Cast Iron pipe tap
Cast Iron pipe tap
(OP)
Ladies and gents,
I have a cast iron part that was mis machined. There were thru holes drilled into the part that need to be 'removed'. So we are going to pipe tap the part and install plugs.
My question: What is the best type of material to use for the plugs to create a seal? The plugs need to be permanent. Ideally, we would install a plug and then cap weld. We can't weld these parts because they are Cast Iron. (My mind is going towards having a soft male material (i.e. cast iron) in the hopes that the threads form to one another)
Cheers,
I have a cast iron part that was mis machined. There were thru holes drilled into the part that need to be 'removed'. So we are going to pipe tap the part and install plugs.
My question: What is the best type of material to use for the plugs to create a seal? The plugs need to be permanent. Ideally, we would install a plug and then cap weld. We can't weld these parts because they are Cast Iron. (My mind is going towards having a soft male material (i.e. cast iron) in the hopes that the threads form to one another)
Cheers,





RE: Cast Iron pipe tap
Is this a real large part?
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P.E. Metallurgy, Plymouth Tube
RE: Cast Iron pipe tap
RE: Cast Iron pipe tap
RE: Cast Iron pipe tap
The two (CS and CI) are usually not interchangeable, that could raise some issues.
I have seen tapered plugs friction welded into place.
Anything with threads is less than permanent.
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P.E. Metallurgy, Plymouth Tube
RE: Cast Iron pipe tap
RE: Cast Iron pipe tap
I'll look for the carbon numbers. The other thought is to use locktite or similar.
RE: Cast Iron pipe tap
RE: Cast Iron pipe tap
RE: Cast Iron pipe tap
My limited experiences with PMI have resulted in doubts, similar to EdStainless. Without knowing the carbon content, it is hardly PMI at all.
There are some helpful test that mere mortals can use to make cast iron reveal itself.
- TIG weld melt a small spot on an edge. No filler. File test when cool. Many irons get very hard when allowed to cool quickly like that.
- Polish and etch an area, and look at the structure.
https://www.youtube.com/watch?v=8DPhc5K_thg
- Drill a small hole or shallow drill point in a safe area with a new drill bit. True cast iron essentially makes dust. Mildish steel makes long curly chips. Ductile iron is somewhere in between.
How are you sure that the errant holes are not in an area that will be highly stressed in service ?
RE: Cast Iron pipe tap
The PMI was done with: PMI Master Plus / Niton XLt 898 XRF.
Carbon content was found to be >1.8%, Fe ~86%, Si ~1.35%
Those are interesting ways to check for CI. Thanks for the info.
The holes are most definitely NOT high stress.
RE: Cast Iron pipe tap
"Even,if you are a minority of one, truth is the truth."
Mahatma Gandhi.
RE: Cast Iron pipe tap
Were several PMI tests done? What method of cleaning was used?
The attached image suggests that " Nitron XRF units are capable of
detecting elements from 12 - 92. "
Carbon's atomic number is 6.
Carbon composition is the main distinction between cast iron and steel. Cast iron typically contains more than 2 percent carbon, while cast steel often contains between 0.1–0.5 percent carbon.
RE: Cast Iron pipe tap
Aidan McAllister
Metallurgical Engineer
RE: Cast Iron pipe tap