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Design


Design
It is recommended that consultation with the company's project engineers should take place when first designing any component to be produced by the process.  Simultaneous engineering of the product can generate savings in lead times and help minimise tooling and development costs.  Such involvement is not always possible and the following is offered for guidance.

Tolerances
The tolerances below are the recommended minimum for functional details.  For non functional dimensions, wider tolerances should be considered which will result in a more economical design.  In order to obtain the best possible use of tolerances, castings should be dimensioned from datum planes nearest to the centre line of the component.

Hole Tolerances
Minimum tolerances for holes are:-
Up to 6mm (0.25")+/- 0.75 (+/- 0.003").
Up to 12.7mm (0.50)+/- 0.10 (+/- 0.004").
Over 12.7mm (0.50")+/- 0.13 per 25mm (+/- 0.005" per inch).

Flatness and Straightness
The shape and section of the component concerned and the alloy being cast will have a large bearing on the flatness and straightness achieved in the 'as cast' product.  As a general rule, a tolerance of +0.13mm (+0.005") per 25mm (1") of casting length will apply, up to a maximum of 0.5mm (0.20").

Ovality
Will be held within the linear casting tolerances.

Wall Thickness
A minimum tolerance of +/- 0.25mm (+/- 0.10") should be allowed on wall thickness.

Angles 
A tolerance band of +/- 0.5 maximum will generally apply for cast angles.  However, their accuracy will depend to a large extent on the mass and configuration of adjoining metal sections.

Radii
A normal tolerance for both internal and external fillet radii would be +/- 0.25mm (+/- 0.10") of radius.

Mechanical Straightening and Sizing of Components
Provided that the configuration and mass of the component permits, tolerances will be held or improved by mechanical sizing.

Metallurgy
Choice of specification, its composition, mechanical and physical properties, corrosion resistance, type of application, additional process requirements and special treatments will depend on the function of the component and the precise number of castings to be produced.
The foundry is able to cast the following alloy ranges:-
STEELS:  Corrosion and heat resisting in ferritic, martensitic or austenitic conditions, together with the high strength precipitation hardening alloy steels.  Case hardening, nitriding, low and medium carbon, low and medium alloy steels and tool steels.
COPPER ALLOYS:  Brasses, bronzes, gun-metals and beryllium coppers.
COBALT ALLOYS:  Many grades of the cobalt/chromium alloys with high or low carbon contents.
ALUMINIUM ALLOYS:
SPECIAL NOTE ON SPECIFICATIONS
BS3146 Parts 1 and 2 cover investment castings in carbon, low alloy steels, nickel and cobalt alloys.
BS1490 covers the cast aluminium alloys.  Castings should be ordered to these specifications or to equivalent casting specifications wherever available.
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The Glen Foundry Group Anderson Stewart Castings Precision Tooling The Glen Foundry The Glen Foundry