Not looking to start another retarded "my rifle's penis is bigger than your's" thread (although I have little doubt it will eventually end up there).  I have several AR's some of which are tested and others which aren't, so I've got no hidden agenda in asking...

I tried a few different searches here and elsewhere, but had no joy finding what I was looking for - that could mean my search terms aren't quite up to par.

Just a serious technical question...

Among those manufacturers and suppliers who DO test their bolts or other components, is there any data regarding rates/numbers of failures during testing?

Is there any mfr who is willing to say "Out of every 100,000K bolts tested, we identify X number of components which fail to meet the standard/pass the test."

I am a believer in taking as much guesswork out of tool selection as possible, I'm just curious as to how many potentially substandard parts are culled from the lot by this process.

If 1 out of every 1,000 are culled, that's a pretty significant ratio which says alot about the efficacy of testing.  1 out of 100K is still pretty notable, but not quite as alarming.

1 or 2 per million would lead me to believe the testing is less of a factor in quality.

Any gouge on this?  Are these numbers set forth somewhere?  Trade secret?  

I'm guessing it's far more than would be measured per million, but nowhere near 1/1000.

Try to keep it on an intelligent level, guys.  We can already close our eyes and click the forum at random with a pretty good chance of hitting a thread full of "Kool-Aid" references and bruised egos...

Magnetic particle testing only find defects on the surface.  It does so because steel is ferromagnetic and the "lines" of magnetization applied in the MT process will concentrate at ALL discontinunities on the SURFACE.  This includes all holes, lug corners and any other edges.  Such indications are NORMAL.  MT's only value here is finding defects on the relatively flat surfaces like the cam pin hole web.

It cannot find defects located deep in the material.  And that includes defects in the center of the cam pin hole web, a HIGHLY stressed area.  Defects in other areas outside of the lugs and bolt face.

Now, specifications for the military are "written in blood".  The MT specification (MT is the proper NDT term, Magnaflux is a trademark process and MPI is military) arose out of the early life of the M16, material science has progressed to make such testing unnecessary IF the proper material is utilized.  But if the letter of the TDI is followed, lesser materials and specifically poor processing WILL make life short for any bolt.

ASNT is the most recognized authority in such matters.  My experience dealing with ASNT level IIIs with regards to MT and UT is the basis of my judgement and I have had them run MT, PT, RT and UT on some bolts.  Their judgements were PT is by far the best NDT for both bolts and carriers due to geometry.

Now for the materials engineering.  Bolts with significant defects that are missed by NDT will fail in a very low cycle fatigue regime.  That is 1-100 rounds.   The failed part's fracture line will show the defect, usually just below the surface along with large areas of ductile faliure.

Bolts which fail in the 101-5000 round counts which fail do not do so from any INDICATABLE defect but from MATERIAL FATIGUE.  These failures are noted by the absence of any ductile failure.  This is typical low cycle fatigue in the hardened steels used in firearms.

The most common fracture point is the web of the cam pin hole.  The most common problem is severity of quench.  This is not anything that can be detected by MT/MPI.  Buy quality, not specifications.  

Good read.

Now for the other section of materials engineering.  Shot peening.  This WILL help by turning the surfaces peened into a material having residual compressive stress.  This MUST happen before the heat treatment but the process of heat treatment also involves carburizing the surface of the steel.  When the steel is above the austentic point, its structure changes from face centered cubic to body centered cubic, slightly increasing the volume which "opens up" the surface to absorb carbon.  When this happens, a slight increase in packing factor which when the metal cools, negates the compressive stress imparted by shot peening.  The net effect?  Nil.

That is GREAT information, Keith - thanks for breaking it down.

Do you have any insight on failure rates during testing?

In other words, is there any statistic whereby a company can say "By performing these tests, we identified XXX number of inferior components which were prevented from reaching the end user"?

I don't place too much emphasis on statistics, however I think it would be telling if a testing regimen culled a ridiculously high percentage of components.  

