together and scribe the
joint.

John Martin
  #14   Report Post  
JTMcC
 
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Default cut pipes to weld a "T"


"SteveB" wrote in message
news:dNPpb.1834$L77.1404@fed1read03...

"Karl Townsend" wrote in message
ink.net...
I need a "T" made out of two six inch 1/8" wall thickness pipes.

I need a way to mark a chalk line on each pipe so I can cut it with a

torch
and then fit the two together and weld.

I did a layout like this in drafting class thirty years ago. Made each

piece
out of paper. Cut them out and wrapped around the pipe to mark the

lines.
I
don't remember much else about it.

Anyone know how this is done?

Karl




Go to a welding store and buy a "Wrap Around". There are different sizes.
There are instructions and marks on it that allow you to cut out the

desired
shape you need to get a repeatable pattern. I believe you can even order
one specific to your use from them.

Steve


A wraparound won't give you the ordinals to cut a branch.

JTMcC.





  #15   Report Post  
Pooty Tang
 
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Default cut pipes to weld a "T"

On Mon, 03 Nov 2003 17:05:40 GMT, "Karl Townsend"
wrote:

I need a "T" made out of two six inch 1/8" wall thickness pipes.

I need a way to mark a chalk line on each pipe so I can cut it with a torch
and then fit the two together and weld.

I did a layout like this in drafting class thirty years ago. Made each piece
out of paper. Cut them out and wrapped around the pipe to mark the lines. I
don't remember much else about it.

Anyone know how this is done?

Karl







  #16   Report Post  
Pooty Tang
 
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Default cut pipes to weld a "T"

Karl,

You can lay this out using a 6" red rubber ring gasket (the gasket
without bolt holes) and a wrap-around or center finder attachment on
your tri-square. If you happen to find one of the old asbestos ring
gasket, that one works better.

I'll try to describe the procedure. If I do not make this clear or
understandable, I can take pictures tomorrow and send them to you.

Draw a line length ways on the pipe. Using the wrap-around or center
finder, find the opposite side and draw a line.

Mark a line thru the center of the gasket.

Now, take the gasket and lay it on the pipe with the center mark on
the line and the outer ring of the gasket at the edge of the pipe.
Wrap the gasket around the pipe and using soapstone,
scribe around the gasket. Repeat this on the opposite side.

What you'll have is two arcs drawn on the pipe. For lack of a better
way to describe it, these arcs would be the "lips" of the fishmouth.

Now, turn the pipe 1/4 turn from the "lips" and scribe the "corners"
of the fish mouth using the gasket. Wrap the gasket around the pipe
and align the outer ring with the two arcs from the "lips". Scribe
this line on both sides. This is the "corners".

You may have to trim some for an exact fit but this will be very
close to final fit. When you're happy with the fishmouth fit, lay it
on the pipe you're gonna cut into and scribe your line.

Rule of thumb on this "junkyard welder" tip is to use the gasket size
for the pipe size you'll be cutting into: 4" branch off 6" pipe, use
6" gasket; 4" on 4", use 4" gasket; etc..

Let me know if you need further clarification on this. Once you do it
a couple of times, it'll be easy. And, fun too.



On Mon, 03 Nov 2003 17:05:40 GMT, "Karl Townsend"
wrote:

I need a "T" made out of two six inch 1/8" wall thickness pipes.

I need a way to mark a chalk line on each pipe so I can cut it with a torch
and then fit the two together and weld.

I did a layout like this in drafting class thirty years ago. Made each piece
out of paper. Cut them out and wrapped around the pipe to mark the lines. I
don't remember much else about it.

Anyone know how this is done?

Karl



  #17   Report Post  
spitfire2
 
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Default cut pipes to weld a "T"

JTMcC wrote:

"SteveB" wrote in message
news:dNPpb.1834$L77.1404@fed1read03...


"Karl Townsend" wrote in message
hlink.net...


I need a "T" made out of two six inch 1/8" wall thickness pipes.

I need a way to mark a chalk line on each pipe so I can cut it with a


torch


and then fit the two together and weld.

I did a layout like this in drafting class thirty years ago. Made each


piece


out of paper. Cut them out and wrapped around the pipe to mark the


lines.


I


don't remember much else about it.

Anyone know how this is done?

Karl





Go to a welding store and buy a "Wrap Around". There are different sizes.
There are instructions and marks on it that allow you to cut out the


desired


shape you need to get a repeatable pattern. I believe you can even order
one specific to your use from them.

