The Shell Mold Process

Hiler Industries boasts two modern foundries that produce millions of castings every year — all using the shell mold process. Since 1946, we have been providing our customers the highest quality castings, in a variety of metals, all with an excellent surface finish and near-net shape.

Superior Machining Qualities
A major benefit of shell molding is the excellent machining characteristics achieved through this process. Many photomicrograph inspections have shown that shell castings have what might be termed “cooling rate inversion.” Unlike green sand castings, permanent mold and die castings — which all have hard skins and “soft” interiors — shell mold castings have “soft” skins and hard or dense interiors. As a result, shell mold castings have superior machining qualities vs. green sand and other types of castings.

Less Weight
Another major benefit is that less machining stock is required. Over the years, we have found that .060 stock is more than ample. In fact, if the job were to be machined in our machine shop, we would add only .040 stock. This is helpful in two ways:

  • The casting will weigh less, and thereby cost less
  • Less machining stock is removed, which improves machining time and lowers machining cost

There have been times when we worked with customers and eliminated machining entirely.

General Tolerance Information (Unit of Measure: Inches)

Same side of parting line:

± .020 for 1st 3"

Add ± .003 / inch over 3"

Across parting line:

± .030 for 1st 3"

± .003 / inch over 3"


Typically 1°

Certain applications at 0° draft.

Typical Finish Stock:

.060" maximum

Hole size cast into part:



Less than 0.5"

Equal to diameter

0.5" - 1.0"

Equal to 1.5 times diameter

Greater than 1.0" Equal to 2 times diameter

Note: The above information is modified by the individual casting complexity and to agreement between the customer and Hiler Industries. For example, we have held some dimensions to ± .010, obtained less than 1° draft, and used some finish allowances less than .030.

AFS - Shell Mold Surface Finish