ROCBOLT Technologies and ROCBOLT Resins
About Us

History of JENNMAR


Mary and Frank Calandra, Sr., parents of JENNMAR’s two common stockholders, Jack Calandra and Frank Calandra, Jr., originated Frank Calandra, Inc. as a proprietorship in 1922. JENNMAR was incorporated in 1965, but from 1922 until 1972 the company was engaged in various businesses related to the coal mining industry.

Frank Calandra, Jr.

In 1972, JENNMAR began to change the primary focus of its business to the manufacturing of roof support systems for coal mines. Today, JENNMAR's reach extends around the globe and into the tunneling and civil construction industries as well.


Frank Calandra, Inc. originated as a proprietorship


Began to change the primary focus of our business to the manufacturing of roof support systems


Continued to grow with the introduction of our first specialty bolt, the COMBINATION® Bolt

Began construction and operation of our West Virginia plant


Expanded with manufacturing facility in Winchester, Kentucky


Acquired Valley Steel’s mine roof bolt manufacturing plant in Flora, IL


Received patents on the INSTáL® Bolt


Gained access to the western region’s coal producing areas through the acquisition of a local mine roof bolt manufacturer in Helper, UT


Expanded our facility in Winchester, KY


Opened a new manufacturing facility in Clearfield, UT

Began construction of facility in Tazewell County, VA


Became associated with cable bolt and cable truss technology

Expanded our roof support systems manufacturing facility in Reedsville, WV


Established a manufacturing facility in Sydney, Australia


Began construction of a 130,000 sq. ft. steel service center adjacent to the Nucor Steel Mill site in Berkley County, SC


Looking toward Asia for future production


R&D department launches Prop Program


JENNMAR China produces first roof bolt for Asia market in August

Affiliate company, J-LOK begins producing its own line of specialty resin for JENNMAR bolt systems


JENNMAR Specialty Products begins production


JENNMAR West Kentucky and J-LOK Corporation in Earlington Kentucky are commissioned

JENNMAR Australia moves into modern roof bolt complex in Narellan, Australia

J-LOK Australia offers a line of resin to complement JENNMAR Australia’s products

JENNMAR Canada project begins


JENNMAR Canada moves from a small leased space to our new 50,000 square foot building in Sturgeon Falls, Ontario

JENNMAR opens a manufacturing facility in Santiago, Chile, known as JENNMAR Latin America, and sales offices are formed in Mexico, Peru and Spain

JENNMAR Europe places sales offices in Gijon, Spain


JENNMAR completes purchase of Merol, Poland’s largest independent ground support provider to coal and hard rock markets


Acquires MultiTex in the Czech Republic, further expanding JENNMAR’s hydraulic expandable rock bolt capacity


JENNMAR purchases a resin company in Johannesburg, South Africa establishing a presence on 6 continents!

Establishes JENNMAR Civil to more fully address the needs of the civil construction industry

Acquires McSweeney’s, a leading manufacturer of forged drill steel products.


Divested Canadian assets

Through joint ventures with DSI, established ROCBOLT Technologies in South Africa and ROCBOLT Resins in Australia


Acquired SanShell and TungsteMet expanding roof and miner bits capabilities and adding carbide tooling capabilities


Acquires DSI Mining Division in US; Sells Global Operations to DSI; Established additional ROCBOLT Technologies joint ventures with DSI in China, joining ROCBOLT Resins in Australia and ROCBOLT Technologies in South Africa