Technical Data

Technical Data

The lost wax process is ideally suited to the manufacture of complex, high accuracy castings, in most alloys.

This process has the advantage of needing the least amount of finishing after forming, minimising subsequent machining and finishing. However, McKenna Precision Casting welcomes enquiries for castings in any alloy, and will fully assess each enquiry against the capabilities of the investment casting process.

  • All types of Stainless Steels
  • Cobalt – Nickel based alloy
  • Aluminium Alloys
  • Brasses
  • Bronzes

McKenna Precision Castings yield rates are well above the industry norm.  We aim for, and generally achieve, in excess of a 95% yield for each batch produced.

Our process is designed to produce castings from a few grams in weight up to 30kg.

The current size limit is that castings are no larger than 350 x 250 x 250mm (except for aluminium where it is 650 x 650 x 550mm), subject to component geometry.

McKenna Precision Castings manufactures precision components, and is capable of working to very tight dimensional tolerances. Please follow the links for more detailed information on linear tolerances, flatness and straightness, ovality, concentricity, angles, radii, mechanical straightening and sizing, and surface finish.

Other Facilities and Services

McKenna Precision Castings boasts a comprehensive range of in-house facilities, and is able to offer a wide variety of services to our customers.

These include:

  • Advice and assistance with original component design.
  • Production of 3D CAD component/casting drawings.
  • Full tool-making and validation facilities in-house.
  • In-house dimensional checking facilities.
  • Orthopaedic machining and polishing.
  • A fully equipped 3D CAM controlled tool room.

In general a tolerance of ±0.13mm (±0.005 inch) per 25mm (1 inch) in length will be achieved.

On relatively small components, up to 13mm (0.5 inch) a tolerance of ±0.1mm (±0.004 inch) is possible.

On smaller dimensions of approximately 6mm (0.25 inch) a tolerance of ±0.08mm (±0.003 inch) can be attained.

Critical dimensions are best advised at the quotation stage however it is sometimes possible to “tune in” any critical dimensions after the initial sampling stage. An increased level of dimensional accuracy may well call for specialist tooling and production control techniques, with a proportionate increase in component cost.

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 inch) per 25mm (1 inch) of casting length will apply.

A tolerance of ±0.13 (±0.005 inch) will apply up to 25mm (1 inch) diameter and ±0.13mm (±0.005 inch) per 25mm (1 inch) of diameter thereafter.

Concentricity

Concentricity between outside and inside diameters in the “as-cast” product will be dependant upon component size and the relative sizes of the outside and inside diameter, for example:

 

OD ID Eccentricity as cast
25mm (1 inch) 12mm (0.5inch) ±0.1 3mm (±0.005 inch)
50mm (2 inch) 25mm (1 inch) ±0.25mm (±0.010 inch)

A tolerance band of ±0.5 degree will generally apply for cast angles, however, their accuracy will depend to a large extent on the mass and configuration of adjoining metal sections.

A normal tolerance for both internal and external radii would be ±0.4mm (±0.016inch) per 25mm (1 inch) of radius.

Surface Finish

Mechanical Straightening and Sizing of Components
  • Various surface finishes are available including Stainless steel shot blast, Aluminium Grit blast, Glass bead Peen etc.
  • A surface roughness of between N7- N8 (1.6 – 3.2 Ra micrometres) can be achieved.
  • Additional surface treatments are also available such as Pickle and Passivation, Electro-Polishing, Painting, Alochroming etc.

Other Resources

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