WATER PUMPING WINDMILLS
ORIGINATORS OF THE HIGH CAPACITY WINDMILL PUMP
IRRIGATION, AGRICULTURAL DRAINAGE, FARM AND RANCH WATER SUPPLY, DOMESTIC AND COMMUNITY WATER SUPPLY, FILL PONDS, LAKES AND RESERVOIRS
WINDMILL SYSTEM TOOLS AND USEFUL ENGINEERING INFORMATION
Wind Powered Energy Systems should be designed to operate with maximum efficiency in the common wind speeds encountered at the sites where they will be used. Commercial wind power systems are usually located, by choice, where average wind speeds are high and hence the return on investment is maximized. Maximum operating efficiency in high wind speeds is a requirement at such sites and high operating efficiency in low wind speeds is of little concern. Not all users have this option as most smaller wind power systems are located at sites acquired for reasons other than access to consistent strong winds. This requires most users of small wind power systems to maximize the use of the winds they have available at their site, which is typically less that are found at suitable commercial wind power locations. At such sites, wind power systems must have optimal performance in lower wind speeds as opposed to operating at maximum efficiency in the higher wind speeds that most sites see only rarely. It is common for most manufacturers of wind electric systems today to strive to achieve maximum efficiency in the higher wind speeds while paying little attention to maximizing efficiency in the lower wind speeds.
This makes sense in strong winds as the amount of energy available is obviously higher, but it does not make sense at sites where strong winds are not available a reasonable amount of time. In real life, strong winds are neither common nor consistent for the large percentage of users, so achieving maximum operating efficiency in such strong winds is a moot point.
If any Wind Powered Energy System does not make effective use of the common winds available, the user is likely to be dissatisfied with the result of their investment. If on the other hand, a system is well planned to take maximum advantage of the actual winds available, the result is likely to be a satisfied customer who gets what they want. Many hours of efficient / productive work in the lower / common wind speeds at any site is much more desirable than using equipment that provides high output in strong winds, but does little or nothing in the common winds.
Tom Conlon - Senior Engineer - Iron Man Windmill Co. LTD
One CUBIC METER of WATER is:
2204.62 Pounds
1000 Kilograms
61,023.74 Cubic Inches
35.3147 Cubic Feet
264.17 Gallons
1.0 Metric Tons
One CUBIC FOOT of WATER is:
62.46 Pounds
28.331 Kilograms
1728 Cubic inches
7.4805 Gallons
0.028317 Cubic Meter
One GALLON of WATER is:
8.355 Pounds
3.790 Kilograms
231 Cubic Inches
0.13368 Cubic Feet
0.003785 Cubic Meter
WARNING! Verify that all data and results are correct before using!
WEIGHT
Enter amount in the appropriate cell below, then click any empty cell!
Kilogram (Kg)
Pound (Lbs)
Newton (N) Force
Kilonewton (kN) Force
Grain (Gr)
Gram (G)
Milligram (Mg)
Ounce (Oz)
Ounce (Troy)
Ton, Metric
Ton, Short
Ton, Long
VOLUME
Cubic Meter (M3)
Cubic Centimeter (Cm3)
Cubic Foot (F3)
Cubic Inch (In3or cu in)
Cubic Kilometer (Km3)
Cubic Millimeter (MM3)
Gallon (Gal)
Liter (Lt)
Ounce Fluid (Fl Oz)
SPEED
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LENGTH & DISTANCE
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AREA
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AREA TO DIAMETER
Area:
Area Unit:
Ø Unit:
 
PRESSURE
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TEMPERATURE
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FEET, INCHES, FRACTIONS
Feet:  
Inches:
Fractions:
Result In:
 
H20 PRESSURE / ELEVATION
Elevation:
Unit:
To:
 
VOLUME FROM DIMENSIONS
Length:
Width:
Height:
Dimension Unit:
To Cubic Unit:
 
CIRCLE CALCULATOR
Enter the circle area, dia. or circ. and click calculate for the solution to others.
