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Superb quality instruments of solid persplex plastic
Precision engraved


Flow Calculators:


Pipe Flow Calculator for liquids and gases (Turbulent Flow)

Model M.5

The majority of practical problems fall within the Turbulent Flow range and this calculator determines the required pipe size, flow or pressure loss for any liquid and also for any gas (at low pressures) flowing under turbulent conditions.


Pressure loss, flow or pipe sizes are found from the front of the calculator by a simple setting of two dials to the known details of length, viscosity, specific gravity, etc. Scales on the reverse side permit an instant determination on whether the flow conditions are Turbulent or Laminar. Viscosities of over 50 liquids at various temperatures are also given on the reverse side along with their specific gravities. Further scales are incorporated for viscosity conversion, including Redwood, Saybolt, Centistokes, and on the metric model, Engler degrees.

Scale Ranges:
Diameter: 1/4" to 40" Liquid Flow: 5 to 1,000,000 g.p.h.
Length: 5 ft. to 5,000,000 ft.
Gas Flow: 50 to 1,000,000 c.f.h.
Pressure Drop: .01 to 500 lbs./

Metric model also available.
7 5/8" diameter


Gas Flow Calculator for low or high pressure flow (with velocity scales)

Model M.8

This instrument is for calculations relating to the flow of all gases in pipes. It has two pressure loss scales, one dealing with the majority of the problems where the Terminal pressure is substantially atmospheric and the other for pipes at pressure up to 4,000 lbs./sq. in. Handles all fuel gases, air, nitrogen, carbon dioxide, etc, and is widely used for sizing factory compressed air and fuel gas systems, pipelines in chemical plants, coke ovens and process plants, manufactured gas and natural gas distribution.

Scale Ranges:
Diameter: 0.4" to 60"
Length: 10 ft. to 300 miles
Flow: 150 to 16,000,000 c.f.h

Metric model also available.
7 5/8" diameter

Model M.8A (for cast iron and steel pipes)
Model M.8B (for plastic pipes)


Water Flow Calculator

Model M.7

For steel, cast-iron, non-ferrous, plastic, asbestos cement, concrete, vitrified and coated pipes and also open channels in earth, rock, concrete, metal and wood.

One side of the calculator solves the rational formula for water flow in pipes and ducts of circular sections. The answers have been checked against a large number of well-authenticated practical tests on actual pipelines from small metal tubes to long concrete tunnels up to 18 feet diameter and give accuracy appreciably better than usual formulas.

Flow: 1.5 to 1,000,000 g.p.m.
Diameter: 0.5" to 240"
The reverse side solves the Manning formula for the flow in open channels. Flow 50 to 5,000,000 g.p.m,
Channel area: 0.7 to 2,000 sq. ft.

Metric model also available.
7 5/8" diameter


Steam Flow Calculator

Model M.9

Determines the pressure loss of steam flowing in pipe lines under any conditions from high vacuum up to the critical pressure of 3,200 p.s.i., and at all velocities up to and including sonic flow. Valves, bends and fittings contribute considerably to the total pressure loss and a section is included to give the equivalent lengths of a wide variety of these fittings so that accurate allowances can be made for them.

The design for the calculator is based upon the modern rational formula. It takes account of the deviation of steam from the laws of a perfect gas and for the variation of its viscosity with temperature and pressure. Pipe sizes up to 48" diameter.

Metric model also available.
7 5/8" diameter


Orifice and Nozzle Flow Calculator

Model M.18 

This calculator determines the flow rates of fluids through the various types of flow measuring nozzles and orifices, including: Orifice Plates, Nozzles, Venturi Nozzles, Venturi Tubes, Pitot Tubes, Quarter Circle Orifice Plates and Conical Entrance Orifice Plates.