Steve



A wraparound won't give you the ordinals to cut a branch.

JTMcC.









Just cut the main straight-through pipe so that you take out a 90 degree
"bite" from one side going in as far as its centre line.

Then cut the end of the branch pipe to a 90degree "V" to match the
"bite" in the main pipe.

Fit together, clamp and weld!

ave.

  #18   Report Post  
geoff merryweather
 
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Default cut pipes to weld a "T"

On Mon, 03 Nov 2003 21:24:21 GMT, "Karl Townsend"
wrote:

I've just ****ed away 1 1/2 hours trying to get something to work here. The
first link needs a postscript printer - ain't got it.

Use Ghostscript - lets you do Postscript on an ordinary printer.
Geoff
  #19   Report Post  
Karl Townsend
 
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Default cut pipes to weld a "T"

Thanks

I'll start with this for a ruff fit, and then use the soap stone scribe idea
for a final fit.


Karl



  #24   Report Post  
Larry Jaques
 
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Default cut pipes to weld a "T"

On Thu, 6 Nov 2003 14:50:44 +0000 (UTC), DejaVU
brought forth from the murky depths:

Larry Jaques scribed in


Wasn't the OP asking for a tool handle? Did he ask for
mil-spec welding info? "Why seek perfection for a bloody
pipe/handle?" I ask in earnest.


the 'OP' wants to join 2 bits of 6 inch pipe

if that makes a tool handle, I'll be jiggered


Oops. I must have combined two messages. Mea culpa.

(Note to Jim: Now I clearly see why you wanted to use
pipefitting techniques or whatever.)


-- Friends Don't Let Friends Eat Turkey and Drive --
  #25   Report Post  
JMartin957
 
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Default cut pipes to weld a "T"

On 06 Nov 2003 02:01:37 GMT, (JMartin957) brought
forth from the murky depths:


On 04 Nov 2003 19:02:50 GMT,
(JMartin957) brought
forth from the murky depths:


Hold the end of one pipe on a piece of paper (or use a coin the same
size if possible, and draw a circle. Fold the paper in half so the
arcs line up and cut out the circle. Wrap that around the pipe, mark,
cut, and grind to suit. Flop the cut piece over and weld it.
Easy enough?



Easy enough, but it won't work.

Your way, you'll get an arc (a half-circle, actually) with a chord length
equal
to the pipe diameter, and with the arcs tangent at 90 degrees to the

chord.

Wasn't the OP asking for a tool handle? Did he ask for
mil-spec welding info? "Why seek perfection for a bloody
pipe/handle?" I ask in earnest.

P.S: I grant that your method would be much prettier.


Larry:

It's not a question of perfection. What you suggested he do just plain

won't
work. It won't even come close. Try it and see. Or, if you want, work out
the math.


Take 1" (example) pipe, cut in half.
Hold end to paper, draw 1" circle.
Fold paper in half at circle.
Cut out 1" x 1/2" semicircular arc.
Fold paper around end of one pipe.
Draw arc.
Rotate pipe 180 degrees, draw arc.
Cut out arcs.
Grind to fit pipe. (requires no math
Weld together.

What won't work?



I guess you didn't try it, did you? Because if you did, you'd know exactly why
it won't work.

You are talking about using the pattern to cut the point on the end of a piece
of pipe, rather than a vee in the middle, but no matter because it's the same
thing.

Given your example, the two ends of the arc on your pattern are exactly 1"
apart. On the piece of pipe you want to cut, the two points or the bottoms of
the vees will be 1" apart, as that is the diameter of the pipe. But, when you
wrap your pattern around the pipe, the ends of the arcs won't make it halfway
around the pipe - because halfway around the pipe is really 1.57", or pi over
2. Because the paper has to wrap around the surface of the pipe, doesn't it?

And not only will your pattern not stretch halfway around the pipe, as it
should, but when you trace it you'll find that the ends of your arcs meet the
square end of the pipe at an angle (tangent) of 90 degrees. Not at 45 degrees
as they should.

The poster who suggested using a rubber ring as a pattern will get the same cut
you do, although with the flex and stretch of the ring he'll get closer.

John Martin


  #26   Report Post  
Larry Jaques
 
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Default cut pipes to weld a "T"

On 06 Nov 2003 22:25:59 GMT, (JMartin957) brought
forth from the murky depths:

work. It won't even come close. Try it and see. Or, if you want, work out
the math.