Area:
Dia:
Circ:
WIND SPEED LEVELS AND EQUIVALENTS
Wind Level Meters Per Second Kilometers Per Hour Miles Per Hour
0 0.0 - 0.2 0.7 0.0 - 0.4
1 0.3 - 1.5 0.8 - 5.4 0.5 - 3.4
2 1.6 - 3.3 5.5 - 11.9 3.5 - 7.4
3 3.4 - 5.4 12 - 19 7.5 - 12.1
4 5.5 - 7.9 19.1 - 28.4 12.2 - 17.7
5 8.0 - 10.7 28.5 - 38.5 17.8 - 24.0
6 10.8 - 13.8 38.6 - 49.7 24.1 - 30.9
7 13.9 - 17.1 49.8 - 61.6 31.0 - 38.3
8 17.2 - 20.7 61.7 - 74.5 38.4 - 46.4
9 20.8 - 24.4 74.6 - 87.8 46.5 - 54.6
A WORD TO THE WISE
With interest in Green Energy growing, we hear of new wind energy systems nearly every day. An increasing number of new companies in this field are making claims for the performance of their products that are unsupportable. One company is claiming to be "PRODUCERS OF THE WORLDS MOST POWERFUL WINDMILL." They publish the pumping capacity of their windmill which shows, upon examination, that their claims require about 280% more energy than exists in the wind speeds they list! Of course, if the required energy is not in the wind to begin with, then the work obviously cannot be done. Claims like this are made by those who are either new to this industry and lack knowledge and experience or are looking to extract funds from the gullible. BEWARE and check such claims thoroughly yourself before opening your wallet and shelling out your money. We offer information on how to evaluate the performance of wind powered pumping systems and performance claims here.
WATER AND PIPE FORMULAS
An Elevation of One Foot of WATER = 0.4334 lbs per Sq In
To determine the Head in feet when the pressure in sq. in is known, multiply by 2.3
Friction of water in pipes increases as the square of the velocity.
Doubling the diameter of a pipe increases its capacity 4X.
Pipe is able to deliver water in gallons per min. equal to 0.0408 X the square of the diameter, X the velocity in ft. per minute.
PUMP CYLINDER CALCULATIONS
Piston Area = R2 x 3.1415
CU. FT. in one foot elevation = R2 X 3.14159 X 12 ÷ 1728
Lbs. in one foot elevation = R2 X 3.14159 X 12 ÷ 1728 X 62.425
Gallons in one foot of elevation = R2 X 3.14159 X 12 ÷ 231
Pump Rod Load in Lbs = R2 X 3.14159 X elevation (Ft) X 0.434 + weight of pump rod
The weight of water in a length of pipe is obtained by multiplying the length in feet by the square of the diameter in inches X 0.34
WIND ENERGY AND WORK
By Tom Conlon CEO / Senior Engineer, Iron Man Windmill Co. LTD
THE ENERGY IN THE WIND CAN BE DETERMINED USING THE FOLLOWING:
0.5 x the density of air (Kg per M3 or usually 1.23 at sea level) x wind speed in M per second3 x rotor area (m2) x betz (0.59) = Kw
The result of this formula is in Kw and is theoretical. It does not take into account efficiency losses which must be considered. The Betz factor must be considered and cannot be ignored. Betz can be described as wind seeing all wind energy devices as an imperfect wall - a resistance to the free movement of the wind. A portion of the wind will always move around a wind energy device rather than through it. This factor affects all wind energy devices of every type, including ducted or shrouded devices and is unavoidable. For calculation purposes, wind energy devices with ducts or shrouds assume an area equal to the area defined by the overall dimensions of the shroud or duct. 0.59 is the maximum amount of usable energy available for a wind energy device of perfect design. In the real world, all wind energy devices see losses greater than this. A multi-bladed water pumping windmill of very good design is able to operate with an overall system efficiency of about 30% in lower wind speeds. For comparison, the average modern automobile operates with an overall system efficiency of about 15%! Be sure to understand the efficiency notes below.