The rates of flow are calculated in accordance with the standard flow formula:
            W = 1890 C d2√hp
where W = mass flow, lb./h
             d = orifice or nozzle throat diameter, inches
             h = pressure difference p.s.i.
             p = density of fluid upstream, lb./ft3
             c = overall orifice or nozzle co-efficient

Liquids, gases or steam are handled with equal facility, the flow being obtained in terms of either volume or mass whichever Is desired. The Flow Coefficient of the various recommended orifice or nozzles vary according to type, diameter, and the relative size of pipe in which they are fitted. The reverse side of the calculator determines these coefficients for liquid flows and also the correction which may be necessary for gas flows to allow for expansion should the pressure loss across the orifice or nozzle be large.

Gas densities in Kg/m3 are quickly obtained for any gas according to pressure, temperature and specific gravity, a special section being provided for this purpose. This considerably facilitates the calculation of gas flows. An instruction booklet is included with each calculator, giving additional information, examples, and particulars of the slight correction necessary for very low Reynolds Numbers and rough pipes.

Scale ranges:
Pipe bore: 2" to 50"
Orifice diameter: .25" to 20"
Flow Rate: 40 to 3,000,000 ft3/h or lb/h

Metric model also available.
8" diameter


Ducting Calculator

Model M.12

A complete calculator for determining duct sizes, velocities and pressure losses for large or small ducting systems passing either warm or cold air. It is double sided and divided into sections which handle all aspects of duct sizing calculations. It gives answers for either round, square or rectangular ducts.

Velocity: One section of the calculator gives the velocity in the duct or sizes the duct for any specific velocity requirement.

Pressure Losses: A separate section deals with the pressure loss in the straight portions of the duct.

Pressure Loss in Fittings: On many installations a large proportion of the pressure loss occurs in the various bends, branches, and other fittings and a section deals specifically with this giving the loss in velocity heads for a wide variety of fittings and providing scales to convert this to actual pressure loss.

Warm Air Heating: This section gives the volume of air required for warm air heating according to the heat requirements and the temperature differential between warm air and the room. In addition a further section gives heat losses from the surface of the ducting carrying warm air.

Duct sizes up to 100" diameter and the equivalent rectangular or square.

Metric model also available.
7-5/8" diameter


Streamline (Laminar) Flow Calculator

Model M.6

This instrument is designed to solve the streamline flow formula applicable to the flow of more viscous liquids such as fuel oils, lubricating oils, syrups, etc. through pipe lines and also the flow of liquids of low viscosity in small pipes. The latest design includes viscosity conversion scales for Redwood, Saybolt, Engler and Centistokes.

Scale ranges:
Liquid flow: .001 to 15,000 g.p.m. Pipe dia. 0.1" to 13"
                      .001 to 15,000 tons/hr.
Pressure drop: .01 to 600 lbs./sq. in.

Metric model also available.
Length 6 to 3,000 ft.
5-5/8" diameter


Tank Capacity Calculator

Model F.11

Calculates capacities of rectangular and cylindrical tanks or containers in cu. yards, cu. meters, cu. feet, gallons, gallons (Imp.) and liters. To operate, it is only necessary to set the scales to the known sizes of the container and read off the cubic capacity in any required units. Alternatively, the scales are set to the known cubic capacity or volume and the container sizes may then be determined.

Special section covers part-full horizontal cylindrical tanks filled to any level.

Capacity range:
Tank length: 1 ft. to 250 ft.
Tank width: 1 ft. to 250 ft.
Tank depth: 4 in. to 100 ft.
Diameter: 4 in. to 100 ft.
Volume: 0.1 to 10,000,000 (cu. ft., gals, or liters)
7-1/2" diameter

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Technical Calculators:


Industrial Heating Calculator

Model M.19

An instrument designed to simplify the calculations for all the larger heating installations where a full analysis of the heat losses must be made.

Heat losses through the structure are handled on one side of the calculator, each wall, floor, window, etc. being treated individually by simply setting length and width and using the temperature difference and the heat transfer coefficient to obtain the heat loss. The heat loss from air change is obtained in a similar manner.

