there is a great discussion on pipe versus tube in the hardcore section.
And from what Woody posted scedule 40 is a 1.33 wall thickness so the OD would be differant between tube and pipe.
hardcore 1/4 eliptical question
There is a PILE of reading available at
http://www.pirate4x4.com/tech/billav...0/index1a.html on steel materials....
In general/simplest terms, the welded seam of water pipe is inconsistent enough to be considered a significant weak point in the material.
"Contnuous (butt welded) pipe process.
The continuous process produces a full range of pipe sizes from only a few different widths of skelp. The coils of skelp, or strip, are fed into the mill and their ends welded together to provide a continuous flow. The strip passes through a pre-heater and into a furnace. The heated strip is shaped into an arc of about 270° in a forming stand before passing into the welding stand. There a nozzle applies oxygen to the edges to further heat them as they are pressed and welded together. The pipe's OD and wall thickness are reduced in a stretch-reducing mill. Pipe is then cut to length, reduced to the required size in a sizing mill and water-cooled before being straightened. It is then ready for finishing "
"Typical Electric Resistance Welded tube process
Steel strip is unwound from coils and side-trimmed to control width and condition the edges for welding. The strip then passes through a series of contoured rolls which progressively cold-form it into a circular shape. The edges are forced together under pressure and welded by heating the steel to temperatures between 2200° F and 2600° F using copper contacts or coil induction. Weld flash is removed from the the inside and outside surfaces of the newly-formed pipe, and the weld zone is heat treated to ensure homogeneity between the base metal and weld. The weld is subjected to in-line nondestructive testing, and the tube then passes through a series of sizing rolls to attain its precise finished diameter. It is then straightened and cut to the desired finished length.
DOM tube being constructed, starting as ERW and then being drawn over a mandrel.
The manufacturing process for DOM tubing begins with coils of steel, which are slit to the proper width for the desired tube size. The strip is cold formed and passed through an electric resistance welder which joins the edges together, under pressure, to complete the tubular shape. After testing the weld's integrity, the tubing is cut to length for further processing"
"Q: Is pipe only for plumbing?
A: Certainly not. In fact, the word "pipe" is often grossly misused. It is, of course, not a designation of any particular product or material, and therefore confers no meaning in terms of any particular mechanical properties (strength, ductility, impact resistance, etc.) Pipe is a type of steel tube, usually intended to convey liquid or gas. I say usually because, in the construction industry, material labelled "pipe" is frequently used in the construction of bridges, buildings, oil rigs etc. Pipe, like any steel tube comes in various grades and conditions - some quite suitable for building 4x4 parts, and some not at all - just like other steel products. You have to know what you're dealing with, what its condition is, and what its properties are before you can decide. Here is some comparative data on one common type of pipe, though again, it is in no way representative of all "pipe"
The ASTM A-53 spec is the American Society for Testing and Materials specification that covers seamless and welded steel pipe intended for mechanical and pressure applications, including ordinary uses in steam, water, gas, and air lines. Note that it says "mechanical applications" whcih means building things. Also note that the yield strength of this most common type of pipe is 30,000-35,000 compared to 32,000-40,000 psi for common 1010 ERW, CREW, and HREW compared to 70,000 psi for 1020 DOM and 90,000 psi for 4130 Cr-Mo DOM."
"Industry publications will list pages of tables of these "standard" dimensions. For example. A 1" pipe will have an OD of 1.315" and a wall thickness depending on its schedule as follows.
Schedule 40 - 0.133
Schedule 80 - 0.179
Schedule 160 - .250"