If it resulted in a statistically insignificant number of failures, then that supports the sentiment for buying materials/quality versus testing/procedure.

If I read correctly, then you are saying that a bolt which has already surpassed the 100 cycle mark has already exceeded the point at which MT would have been a benefit - and that failures beyond that point would be unlikely to have been predicted by this sort of testing?




ETA: I replied before you had a chance to complete the info on shot peening.  I'm gonna need to digest that before I can ask further questions in that direction.  I never knew what I didn't know...

To address the OPs question––I've never seen any data(and I've looked as much as I know where to look) that would address the frequency of failures (indications) discovered when mag testing the bolt or barrel. I suspect that its a military requirement  that will never be eliminated whether it makes any sense or not. I'd personally rather see some evidence of 100% hardness checking on critical parts––barrel, bolt, bc, cam pin, etc––but with the exception of seeing such evidence on a couple of Colt BCs in photos, that evidence isn't to be found. I suspect that all of the evidence we're looking for is highly proprietary to the various manufacturers.

so after all that, what makes one companies bolts better than another?

and what companies possess these qualities?

Anyone remember the phrase:

"You can't inspect in quality"


I would rather have a part from a manufacturer with excellent processes than one with 100% inspection.

Unfortunately, in this case we can't get a look at the process, which is a much better indicator of actual quality than whatever inspections are done on a part after it is made.

-Z

You are looking for much of the correct information.

The one other interesting piece of information is, are we conducting the right test.

One would need to know:

- Of pieces that passed inspection, what percentage fail in actual use.
- Of the pieces that failed inspection, what percentage fail in actual use.

There may or may not be a correlation between passing inspection and actual function of the part.  

-Z

I don't so much question whether it makes sense or not.  I understand the .mil's adherance to strict protocol on matters like this as it helps prevent (or at least slows) the sort of "creep" that can slip in unnoticed on high volume issues over the course of years and decades.

I also suspect it is proprietary info (the statistics reagarding failure rates), but I can't help but wonder if it's closely guarded in order to:

A) Avoid disclosing a high number of failures which would introduce concerns among third parties (unfounded or otherwise) over quality of materials - no company wants to say they have XXX number of production components which failed to meet an "industry standard"...

or

B) Avoid disclosing a low number of failures which would provide a counterpoint of "See how much of a non-issue this sort of testing really is, it won't prevent any significant number of failures - and even that miniscule amount would be found out within 100 rounds" - thereby marginalizing a marketable selling point which has set it apart from competitors.



Exactly!


Again, no agenda - I'm legitimately curious.

NDT failures are generally a trade secret.  Why?  It gives statistical merit to the visible portion of manufacturing.  While the customer will have the lot Mill Test Records, NDT procedures, scrap rate is kept a trade secret.  

Also, scrap impacts the bottom line.  It is lost opportunity.  And there is the reason to minimize the scrap rate.  Better materials, like Vacuum Arc Remelt steels and ultra fine grain processed materials cost more but save far more in material.

Now my NDT experience deals mostly with welding and since most processes have considerable operator skill involved, NDT there becomes an HR issue..  And yes, the NDE staff keep these highly confidential even though rework and the welder's stamp are patently visible.

Customers would LOVE to have the welder qualifications and stamps but these are generally not provided.  Weld procedures and procedural qualification records are provided.  And since welder stamps change, an internal record of the welder's stamps remains in-house.

And finally, specification are written in blood are slow to be implemented but damn near impossible to eliminate.

Thanks again, Keith.  Makes sense when you spell it out like that...

Welcome...I have been around this stuff for 15 years.  Still yet to get my ASNT III.  Although I call for their services...conflict of interest.

That is what I would think.  This is why I started a thread a couple days ago asking if anyone who insists on MP tested bolts does periodic re-inspections with MP or Dye Penetrant (PT).

The thread appears to have been ignored.

