How to check parts for cracks
- Thread starter glenn742
- Start date
Magnaflux is a manufacture that makes (as I believe) every product available
for NDT testing, incl. penetrating dye.
I think what you meant is LPI - Liquid penetrant inspection, or MPI - Magnetic particle inspection.
You mentioned they are old shotguns so I would assume they are carbon steel therefore,
mag particle would work just fine. However, sometimes gun parts can be complex in nature,
LPI would be my first method of choice. A flourescent penetrant dip with water-wash and developer
to be exact but, if all you have is spot-check then that will work also. Only down side to spotcheck
is it might be tricky to wipe off the penetrant from all areas before applying developer.
Hope that helps.
for NDT testing, incl. penetrating dye.
I think what you meant is LPI - Liquid penetrant inspection, or MPI - Magnetic particle inspection.
You mentioned they are old shotguns so I would assume they are carbon steel therefore,
mag particle would work just fine. However, sometimes gun parts can be complex in nature,
LPI would be my first method of choice. A flourescent penetrant dip with water-wash and developer
to be exact but, if all you have is spot-check then that will work also. Only down side to spotcheck
is it might be tricky to wipe off the penetrant from all areas before applying developer.
Hope that helps.
I suspect that dye penetrant is the way to go for home testing. The rest of the options require large and expensive machines. So it means taking the stuff out to somewhere else to get an inspection done.
In this you tube video it's pretty obvious that there's no big time limitations. Even the cleaning operation could be done by spraying down the part then allowing a few hours or overnight for any cleaner in the cracks to evaporate. From there the window of use with the dye is clearly long enough that it allows for a detailed probing with patches and pokey things to clean out internal corners and other spots. So this really does look like the way to go.
In the video the focus is on the big split crack. But note the small radial cracks that show up around the rim. A good example of the sort of things that you'd REALLY be looking for which are invisible or hard to see which then shows up more clearly with the testing.
https://www.youtube.com/watch?v=Vv210Wt32jA
In this you tube video it's pretty obvious that there's no big time limitations. Even the cleaning operation could be done by spraying down the part then allowing a few hours or overnight for any cleaner in the cracks to evaporate. From there the window of use with the dye is clearly long enough that it allows for a detailed probing with patches and pokey things to clean out internal corners and other spots. So this really does look like the way to go.
In the video the focus is on the big split crack. But note the small radial cracks that show up around the rim. A good example of the sort of things that you'd REALLY be looking for which are invisible or hard to see which then shows up more clearly with the testing.
https://www.youtube.com/watch?v=Vv210Wt32jA
I am an NDT tech.... For liquid penetrant inspection, precleaning is critical, as is watching the part after you apply the developer. Don't do too many pieces at once. If there are cracks you will see them grow in the developer. Be aware that you may also see scratches with this method. While not completely straight forward, if you do find a crack, and clean it and test it again, and the indication occurs again, it is probably a crack. If it does not occur the second time, it probably is not a crack.
