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Posted: 9/2/2010 9:16:21 AM EDT
Ok I don't have an x-ray machine or access to the fancy stuff. I have a Remington receiver the I am told has a cracl in the transition between the receiver flat and the crown just forward of the ejection port. I cannot see it from any angle with a magnafying glass. In some lights it looks as if it might be cracked. I cannot tell.Is there a better more conclusive way to be sure if there is or is not a crack?

Here is one pic that I could get. I know the ridge on the face of the receiver that is just below the transition point is just a machining cut and not a crack.

Link Posted: 9/2/2010 9:28:56 AM EDT
[Last Edit: 9/2/2010 9:35:20 AM EDT by pogo]
I can't see anything in this pic. It could just be a scratch.

You might try a dye penetrant test. I don't recall specifics, but it is a red colored low viscosity fluid and a spray can. Wipe it on the area you want to test, wipe it clean, and then spray a white powder on it to draw any colored fluid back out, staining the white powder.

Something like this: http://www.pegasusautoracing.com/productdetails.asp?RecID=1207

I know nothing about this specific product, but it looks like what I would be looking for.

They have a better explanation of the test than I do:

Many cracks that extend to the surface of metal parts are completely invisible to the naked eye. This is because they may not open up to a visible size except when subjected to operating stresses or high temperature. Yet, these small invisible cracks can continue to grow until they fail catastrophically. This quality dye penetrant system can make many of these small cracks visible because the low viscosity penetrating dye wicks into the tiniest of cracks. Later, when the developer is applied, the red dye bleeds out of the crack making it clearly visible to the naked eye. This handy, low cost system allows you to perform these tests yourself. Because it is designed to be used with visible light you don't need an expensive, high powered source of black light to use it. Kit includes one can each of Penetrant Dye, Cleaner/Remover, and Developer –– enough for up to 500 small scale tests.
Link Posted: 9/2/2010 10:40:17 AM EDT
Magnaflux
Link Posted: 9/2/2010 11:09:03 AM EDT
Originally Posted By Flamethrower:
I cannot tell.Is there a better more conclusive way to be sure if there is or is not a crack?



Hillbilly Magnaflux.

Dip it in gasoline, let it soak for a few minutes.

Pull it out, carry it out in the sunlight and watch the spot you suspect.

If there is a crack, the gasoline won't evaporate as quickly out of it - the line will be visible for a bit while the rest of it evaporates away.



Link Posted: 9/2/2010 12:21:01 PM EDT
Originally Posted By bfarrin1:
Originally Posted By Flamethrower:
I cannot tell.Is there a better more conclusive way to be sure if there is or is not a crack?



Hillbilly Magnaflux.

Dip it in gasoline, let it soak for a few minutes.

Pull it out, carry it out in the sunlight and watch the spot you suspect.

If there is a crack, the gasoline won't evaporate as quickly out of it - the line will be visible for a bit while the rest of it evaporates away.





Gasoline wont hurt the finish correct? I know stupid question but I have never needed to pour gas on a gun yet.
Link Posted: 9/2/2010 3:32:05 PM EDT
[Last Edit: 9/2/2010 3:32:19 PM EDT by bfarrin1]


It'll be fine, oil it after you are done.




Link Posted: 9/3/2010 4:33:24 AM EDT
Originally Posted By pogo:
I can't see anything in this pic. It could just be a scratch.

You might try a dye penetrant test. I don't recall specifics, but it is a red colored low viscosity fluid and a spray can. Wipe it on the area you want to test, wipe it clean, and then spray a white powder on it to draw any colored fluid back out, staining the white powder.

Something like this: http://www.pegasusautoracing.com/productdetails.asp?RecID=1207

I know nothing about this specific product, but it looks like what I would be looking for.

They have a better explanation of the test than I do:

Many cracks that extend to the surface of metal parts are completely invisible to the naked eye. This is because they may not open up to a visible size except when subjected to operating stresses or high temperature. Yet, these small invisible cracks can continue to grow until they fail catastrophically. This quality dye penetrant system can make many of these small cracks visible because the low viscosity penetrating dye wicks into the tiniest of cracks. Later, when the developer is applied, the red dye bleeds out of the crack making it clearly visible to the naked eye. This handy, low cost system allows you to perform these tests yourself. Because it is designed to be used with visible light you don't need an expensive, high powered source of black light to use it. Kit includes one can each of Penetrant Dye, Cleaner/Remover, and Developer –– enough for up to 500 small scale tests.


I have seen this stuff in use before. It seems to work ok. I may have to give it a try along with the other method.

Thanks guys I will let you know how it turns out.
Link Posted: 9/3/2010 5:46:38 AM EDT
Originally Posted By Flamethrower:

I have seen this stuff in use before. It seems to work ok. I may have to give it a try along with the other method.

Thanks guys I will let you know how it turns out.


Regardless of the fluid you are using (low viscosity) it is going to work the same.

Gasoline seems to be readily available for most folks, penetrating oil(Kroil for me) also works very well.

Aerosol tracing powder is what I've used in the past to "draw it out" if you can't easily see the line with the naked eye or with low magnifaction(loupe).

I'd think on a potentially cracked 870 receiver, I'd dip it in whatever, sit it in the sun for a bit then grasp the front and the rear of the receiver and give it a good twist then a squeeze up front and see what comes bubbling out of the "crack" ,if anything.



Link Posted: 9/4/2010 6:38:28 AM EDT
Link Posted: 9/5/2010 5:29:51 PM EDT
[Last Edit: 9/5/2010 5:32:30 PM EDT by sinsir]
Originally Posted By pogo:
I can't see anything in this pic. It could just be a scratch.