In addition, this calculator has an ingenious method for determining pipe sizes which saves considerable time. It is only necessary to decide what pressure loss can be allowed per 100 ft. run and all pipe sizes can be read off immediately according to B.T.U. carried and flow to return temperature drop. At the same time the water flow in the pipe is shown; or the pipe size can be obtained directly from the flow, if desired. Radiator size, boiler size, and pump size are also obtained and a further section gives heat losses from piping either insulated or left bare.

Metric model also available.
7-5/8" diameter.


Electric Lighting Calculator

Model M.13

This calculator has been designed to give quickly and accurately the number and size of lighting fittings for any installation by the lumen method. It indicates a logical and easily followed design sequence with each step dealt with by an individual section of the instrument.

Number and Size of Fitting:
On the front of the calculator simply set two dials to length of room, width of room, required illumination and coefficient of utilization and the size of each fitting can be read immediately opposite the chosen number of fittings and vice-versa.

Room Index:
To find the coefficient of utilization for any fitting it is necessary to know the Room Index and scales are provided on the front of the calculator to rapidly determine this index for any size of room and height of fittings.

Coefficient of Utilization:
On the reverse side of the instrument are engraved the coefficients of utilization for a wide range of standard lighting fittings.

Metric model also available.
7-5/8" diameter.


Warm Air Heating Calculator

Model M.11

A complete method for designing warm air heating installations once the room heat requirements have been determined.

Gives warm air volume, heater size, duct size, pressure loss, equivalent length of duct fittings, velocities, and also heat loss from ducting. Deals with installations up to 24 inch diameter duct size.

Metric model also available.
7-5/8" diameter


Combustion Efficiency Calculator

Model M.25

The efficiency of a boiler is determined largely by the heat lost to any excess air supplied and the loss in high temperature flue gases.

This calculator determines the efficiency from the CO2 content of the flue gas and the flue gas temperature. At the same time, it also indicates the percentage of excess air being supplied.

Gives answers for coal, coke, manufactured gas, natural gas, and fuel oils (residual and distillate.) Calibrated in metric units.

5-3/4" diameter


Psychometric Calculator for Air Conditioning and Meteorology

Model M.24

This calculator determines all the properties of moist air directly from any of the three basic sources of measurement. By a single setting of: Wet Bulb to Dry Bulb Temperature (screen or aspirated) or, Wet Bulb Temperature to Depression (screen or aspirated) or, Dry Bulb Temperature to Relative Humidity it gives:

Dew Point
Frost Point
Latent Heat
Sensible Heat
Vapour Pressure
Moisture Content
Specific Enthalpy
Specific Volume
Specific Humidity
Mixing Ratio
Vapour Density
Altitude Correction

High accuracy eliminates interpolation from tables and charts as temperature scales are calibrated in 0.2 deg. settings to 0.1 deg. or less. The Relative Humidity scale is also very accurate.

The basic properties are per Kg. of dry air at standard atmospheric pressure of 1013.25 mb. on the metric model and per lb. of dry air at standard atmospheric pressure of 14.7 psi on the English model. The specific humidity and mixing ratio are given for any barometric pressure down to 300 mb. on the metric model and 4 psi on the English model. Additional scales allow for correction of the wet bulb depression for the effects of low barometric pressure on altitude. The properties of mixed air from two or more different streams can also be obtained.

Scale Ranges:
Wet bulb temp.
Ice bulb temp.
Dew point
Frost point
Dry bulb temp.
Scale Ranges:
0 to 29 deg. C
-50 to 0 deg. C
-53 to 29 deg. C
-50 to 0 deg. C
-53 to 44 deg. C
0 to 22 deg. C
Scale Ranges:
24 to 80 deg. F
-50 to 32 deg. F
-56 to 110 deg. F
-50 to 32 deg. F
-58 to 110 deg. F
0 to 35 deg. F

Metric or English model
7-3/4" diameter

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Production Calculators:


Production Engineer’s Calculator

Model F.5

Machine Horsepower Requirements: Computes machine horsepower required for any given combination of cutting speed, feed, depth of cut and material.

Batch Production Times: Calculates batch production times for a given quantity and time each (or number per hour), or vice-versa.

