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black iron threaded fittings and steel pipe

Fittings have ratings called class. The class is a standard defined by the ASME/ASTM. In particular we care about Class 150 defined in ASME/ANSI B16.3 Malleable Iron Threaded Fittings. This is the standard reference for threaded malleable iron pipe fittings for classes 150, and 300 that defines the following:

(a) pressure-temperature ratings (b) size and method of designating openings of reducing fittings (c) marking (d) materials (e) dimensions and tolerances (f) threading (g) coatings

Iron fittings and pipe most often comes in black or galvanized finish coat. Galvanized pipe and fittings have been dipped in molten zinc to help prevent rust. Black fittings and pipe may not actually be black. It's probably better to think of black as meaning not galvanized. The fittings are usually gray, bare metal. The pipe may be bare steel, painted black, coated with black tar/asphalt, or bare steel dusted in gray graphite. I prefer the raw or graphite steel over others. Tar/asphalt is easy to clean or burn of. Paint can also be cleaned or burned, but tends to be more difficult to get down to bare steel. It can be difficult to tell the difference between paint and tar/asphalt.

Black iron pipe fittings are often called cast iron, but are actually most often cast from malleable iron, which has properties similar to mild steel. Malleable iron is easily weldable. True cast iron is difficult to weld. Malleable iron cast fittings typically are certified as either class 150 malleable iron (150# malleable) (most common home use) or class 300 malleable iron (300# malleable) (commercial building use). These fittings are almost always threaded with NPT (National Pipe Tapered). There are true cast iron fittings and pipe, but these are used more for DWV (Drain, Waste, Vent), steam, or when specified by code in certain municipalities. Do not confuse class 150 malleable with class 150 cast.

steel pipe (black iron pipe)

Pipes have ratings called schedule.

Black iron pipe is actually made form steel. The name refers to the black cast iron fittings the pipe screws into. The diameter of a pipe roughly specifies the inside diameter. The schedule of a pipe refers to the thickness of the wall. This measurement is very nominal and may even seen arbitrary or simply wrong for small sizes such as 1/8" diameter schedule 40 pipe, where the inside diameter is slightly larger than 1/4" (so it's easy to confuse it with 1/4" pipe). Also remember that due to the welded seam you can't rely on a given sized rod fitting or sliding smoothly inside a pipe. Trivia: it it's measured by the inside diameter it's called a pipe; if it's measured by the outside diameter it's called a tube.

Pipe used with threaded fittings is generally made from seam welded steel. Flat steel sheets are rolled into a cylinder. The gap between rolled edges it welded to form a seam. The seam on the outside ground smooth. The inside seam is left and is easily seen and felt. The most common pipe wall thickness is referred to as schedule 40. Heavy duty, high pressure pipe is referred to as schedule 80. There are many other schedules and classes of pipe.


Short pieces of pipe that are threaded on both ends are called nipples. Nipples generally come in precut 1/2" increment lengths from slightly longer than 1" up to 12". The shortest 1" length is referred to as close or closed, and are slightly longer than 1" (how much longer depends on the diameter). The other nipple lengths are exactly as specified and are measured from the ends of the pipe, not from the ends of the threads. That is, the threads are included in the length. This means that when you screw both ends of the nipple into a fitting that the space between the fittings will be shorter than the length of the nipple. Also not that it's nearly impossible to exactly fit measurements using threaded pipe. A pipe may screw much more deeply into one fitting to get a seal than a different fitting. If a seal is not required then it's possible to coarse adjust spacing over a small range, but don't rely on this. This spacing between a sealed fit, a snug fit, and loose may only be one turn.

Special couplers used to pull together and close two sections of pipe are called Left/Right Nipple And Coupling Sets.

Removing galvanization

Avoid welding galvanized pieces as they will release poisonous fumes. See Metal Fume Fever for more safety information. This does not mean welding galvanized steel should never be attempted under any circumstances. Even outdoors you will should use a fan to keep fumes away from your face.

It is easy to remove the galvanization from iron. Simply soak the parts in plastic bucket filled with hydrochloric acid (HCL, or muriatic acid). Muriatic acid at a strength of 31.45% HCL is available at most hardware stores. It can be used full strength or diluted 1:1 with water. Hydrochloric acid quickly dissolves zinc, but it only very slowly attacks iron. You can tell when the part may be removed when the acid bath stops fizzing. Remove the part and wash with water. The acid should have almost no effect on the iron.