You might try a dye penetrant test. I don't recall specifics, but it is a red colored low viscosity fluid and a spray can. Wipe it on the area you want to test, wipe it clean, and then spray a white powder on it to draw any colored fluid back out, staining the white powder.

Something like this: http://www.pegasusautoracing.com/productdetails.asp?RecID=1207

I know nothing about this specific product, but it looks like what I would be looking for.

They have a better explanation of the test than I do:

Many cracks that extend to the surface of metal parts are completely invisible to the naked eye. This is because they may not open up to a visible size except when subjected to operating stresses or high temperature. Yet, these small invisible cracks can continue to grow until they fail catastrophically. This quality dye penetrant system can make many of these small cracks visible because the low viscosity penetrating dye wicks into the tiniest of cracks. Later, when the developer is applied, the red dye bleeds out of the crack making it clearly visible to the naked eye. This handy, low cost system allows you to perform these tests yourself. Because it is designed to be used with visible light you don't need an expensive, high powered source of black light to use it. Kit includes one can each of Penetrant Dye, Cleaner/Remover, and Developer –– enough for up to 500 small scale tests.


well you could ask an NDT tech -

dye pen would be the route to go, just stop by most welding shops, like an airgas supply and ask for it. i think they cary the magnaflux brand. it will cost about $15 a can +/- there will be 2 types w or s - water or solvent , if you get the w type, you will need 2 cans , 1 being the dye, and 1 the developer, the solvent type has 3, with the 3rd being the solvent for cleaning the dye.
step 1- clean the part free from grease and oil, let it dry
step 2- spray a little dye in a dixie cup, and paint it on with a small paint brush, i say this because a little of this stuff goes a long way, and makes a hell of a mess. let it sit for 10 min
step 3 - with a dry rag, wipe off the extra dye, and recoat with dye, let it sit 10 min
step 4 - with a dry rag, clean off the extra dye, when you think that you have most of it, spray a clean rag with water or solvent, wipe it clean, this may take 2 or 3 times.
step 5 - spray a light and even coat of the delveloper, wait untill dry, if there is a crack it will show.

note, do not spray the solvent directly on the art, if it is a hairline fracture, you could wash any dye out of it.
i hope this helps.
here are a few pic of an ar bolt i did.....


the damm thing blead out so much i could'nt tell where all the cracks were, so i just wiped it clean with a dry rag, and put it under the scope, the dye will stay in the cracks and makes it easy to see



Link Posted: 9/5/2010 5:53:22 PM EDT
[Last Edit: 9/5/2010 7:46:59 PM EDT by AeroE]
Link Posted: 9/5/2010 5:57:06 PM EDT
Easier way...Compressed air against the suspect area. That metal is thin enought that if there is a crack, the air should get through and you'll feel it on the other side.

Another option...get a really bright flash light and use your hand to cup/seal the beam it against the suspect area. Turn the light on and go into a room with no windows and no lights on, close the door and look for any light making it through the suspect area.

Wes
Link Posted: 9/5/2010 7:10:19 PM EDT
Originally Posted By AeroE:
A couple years back I got involved in a huge cluster involving penetrant inspection of some 15-5PH parts I sized. The bottom line was the surface had smears all over causing thousands of indications. The first parts had no been pickled, then after they were the surface cleaned up some but still had far more indications than anyone had every seen.

We finally got all that sorted out, the vendor said they were good to go, and when I looked at the parts under the scope I found failing voids in just about the worst possible location on two of the parts.

The whole thing was a big pain in the ass. The only real expert was the technician in our failure analysis lab; the guy was sharp. The three metallurgists were basically useless.



lol .. ya smears and surface flaws can be a big PITA, i cant tell you how many times i had to sort things out that were indicated by other techs. DP is one of those jobs that they give to the new hires, and can often give false positives if they don't do it right. you should see how bad folks screw up UVDP... i mostly do AE on composites now, but i also do UT angle beam flaw detection, c-scan, and remote thickness inspections using a robotic crawler, and have shot 1 or 2 x-rays in the past and ran a few MP test ... personaly though i love being in the lab looking under the scope doing FA.... on another note most metallurgist are about useless anyhow , one time i found a signifiant flaw (delamanation) in the dome head of a code pressure vessel, it caused one hell of a shit storm, and resulted in the MFG, rewriting the QC program, and inspecting every vessel made from that lot of steel ... .. the metallurgist was dumbfounded, and said more then once i was wrong, although they found at least 2 more in that lot

Link Posted: 9/5/2010 7:59:29 PM EDT
[Last Edit: 9/6/2010 12:38:04 PM EDT by AeroE]
Link Posted: 9/6/2010 5:40:27 AM EDT
over the last 3 months, I've been going round 3 with an engineer from a large company, I was working for the mfg, doing the last stage of qc, AE on FRP vessels. if you know AE and composites, it is a very sensitive inspection method which requires a significant amount of interpretation, and an experienced operator. what he couldn't seem to understand is - yes you can detect minor flaws or defects, such as entrapped air,dry glass,resin rich areas, ect, that will produce data during the AE examination, however, it doesn't mean that it is or will be structurally significant to the operation of the vessel. we argued that fact, even though the follow up inspections, by the buyers own qc, based on my reporting determined that all the flaws or defects, which were confirmed visually, were within the contractual standards for such flaws. still we argued - this is what happens when people read a standard, and think they know more then the guy who has been doing it 15+ years
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