THE AMOUNT OF ENERGY (IN Kw) REQUIRED TO LIFT A CERTAIN AMOUNT OF WATER TO A CERTAIN Elevation CAN BE DETERMINED USING THE FOLLOWING:
Cubic Meters (M3) Per Minute x Pumping Elevation (M) x 0.16316 = Kw
Or, if you prefer to use gallons & feet:
Gallons Per Minute x 8.33 (Lbs per Gallon) x Pumping Elevation (in Feet) x 0.0000226 = Kw
Note on the above! The result using this formula is the theoretical amount of energy required to do the work. It does not include mechanical losses, fluid resistance losses, electrical losses etc. The result from this formula will be considerably lower than the amount of energy actually required. Be sure to understand the efficiency notes below.
EFFICIENCY OF WIND ENERGY SYSTEMS
The modern water pumping windmill is a highly refined invention having made it's first appearance in 1854 and undergone significant improvement for 78 years, and has earned the right to claim a relatively high degree of mechanical efficiency. Let's take a closer look.
Here is a list of the losses that must be considered when designing or evaluating wind energy systems.
1. Betz - It is an inescapable law of nature that whenever energy is converted from one form to another or is moved, there is loss. When there is movement of air and it comes up against an obstacle, such as a wall, it does the obvious, it simply goes around it. Such is also true regarding all wind energy devices of every type. A wind energy device is not a true wall in that it does not cause all the wind coming into contact with it to go around it. It is in fact an imperfect wall that allows a portion of the wind to pass through it, giving up a portion of its energy in the process. In 1919, the German physicist Albert Betz showed that the MAXIMUM amount of energy that can be RECOVERED from wind is 59.3%. If a wind energy device is not able to convert the maximum amount of energy possible, it will either allow more wind to pass through the device unused, or will provide an excessive obstacle to the movement of wind causing an excess of wind to pass around the device unused. There is no avoiding this. Remember, Betz defines the MAXIMUM amount of energy obtainable with a PERFECT wind energy device! The actual amount recovered will always be less. Some windmills in the past have attempted to use shrouds or ducts to force more wind through a rotor and some have gone on to claim new heights of efficiency, only to have reality smack them in the face. In fact, the working area of the wind energy device is the area of the duct and wind energy device combined, so there is no real improvement, only the added expense and complications imposed by the duct or shroud.
2. Resistance to the rotation of the wind wheel. If you have a well balanced disc mounted on good bearings and spin it, it will eventually stop spinning. If you place it in a vacuum and spin it, it will spin much longer! The reason there is less resistance to turning in a vacuum is that there is little air to cause aerodynamic friction. A wind energy device is no different. A wind energy device of excellent design works with an efficiency of about 60%. If you want to reduce the resistance to turning, you can reduce the surface area of the wind energy device. Unfortunately, your wind energy device will now allow more wind to pass through unused and the result is actually increased energy losses. You can reduce the amount of supporting structure in the wind wheel, certainly increasing efficiency. Unfortunately, it will also weaken the wind energy device causing failure in unacceptably light winds.
3. Bearings - Yes, as good as bearings can be, there are still energy losses here that must be considered. Traditional windmill bearings were almost always made of Babbitt metal, which has a very long life, improves with age as journals become finely polished in use and are actually quite efficient. Babbitt is still the bearing material of choice used in the large percentage of internal combustion engines today, and for good reason. Ball and roller bearings have been used since they first became available in the last century, but early on, it was found that they simply do not have the lifespan as experienced with Babbitt bearings for reasons beyond the scope of this writing. Since ball and roller bearings are being used in almost all new windmill designs today, we will discuss the efficiency of these bearings. A good ball or roller bearing that is accurately mounted and properly lubricated should be 95% to 97% efficient per bearing! The more bearings, the lower the efficiency. A windmill with 2 bearings will have about half the bearing loss as a windmill with 4 bearings. Fewer bearings = lower cost - increased performance - reduced maintenance = good design.
4. Gears - of excellent quality with an accurate tooth design and very fine finish operate with an efficiency of about 95% per set of gears. Increased loads increase loss. Like bearings, fewer gears = lower cost - increased performance - reduced maintenance = good design. Some windmills of improved design use ballanced gear sets. This allows direct mechanical loading instead of an overhanging load. Direct mechanical loading from ballanced gearing increases working life of the components and reduces overall friction. The use of gears is required to provide the leverage required to allow pumping in light winds and from deep wells.