It seems silly to me be wrapped around the axle about factory MP testing for a brand new gun and then at same time not bother to do periodic retesting once the bolt is in service.

A can of cleaner, dye, and developer can be had for about $20 - $25 total and an inspection would only take a few minutes.

I use a Magnaflux yoke at work with dry powder for MP testing weldments from time to time, and at least that setup would be a very cumbersome method of checking a small intricate part like a bolt.

Yeah, I get the used cans thrown my way yet they still have PLENTY for a few bolts.  But unless you have an ultrasonic cleaner with a good solvent, most bolts get too dirty and won't reliably indicate PT.  But 15 minutes in paint thinner with sonication cleans it up great.

I doubt you will find indications before the bolt breaks.  Crack propagation in these materials and under those stresses is a rapid thing.

While machined, heat treated, parts can "show indications" (i.e. crack) on their own without being put under operating stresses, due to quenching, hydrogen embrittlement, etc, my assumption is  that the mag testing and proof testing we're talking about on the ARs, of the bolt and barrel go hand-in-hand. That is, there wouldn't be any reason to mag a part if it hadn't been proof tested with an overload.

In other words, in my view magging and stamping a part that hasn't been proof tested is hype, and the only thing it proves for sure is that the manufacturer owns a stamp.
The magging process itself is controlled by mil and industry standards, and can itself be performed at various levels of competency and thoroughness––all legitimate provided they comply with whatever the part designer specifies in his engineering data.

My philosphy is to buy parts from manufactuers who have a tangible stake in the integrity of the part and not how they happen to be marked.  If fake airplane parts can get into the system with all of the appropriate markings and paper trails in place, for sure civilian weapon parts, with no regulatory agency supposedly controlling them, can
too.

These Vacuum Arc Remelt steels, is 9310 one of those?

Google seems to suggest it is.

Almost any steel can be processed this way.  It reduces gas micro inclusions.  But it is expensive as the furnace is inductive and these are typically small.  Which is why A36 or A516 will never be processed...millions of tons are used each year.  And since a typical military contract involves thousands of pounds, there might not be a cost advantage for high cycle fatigue resistance, if the primary specifications can be met with the VAR alloy.  Remember, lowest bidder.  

Now with respect to MT after proof testing...well, yes, it can show more defects.  And since proof loads at 70 KSI are done remote, there is no liability to do such testing.  But there could still be a few bolts that suffer LCF and have passed this testing IF the material is excessively hard.

Sure, that "MPI" stamp is a "low stress stamp" but we are talking about 170 KSI yield materals here.  That ARE yielding.  Which is why the stamp is put in a low stress area.  And probably the easiest location to indicate a flaw with MT.

So what does this mean?  Well, military bolts are minimum specification.  Made at minimum cost.  Yes, they are far better than no-name gunshow crap.  But compared to somethng made with a brand-name steel?  Domestic, like, oh say Carpenter?

No, I don't work for Carpenter.  But I am a customer.  And while you will pay 300% more than for the same alloy from China, the peace of mind is worth it.  And if you were to take metallographic samples, etched with FeCl3/HCl under 150 power magnification, quality IS visible.

I would think the shot peening induced plastic deformation would be completely erased before the phase trasformation. Assuming there wasn't enough for recrystallization or grain growth, full recovery of the material would be likeley and be the reason for elimination of these compressive stresses.

Excellent point.  Unless they used shot peening post heat treatment.  Not having the specifics, I can only assume.

<––––Another ASNT Level III whom feels that way.  The only value I can think of in choosing mag over penetrant is that  DC mag does go sub surface...ever so slightly.

That said, when one is actually tasked with determining the correct test methods at the correct steps in the manufacturing process things do arise which can change the test methods chosen.