Take 1" (example) pipe, cut in half.
Hold end to paper, draw 1" circle.
Fold paper in half at circle.
Cut out 1" x 1/2" semicircular arc.
Fold paper around end of one pipe.
Draw arc.
Rotate pipe 180 degrees, draw arc.
Cut out arcs.
Grind to fit pipe. (requires no math
Weld together.

What won't work?


I guess you didn't try it, did you? Because if you did, you'd know exactly why
it won't work.


No, I didn't.


You are talking about using the pattern to cut the point on the end of a piece
of pipe, rather than a vee in the middle, but no matter because it's the same
thing.


Um, to me, ARC and VEE sound pretty similar. I was talking
about cutting the relief in the pipe.


Given your example, the two ends of the arc on your pattern are exactly 1"
apart. On the piece of pipe you want to cut, the two points or the bottoms of
the vees will be 1" apart, as that is the diameter of the pipe. But, when you
wrap your pattern around the pipe, the ends of the arcs won't make it halfway
around the pipe - because halfway around the pipe is really 1.57", or pi over


OK, you got me with the actual size, but I said to hold the end
of the pipe to the paper and draw the circle.


2. Because the paper has to wrap around the surface of the pipe, doesn't it?


With a 1" pipe, yes. Not even close with a 6-incher.


And not only will your pattern not stretch halfway around the pipe, as it
should, but when you trace it you'll find that the ends of your arcs meet the
square end of the pipe at an angle (tangent) of 90 degrees. Not at 45 degrees
as they should.


See above stretchmarks. As to the angle, why would a cut
which was radiused to the OD of the pipe -not- fit? The ends
of the arc would be to the outside of the pipe, not the inside,
so there would be no 90° step. I'll give you the fact that I
didn't address the proper fit for a certified weld, but I'm a
certifiable jury rigger. So sue me.


-- Friends Don't Let Friends Eat Turkey and Drive --
  #27   Report Post  
JMartin957
 
Posts: n/a
Default cut pipes to weld a "T"


On 06 Nov 2003 22:25:59 GMT, (JMartin957) brought
forth from the murky depths:

work. It won't even come close. Try it and see. Or, if you want, work

out
the math.

Take 1" (example) pipe, cut in half.
Hold end to paper, draw 1" circle.
Fold paper in half at circle.
Cut out 1" x 1/2" semicircular arc.
Fold paper around end of one pipe.
Draw arc.
Rotate pipe 180 degrees, draw arc.
Cut out arcs.
Grind to fit pipe. (requires no math
Weld together.

What won't work?


I guess you didn't try it, did you? Because if you did, you'd know exactly

why
it won't work.


No, I didn't.


You are talking about using the pattern to cut the point on the end of a

piece
of pipe, rather than a vee in the middle, but no matter because it's the

same
thing.


Um, to me, ARC and VEE sound pretty similar. I was talking
about cutting the relief in the pipe.


Given your example, the two ends of the arc on your pattern are exactly 1"
apart. On the piece of pipe you want to cut, the two points or the bottoms

of
the vees will be 1" apart, as that is the diameter of the pipe. But, when

you
wrap your pattern around the pipe, the ends of the arcs won't make it

halfway
around the pipe - because halfway around the pipe is really 1.57", or pi

over

OK, you got me with the actual size, but I said to hold the end
of the pipe to the paper and draw the circle.


2. Because the paper has to wrap around the surface of the pipe, doesn't

it?

With a 1" pipe, yes. Not even close with a 6-incher.


And not only will your pattern not stretch halfway around the pipe, as it
should, but when you trace it you'll find that the ends of your arcs meet

the
square end of the pipe at an angle (tangent) of 90 degrees. Not at 45

degrees
as they should.


See above stretchmarks. As to the angle, why would a cut
which was radiused to the OD of the pipe -not- fit? The ends
of the arc would be to the outside of the pipe, not the inside,
so there would be no 90° step. I'll give you the fact that I
didn't address the proper fit for a certified weld, but I'm a
certifiable jury rigger. So sue me.



Larry:

I've seen other posts from you here, and you seem like a decent guy. I really
haven't had any intention to insult or demean you.

