Buying and Identifing DOM tube

BIONBlazer

New Member
Joined
Oct 30, 2006
Location
knoxville
Anyone know how to tell if a piece of tube is really DOM? I know DOM is a process and not a type of tube. I bought one piece of "DOM" which turned out to be schedule 80. it was 1.40 inside and 1.90 outside. was sold as a piece of .25 wall 1.5 DOM. But the wall thickness is .202 There is a slight very tiny weld seam inside. It has a black coating on it. that alone should have given it away. so i know now it wasnt DOM.

Second. I got a 14 foot piece of 2" that measures slightly more than 2" outside with a micrometer (2.003 inches) and inside its approx (1.52 inches with the micrometer). Its .2002 wall thickness. its got blue writing on it that tells the length and lot # and says HEAT on it.

Please educate me on identifing DOM verses other similar type of tube. is there a grind method or any other method to tell?
At first i assumed that if there is no seam on the inside its DOM but im thinking thats not the case.

Please help me and others to be educated and know what they are buying.
 
While I'm not an expert, most DOM I've seen usually (but not always) has "ASTM A-513" or the alloy "1020"/"1026" or similar coding on the tube. I've seen the outer finish anywhere from a black "parkerized" type finish (NOT like the BMI you purchased :eek:) to a very shiny "almost chrome" finish.

I was told the finish (& amount of oil left on the steel) were indicators of how it was meant to be stored post distributor... inside/controlled climate, outside/covered/ or outside/uncovered as examples... or how it meant to be processed by the purchaser...

DOM may show "bluing" where it was welded, but there's NO seam showing inside or out...

HTH

:popcorn:
 
Thanks for your help. more info. this piece was stored outside and has surface rust. with some steel wool i am able to get the following numbers. looks like there is a seam on the outside but not 100% sure. you cant feel it. no seam on inside.

The below may not be 100% accurate due to it being hard to read.

MST MIL-T-16288E CL G 2.000 0.0 X 1.65 MIN WAL LENGTH 14.000FT HEAT 23642 LOT #6 ITEM 001/0 CO-1311200 Q-02-03 MADE IN USA
 
I can't decode those numbers but if there's no seam your good to go. All the welded tubing I've ever seen has an obvious seam, especially easy to see on the inside.
Like Caver Dave said "DOM has no seam inside or out"
 
No seam inside or out. Actual outside dimension should be a true 1.75" or whatever OD you are looking for. an OD of 1.90 is a dead giveaway that its not standard tube...

on all the new DOM tube I've had mandrel marks (heat/mill scale type) on the outside of the tube that resembles the pattern on a candy cane.

mechanical tube should have a clean cut end and have a slight internal bevel.

The lot and heat # is useless for you. That is used to trace the orgin of the metal and the makeup of the chemistry of the metal. It is used for ASME code fabrication, etc. to hold the industry to standards for special requirements. When/if a vessel ruptures, then the heat and lot # can be traced to the manufacturer of the steel and, if made incorrectly, is held liable for damages, etc. etc.

Unless you know the manufacturer, it would be hard to track that by the heat and lot #. You're best bet, IMO, is to use the Item # and search metal suppliers to see if that number matches up to anything they have.

All the DOM tube I have purchased has specifically on there the size, wall thickness, metal type (4130, 1020, etc.) and say DOM on there.
 
again thanks for all the tips. this piece does indeed have the slight beveled end edge on the inside and has no seem inside or outside. I cant see any "candy cane marks"...if anything the marks run long ways on the tube.

Maybe I learned what not to get one the schedule 80 and actually got a piece of DOM this time? fingers crossed.
 
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