When the TDP was written we do not really know what defect they were most concerned about. Experience and testing may have shown, at that time, that mag was best option.  Or even something as simple as the fact that the supplier back then did not have a penetrant capability but they did have mag capability.  Also, it could have just been a cary over from another TDP and they had a good history of reliability with mag particle and did not want to go through gauge R&R to prove out PT.  

I have been involved in programs where the alloys, heat treatments and test methods are carry overs from the 1950's but the customer did not want to go to the expense of changing drawing, specifications, FAA aprovals etc... for something that is working and its service life is very predictable.

Edited for typo

This right here, shot peening, would make penetrant difficult to impossible.  This may be the very reason mag is used for locating processing/manufacturing defects.

A study done by an independant laboratory has shown that as many as 1 in every 100 bolts produced will not pass a HP/MPI test. That is why we test each and every bolt we sell, to make sure that every bolt we sell is 100% reliable. When you demand the best, Demand Fictional Company Parts!

-Fictional Company

I think that would be a pretty strong add for paying 5-15% more for a company's bolt. However, noone has produced an add even similar. Leading me to believe the failure rate is VERY LOW. Another thing, I have cruised these boards for a while, and this came up a while back. Someone in the industry (not officially) stated the failure rates were all but insignificant.

Also, the military HAS done studys on bolt failure. That is why the replacement schedual for the M4 is around 5K rounds IIRC as the average failure occurs in that area roughly (I forgot the exact number, I am sure others have seen the PDF file on it though).

So let me ask this? How many people here have weapons without MPI bolts that have passed 5K rounds (even in dedicated FA upper/lower combo's?)

I am betting lots of bushy's and whatnot.

There are 50K+ people on this board. How often do we see a "my bolt broke" thread?
Not too often.
How many MORE bushmasters than Colts are out there? A LOT! I would wager.

Seems to me HP/MPI is worth nothing more than the extra confidence that it gives some people, and FYI, batch testing is acceptable per the TDP from what I recall.

This may be unscientific, but all I need to know from a practical standpoint.  Pat Rogers observations on bolt failures in carbines classes:



All from Page 3 of this tacked thread:  What Parts Break in a Carbine Course?

This thread is good.  Sticky it.

Sorry to high jack the thread, but if i have, say, gallons of materials to "magnaflux" would
this be as good as MT. Set me straight as i am no metalurgist but work around pipe that
needs to be tested before it is put through a tunneling process. This liquid shows surface
flaws that would indicate a crack. Is this gtg or no.

Let's see if I get this right...

Shot peening changes the direction and quality of inherent stresses in the metal?  And this prepares the metal for the following steps that make the steel "tougher" while at the same time relieving the crystalline stresses in the steel?

I've followed that discussion as well, and it seems to align with what Keith has contributed.  Those bolts/components which are going to fail in a manner which was predictable by MT would be expected to do so within the first 100 rounds fired.  Those which fail at a round count of greater than 100/less than 5K would not have been caught by MPI testing (MT per Keith's terminology) and the testing is therefore immaterial for those components (would not have detected a fault of that nature).

So in essence, if your bolt has exceeded the 100 round mark sans failure, then you have already surpassed the point at which MPI (MT) would have provided a benefit.  

I'd go a step farther and say that since NO weapon which has not been proven with ample cycles (far beyond the 100 round benchmark) should ever be considered an operationally relied upon weapon (for a myriad of reasons beyond bolt characteristics), then the MPI/MT testing provides little benefit from that viewpoint (although it could prevent some headache in supply chain/down time on a platform which is new into the pipeline and may need a bolt replacement early on - again, this is in the "proving" stage, not the operational stage of a weapon's lifespan).

I'm still wrapping my head around the shot peening.  Late shift last night and on duty again today, so I'm not quite up to par as of yet...

All in all I'm learning a lot from these responses, and no one's posted that damn chart or shot off on any tangents (although the "carbine course" thread could lead us there).

