steel grade
 

Does it matter if the grade of box section steel is not erw? had a quote of £92 for 40 meters plus delivery off a guy in ebay.
Cheers

If the steel is not ERW it will be Hollow Rolled Section or known as black by most production welders. Theres nothing wrong with using it for a chassis but it will very dirty to work with, it's not known as black for nothing. It will be at least 2mm wall so you might want to put a weld prep or 45' camfer on the ends if using a hobby MIG welder.

This is what I used and as talon says its absolutly manky I wiped mine down with gunwash celly thinners came up a treat

Apparently you should use erw as it behaves differently (god forbid) in the event of an accident

I think it deforms to help absorb the impact and lets face you would need all the help you can get as there isnt much protection in these cars!

You would think that the book lists a certain type of steel for a reason, if it didnt matter the book would probably say that you could use either.

But it doesn't! The book just says "Rectangular hollow sections: 25 x 25 mm square 16swg" (page 30), then it goes on suggesting having a look in the offcut piles of fab shops, and you can't be sure of the grade of steel you find in the skip! The recommendation to use ERW appeared on this forum, as these tubes are cleaner and more precise.

All I could get here in Lithuania was black tubes, albeit of the correct thickness (1.5 nominal, about 1.7 measured). I got a habit of using cotton gloves when handling steel. I went over each length with an emery sponge and a rag, wiping off the occasional surface rust and the loose black oxides. Then on it was quite workable. On the upside, the square section tubes for the whole chassis cost me only 33 quid!