Steel Plate Tolerance Specification

From electronics (circuit board specification) bow is where the sheet takes the form of a section from a cyclinder where two opposite sides stay parallel and the sheet forms a basic arch shape where all four corners could still contact a plane surface (Just like a section cut from the side of a pipe parallel to its length.).

Warpage/twist on the other hand was considered to be where opposite edges are twisted into a skew condition such that when diagonal opposite corners were on a plane it meant that the other corners could not be in the same plane.

Note that it is possible for an item to have both bow and twist incorporated into it.

(Answering your question, they could both be caused by the same thing (phenomenon) being the outcome of stress relieving during the cutting/shaping process, just that they are described in a different way.

For circuit board material they are described and specified in relation to the offset they create relative to a flat plane and expressed as a percentage of the minor dimension (width) of the finished item.

Thank you for your help! You have confirmed my opinion on these conditions.

I should have been more clear on my requirements. The Bow and Warpage spec is for the raw material, not the finished part. My vendor will be cutting the part from a 8' x 25' x 1.5" thick A36 Plate. The part is 22.5 long by 1.5' tall so the amount of bow/warpage allowed by ASTM will not have an impact any more than any other material we process. We will cut with HiDef Plasma on a submerged water table so the process should be easily controlled.

Thanks again for the help!

Terry Lewis

Akkerman, Inc.

Manufacturing Engineer

check us out on the web at www.akkerman.com

The warpage you refer to is inevitable in a flame cut piece of the dimensions stated. Submerged plasma cut is a good alternative if you have access to that type of facility. As for tolerances, wapage and bow can be dealt with to a degree during assembly, while thicknesses are a mill requirement. +0/-3 for cold and hot rolled if I remember correctly. May we inquire as to the finished product?

May we inquire as to the finished product?

Akkerman, Inc. is an OEM building Trenchless Boring Equipment. This particular application is for our Jacking Skid. The Tunnel Boring Machine (essentially a dirt submarine) is placed on the skid to launch and is pushed through the ground by a hydraulic jacking frame.

Check us out on the web at www.akkerman.com

Thanks again for the help!

Terry Lewis

Akkerman, Inc.

Manufacturing Engineer

Hi Mr.Terry Lewis,

If plate is gas cut then due to heat there is all possibility of wrapage also bow formation. Wrapage is twist formation in length of plate and bow means plate taking shape of bow. It may be necessary to straighten up the plate after gas cutting which laborious process if done manually. I suggest should consider cutting the plate on Water Jet cutting Machine where there is no generation of the heat also cutting finish will be much better than gas cutting. Of course it will be expensive process but above problems can be avoided. It will need progressive cutting as machine can not cut such a long job.

It all depends on your final requirement of the finish.

Regards,

Suresh Sharma.

You did not mention what the temper is. The material in the HAZ (Heat Affected Zone) will exhibit a very hard temper (brittle) along the cut line and quickly deteriorate to T-3 (since this is A-36). You may wixh to consider a post hot-work treatment to restabilize the material. This will have the added effect of eliminating material deformation due to localized stresses.

You could contract the job out to a large shipyard. They have the facilities to cut and form large plates and control parameters.