The question that arises from the carbine course tangent is:

Among that picture book "full of broken bolts from the makers who do not build to the standard", which of those failures WOULD have likely been detected with the sort of testing we are speaking of, and which would have "passed" the test, yet failed anyhow due to mechanism MT would not have detected?

If the belief that those bolts which "failed" the test should have "failed" mechanically within 100 rounds holds true, then you would have to assume that there are folks running these courses with near virgin rifles (or at least bolts) for the lack of MT to have been significant as a factor in their unanticipated failure.  While I'm sure there are those that fall into this category, I hope not enough shooters have committed this error to fill a book.  

The remainder of those photo'd failures (those which occurred in the cyclic range between 101-5K rounds), would be attributed to substandard materials/processing, not the lack of testing.  Those which fail beyond 5K are immaterial as they have exceeded the reccommended lifespan, and failure should be anticipated (although many of us, myself included, possess bolts which are functional far beyond that mark - that's a bonus, not a benchmark).


Not looking to argue superiority of a specific manufacturer's bolts, that can be surmised relatively well anecdotally (assuming reporting parties are impartial with no agenda), just curious how much of that superiority can be attributed to their testing regimen, versus the simple superiority of their materials and processing.

Eddy current for barrels and bolts...no. Eddy Current is predominantly for non-ferous materials. It would also be very expensive.  I do believe they are now doing ET on some ferous materials but that is not my area of expertese. I am not a Level III in ET.

By Gamma I think you mean isotope radiography.  Way expensive and not practical for the type of defects.  The central beam of radiation would have to land right on top of a crack. Think of it this way, you bolt  two sheets of 1/4" steel together, face to face, (not end to end) with say a 1/8" gap inbetween them. Now take a shot with eithe x-ray or gamma ray beam pointing at the face/flat surface of the two plates.  The image on the film will not show the 1/8" gap.  Now, take the two plates and stand them on end and shoot them  with the beam straight down on the end. Obviousley the resultant image on the film will now show the 1/8" gap.  Radiographic inspections rely on changes in subject density to locate defects.  

I have done x-ray inspection of bolt stops and triggers (these were investment cast) looking for shrinkage voids. When looking for voids it actually works well, but for tight cracks not so much. Radiography relies on a sufficient change in subject density  to show up on the film as a density change.

I hope I articulated this well.

Magnaflux and MT are the same thing. Magnaflux is a brand name.

I know you would know this, but the Magnaflux company also sells penetrant products, so the term "Magnaflux" can be confusing... probably what he is refering to.

again I ask,

so if these testing procedures are bassically irrelevant, hwo can we determine which brands of bolt are better?

As long as it is for steel and you know how to use it, this is perfect.  Bear in mind, you need to clean the bolt with a good solvent and possibly ultrasonic.  The cheapie Harbor Freight units work great.  Use water in the US, put the bolt in a small Rubbermaid container and hit is for a cycle.  Acetone/alcohol/glycols are better as they are "harder" due to hydrogen bonding.  Mineral solvents are "softer" meaning they have a lower bulk modulus and aren't as aggressive.  Whatever you use, make sure to cover the solvent container to reduce vapor flammability issues.

Once cleaned and dried, apply the dye, let soak for 30 minutes, then wipe clean.  DO NOT RINSE.  A slighty damp cloth can be used.  NOT WET.  Let dry, the spray developer and inspect.  Digital photos after the developer has dried and then after 30 minutes will discern between residual and a real indication.  Get good with digital macrophotography, this really helps differentiate between residuals and actual cracks have a time-dependent indication.

Glad to see an ASNT-III here.

I didn't see anything in this thread which would lead one to believe that testing is irrelevant.

"Irrelavent" may be a bit severe of a term for the testing procedures - I would lean towards "their importance is overstated"...

I think the overriding issue is material selection, along with proven processes.  

Someone here should be able to contribute some info as to exactly what those material/process specifics may be - I just shoot them...