5. Other Power Transmission related energy losses - such as pump rod guides, arm bearings, fluid resistance on the pump rod contribute to more losses. These losses vary significantly from design to design and can run from about 5% in a good system to 20% in a poor system.
6. Pumps - are always a significant concern regarding efficiency. The common – now obsolete – windmill pump made of brass or bronze tubing with a polished bore using treated leather seals are dependable and have a relitivelly long life. They also suffer from significant friction losses of about 50%! For many years, Iron Man Windmill Co. has worked to minimize pump losses and improve performance and has achieved considerable success. Windmills using Iron Man Pumps are see an increase in pump performance of 50% for a total efficiency of 75%.
7. Fluid Friction - The movement of water in pipes, through valves and around restrictions eats up energy. In an excellent system with smooth pipe of the proper size and very good check valve design, fluid efficiency can be quite high - 95% or so. Most windmill systems when pumping from deep wells, through long pipelines or at high speeds can have a much lower efficiency and which can drop by as much as 50% if the pipe used is of insufficient size.
8. Electrical - early in the 1970's we did much work developing 3 bladed electric generating windmills. While such electric generating windmills can operate efficiently and do a very good job of providing electricity in strong winds, they provide little if any usable power in lower wind speeds, which are the most common wind speeds at many locations. With the electric generating windmill, the power of the wind is converted to mechanical energy. The mechanical energy is then converted to electrical energy. The electrical energy is then transmitted to a control panel and converted to be either stored in batteries or connected to the utility power grid by processing the power generated by a synchronous inverter. If the power is to be used for pumping, the energy must then be converted or regulated into a usable form and then transmitted to the electric motor that operates the pump. Then the electric motor converts the electricity to back to mechanical energy. The mechanical energy is then used to operate a pump. Pumping water with an electric generating windmill is an expensive and highly inefficient process that results in little water for the investment. While there have been many recent attempts at accomplishing this using modern electronics, such systems still fall far short of being practical.
Ok, now take the total of the losses described above and assuming a wind energy device of very good design with a standard pump, you will make an interesting discovery! 0.60 (wind wheel) x 0.95 (bearings) x 0.95 (gears) x 0.50 (pump) x 0.90 fluid and pump rod losses = system efficiency = 24% The same windmill using an Iron Man Windmill Pump will see an efficiency of: 0.60 (wind wheel) x 0.95 (bearings) x 0.95 (gears) x 0.75 (pump)* x 0.90 fluid and pump rod losses = system efficiency = 37%
* The pump efficiency shown is obtained with Iron Man Windmill Pumps using our proprietary seals and valves.
For other makes of pumps, an efficiency of 0.50 or 50% should be used.
It is interesting to note, that most modern automobiles have an operating efficiency of about 15%!
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IRON MAN STAINLESS STEEL WELL PUMP DIMENSION AND PIPE SIZE DATA
S.S. Pump Size (mm) Inch Equiv. For Pumping Capacity Calculation Well Pipe for Open Top Configuration Well Pipe for Closed Top Configuration
∅25 0.98″ 1″ 1-1/4″ 1-1/4″
∅32 1.26″ 1-1/4″ 1-1/4″ 1-1/4″
∅40 1.57″ 1-1/2″ 2″ 1-1/2″
∅50 1.97″ 2″ 2″ 2″
∅60 2.36″ 2-1/2″ 2-1/2″ 2″
∅75 2.95″ 3″ 3″ 2-1/2″
∅80 3.15″ 3″ 4″ 3″
∅100 3.94″ 4″ 4″ 3″
∅125 4.92″ 5″ 6″ 3″
∅150 5.90″ 6″ 6″ 4″
∅200 7.87″ 8″ 8″ 6″
∅250 9.84″ 10″ 10″ 6″
NOTE: Size is piston diameter. Open top configuration allows piston to be removed from pump by pulling up pump rod only. No need to remove well pipe. Well pipe cost is higher, but maintenance is simple. Recomended for wells 100ft (30M) or more.pumping capability is desired. Closed top configuration allows smaller diameter well pipe to be used, but is more difficult to maintain and pumping capacity is slightly decreased. Recomended for shallow wells only. The use of pipe in sizes smaller than listed above will result in decreased pumping capacity, increased loading and reduced life of components and possable breakage of the pump rod or shear pin in strong winds.