What you wrote here, however, was simply wrong. I tried to point out to you in
a couple of ways exactly why it was wrong. I suggested at least twice that you
actually try what you had recommended. Nothing more complicated than tracing
the end of a pipe (or even a can) on a piece of paper, cutting along the line,
and wrapping it around the pipe to see the pattern. You couldn't be bothered.

I tried going through your latest reply, but it's just gibberish. "See above
stretchmarks." What above, what stretchmarks? "a cut which was radiused
to the OD of the pipe". Whatever that means. "The ends of the arc would be to
the outside of the pipe, not the inside, so there would be no 90° step."
Simply can't follow you there, either.

Obtaining the proper fit for a certified weld has nothing to do with this, as
the method you proposed won't even come close. But, since ou couldn't be
bothered to even try it, I guess you'll never know.

Over, and out.

John Martin
  #30   Report Post  
Larry Jaques
 
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Default cut pipes to weld a "T"

On Sat, 08 Nov 2003 02:21:57 -0500, Gary Coffman
brought forth from the murky depths:

On Thu, 06 Nov 2003 18:28:30 GMT, Larry Jaques wrote:


What won't work?


What won't work is trying to stretch a diameter
around half a circumference. In other words, the


I picked up on that this morning when replying to
John. Thanks.


-- Friends Don't Let Friends Eat Turkey and Drive --


  #31   Report Post  
Pooty Tang
 
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Default cut pipes to weld a "T"

On 06 Nov 2003 22:25:59 GMT, (JMartin957) wrote:


I guess you didn't try it, did you? Because if you did, you'd know exactly why
it won't work.

You are talking about using the pattern to cut the point on the end of a piece
of pipe, rather than a vee in the middle, but no matter because it's the same
thing.

Given your example, the two ends of the arc on your pattern are exactly 1"
apart. On the piece of pipe you want to cut, the two points or the bottoms of
the vees will be 1" apart, as that is the diameter of the pipe. But, when you
wrap your pattern around the pipe, the ends of the arcs won't make it halfway
around the pipe - because halfway around the pipe is really 1.57", or pi over
2. Because the paper has to wrap around the surface of the pipe, doesn't it?

And not only will your pattern not stretch halfway around the pipe, as it
should, but when you trace it you'll find that the ends of your arcs meet the
square end of the pipe at an angle (tangent) of 90 degrees. Not at 45 degrees
as they should.



-----The poster who suggested using a rubber ring as a pattern will get the same cut
-----you do, although with the flex and stretch of the ring he'll get closer.

John Martin


And I assume that you didn't try the ring gasket wrap method because
if you did, you would have seen that it does indeed work! I do it all
the time. Don't need no formulas or pi or calculators.
Turn off your calculator, get off your ass and go out in your shop and
try it.

Geez, the guy asked for help laying out a piece of pipe not a lesson
in math. Hell, if we all understood how to mathmatically design a
template for this stuff we wouldn't ask for help.

Instead of telling everybody else how wrong they are and why according
to your calculator, their idea stinks, why don't you whip up a
template for the guy so he can get his pipe cut because all the rest
of us don't know what we're talking about.

I'm gonna go cut some pipe.

James
  #32   Report Post  
Gary Coffman
 
Posts: n/a
Default cut pipes to weld a "T"

On Sat, 08 Nov 2003 15:40:14 GMT, Larry Jaques wrote:
On Sat, 08 Nov 2003 02:21:57 -0500, Gary Coffman
brought forth from the murky depths:
On Thu, 06 Nov 2003 18:28:30 GMT, Larry Jaques wrote:
What won't work?


What won't work is trying to stretch a diameter
around half a circumference. In other words, the


I picked up on that this morning when replying to
John. Thanks.


You're welcome. It should be obvious that what you
really have to do to project a 2D figure onto a 3D
surface. What may not be so obvious is that wrapping
the 2D figure around it won't do that, because the
projected figure on the pipe surface is an ellipse,
not a circle.

The easiest way to generate the correct figure is to
hold the 2D template *flat* above the pipe, and drop
perpendiculars down to the pipe surface to form the
required curve. (A stiff template and a long marking
pen will do for the precision needed for welded joints.)

BTW, the flat projection method will also correctly
describe the elliptical mating hole you need to cut
in the other pipe.

Gary
  #33   Report Post  
Old Nick
 
Posts: n/a
Default cut pipes to weld a "T"

On Sat, 08 Nov 2003 19:13:39 -0500, Gary Coffman
wrote something
.......and in reply I say!:

Just mumbling....Place a highly directional light directly above the
work, then trace the shadow? Saves the steady hand requirement.

