Kit Construction - Hints & Tips For The Modeller

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Brass, Whitemetal and Nickel Silver Kits

A few hints and tips to remove some of the 'myths' surrounding the construction of brass, nickel silver and whitemetal kits. These techniques are of equal value for scratchbuilding and are recommended for the use of adult scale modellers only.

This section includes:
Introduction | Working With Whitemetal | Brass & Nickel Silver

Introduction

For some reason the art of constructing kits manufactured from brass, nickel silver or whitemetal has been made to sound like 'black magic'. A skill only available to the 'select' few. This is no more than a myth. The skill is very simple to learn and can be aquired by anyone with a little practical ability and a few basic tools.

We assume throughout that the parts have been cleaned (use a fibreglass scratch brush) and that the parts have had all flash/sprues removed and several dry runs have taken place to ensure the best fit, and most important of all that the kit will build square and true. Use plate glass or another flat surface to ensure your model builds true. Follow the basic saying 'measure twice - cut once'. Use anything at your disposal to hold items together during the dry run and when soldering. Remember however that when soldering brass and nickel silver that the heat is transfered to the metal and the metal becomes hot - very hot!

Working With Whitemetal

As whitemetal melts at a temperature similar to that of normal electrical (60-40) solder, it is easy to see how so many soldering disasters have occurred with whitemetal kits. These disasters can be avoided by using the correct soldering materials and altering the soldering process as follows:

It should also be remembered that soldering these materials requires the use of a phosphoric acid based flux. Always use in a well ventilated room and avoid inhaling any gas expelled during the soldering process. Always wash well any spills in contact with the skin. Always follow the COSH directions on the bottle.

Materials:
Low temperature solder (melting temperature 70^o-80^o).
Phosphoric acid based flux.
Sensible soldering iron (less than 30w).

Soldering Process:
Whitemetal is soldered using the phosphoric acid flux to 'draw' the solder from the tip of the soldering iron into the joint. Ensure the soldering iron tip is clean and free from the contamination of other solders. When low melt solder is taken from the stick onto the tip, it forms a 'horn'. This horn allows the soldering of the joint without the need for direct contact with the whitemetal. Hold the parts together, apply the flux using a low quality paint brush and introduce the iron tip to the fluxed joint. As a beginner make contact with the whitemetal using the solder horn only. As you become more experienced you will discover that contact between the soldering iron and whitemetal can occur for a short time. On large 'seams' tack both ends before soldering the full joint. Always check for the best fit. Small items ie less than 1mm diameter are best left to the quality cyanoacrylate super glues available today.

Practice Technique:
At the beginning of this section it was stated that whitemetal melts at around the same temperature as normal 60-40 solder. 60-40 solder is therefore similar in its thermal properties to whitemetal. The practice technique is therefore simple. If you can solder normal solder with low temperature solder, you can construct a whitemetal kit. Simply double/trebble and twist 60/40 solder to make a more robust practice piece. Apply phosphoric acid flux all over the 60/40 solder then using the low temperature solder horn, practice the 'transfer' process by touching the 60/40 solder with the low temperature horn. If done correctly the spaces between the 60/40 solder will fill with low temperature solder forming a very strong bond. After some time you will carefully and quickly be capable of soldering two pieces of 60/40 solder together tip to tip, or to form a cross. When constructing a kit however it is normal practice to glue small items so do not worry if you cannot reach this level.

First Aid:
Two remedial methods are availble when mistakes occur. Boiling water can be used to separate items incorrectly joined. Carefully boil water in an old pan and drop the items into the water. The items will part allowing construction to re-commence. If a part is damaged by the soldering iron, or if 'pit holes' are found in a new casting. Simply apply phosphoric acid using a paint brush and very carefully rebuild the part as required using the solder horn. File to achieve the correct profile.

Brass & Nickel Silver

The assembly of brass and or nickel silver kits, or scratchbuilding from these materials is as simple as general soldering ie normal electrical soldering. Providing the metal is clean, and the correct materials are used it is a very simple process. When soldering brass/nickel silver, it is important to remember that the metal acts as a heat sink that may inhibit the soldering process, and burn your fingers! It is therefore much more important to use 'tools' to hold brass/nickel silver when soldering.

It should also be remembered that soldering these materials requires the use of a phosphoric acid based flux. Always use in a well ventilated room and avoid inhaling any gas expelled during the soldering process. Always wash well any spills in contact with the skin. Always follow the COSH directions on the bottle.

The materials and techniques for soldering are described in the following sections.

Materials:
1). Phosphoric acid based flux
2). 145^o and 188^o Solder (some modellers use normal 60/40 electrical solder rather than 188^o solder)
3). Soldering Irons - 30w and 70w (on larger scale kits a micro blow lamp)

Soldering Process:

Basic Structure.
Having ensured best fit simply paint the joint with phosphoric acid flux and apply the pre-tinned soldering iron with 188^o solder to the joint. The solder will flow along the joint depending upon the metal size and heat available. On large seams tack both ends prior to 'seaming' the joint. If the soldering iron appears to 'stick' to the metal, a larger soldering iron is usually required.

Detail Parts.
Most small detail parts can be added to the main structure using the above technique. However as the main structure increases in size, the more it acts as a heat sink. If more heat is applied, it is possible to desolder the main structure or other detail parts. This is easily avoided by using a lower temperature solder eg 145^o solder. This is applied as above.

Lost Wax Parts.
Lost wax is the term used to describe cast brass parts. As they are often solid brass it is often necessary to tin these parts with 188^o solder together with the superstructure, before fixing together with 145^o solder.

Whitemetal Parts.
Brass/nickel silver solders at a much higher temperature than whitemetal. It is therefore not technically possible to solder whitemetal to brass using normal 188^o solder. It is however possible to achieve a solder join between brass/nickel silver and whitemetal by first tinning the brass/nickel silver usually with 188^o (or 145^o) solder. As described in the whitemetal section above, 188^o solder or normal 60/40 electrical solder is similar in its thermal properties to whitemetal. Brass/nickel silver tinned with the higher temperature solder can be soldered to whitemetal using low melt solder - melting temperature 70-80^o.