BEAUFORT WIND SCALE
Windspeed(MPH) Description - Visible Condition
0 Calm - smoke rises vertically
1 - 4 Light - air direction of wind shown by smoke but not by wind vanes
4 - 7 Light Breeze - wind felt on face; leaves rustle; ordinary wind vane moved by wind
8 - 12 Gentle Breeze - leaves and small twigs in constant motion; wind extends light flag
13 - 18 Moderate Breeze - raises dust and loose paper; small branches are moved
19 - 24 Fresh Breeze - small trees in leaf begin to sway; crested wavelets form on inland water
25 - 31 Strong Breeze - large branches in motion; telephone wires whistle; umbrellas used with difficulty
32 - 38 Moderate Gale - whole trees in motion; inconvenience in walking against wind
39 - 46 Fresh Gale - breaks twigs off trees; generally impedes progress
47 - 54 Strong Gale - slight structural damage occurs; chimney pots and slates removed
55 - 63 Whole Gale - trees uprooted; considerable structural damage occurs
64 - 72 Storm - very rarely experienced; accompanied by widespread damage
73+ Hurricane - devastation occurs
TAPS AND TAP DRILLS FOR INCH THREADS
Thread Size Tap-Drill Sizes Clearance Holes
SizeDIA Close FitNon-Struct (1/64 OS)
0-80-UNF 3/64 .0469 No. 53 5/64
1-64-UNC No. 53 .0595 No. 49 No. 43
1-72-UNF No. 53 .0595 No. 49 No. 43
2-56-UNC No. 50 .0700 No. 44 No. 38
2-64-UNF No. 50 .0700 No. 44 No. 38
3-48-UNC No. 47 .0785 No. 39 No. 33
3-56-UNF No. 45 .0820 No. 39 No. 33
4-40-UNC No. 43 .0890 No. 33 1/8 or No. 30
4-48-UNF No. 42 .0935 No. 33 1/8 or No. 30
5-40-UNC No. 38 .1015 1/8 No. 28 or 9/64
5-44-UNF No. 37 .1040 1/8 No. 28 or 9/64
6-32-UNC No. 36 .1065 No. 28 No. 23 or 5/32
6-40-UNF No. 33 .1130 No. 28 No. 23 or 5/32
8-32-UNC No. 29 .1360 No. 19 No. 15
8-36-UNF No. 29 .1360 No. 19 No. 15
10-24-UNC No. 25 .1495 No. 11 13/64
10-32-UNF No. 21 .1590 No. 11 13/64
12-24-UNC No. 16 .1770 No. 2 15/64
12-28-UNF No. 14 .1820 No. 2 15/64
1/4-20-UNC No. 7 .2010 E or 1/4 17/64
1/4-28-UNF No. 3 .2130 E or 1/4 17/64
5/16-18-UNC 'F' .2570 5/16 or O 21/64
5/16-24-UNF 'I' .2720 5/16 or O 21/64
3/8-16-UNC 5/16 .3125 3/8 or V 25/64
3/8-24-UNF 'Q' .3320 3/8 or V 25/64
7/16-14-UNC 'U' .3680 7/16 29/64
7/16-20-UNF 25/64 .3906 7/16 29/64
1/2-13-UNC 27/64 .4219 1/2 33/64
1/2-20-UNF 29/64 .4531 1/2 33/64
9/16-12-UNC 31/64 .4844 9/16 37/64
9/16-18-UNF 33/64 .5156 9/16 37/64
5/8-11-UNC 17/32 .5312 5/8 41/64
5/8-18-UNF 37/64 .5781 5/8 41/64
3/4-10-UNC 21/32 .6562 3/4 49/64
