round tubing vs pipe question

[americanmusc1e]

I didn't know exactly where to post this, but I have a question on round tubing.

Is there a major strength difference between schedule 40 (or schedule 80 for that matter) pipe and round tubing? and will it matter in my case?

I'm needing to build a few things for my truck including a new engine crossmember and eventually some bumpers and whatever. I seem to recall reading somewhere that you are not supposed to use "water pipe" in any structural application, but I have access to a large amount of free schedule 40 pipe. Some of it is galvanized, but I have welded on galvanized stuff before. I am aware that the galvanizing needs to be removed around the weld and its important to keep adequate ventilation. Assuming that my welds are good and my creations are properly engineered, can I use the schedule 40 or should I look into buying what I need?

[dznucks]

without going into the weeds of the differences between the two, for your purposes think of it like this..... Pipe is designed to handle internal pressure from transferring some type of pressurized liquid or gas, typically it is brittle and not forgiving. Tube is deisnged to be structural, handling loads in many different direction and even having some elasticity(flex).

Think about the application and decide which is better. for example, I would make the engine cross member out of tube because it will be handling loading of many different types and should be able to flex under heavy engine loads to avoid cracking. on the other hand, a bumper could be made of anything since it is ultimately sacrificial.

You will also want to think about the criticallity of the specific peice. you can drive down the road with a cracked bumper, but not with a cracked engine crossmemeber.

[mmiddle]

2x Pipe is not for structure.

[davidfre21]

I've ran sch 40 and 80 1" and 2" pipe for bridge cross bars and other random BS without any issues. I don't know if id do an engine xmember though. Most tubing is seamless which helps with the strength. But some of the piping I've come across in the field is also.
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[LONGHAIR]

Tubing is for "building things".
Pipe is for transferring/storing things. Liquid, gas, etc.

Tubing is measured on the outside diameter. When the wall thickness gets greater, the inside diameter gets smaller.
Pipe is measured by the inside diameter. When the wall thickness gets greater, the outside diameter increases.

[chevyrestoguy]

Tubing should always be called out by it's outer diameter and it's wall thickness. Pipe is measured by Schedule numbers, which is an inside wall thickness. It scares me when I hear guys doing chassis work with pipe. It's designed to move liquids or gasses, and is not for structural applications.

If you're doing small jobs, go to your local steel yard and look through their scrap bin or their cut pile for the tubing you need. They'll make you a great deal on it, and you'll be getting the right material to start with.