Machining Times: Calculates machining times for turning, milling, drilling, etc. for given feed rate, cutting speed, diameter, length and number of cuts.

Speed, Feed, and Spindle R.P.M. Calculations: Works out speeds, feeds, spindle r.p.m., etc. including conversion between feed/min. and feed/rev.

An indispensable tool for any production engineer and a great timesaver. All scales have extremely wide range, sufficient to cover almost any size of work.

7 ½" Diameter


Power Press Calculator

Model F.46

Eliminate trial-and-error lengthy calculations. A simple setting of one or two dials gives instantly:

  • Press tonnage required for all kinds of punching and blanking operations.
  • Press tonnage required for all kinds of drawing and forming operations.
  • Limiting deep drawing ratios for all sizes and shapes of shell.
  • Die clearances for punching and blanking.
  • Gauge and thickness conversion.

An indispensable aid in any design, tooling or production department concerned with presswork. Results in more efficient uses of presses and minimizes danger of breakdown due to overloading. Suitable for presses up to 1,000 tons and metal thickness up to 0.5″.

7 ½" Diameter Dual English-Metric


Gear Horsepower Calculators

Model F.42

These calculators are used for determining the horsepower transmitting capacity of gears of all kinds and sizes. Each calculator reduces the previous laborious calculations to a simple matter of setting dials and reading out the answer. Completely reliable and with scale ranges to cover almost any condition or size of drive.

7 ½" Diameter
Spur and Helical Gear


Screw Thread Metric Converter

Model F.45

An economically priced, simple-to-use screw thread selector and converter. This unit is quite comprehensive, covering all standard American and British threads up to 1 ½ diameter. All modern screw thread details are at your fingertips, including: tapping and clearance drill sizes, threads per inch, root areas for strength calculations. (all with metric equivalents), plus a rapid and ingenious system for quickly determining the closest equivalent metric thread in the ISO fine and coarse series. A “must” for every engineer and designer.

5 ½" Diameter


Calculator for Plate Bending Presses

Model F.9

An ingenious, simple-to-use, instrument which, by a simple setting of two dials, immediately computes the bending load, in tons, required to bend any size of steel plate.

Equally quickly it will determine the maximum plate sizes which may be bent in any particular bending press. Robust construction for regular daily use in workshop or office and requires no mathematical ability, or knowledge of slide-rules to operate. Should form part of the equipment of every fabricating shop.

For plate thicknesses from ½" to 8" and bending loads to 5000 tons.

Double sided Dual English-Metric
Main dial 7 ½" diameter, ¼" thick


Work Study Engineer’s Calculator for Standard Time Calculations

Model F.39

Indispensable to Work Study Engineers in any industry, this unit rapidly converts observed times to basic or normalized at any required standard rating level. An additional section is provided for rapid calculation of percentage additions or reductions to times.

5 ½" diameter


Estimator’s Universal Calculator

Model F.4

A reduced size simplified version of the Production Engineer’s Calculator (Model F.5), incorporating the machining time and speeds and feeds sections only.

A valuable tool for the personal use of estimators and foremen.

5 " diameter


Machining Time Calculators

Models F.1, F.2, F.3

These calculators provide a complete system of unequalled simplicity for determining consistent machining times, quickly, easily, and accurately, without time study. The information they provide is so complete that they may be used by personnel with very limited experience.

Three separate calculators are available, as described below, one for each of the most common groups of machining operations. In each case the total floor-to-floor time for a particular operation is obtained by adding together time elements determined in three separate places on the calculator.

Cutting Time: Read off directly on the front of the calculator after setting dials to relevant details of operation. Information on cutting speeds and feeds is also incorporated.

Loading & Handling Time: Separately determined by a simple setting of dials on the reverse side of the calculator. All necessary allowances relating to weight, size, accuracy, type of operation, etc. are taken into account.

Set-up Time: Determined in another section of each calculator.

Lathework Calculator (Model F.1)

Calculates times for turned components of all kinds on center lathes, turret lathes and boring mills. Extremely wide range.