3/4-16-UNF 11/16 .6875 3/4 49/64
7/8-9-UNC 49/64 .7656 7/8 57/64
7/8-14-UNF 13/16 .8125 7/8 57/64
1"-8-UNC 7/8 .8750 1" 1-1/64"
1"-14-UNF 59/64 .9375 1" 1-1/64"
TAPS AND TAP DRILLS FOR METRIC THREADS
Tap Size Thread Size Tap-Drill Sizes Pitch Tap-Drill Sizes (mm) Tap-Drill Sizes (in)
M1.6 1,6mm 0.0630 0.35 1,25mm #55
M2 2mm 0.0787 0.4 1,6mm #52
M2.5 2,5mm 0.0984 0.45 2,05mm #46
M3 3mm 0.1181 0.5 2,5mm #39
M3.5 3,5mm 0.1378 0.6 2,9mm #32
M4 4mm 0.1575 0.7 3,3mm #30
M5 5mm 0.1969 0.8 4,2mm #19
M6 6mm 0.2362 1 5mm #8
M8 8mm 0.3150 1.25 6,8mm H
M8 8mm 0.3150 1 7mm J
M10 10mm 0.3937 1.5 8,5mm R
M10 10mm 0.3937 1.25 8,8mm 11/32
M12 12mm 0.4724 1.75 10,2mm 13/32
M12 12mm 0.4724 1.25 10,8mm 27/64
M14 14mm 0.5512 2 12mm 15/32
M14 14mm 0.5512 1.5 12,5mm 1/2
M16 16mm 0.6299 2 14mm 35/64
M16 16mm 0.6299 1.5 14,5mm 37/64
M18 18mm 0.7087 2.5 15,5mm 39/64
M18 18mm 0.7087 1.5 16,5mm 21/32
M20 20mm 0.7874 2.5 17,5mm 11/16
M20 20mm 0.7874 1.5 18,5mm 47/64
M22 22mm 0.8661 2.5 19,5mm 49/64
M22 22mm 0.8661 1.5 20,5mm 13/16
M24 24mm 0.9449 3 21mm 53/64
M24 24mm 0.9449 2 22mm 7/8
M27 27mm 1.0630 3 24mm 15/16
M27 27mm 1.0630 2 25mm 1
IRON MAN / AERMOTORWHEEL ARM & HUB THREADS
windmill size letter hub thread tap drill
4ft Z M6-1 5mm
6ft X 11/32-18NS 15/64"
8ft A 13/32-16NS 19/64"
10ft B 15/32-12NS 21/64"
12ft D 19/32-13NS 15/32"
14ft E 23/32-11NS 9/16"
16ft F 25/32-10NS 39/64"
20ft L 1-8NC 7/8"
These threads are based on a standard originally used by the Aermotor company of Chicago on later 602 windmill wheel arms and hubs in the tumultuous days prior to the wide spread adoption of national thread standards and are defined as a "National Special Thread" specification. This was the result of the need for a thread that was larger after hot galvanizing and in its original form, was found to have problems jamming and break off. The male thread of the wheel arm was re-designed to fix this problem but the basic NS thread standard continued in use for reasons of interchangeability, as many thousands of windmills had already been shipped using this standard. These special threads are still in use by most manufacturers of American standard windmills for sale in the US market and for some export class and foreign made windmills. Iron Man Windmills use this thread system for windmills and related parts sold in the US, but windmills supplied beyond US borders are provided with ISO standard metric threads.