Also, getting into a fringe topic of "whose is better" spins this thread into the same tangent as every other - a penis measuring contest.  The original question was regarding the impact of industry standard testing procedures in identifying potential problems - and I've learned a good deal about that from the responses thus far.

There are tons of threads in this particular sub-forum regarding which bolts break and the manner in which they do it.  The link on pg 1 of this thread takes you to the carbine course thread which covers it pretty well.

LOL !  I read the title & thought  hmmmmmmm aint gonna get a decent answer w/o a ASNT-LIII & here they are, thanks for picking this one up. AWS CWI here.







Looking for some API 1104 work

You never know who might be around to contribute their knowledge....

Lucky to get that sort of input!

A lot of good input, by many people, in this thread.  

I was wishing that someone would post a link to that NAVSEA report about bolt failures.

Or a free link to the Westpoint Engineering Dept. study.  All that is now available is pay.

Two things are pretty obvious. What they're made out of and how they're made.

so how is BCM better than DPMS in this regard?

Just from what they have on their page, it doesn't seem any different, save that they really stress the MPI.

Keith said that Carpenter is a good steel and I know there is at least one company that makes bolts out of that.

I just purchased (but haven't received) a bolt that's made out of 9310 and has all the sharp corners radiused.
The little I know of mechanical engineering, 90* corners are stress risers and a good place for a part to break, but we'll see how it works out.

testing   procedures of the bolts/barrels of M4 carbines



MIL-C-71186(AR)

3.4.4 Hiqh pressure resistance. Each barrel assembly end
bolt shall withstand the firing of one Government standard M19?,
5.56mm high pressure test cartridge conforming to MIL-C-46936.
After proof firing, parts shall be free of cracks, seems and
other injurious defects as evidenced by visual and magnetic
particle inspection.
3.4.5 Functioning. Each carbine shall operate without
malfunctions or unserviceable parts. The cyclic rate of fire for
a 30 round continuous burst using a 30 round magazine shall be
within 700 to 97o rounds per minute when firing Government
standard t4855, 5.56mm ball cartridges conforming to MIL-C-63989.
3.4.6 Tarqetinq and accuracy. A series of 10 rounds fired
from each carbine at a range of 91.4 meters shall be within the
extreme spread and targeting area (heavy outline) specified in
Figure I when the front and rear sights are set as follows. The
normal rear sight peep (sight rotated fully rearward) shall be
used with the rear sight set centrally in the slot for windage


4.7.4 High-pressure resistance test. This test shall be
performed during individual carbine testing in accordance with
TABLE III, using a fixture for holding the bolt and barrel
assembly per drawing 11837944.
4.7.4.1 Test cartridqe. One (1) high-pressure test
cartridge (see 3.4.4) shall be fired in each bolt and barrel
assembly. Unless otherwise specified, the bolt and barrel
assembly shall be tested concurrently. After proof firing,
cartridge cases shell be examined for bulges, splits, rings and
other defects caused by defective chambers of the barrel
assembly.
4.7.4.2 Barrel inspection. The barrel assembly shall be
magnetic particle inspected in accordance with MIL-STD-1949
utilizing a current of 400 to 500 amperes for circular continuous
magnetization. The barrel assembly shall be examined for
evidence of cracks, seams and other injurious defects.
4.7.4.3 Bolt inspection. The bolt shall be magnetic
particle inspected in accordance with MIL-STD-1949 utilizing
standard five turn magnetizing coil with a current of 200 to 300
amperes. Both circular and longitudinal continuous magnetization
with wet fluorescent solution shall be used. The bolts shall be
examined
defects.
for evidence of cracks, seams and other injurious.