The easiest way to generate the correct figure is to
hold the 2D template *flat* above the pipe, and drop
perpendiculars down to the pipe surface to form the
required curve. (A stiff template and a long marking
pen will do for the precision needed for welded joints.)

BTW, the flat projection method will also correctly
describe the elliptical mating hole you need to cut
in the other pipe.

Gary


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  #34   Report Post  
Gary Coffman
 
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Default cut pipes to weld a "T"

On Mon, 10 Nov 2003 05:14:37 +0800, Old Nick wrote:
On Sat, 08 Nov 2003 19:13:39 -0500, Gary Coffman
wrote something
......and in reply I say!:

Just mumbling....Place a highly directional light directly above the
work, then trace the shadow? Saves the steady hand requirement.


The light source would have to be at virtual infinity (sunlight would
work). Otherwise you'd get geometric distortion of the shadow.

Ray trace on a piece of paper and you'll see why.

Gary
  #35   Report Post  
Old Nick
 
Posts: n/a
Default cut pipes to weld a "T"

On Sun, 09 Nov 2003 19:25:10 -0500, Gary Coffman
wrote something
.......and in reply I say!:

*highly directional* as in spot, would, as we have all seemed to
agree, be enough for non-mil-spec non-HP welds IMO. I reckon it would
give as good as using a marker pen, unless you jigged the pen.

But yes, the sun would be good. You would of course have to allow for
the movement of the sun in the sky between drawing one side of the
pipe and the other. .......

Just mumbling....Place a highly directional light directly above the
work, then trace the shadow? Saves the steady hand requirement.


The light source would have to be at virtual infinity (sunlight would
work). Otherwise you'd get geometric distortion of the shadow.

Ray trace on a piece of paper and you'll see why.

Gary


************************************************** ****************************************
Until I do the other one,this one means nothing
Nick White --- HEAD:Hertz Music

remove ns from my header address to reply via email

!!
")
_/ )
( )
_//- \__/


  #36   Report Post  
Ted Edwards
 
Posts: n/a
Default cut pipes to weld a "T"

Gary Coffman wrote:

The light source would have to be at virtual infinity (sunlight would
work). Otherwise you'd get geometric distortion of the shadow.


While that is theoretically true, I doubt that the error induced from a
light source a few feet away would matter for a welded joint. Just use
a short piece of offcut from the pipe for producing the shadow.

Ted


  #37   Report Post  
Don Wilkins
 
Posts: n/a
Default cut pipes to weld a "T"

On Mon, 10 Nov 2003 03:49:38 GMT, Ted Edwards
wrote:

,;Gary Coffman wrote:
,;
,; The light source would have to be at virtual infinity (sunlight would
,; work). Otherwise you'd get geometric distortion of the shadow.
,;
,;While that is theoretically true, I doubt that the error induced from a
,;light source a few feet away would matter for a welded joint. Just use
,;a short piece of offcut from the pipe for producing the shadow.


I think one could use a laser pointer. Set the pointer on the inside
of the perpendicular pipe and draw the outline on the other pipe. Then
do the same with the laser pointer moved around the outside. The
proper cut should be between these two outlines. Cheat a bit to the
large size and cut.

  #38   Report Post  
Grant Erwin
 
Posts: n/a
Default cut pipes to weld a "T"

One more time. I've watched this done hundreds of times in commercial
shipyards. A new piece of soapstone is flat, and about 6" long. If
you sharpen one end, and then lay the soapstone (available at any
welding supply store) on the pipe so it projects over the gap onto
the target pipe, then you can move the soapstone around the pipe and
scribe the line of intersection. Cut this line with a torch and clean
up a little with a grinder, then slide the other pipe into the cut
and scribe it off the edge of the cut. Then take the other pipe back
out and cut to the scribe line and clean it up with a grinder. Then
fit up and weld. This process is called "scribing in" and is used in
many ways in shipbuilding. You can cut the pipes in either order.

The scribing only takes a few seconds. No need for a precision light
source!

Grant Erwin

I think one could use a laser pointer. Set the pointer on the inside
of the perpendicular pipe and draw the outline on the other pipe. Then
do the same with the laser pointer moved around the outside. The
proper cut should be between these two outlines. Cheat a bit to the
large size and cut.


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