What makes the problem even worse is that most suppliers who might have what you're looking for in stock don't have people manning the phones who know jack about steel, tubing, grades or whatever to begin with. You might call an outfit who has tons of good material in the racks but the telephone people have no idea what you're talking about. Most of the time if you're not buying plumbing pipe they don't have time to deal with you. One of the problems is the 'lingo' of the materials industry. These people speak a different language than I do. I've been buying steel for well over 50 years and I have yet to figure out what language they're speaking most of the time.
Duane knows these folks very well and he can buy pretty much anything that's ever been made by any mill in the world but he's conversant with the 'Lingo' of the suppliers although I've seen it backfire on him a few times when the 'interpretation' didn't work out to well.
For most of us who are building bikes there are only a few types of material that we'll ever have to order. The most common is regular old 'Cold-Rolled' steel plate or 'Bar Stock' for flat parts and ERW or DOM tubing for the 'round' stuff.
In most cases you'll never have to worry about the material grades for flat stock as it's almost always C1018 for Cold Rolled material and this is more than adequate for motorcycle projects where you need to make axle plates, brackets or whatever.
When it comes to tubing however you have to make some educated guesses as to what you'll be needing. Generally speaking about 75% of all motorcycle frames are made from regular old grade 1008 carbon steel ERW tubing. This is about the bottom of the barrel with respect to quality and strength. This is what most factory frames are made from, especially the old ones. ERW stands for 'Electric Resistance Welded'. Basically this type of tubing is made from long segments of Cold-Rolled steel plate that is run through a series of dies and formed into tubing and then welded along the seam. The weld is smoothed on the outer surface of the tubing but left 'proud' on the interior of the tube. ERW is available in several different grades all the way from C1008 to C1026 from some mills.
The next step up in tube material is what we call DOM. In the bike business this is supposed to be some kind of mystical material that is super strong but in reality it's just regular old ERW but the tubes have been 'Drawn Over Mandrel' (DOM) to flatten down in the interior weld seam. Like ERW it comes in a variety of grades ranging from around ASTM 1020 to 1026. There is no difference in the initial 'strength' between ERW and DOM but that's a myth that is hard to get rid of.
In the 'steel trade' these types of tubing are often referred to as 'Mechanical Tubing' since they're typical application is in the building trades for steel framed structures and/or 'machine fabrication'.
A lot of folks don't realize that building a bike is basically like building a machine. One of the few builders I ever meet who did appreciate this was Indian Larry and he did understand the mechanical aspects of bikes as opposed to the visual elements and I personally think his work became so popular because he focused on the mechanical parts of the bike but that a story for another time.
The point of this article is to warn people about buying tubing that is represented as being one thing but when you get it it's something different. In the past year I've have literally dozens of emails from people who have ordered tubing from both online and store-front steel suppliers and they're not to sure they got what they asked for. How do you protect yourself and how do you know what you've got in your hands?
The first thing to look at is the tubing itself. Does it have any grade stamps stenciled on it? The snapshot below shows a typical piece of 1026 DOM. Sorry about the poor quality of the photo but my phone does not like to do closeups. If you squint your eyes you'll see some light white text on the tube. Basically what the stencil signifies is that it's made at such and such mill: it's type is ASTM-A513-5 (DOM) and it's Grade is C1026 (carbon steel 1026): and then the O.D. which in this case is 1.5-inches.