7 ½" diameter

Milling Calculator (Model F.2)

Calculates times for all kinds of milling operations on vertical or horizontal milling machines. All types of cutters, fixtures, dividing heads, etc.

7 ½" diameter

Drilling, Reaming & Tapping Calculator (Model F.3)

Calculates times for drilling, reaming, or tapping holes of all sizes in lathes, single and multi-spindle drills.

7 ½" diameter


Welding Time Calculator
For MIG Co2 Wire Welding

Model P50A

A disc calculator for rapid and easy calculation of welding times. Covers almost all types and sizes of butt and fillet weld. Indispensable to Estimators and Manufacturing Engineers. Completely new and based on the most up-to-date information on MIG wire welding times and is suitable for almost all kinds of welding and fabrication work, large or small in size.

Eliminates laborious calculations – by a simple setting of dials, it calculates:

  • Arc time for full weld. (Also indicates suitable wire feed rates for given current amps.)
  • Additional sealing run preparation time, for sealed welds.
  • Total wire length usage; number of stops; stop time ancillaries.
  • General ancillaries.

Scope- for semi-automatic MIG welding
Fillet welds – 1/8" to 1"
Butt welds – backed, unbacked and sealed for plates from 1/16" to 1" thick
Weld lengths – ½" to 35 feet
Welding wire size – .030" to 1/8" dia. (solid and flux-cored).

Quality and reliability – substantially made from high grade, non-warping acrylic with fully engraved scales. Sturdy construction to give many years of use, and supplied complete with attractive case and instructions.

7 ½" diameter x 5/16"


Welding Time Calculator for Manual Metal Arc Welding

Model P51A

A calculator for rapid and easy calculation of welding times for all sizes of fillet weld. Indispensable to Estimators and Manufacturing Engineers.

Completely new and based on the most up-to-date information. Calculates accurate and consistent welding times, and number of electrodes required. Covers all kinds of fabrication work produced by manual metal-arc (stick type) welding. Equally suitable for the small or large shop.

Eliminates laborious calculations. A simple setting of the dials to the weld sizes and details, and it calculates:

  • Arc times for full welds.
  • Deslag and brush times.
  • Ancillary time (electrode changes, etc.)
  • Total weld times.
  • Number of electrodes required.

Scope – the calculator has a wide range suitable for almost any size of fabrication, large or small, and covers the following:

Fillet welds – 1/8" to 1"
Weld lengths – from 1" to 1,000 feet
Welding position – any
Electrode types – cellulose; rutile; rutile heavy; basic hydrogen controlled; (with ASW references).

Quality and reliability - made from high grade, non-warping acrylic with fully engraved scales. A high quality instrument of sturdy, careful construction to give many years of regular, daily use. Supplied complete with an attractive case.

7 ½" diameter x ¼"


Flame-Cutting Calculator
For Machine or Manual Flame Cutting

Model P.56A

A disc calculator for rapid and easy calculation of flame-cutting times and quantity of gas and oxygen consumed. Indispensable to Estimators and Manufacturing Engineers.

Completely new and up-to-date, this unit covers machine and manual flame-cutting of all sizes of plate up to 12" thick, with allowance for operator skill and material quality.

Eliminates laborious calculations – simple and easy to operate, the calculator has four sections which, by a simple setting of dials, successively calculates:

  • Lengths of cut for circular arcs (to simplify profile length calculation.)
  • Flame-cutting times for almost any size of plate or profile shape (also indicates cutting speeds.)
  • Quantity of pre-heat oxygen and gas comsumed (acetylene, propane or natural gas.)
  • Quantity of cutting oxygen consumed.

Scope: for manual or machine flame-cutting of steel plates up to 12" thick. Any cut from ½" to 60 feet long, using acetylene, propane or natural gas. Made from high-grade, non-warping acrylic with multi-color engraved scales. A high quality instrument of sturdy construction designed to give many years of use. Supplied with instructions and case.

7 ½" x ¼"

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