FRACTIONAL EQUIVLENT TABLE
64ths 32nds 16ths 8ths 4ths MM Decimal
1/64         0.39624 0.0156
2/64 1/32       0.79502 0.0313
3/64         1.19126 0.0469
4/64 2/32 1/16     1.58750 0.0625
5/64         1.98374 0.0781
6/64 3/32       2.38252 0.0938
7/64         2.77876 0.1094
8/64 4/32 2/16 1/8   3.17500 0.1250
9/64         3.57124 0.1406
10/64 5/32       3.97002 0.1563
11/64         4.36626 0.1719
12/64 6/32 3/16     4.76250 0.1875
13/64         5.15874 0.2031
14/64 7/32       5.55752 0.2188
15/64         5.95376 0.2344
16/64 8/32 4/16 2/8 1/4 6.35000 0.2500
17/64         6.74624 0.2656
18/64 9/32       7.14502 0.2813
19/64         7.54126 0.2969
20/64 10/32 5/16     7.93750 0.3125
21/64         8.33374 0.3281
22/64 11/32       8.73252 0.3438
23/64         9.12876 0.3594
24/64 12/32 6/16 3/8   9.52500 0.3750
25/64         9.92124 0.3906
26/64 13/32       10.32002 0.4063
27/64         10.71626 0.4219
28/64 14/32 7/16     11.11250 0.4375
29/64         11.50874 0.4531
30/64 15/32       11.90752 0.4688
31/64         12.30376 0.4844
32/64 16/32 8/16 4/8 2/4 12.70000 0.5000
33/64         13.09624 0.5156
34/64 17/32       13.49502 0.5313
35/64         13.89126 0.5469
36/64 18/32 9/16     14.28750 0.5625
37/64         14.68374 0.5781
38/64 19/32       15.08252 0.5938
39/64         15.47876 0.6094
40/64 20/32 10/16 5/8   15.87500 0.6250
41/64         16.52524 0.6506
42/64 21/32       16.67002 0.6563
43/64         17.06626 0.6719
44/64 22/32 11/16     17.46250 0.6875
45/64         17.85874 0.7031
46/64 23/32       18.25752 0.7188
47/64         18.65376 0.7344
48/64 24/32 12/16 6/8 3/4 19.05000 0.7500
49/64         19.44624 0.7656
50/64 25/32       19.84502 0.7813
51/64         20.24126 0.7969
52/64 26/32 13/16     20.63750 0.8125
53/64         21.03374 0.8281
54/64 27/32       21.43252 0.8438
55/64         21.82876 0.8594
56/64 28/32 14/16 7/8   22.22500 0.8750
57/64         22.62124 0.8906
58/64 29/32       23.02002 0.9063
59/64         23.41626 0.9219
60/64 30/32 15/16     23.81250 0.9375
61/64         24.20874 0.9531
62/64 31/32       24.60752 0.9688
63/64         25.00376 0.9844
64/64 32/32 16/16 8/8 4/4 25.40000 1.0000
NPT - AMERICAN STANDARD TAPERED PIPE THREADSALL UNITS ARE INCH
Pipe Size Threads per InchTPI - pitch Approximate Length of Thread Approximate Number of Threads to be Cut Approximate Total thread Makeup, Hand and Wrench Nominal Outside Pipe DiameterOD Tap Drill
1/16" 27       0.313  
1/8" 27 3/8 10 1/4 0.405  
1/4" 18 5/8 11 3/8 0.540 7/16
3/8" 18 5/8 11 3/8 0.675 37/64
1/2" 14 3/4 10 7/16 0.840 23/32
3/4" 14 3/4 10 1/2 1.050 59/64
1" 11-1/2 7/8 10 9/16 1.315 1-5/32
1-1/4" 11-1/2 1 11 9/16 1.660 1-1/2
1-1/2" 11-1/2 1 11 9/16 1.900 1-47/64
2" 11-1/2 1 11 5/8 2.375 2-7/32
2-1/2" 8 1 1/2 12 7/8 2.875 2-5/8
3" 8 1 1/2 12 1 3.500 3-1/4
4" 8 1 5/8 13 1 1/16 4.500 4-1/4
6" 8 1 3/4 14 1 3/16 6.625 6-11/32
8" 8 1 7/8 15 1 5/16 8.625  
10" 8 2 16 1 1/2 10.750  
12" 8 2 1/8 17 1 5/8 12.750  
14" 8 14.000  
16" 8 16.000  
* The taper is 1/16 inch in an inch, which is the same as 3/4 inch in a foot (angle 1º  47') NPT threads are not interchangeable with NPS - National Pipe Straight - threads. NPT threads may look similar to ISO 7/1 threads. However, ISO and NPT threads should not be mixed. ISO threads have 55º  taper angle versus 60º  for NPT. The NPT root and crest configurations are also different from ISO. For ISO threads pitch is usually measured in millimeters (may be expressed in Inch). The pitch are different.