If you have not used hydrochloric acid before then you should familiarize yourself with its safe usage. The reaction with zinc is extremely energetic. It will bubble and fizz and release acid fumes and hydrogen gas. Hydrogen is flammable. You do not want to be downwind of the acid fumes as they will burn your eyes and lungs. Even a small whiff can be very painful.

coping (miter)

Cutting a pipe so that it may be welded to another pipe requires a saddle cut. There are coping calculators that print templates to trace onto the pipe to be cut. There are tools to imprint a cut pattern and transfer this to a pipe to be cut. There are tools to clamp and pipe and hole saw at the desired angle and just cut the hole directly without calculating the cut line.

Search for "tube coping calculator" and "tube miter calculator" and "tube saddle calculator" and "tubing notcher".

lamp, small table

Use 1/8" steel NPT fittings.

  1. 2 - tee fittings Anvil 8700120309, Malleable Iron Pipe Fitting, Tee, 1/8" NPT Female, Black Finish
  2. 3 - 90 degree elbow fittings Anvil 8700123550, Malleable Iron Pipe Fitting, 90 Degree Elbow, 1/8" NPT Female, Black Finish
  3. 3 - plug fittings
  4. 3 - 3" nipples Anvil 8700136255, Steel Pipe Fitting, Nipple, 1/8" NPT Male x 3" Length, Black Finish
  5. 1 - 1-1/2" nipple Anvil 8700136107, Steel Pipe Fitting, Nipple, 1/8" NPT Male x 1-1/2" Length, Black Finish
  6. 1 - 12" nipple Anvil 8700136701, Steel Pipe Fitting, Nipple, 1/8" NPT Male x 12" Length, Black Finish


NEMA power cord blades: Wide/White/Neutral, Narrow/Black/Hot

HPN Heater cord -- HPN cord (AKA HPD cord -- HPN is specifically Neoprene (a brand name of Dupont), whereas HPD is generic rubber): Heater, Parallel, Neoprene. Required for heater applications, such as heaters, irons, and toasters. Works well for other applications because the neoprene insulation is soft, flexible, and resists burning.

wire abrasion protection

Wire should have abrasion and/or stress relief at points where it passes through a hole or turns a sharp angle. Braided sleeves for this purpose are available. The braided sleeve may be made from fiberglass, plastic, or stainless steel.

Braided Sleeving


My favorite brand of black-iron fittings is Anvil, which are made in the USA. My second favorite brand is TSP (Tri Sinar Purnama), which are made in Indonesia. SCI is another common US-made brand. Their fittings are fine, but a bit ugly. They have a nice web site, which is easy to browse. My least favorite brand is Mueller, which is made in China. Unfortunately, most consumer retail stores seem to be moving to Mueller. My main complaint is that their fittings are ugly, both in terms of their finish and the haphazard way they cast marks and codes into the iron with no sense of style or craftsmanship. Granted, most people using pipe don't care how it looks. Style is not usually associated with iron pipe.

Anvil International http://www.anvilintl.com/product/pipefittings.aspx or http://www.anvilintl.com/products/anvil-pipe-fittings/cast-iron-fittings/cast-iron-threaded-fittings -- These fittings have a trademark image of a blacksmith's anvil. The image may be raised or recessed. These cast, threaded fittings are made in the US. The company is large and own many other name brands. It's possible they may own the Mueller brand, which they use to sell cheaper products made in China.

TSP (Tri Sinar Purnama) http://www.trisip.com -- These fittings have a simple TSP in an oval trademark. One of my favorite cast, threaded fittings.

Jinang (trademark looks like a spiral inside of a diamond)

SCI (Smith-Cooper International) http://www.smithcooper.com/cat.php?g=2757

Mueller Industries http://www.muellerindustries.com/ -- These fittings have a fancy, geometric M trademark. They are made in China. It appears that it might have once been a US company. Anvil appears to have control of part of the name brand, but not for cast, threaded fittings.

Grinnell -- These fittings have a simple, bold G trademark. Originally a Canadian company. Have they discontinued or spun-off their cast iron threaded fittings?

Ward (J. P. Ward) -- The Ward brand is cast in raised sanserif capital letters. Simple, if a bit boring, but looks good on the 1/8" fittings.

other brands






copper fittings (soldered)

alternatives to copper fittings

If you have a design based on soldered copper fittings and you need to convert to a more durable or corrosion resistant material it may be possible to switch to stainless steel. There is no drop-in replacement that I know of, but socket weld (SW) fittings may work. There are two main styles for welding flanges, Fixed Socket Weld (FSW) and Swivel Socket Weld (SSW). There are lots of others, such as Tube Socket Weld (TSW).

Stainless materials commonly found are Stainless Steel SS316 and SS304 and Alloy 400 (Monel nickel alloy). SS304 is cheaper and common. SS316 costs a bit more but is better suited to food handling. What makes SS316 ideal for food handling is its better resistance to acids, alkalis, and chlorides (notably sodium chloride -- table salt). SS304, can suffer from pitting corrosion when exposed to salt.