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[ARCHIVED THREAD] - What does MP testig mean/do? (Page 1 of 2)
Posted: 1/29/2008 12:18:49 PM EDT
| What does MP testing on a bolt do? |
Magnetic Particle tested/inspected is to insure against cracks and or flaws to prevent failure |
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MP testing is only valid after a proof round and shot peening (if required) testing is only valid after all mechanical process are complete because flaws can be caused or exposed through these processes. MP tested bolts are certified as acceptable at the time of inspection only (like all inspection) A bolt that has been MP tested could fail with in 100rds or never fail but the MP testing insures that the bolt was tested and found acceptable prior to you putting your $$$$ out for a bolt you may bet your life on. |
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Manufacturing processes, including and especially heat treating and plating, can cause new parts to crack prior to proof testing and/or service use. In my opinion, however, it's of questionable value in AR-type parts that are not especially hard or plated with heavy metals--cad, chrome, etc. Mag testing after proof testing is of much more significance, and is even more significant after the part has been subjected to normal service use--the more use, the more signifacnt MP testing becomes to detect cracks. Mag testing does not predict whether a part will crack and/or fail. |
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Proof load fired through barrel/Bolt then MP Test, Best way to weed out the crap. I will not fire an AR15 that does not use an MP tested barrel & bolt, But that is just Uncle Sams & My preference. MP TESTING |
+1..... My preference aswell |
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As a USGI marking MP is a proof marking that means Magnaflux and Proof fired (or Magnetic particle). On USGI rifles both bolts and barrels are required to be proofed and marked MP, and they are so marked only after testing has been done and passed. Proofing weapons and using proof marks goes back hundreds of years. Such QC standards are not required in the US though, and most low end manufactures skip it. Regardless reputable manufactures still do. For example, the Remington proof mark is a REP in an oval. As commercial marking in the US MP can mean any number of things. |
I guess that would depend on the industry it’s used in. Aviation relies heavily on Dye Pen, Zy Glow, eddy current ect…… Would you feel safe flying with an airline that disregarded NDTing aircraft parts that require it? My experience tells me no. Dye penning a rifle bolt is one extra step in the QC process that some mfgrs are willing to take to ensure a trouble free product for the end user. |
Hell I won't spend the money on machine work for a hot rod engine without having it 'MagnaFluxed' first. |
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Dye Pen is such an important NDT process in the aviation industry, that would you believe the bolts that hold landing gear wheel halves together are dye penned during each wheel overhaul. Bolts are dye penned at each overhaul and usage cycles are kept track of. When the bolt has reached it’s limit of cycles it’s scrapped. |
Then you can get into the fake China-crap bolts that look just like the real deal Av. bolts.  
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The FAA has a program dealing with the identification and reporting of suspected un-approved parts. Parts receiving inspectors are required to take this training and ALL parts regardless of origin MUST have traceability as well as proper documentation. From individual rivets all the way up to major components. Airlines audit their parts vendors and parts are only accepted from those vendors which meet the requirements of not only the airline, but the FAA. You’d have to be pretty ballsy to try and forge aircraft parts these days. |
That's good I remember reading about the problem with fake bolts 10 or 20 years ago and even the .Mil got burned by them.  
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Agreed. Critical parts used in a vehicle that transports 100's of passengers at a time, NDTing is certainly warranted. And as also stated above however, in many industries it could/should be used to evaluate processes and material lots, but once those are established it becomes a waste. Thats just my opinion. The parts I work with have only been visually inspected for the past 30 yrs and only recently have our customers QA guys started insisting on testing even though we have never had one failure, ever. In my experience, most QA people don't have a f'n clue what they doing or any real world experince with the parts they mandate testing for. Again, YMMV. |
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More than you ever wanted to know.... www.ndt-ed.org/EducationResources/CommunityCollege/MagParticle/cc_mpi_index.htm |
Sorry poppy, there ain't no "better materials" about it when it comes to AR bolts (except for LWRC's enhanced number). Most are still made out of carpenter 158 like they were many years ago. Shot peening was a later improvement. Materials are still 1950's and 60's technology. They all need to be MP tested, IMO. |
What industry are you testing for? I am a QA/QC inspector for refining and chemical as well as structural steel and some of the stuff I see that has "never had anything done to it but visual" still has swastikas on it from when we used to buy valves from Germany between the World Wars. Looking at a part is great to weed out cosmetics but to see what else is there you go to NDT and the type of NDT and the extent of allowable indications all references back to service life requirements, and most of them are less than 25yrs old |
The railroad industry. Maybe i miss spoke, the parts we deal with are not 30 yrs old, our company has been doing this for 30 yrs without fail. The parts are anywhere from 2-10 yrs old with an actual ave service life of probably 40-50 yrs. I apologize if i offended any QC/QA guys here, it's just a sore subject in my industry. QA inspectors(mostly Federal/.gov types) are trying to apply aerospace type procedures to railroads  .