MIL-STD-1949A
3. DEFINITION
3.1 Ambient light. The visible light level measured at the Specimen
surface with the black light on.
3.2 Alternating current. An electrical current that reverses it@
direction of flow at regular intervals.
3.3 Black light. Electromagnetic radiation in the near ultraviolet range
of wavelengths 320 t 380 nanometers (1 nm = lCI-9meters) with those
wavelengths near 365 nm predominating.
3.4 Classification. The initial review of a visible magnetic particle
accumulation to decide if it is held on the test piece by magnetic means or by
non-magnetic means (i.e. if it is a relevant, non-relevant or false
indication).
3.5 Coil 8hOt. Production of longitudinal magnetization accomplished by
passing current through a coil encircling the part being inspected.
3.6 Conditioned water. Water with an additive or additives which impart
specific properties such as proper wetting, particle dispersion, or corrosion
resistance.
3.7 Continuous method. The continuous method of examination consists of
applying or otherwise making available on the surface of the piece an ample
amount of magnetic particles to form satisfactory indications while the
magnetizing force is being applied.
3.8 Contracting agency. ,A prime contractor, subcontractor or government
agency procuring magnetic particle inspection services.
3.9 Defect. An unintended discontinuity with size, shape, orientation or
location which makes it detrimental to the useful service of the part.
3.10 Flux leakage. A local distortion of the normal magnetic flux
pattern
of
a magnetized part caused by a discontinuity in the part.
3.11
Pull wave rectified alternating current. A full wave rectified
single or three-phase alternating current.
3.12 Gauss. This is the unit of flux density or induction in the
centimeter, gram, seconds electromagnetic unit system.
(1 gauss = 10-4
tesla) (In air 1 gauss is equivalent to 1 oersted which equals 79.58 amps per
meter).
3.13 Half wave rectified alternating current. A rectified single phase
alternating current that produces a pulsating unidirectional field.
3.14 Head Shot. Producing circular magnetization by passing current
directly through the part being inspected while being held
in
contact with the
head stocks in a horizontal wet machine.
3.15 Indication. An accumulation of magnetic particles on the test piece

MIL-STD-1949A
4. GENERAL R!Y2UIREF!ENTS
4.1 Principles
of
magnetic particle inspection.
4.1.1 Intended use of magnetic particle inspection. The magnetic
particle inspection method is used to detect cracks, laps, seams, inclusions,
and other surface or slightly subsurface discontinuities in ferromagnetic
materials. Magnetic particle inspection may be applied to raw material,
billets, finished and semifinished materials, welds, and In-se;vice parts.
Magnetic particle inspection is not applicable to nonferromagnetic metals and
alloys such as austenitic stainless steels.
4.1.2 Basic principle. The method is based on the principle that the
magnetic flux near the surface
of
a magnetized material is distorted locally
by the presence of discontinuities. This distortion
of
the field pattern,
termed “flux leakage=, is capable of attracting and holding an inspection
medium of finely divided magnetic particles. The resulting accumulation of
particles will be visible under the proper lighting conditions. Sensitivity
is greatest for discontinuities at the surface.
4.1.3 Magnetization and particle application. Magnetic particle
inspection consists of magnetization of the area to be inspected, application
of suitably prepared magnetic particles while the-area is magnetized or being
magnetized, and subsequent classification, interpretation, and evaluation of
any resulting particle accumulations. Maximum detectability occurs when the
discontinuity has a depth at least five times its opening, a length at least
equal to its depth, and is positioned perpendicular to the magnetic flux. In
order to detect discontinuties in all directions at least two magn,eticfields,
perpendicular to one another in a plane parallel to the surface being
inspected shall be used, except when specifically exempted by the contracting
agency.
4.2 Qualification of inspection personnel. All personnel performing
magnetic particle inspection shall be qualified and certified in accordance
with MIL-STD-41O. Personnel making accept/reject decisions in accordance with
the process described by this standard shall be qualified to at least a level
II per MIL-STD-41O. Personnel performing the processing steps described in
this standard shall be qualified to at least a level I per MIL-STD-41O.
4.3 Acceptance requirements. The acceptance requirements applicable to
the part or
group
of parts shall be incorporated
as
part
of
a written
procedure either specifically or by reference to other applicable documents
such as MIL-sTD-350 containing the necessary information. Applicable drawings
or other’documents shall specify the acceptable size and concentration of
discontinuities for the component, with zoning of unique areas as required by
design requirements. These acceptance requirements shall be as approved or as
specified by the contracting agency
4.4 Written procedure. Magnetic particle inspection shall be performed
in accordance with a wzitten procedure applicable to the parts or group of
parts under test. The procedure shall be in accordance with the requirements
and guidelines of this standard. The procedure shall be capable of detecting
the smallest rejectable discontinuities specified in the acceptance

