How much do you guys add to lenghts for threaded pipe?

Tony Conner

...how to do it, I think "roll out", and "set down" (or "set up"). If the roll is 8", and the set is 15", then:

(8 X 8) + (15 X 15) = 64 + 225 = 289. Hit the square root key on your pocket calculator, and get 17". Multipy 17" X 1.414 = 24.038. This is 23 - 1/32". Subtract the take-away values for 45* els for whatever size the pipe is from the table.

Again, the easier way to do it is with a framing square, and a tape measure. 8" on the tongue, and 15" on the blade. Measure diagonally across and get that same 17". (This is the "run", and it works every time.) Multiply 17" by 1.414, and get just over 24" as the center to center measurement. This is the "travel", and is the center to center length of pipe needed. Subtract for a pair of 45* els, and cut the pipe.

This exact example is right out of the "Pipe Fitter's And Pipe Welder's Handbook, by Frankland. He also wrote the "Pipe Trades Pocket Manual". The second one shows a plain offset. There is some overlap between the two books, but there's enough of a difference that they're both worth picking up.

The big thing to keep in mind is that when you're figuring rolling offsets, is that after you measuring to get the roll and the set, it has TWO parts to the calculation. First, figure the "run" (the 17" dimension in the example), then use that to figure the "travel". For 45* els, the factor is ALWAYS 1.414.

To determine the roll and set, two sets of initial measurements are needed, because there's a horizontal and vertical component. Measure off a wall or existing line to the center of the two pipes you need to connect. Then do the same thing off the floor or ceiling to get the vertical.

If you measure out from the wall to the center of each line and get 48" for one line, and 40" from the other, then there's the horizontal distance (the roll) between the two lines, center to center (48" - 40" = 8"). Do the same vertically. If you're 75" from the floor to the center of one line, and 60" to the center of the other, subtract the two measurements, and there's the 15" set.

Bill N.

How much do you guys add to lenghts for threaded pipe?

Doing some steel pipe installation today (not a normal part of my life) and came to realize how superior I find soldering to be as a method of joing pipe.

The question: Who out there can give me a table or list for how much take up steel pipe is supposed to have?

Thanks,
Bill N.

Ed Wallace_2

adding thread lenth

years ago my old boss would add 1 5/8 inches to lenth of steel pipe for threads i have found it works

Tony Conner

Screwed Fitting Allowanances

This table is out of Audel's "Mechanical Trades Pocket Manual", by Carl A. Nelson. This is the little pocket novel sized book. There's also a much larger, hard covered version by the same author - "Millwrights And Mechanics Guide". The larger one, of course, has a lot more stuff in it, but you can carry the smaller one around in your glove compartment.

Take Away For Screwed Fittings

Pipe Size------90*/Tee----45*----Cplg-----Union

1/8"------------7/16"-----1/4"----1/4"-----3/4"

1/4"------------7/16"-----3/8"----3/8"-----7/8"

3/8"------------9/16"-----7/16"---3/8"-----1"

1/2"------------5/8"------3/8"----3/8"-----1"

3/4"------------3/4"------7/16"---3/8"-----1-1/16"

1"--------------7/8"------9/16"---1/2"-----1-1/4"

1-1/4"----------1-1/8"----11/16"--3/4"-----1-3/8"

1-1/2"----------1-1/4"-----3/4"---7/8"-----1-1/2"

2"--------------1-5/8"-----1"-----1-1/4"---1-3/4"

You get the center to center, or end to center measurement, then, depending upon the size of pipe, and what fitting, subtract the value above from the CTC or ETC you've measured.

[Deleted User]

Confusing statement....

Cool chart TC, but to the untrained person, who doesn't understand the difference between end to center versus center to center it could appear to be confusing. The rule of thumb my pappy taught me is the fitting allowance is basically the same as the pipe you are threading. So if I were to need a piece of 3/4" pipe to fit between two holes 12" on center, then the actual cut and threaded piece would be 12 inches, minus 1-1/2", or 10-1/2" end to end.

When it comes to copper fittings, there are two radius' to allow for. Long turn and close rough. With long turn, the fitting allowance is typically the same as the pipe size. With close rough, the fitting allowance is typically one pipe size less than the pipe you are dealing with.

So, using the same example above, and using long radius tees, the fitting take off, or allowance would be the same, so the pipe end to end would be 10-1/2".

Using the same example, but using close rough elbows, the fitting allowance per fitting would be one pipe size less than the actual pipe size, so 1/2" x 2 would be 1" take off for close rough, or 11 inches end to end.

What gets tricky is when you are using a reducing elbow. Then I find it best to use your tape measure to "eyeball" the take off requirement, assuming 1/2" pipe insertion into the fitting for pipe up to 1-1/4", and 5/8" from 2" through 2-1/2".

Here's a mind bender for you. I have two pipes running parallel and I need to use a 45 degree offset to connect the two. The pipes are 16" center to center, 1" black iron pipe. What's the length of the cut and threaded portion of the pipe supposed to be (without holding the two fittings with each hand in place while holding your tape measure in the air with your teeth) ?

Show me your math!

ME

Tony Conner

There's...

...two ways to do this:

1/ The harder way - 16 X 1.414 = 22.624". This is 22-5/8", so you subtract the take-away values for a 45* el on each
end.

9/16 X 2 = 18/16 = 1-2/16 = 1-1/8"

22-5/8" minus 1-1/8" = 21-1/2"

Cut and thread a piece 21-1/2" long.