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no offense taken The more testing that is done prior to an incident the better the understanding of what happened after the accident. It's also an insurance thing in your industry as the insurance companies can have more proof that all possible inspections were done to prevent an incident It's called CYA for a reason |
Actually, the railroad industry was the early pioneer of the liquid penetrant method. They were the first to discover that if they soaked parts in oil and wiped it all off and then applied a coating of talc they could find cracks which were not visible with the naked eye. They coined iit the "oil and whiteing method" Anyways, no offense taken. I have been on your side, the supplier, and know how gov't oversight can be. |
I have been out of the Aviation industry for over 25 years now,(I have not even looked at my Airframe or Powerplant licenses for 2 decades) Is Dye Penning what we used to call "Zyglo testing"? |
Dye Pen can be seen with the naked eye. Zyglo of course requires a black light to view. |
That's a loaded statement from a production standpoint. The reason for QA/QC is to maintain the quality standards not to increase/decrease the production. A good QC program will factor in manufacturing procedures and help production eliminate any and all indications to reduce the rejection rate and make their job easier, in turn making the production end look great as their failure/ rejection rates disappear. It may take a while and some friction but most QC issues can be solved in the production end with little effort but the change may not be cheap. There for many companies won't make the nessicary changes and will just deal with the repairs or replacement issues later thinking they are saving money. |
Ah, the old "we don't have time to do it right but we have time to do it over philosophy". |
You fellas may not know how much of a relief it is to find out someone is watching when it comes to these things (particularly aircraft). I am a shadetree mechanic and have broken my share of bolts. I broke one last year that had the proper markings on it that signified it was up to snuff. The bolt snapped like a pretzel, however. It could have simply been one bad example, I reasoned. An identically marked bolt snapped soon after. I am pretty sure those bolts were not what they were made out to be (via the markings). I wondered what could happen if one of those puppies was installed in an aircraft... So, in a nutshell I am pleased that at least someone is watching! |
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When I was working for Boeing Military as a machinist, everything I did had my name attached to it. If it ever failed, and negligence in mfg. was the cause, I would be responsible for the consequences. Along with the QC guys who passed it. By the time a plane is delivered, it's paperwork out-weighs it. |
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IMHO it means that the company building my rifle (or supplying the parts) cares enough about quality control to take the time to test their product(s) before it gets in my hands and that they have some kind of mininum standard. I don't mind investing about $10 more for this peace of mind. |
When it comes to AR15 Bolts/Barrels the highest quality pieces are built by the companies that Proof/MP test them, Because Uncle Sam will not purchase one unless the testing is performed. |
Just because Uncle Sam will not buy them does not necessarily mean that they are the best. The gov/mil process of updating specs can be V E R Y S L O W. Sometimes they can be years, even decades behind the technology. I have no doubt there were some issues that led up to the requirement. I am sure there are newer inspection methods that are more conclusive. I would be willing to bet that there are very few catastrophic bolt failures from all manufacturers whether or not they are mp tested or not. I am going to post a thread asking for personal instances of bolt failures. |
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Quoted: I am going to post a thread asking for personal instances of bolt failures.[/quote] Good Idea, But it may be easier just to search the archives; There Have been quite a few posted on this site over the years. I have personally witnessed only 1 Bolt failure & Luckily it was not catastrophic because the shooter picked up on it before he squeezed the trigger. The shooter fired the gun & noticed that it sounded & felt odd, When he pulled back the charging handle to check it out he found the bolt snapped in half at the cam pin hole. |
I concur with the above, and heartily endorse the use of QC and dye testing when warranted, a great example being the aircraft bolts. Measurement and QC are also critical for getting a manufacturing process under control in the first place. I've had formal training in the area of statistical process control, TQM, 6-Sigma, etc. which are way to ensure high quality production with few or no defects. Regarding AR-15 bolts, I think it would be a pretty good assumption that most of the US manufacturers of Bolts and BCG's, have already implemented a stable production process using TQM, 6 Sigma, or similar programs. Of course, you still need QC to monitor the production, but this can be done with sampling. Therefore, if the product is coming off a highly controlled production line like this, you shouldn't worry at all if each