So, for almost 50 years I have had the opportunity to investigate various material/component failures, and with all the variables, two things have been fairly consistent. The first statement that is most often heard, aside from; “Don’t look at me!” is, “It looks like defective material.” Eventually, and more often than not, the actual reason for failure involves something other than material defect; incorrect material, design and engineering misunderstandings relative to material availability and the creativeness of people when it comes to overcoming those obstacles, changes in the application or environment, or a mishap in the installation, assembly, disassembly or earlier repair, etc.
The instances of material defect are very often the least contributory to failure. Perhaps the cleanliness or toughness of the steel was not up to the task. But that is not really a defect. It is a specification problem.
There are of course defects in material. That is true with any product. The point here is, don’t make that the first assumption. Besides, you are more apt to be able to quickly fix the problems that are most often contributory, right there on location, if you can identify them early.
Not to be MOTO (Master of the Obvious) here, if you are in maintenance you already have developed a mental checklist to identify the most frequent culprits; steel grade, toughness, change in temperature, alignment, moisture, chemical environment, load, vibration, lubrication, wear, surrounding forces, surface scratches, gouges, or cuts, new employees (Don’t look at me!!), sabotage, Keyser Söze, Russian interference, inc.
When the usual suspects have been ruled out, begin planning for some failure analysis testing. You will eventually need to provide a specimen of the failed piece (preferably at least 4″ to either side of the break). Contact your supplier and request their assistance. They may contact their local independent testing facilities, may have their own lab, and/or, they may contact the producing mill. I have been reminded; “In maintenance, as in life, most of our wounds are self-inflicted”.
Routine industrial applications can destroy some of the toughest materials known. And that is just during the daily conduct of business. Be mindful of the effects of those forces and respect the potential for catastrophic failure (whether it results from material defect or not). Make use of appropriate safety gear, stay alert, and if you don’t know, ask!
-Howard Thomas, April 9th 2019
REMAINING FIVE POINTS – elaborated
- If the finish shaft involves substantial step downs, or, if only a small portion of the bar needs to finish… share that information.
- Remember, your supplier cannot be responsible for a third parties work, and/or mistakes.
- If liability on the shaft is considerable, consider parking it in another parties driveway.
- Try to “Talk the Talk” Phrases like, “a stick of steel”, or, “cold roll”, or, “a length of steel”, will get you in trouble.
- Share important ancillary facts with your suppliers; have you received steel in the past that has not been straight enough, hasn’t cleaned up, or was inappropriate in another way?
Why share info on details of a finished part with the supplier?
Well, you don’t need to go over everything, but statements like; “It’s going to be a long small diameter shaft with a big lollipop head on one end” will tip off an astute vendor to the potential of post machining stress related problems. On the other hand, a statement such as: “There is only a very small high spot near the middle of a short shaft that needs to finish to 8″ Dia. The rest of the shaft is 7” Dia. That might make a difference on how much stock is needed for allowance on the raw material.
The caution stated in number 2, above, is just a gentle nudge to limit how much responsibility you find yourself mentally assigning to the supplier. In the final phase, except for mill defect, unless the vendor is handling the job from cradle to grave, the responsibility for success or failure is really out of their hands.
Jobbing the actual machining to an outside source is not just about saving money, mostly because it will generally cost more. But, there are times when “potential problems are probable”. Who knows the product better than the supplier? You may want to see if they felt confident making a difficult piece. If so, why not let them. That eliminates lots of “finger pointing” if the job goes south. If the job goes wobbly, who’s wallet comes out? Their product, their method, their machining, their liability. If they screw it up the burden is on them to do it over at their expense.
TALK THE TALK
Like it or not, many terms are esoteric to specific industries. With hydraulic components, a bar of steel is a rod. When dealing with freight haulers and steel coils, they use terms like; “Eye to the sky”, or, “Suicide”. If you find yourself working within the maintenance steel industry, try to use the same terms you hear the suppliers using. It will go a long way to eliminating surprises. Surprises in maintenance are generally not good.
In closing, if you know some relevant history about a specific shaft or application, by all means share it. If the bar diameter did not clean up the last time, share that. If the shaft broke or bent, share that. If you encountered hard spots or glazing, share that.
Now, if your supplier is decidedly not interested in your ancillary comments, or, if they cut you short and enjoin you to just tell them the dimensions of the steel you want, perhaps you should try a second source. No harm no foul. You can always go with the first source. It is always nice to test the waters.
-Howard Thomas, April 1st 2019
The following is a continuation from our last blog on ROUND bar clean up.
It is important to share both your finish diameter AND length. They would like to know if you have a short stubby shaft, where straightness is not often an issue. Or, if it is a small diameter shaft that is 18ft. long. Big difference in how you approach the raw material for the job.
We are not suggesting that you ask the supplier what size they recommend, since a savvy supplier will avoid answering that. Yes, they are there to help you, but they can’t possibly know how talented you are in making a difficult shaft. It always comes down to; When things go South, who’s wallet comes out? Sufficient stock allowance for one, might be trouble for another.
You might also share information on what grinding, or machining method you intend to use; are you grinding or turning on centers, or will it be a centerless operation; which is by far the most common. Clean-up stock and straightness requirements will be different.
What surface finished are they able to supply? Do they have pre-machined, or, rough turned stock, is it fine-turned, cold drawn, hot rolled, or as-forged? Each may have a different allowance for removal that has been left on the bar. There are of course standards that govern each type of finish, BUT, there are variances from one mill to another.
Share “end-use” information with the supplier. What is the application it is being used in. If you are making Hydraulic Rods for instance, that would be an important bit of information you might want to share.
Subsequent Operations that will be incorporated, is also important. Will you be changing the hardness, adding surface hardness or surface-coating? If they don’t seem to be interested, no harm done. They just assume you’re verbose. A good supplier, however, will recognize that your contributions are important to a successful transaction.
In the next post, we will finish up elaborating on the last of the 10 points relative to “Stock Allowance on Round Steel Bar”.
-Howard Thomas, March 6th 2019
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Howard Thomas
Experience
Sr. Acct. Mgr. (US Southwest) / Metallurgical Consultant
Associated Steel Corporation
Jan 2017 – Present
Past Vice President / General Manager
Associated Steel Corporation
Apr 1998 – Jan 2017
Past Vice President / General Manager
Baldwin International
Apr 1974 – Mar 1997
Education
Cleveland State University
Kent State University
University of Denver