2/ The easier way - lay the 16" off on a framing square. 16" down the tongue, and 16" down the blade, and just lay your tape measure diagonally across those two points. (Remember to use either the inside or outside scale for both. Don't take one off the inside and one off the outside.) For bigger offsets, you can use anything that makes a 90* angle. Tool boxes, work benches, corners of rooms, etc.

You can do the same thing with rolling offsets. Lay the roll and set off on a square, multiply the measurement from your tape by 1.414, and that gives you the rolling offset, center to center. Subtract the take-aways.

[Deleted User]

BINGO!!

Give that man a cupie doll! Obviously, you done some major pipe fitting in your day Tony. It cracks me up to see the "fitters" of today holding their fittings, er I should say WAVING their fittings in the air while trying to hold their tape measure with their teeth so they can get a "face to face" dimension.

I was told by an owner of a company that I worked for once that a "face to face" measurement was more accurate than a center to center measurement. I warned him not to use those terms in front of a professional fitter or he'd be laughed off the face of the earth...

The only problem with the carpenters square is that most fitters don't have one in their tool box!

[Deleted User]

yup

i get strange looks from other trades people when i bring in my calculator (for the 1.414 measure) and my dimensional catalog (free from the manufacturers by the way guys) but unless i do the math wrong, my pipes fit cause the math cant be wrong, only the person doing the math...i agree, center to center measure is the most accurate..funny how the strange looks and comments always come from people younger than me tho.

Tony Conner

A Lot Of...

...guys have trouble getting that first dimension - the 16". Measure off a wall, the floor or ceiling, to the center of each pipe, and subtract. If they're in the horizontal plane, use a wall. If it's 40" from the wall to the center of one pipe, and 24" from the same wall to the center of the other, then they're: 40" - 24" = 16" apart, center to center.

And you're right about the square. I don't always have mine right there either. That's why you can use anything like a bench, toolbox, corner of the room etc. Measure 16" down each side, from a corner and mark it. Lay your tape diagonally across the marks, and that measurement is the length of the pipe assembly - center to center. For those without a tape measure - and they ARE out there - what can I say?

Mad Dog

Worked on 12\" Screw pipe as an apprentice

Worked under 2 great old schoolers...Jimmy o'Brien of Nyack, New York and John J. Nolan of Hicksville New York. We did alot of nice large commercial repair work. I'd have to dig it out of my old books, but we had the formula for everything...the toughest one and the one that very few men can do is the formula for a 45 degree "rolling" offset...these guys knew it in their sleep...they were Gods to mee=...still are...ones's a dead man now - miss ya shrimp hog... Mad Dog

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[Deleted User]

Bill here is a web site

that has lots of info to purchase regarding piping books/tools etc.----http://www.pipefitter.com/pfind.html---hope it helps

Al Letellier

figuring offsets

Put the calculators away,guys. Lufkin makes a piper's folding rule ( old style 6 footer) that has the 45 degree run calculated on the reverse side of the ruler. Just find your offset and flip it over...voila...diagonal all figured!!! I have three of them and there all getting old,just like me!!

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Tony Conner

The Bit That...

... a lot of guys find tricky is often getting the initial measurements the "roll" and the "set" so you can do the math. The way I remember it is "roll out" (horizontal), and "set down" (or "set up") for the vertical. Measure off a wall for the roll. If it's 32" from the wall to the center of one line, and 40" from the same wall to the center of the other, then it's 40" - 32" = 8". The set is found the same way, only using the floor or ceiling. If it's 45" from the floor to the center of one line, and 30" for the other, then the "set" is 45" - 30" = 15". Once they've got these, the rest is just some math. There are a couple of steps for a rolling offset, vs just one for a regular offset:

(roll X roll) + (set X set) = (8 X 8) + (15 X 15) = 64 + 225

64 + 225 = 289. Hit the square root key on the calculator, and get 17". This is the "run". The "run" isn't the piece you need to cut, but it will let you figure it out.

17 X 1.414 = 24.038". This is the "travel", and is the center to center pipe assembly needed. Subtract the take-aways for whatever the pipe size is, cut it and thread it.

The simpler way is to lay off the roll and set on a framing square. 8" on one side, 15" on the other, and measure across with your tape. 17", just like the "formal" way. Multiply the 17 X 1.414, and get just hair over 24". Subtract the allowances for the 45*s, and get busy.

Works every time, for every size pipe, every material, regardless whether it's screwed, soldered, Victaulic, socket weld, butt weld, compression fittings, etc. You just need the tables for whatever kind of fittings are being used. If you haven't got the official tables, just measure from how far the pipe extends into a given fitting, to the center line. It may not be quite as accurate as the official tables, but it's a whole lot better than squinting one eye, and holding the tip of your tongue between your teeth while you "eyeball" your tape measure in mid-air

Gary Fereday

AMEN,Amen!

Tis not much else to say you guys filled that up nicely! Now undo it! that is measure across (on angle) and figure the square sides. Old pipe went diagonally across excavation. Had to be made square and fit around excavation. only the Hypotnuse was readilly avalible. Oh by the way We welded it up and it fit like a glove, only two in position welds needed!

munchkin-man

simple way is to

measure to the end of each fitting so end to end. add one inch. This will give you 1/2" on each end of the pipe to thread in to the fittings. On the Rigid multi die you line the selector up with an indicator and when it reaches the oposit indicator you have a 1/2" depth in to the fitting. I have piped several oil tanks, gas piping, steam and hot water boiler jobs this way and never had a leak. The object is to make the pitch to pitch min and you will seat provided you use pipe joint sealer. This will seat the root and the crest of the thread upon reaching the pitch.