and every bolt is not MP tested. The critical factor is actually to have a totally controlled production process that is making the product as it is meant to be. If for example, if a bolt comes off a production line that is running at less than 3.4 defects per million (the six sigma standard), you would be much better off with one of these bolts that was not tested, than getting a bolt from an uncontrolled production line that was MP tested. This is because MP testing only tells you if there is a crack on the bolt at that moment. It doesn't detect the internal defects that might result in a crack after the first 50 rounds on your MP-tested bolt. The bolt that came off the 6-sigma production line has far less chance of having the invisible internal defect (that will someday cause a crack or failure) in the first place, whether you test it or not. I'm not claiming all US bolt producers operate excellent productions lines like this, but the ones that supply high volume to the military, and the ones with excellent reputation probably do. I'm just trying to point out MP is not the ultimate proof of quality. It is better to get something off a superior carefully controlled production line, even if it is just statistically sampled. |
HERE HERE!  I got your back VectorTX. You and I are probably a couple of the only ones that agree and/or understand this quality concept. People don't understand that this is how the Japanese kicked our butts in quality when they started importing cars, electronics, etc.. Luckily the American manufacturers started using some of the same processes to bring the American made quality up to par. |
Zyglo is a brand name (produced my magnaflux), not a method. Kills me when people say they zyglo'ed or magnafluxed something, says nothing about the method used for the inspection. |
Everything stated above is correct, But even after all the best Mfg. processes are used there will always be some bad parts that come off the line & you do not want to be the guy that has a KABOOM next to your face. Remember the key to testing AR Bolts/Barrels is that a "PROOF LOAD" (M197HPT @70,000psi, a normal M193 is loaded to 52,000psi , M855 to 55,000psi) is fired first to stress the part beyond normal operating conditions, Then the MP Test is performed to see if any flaws developed. Someone who worked for Colt stated in a previous thread (When this was discussed years ago on this site, Check the archives if you want to verify) that the bolt rejection rate was something like 4% to 6% after the proof load/Mp test was performed. But in the end it is your face resting against that rifle when you squeeze the trigger! If you feel comfortable using a non tested bolt go right ahead & do so, it is your call. |
I have given up correcting people on this. Been hearing it for 20 years and I will hear it for another 20. |
This is the kind of ignorant response that is making this web site day by day more and more unattractive to participate on. Yes, Zyglo is the brand name of a type of dye penetrant produced by the company MAGNAFLUX. I’ve been trained in, and using these NDT methods for 23+ years. But synonymous with the name, under the dye pen methods of NDT you have two similar, but yet different methods: 1- Spotcheck (basic dye pen NDT method) Visible to the naked eye. Requires no special tooling to view. Spray on the dye, wait the required amount of time. Clean away the excess dye with the provided cleaner, and apply the developer. Any flaws will be visible to the naked eye. 2- Zyglow (fluorescent penetrant NDT method) Fluorescent being the key word here. Spray on the dye, wait the required amount of time. Clean away the excess dye with the provided cleaner, and apply the developer. Any flaws will be visible only with the use of a fluorescent inspection light. A process similar to basic dye pen, but yet a different method requiring specific equipment. 3- Magnaflux or ( Magnetic particle inspection)- utilize magnetic particles in a suspension fluid pored over the magnetized item to be inspected. Again there are versions of Magnaflux that detect flaws visible to the naked eye, and those requiring a fluorescent inspection light. In aviation, anyone with any experience, if asked to Spotcheck, Zyglow or Magnaflux a part will know the differences in the three methods. So yes, if you tell me you Zyglow inspected a part verses Magnaflux inspected a part, I will know the difference. |
Not that big a deal to me. I work across several fields of NDT and am required to write procedures, and techniques, document, qualify, and certify personnel. I cannot use manufacturers names when writing procedures and giving examinations. I agree each field/industry has its tribal knowledge. Back to the topic of this thread, NDT of bolts. I myself have always believed that the heat treating of the bolts is the most important step in the process. A improperly heat treated bolt will pass MP inspection but its service life would be very short. Anyone know if hardness of bolts is verified? My remington 700 bolt has what appears to be a Rockwell Hardness indentation on it. Did I just get the one out of the HT load which is checked or is it done with all Remmy bolts? Is this done with AR's? Your thoughts and knowledge? I am off to a High Power Rifle Clinic. I will check back in on this thread tonight. |
[ARCHIVED THREAD] - What does MP testig mean/do? (Page 1 of 2)
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