O. K. Foundry Co., Inc., Since 1912

Gray and Ductile Iron Jobbing Foundry

Short Run Gray and Ductile Iron Castings

Ductile iron compressor castings.
Ductile iron compressor castings.

OK Foundry makes short run gray and ductile iron castings from 1 lb. to 400 lbs. No-bake cope and drag molding for heavier castings and manual jolt squeeze green sand molding for lighter castings.

Castings in serial production of small lots can be made with lead times as short as 6 weeks. Regular monthly shipments can add up to significant annual quantities iterated with lean batches. Small scale production at OK Foundry is completely automated for planning, scheduling, invoicing and shipping.

No-Bake molding and manual jolt squeeze green sand molding are compatible with many automatic molding machine tools and patterns for lower volume production of legacy parts and prototype or ramp-up production of new parts.

Phenolic Urethane No-Bake Binder (PUNB) for Difficult Castings

600 lb. continuous No-bake mixer.
600 lb./min. continuous No-bake mixer.

To support the widest range of casting sizes, shapes, and configurations, OK Foundry utilizes phenolic urethane binders for cope and drag molding. Phenolic Urethane No-Bake binders (PUNB) create the strongest molds and cores.

Castings with difficult solidification defects can often be cured by using hard molds made with PUNB binders to limit mold expansion during solidification. Cores made with PUNB binders have superior hot strength and PUNB cores in cold boxes are easily reinforced with steel rods to prevent core bending and breakage.

Although phenolic urethane binders are expensive, they help reduce typical heavy section casting defects and support a wider range of tooling options including lower cost materials like wood and medium density foam. Hard phenolic urethane molds may also reduce burn in problems with heavy section castings.

Economic order quantities for 50 lb. castings in No Bake molds start as low as 25 to 50 castings. Heavier castings are economically made with as few as 5, 10, or 15 castings per order.

Manual Jolt Squeeze Green Sand Molding for Short Runs of Light Castings

Green sand jolt squeeze molds.
Green sand manual jolt squeeze molds.

Manual jolt squeeze molding, a process we’ve used at OK Foundry for over 80 years, is still the least expensive process for short runs of light castings, about 15 lbs. or less. Even modern patterns from automatic machines like the Hunter HMP-10 and HLM-10, can be molded on a jolt squeeze machine with a 14 x 19 flask for ramp-up or ramp-down production of light castings that have been setup for automatic molding. Manual jolt squeeze molding is labor intensive, but setups and troubleshooting for very short runs can be more economical than automatic molding.

Economic Order Quantities for Short Run Castings

The number of molds made in a day or shift is a good rough estimate for a minimum economic order quantity of molds. For example, our no bake cope and drag line can make about 25 larger molds a shift, so a minimum economic order for a moderately heavy casting would be 25. Heavier castings can get our best prices starting as low as 10 castings per order. When production castings are planned for monthly releases and lean supply, even these minimum economic order quantities can add up to significant annual volumes. Parts with consistent repetition of orders can be optimized the most, parts with less frequent or unpredictable requirements may require more lead time.

Metal Grades Poured

  • Gray Iron ASTM A48 Class 20, 25, 30, 35, 40
  • Ductile Iron ASTM A536 65-45-12, 80-55-06
  • Aluminum A356.0
  • Silicon Bronze C87300

3D Printed Sand Mold Castings Gallery

Size and Weight Limitations

  • Max weight No-bake castings: 400 lbs.
  • Max sizes of No-bake castings: 8 ft. long x 1 ft. wide, or 6 ft. long x 2 ft. wide, or 3 ft. long x 3 ft. wide.
  • Sizes and weights are rough limits. No-bake molds are flaskless and each is sized to suit the casting.


3D Printed Sand Mold Castings

OK Foundry designs and pours 3D printed sand molds for complex castings. Castings and molds are designed in house and molds are sourced from the leading industrial casting sand printers.

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Cast Iron Boiler Grates

OK Foundry makes OEM or retrofit boiler grate castings to order including optimized machining of burner grate pinholes and traveling grate mounting holes. Foundry tooling and castings can be reverse engineered from worn out grates and low alloy grates are reproduced economically.

Explore Cast Iron Boiler Grates