MIL-STD-1949A
requirements, The written procedure may be a general one if it clearly
applies to all the specified parts being tested and meets the requirements of
\.
this standard. All written procedures shall be approved by an individual
qualified and certified to MIL-STD-41O, Level III for magnetic particle
inspection, and shall be submitted upon request to the contracting agency.
4.4.1 Elements of the written procedure. The written procedure shall
include at least the following elements, either directly or by reference to
the applicable documents:
a.
b.
c.
d.
e.
f.
i.
j.
k.
1.
m.
n.
0.
Identification of the parts to which the procedure applies. This shall
include the material and alloy of which the parts are fabricated.
Identification of test parts used for system performance
verification (see 5.7.2 and 5.7.3).
Areas of the part
to
be examined (include a sketch if necessary).
Directions of magnetization to be used, the order in which they are
applied, and any demagnetization procedures to be used between shots.
Method of establishing the magnetization (prods yoke cable wrap
etc).
Directions for positioning the item with respect to the magnetizing
equipment
The type of magnetizing current and the equipment to be used.
The current level, or the number of ampere-turns to be used and the
duration of its application.
Part preparation required before testing.
Type of magnetic particle material (dry or wet, visible or fluorescent,
etc.) to be used, the method and equipment to be used for its
application,
and,
for the case of wet particles, the particle
concentration limits.
Type of records and method of marking of parts after inspection.
Acceptance requirements, to be used for evaluating indications and
disposition of parts after evaluation.
Post-inspection demagnetization and cleaning requirements.
The procedure identification number and the date it was written.
Sequence of magnetic particle inspection as related to manufacturing
process operations.
4.5 Record of inspection. The results of all magnetic particle
inspections shall be recorded. All recorded results
shall
be identified,
filed, and made available to the contracting agency upon request. Records
shall provide for traceability to the specific part or lot inspected, and
shall identify the inspection contractor or facility and the procedures used
in the inspection.
4;6 Magnetizing and demagnetizing equiPment. Performance
of
a
satisfactory magnetic particle inspection requires magnetization of the part
to a specified level in a specified direction. Magnetization can be
accomplished either by passing an electric current directly through the
material (direct method), by inducing a current to flow in the part under test
(induced current method), or by placing the material within the magnetic flux
of an external source such as a coil (indirect method). The types of
equipment available include yokes, portable units, mobile units, stationary
units, and special application units (e.g. a unit to produce a single or
.—
multidirectional field).

















thats all I am doing unless someone wants more.


all of this you can find on my thread in the colt industry forum where I am collecting all the data on  the MILSPEC and TDP I can find on the M4 sorry If I mad eit all too long

thanks man.  I went through a lot of trouble  for that stuff. I am glad you appreciate it

This is nothing more than amateurs debating.
So we will never know the failure rate of tested bolts.

I want it known that I have never busted a bolt.

























































This is masterbating.

However I do BUST A NUT from time to time.

Funny you should say that when this has been one of the most factual, an informative threads I have EVER seen on here.

You have 2 experts in NDT3 and Keith_J, and yet you call everyone amateurs.

There was ONLY 1 post that even mentioned any brands in this thread. That HAS to be a new record!!!!

Why yes, now the thread is officially mature. We have a masturbation reference!



For those of you who requested it: NAVSEA Report
You will find what you are looking for on page 44.