Model Engineering Glossary

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p (pico)

The prefix p or pico indicates the unit should be multiplied by 10^-12.

See also: Decimal Prefixes.

Parallelogram

See also: Conversion of Units.

Parisian Metal

69 % Copper 19.5 % Nickel 6.5 % Zinc 5 % Cadmium

Parting Tool

A lathe tool used to part pieces of metal.

There are a number of key parameters to remember when using parting tools:

1. height is exactly on centre
2. cutting angle = 35° for aluminium
3. ensure the holder is tight with just enough overhang to make the cut
4. use plenty of cutting fluid
5. Lock the saddle
6. Low speed - 150rpm or less
7. Use parting blades that are at least 12mm deep
8. Check alignment, then check again
9. Hone the tool on a diamond abrasive

more...

See: Lathe Tools.

Partinium

7.4 % Copper 1.7 % Zinc 88.5 % Aluminium 1.1 % Silicon 1.3 % Iron

Permalloy

78.5 % Nickel 21.5 % Iron

Perminvar

45 % Nickel 30 % Iron 25 % Cobalt

Pewter

Traditionally an alloy containing 80% tin and 20% lead.

The image shows a pewter flywheel on a solenoid engine. The outer surface has a hammered finish. more...

Phenol

Trade name: Carbolic acid

Chemical formula: C₆H₅OH

See also: Chemical Table.

Phosphor Bronze

An alloy of copper with 3.5 to 10% of tin and a significant phosphorus content of up to 1%.

Phosphor Bronze Piston and Cast Iron Cylinder

This is quite a favourite of Stuart Models and many others.

The piston is quite shallow in most double acting steam engines - this is due to the fact that the piston does not need to react any side loads as the conrod is supported in a bearing in the cylinder end cap.

This piston has two cast iron rings in the one groove.

This particular cylinder and pistone combination belong to a Stuart Beam engine.

See: Pistons and Liners for more information...

Physical Constants

Avogadro's number, Bohr magneton, ....... , Volume of 1 mol of ideal gas. more......

Pine

Easily worked and used where moderate strength and durability are required. Turpentine is obtained from the pine.

See also: Timber.

Pipe Bending

There are many situations where you want to bend a pipe, but if you do not support it correctly the pipe walls will collapse. more......

Piston Pin

This pin provides the articulated connection between the conrod and the piston.

Piston Rings

Purpose is to improve the sealing performance of the piston and to keep engine oil separate from the combustion chamber.

Pistons

The piston in an engine has 3 basic functions: Seal the combustion chamber, Transfer force and Conduct heat.

Pistons and Liners

There are many different materials that you can use for pistons and liners, some work better than others.

The image shows a piston and the master conrod from my 5 Cylinder Rotary engine.

Plane

A tool for shaping wood.

See also: Review - Crown Tools Bullnose Plane.

Plane

A North American wood that resembles beech, durable in water but not in air.

See also: Timber.

Platinoid

60 % Copper 14 % Nickel 24 % Zinc 2 % Tungsten

Plumbate

Trade name: Red lead

Chemical formula: 2PbO PbO₂

See also: Chemical Table.

Plywood

Lots of commercial plywoods are available in different thicknesses and numbers of plys. For small parts it is quite easy to make your own plywood. The trick is getting flat surfaces, using the right type of glue such as Tite-bond and applying pressure for a good time.

Poplar

A light wood, but not very strong and or very good wear resistance.

See also: Timber.

Potash

Chemical name: Potassium carbonate

Chemical formula: K₂CO₃

See also: Chemical Table.

Potassium Bromide

Chemical formula: KBr

See also: Chemical Table.

Potassium Carbonate

Trade name: Potash

Chemical formula: K₂CO₃

See also: Chemical Table.

Potassium Chlorate

Chemical formula: KClO₃

See also: Chemical Table.

Potassium Chloride

Chemical formula: KCl

See also: Chemical Table.

Potassium Chromate

Chemical formula: K₂CrO₄

See also: Chemical Table.

Potassium Cyanide

Chemical formula: KCN

See also: Chemical Table.

Potassium Dichromate

Chemical formula: K₂Cr₂O₇

See also: Chemical Table.

Potassium Iodide

Chemical formula: KI

See also: Chemical Table.

Potassium Hydroxide

Trade name: Caustic potash

Chemical formula: KOH

See also: Chemical Table.

Pot Metal

88 % Copper 12 % Lead

Propane

Chemical formula: C₃H₈

See also: Chemical Table.

Propeller Manufacture

Making a propeller takes time and patience, the end result can be very rewarding.

Prussic Acid

Chemical name: Hydrogen cyanide

Chemical formula: HCN

See also: Chemical Table.

Pyrolusite

Chemical name: Manganese dioxide

Chemical formula: MnO₂

See also: Chemical Table.

Pythagoras's Theorem

The square of the hypotenuse of a right-angled triangle is equal to the sum of the squares of the other two sides. more......

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