STRESSPROOF® is made by a patented process which consists of drawing the bar through a special die under heavy draft, then stress relieving it in a precisely controlled furnace.

When Niagara LaSalle developed STRESSPROOF® in 1938, it changed the economics of part production. Because for the first time, users could get an improved wearability without case hardening, strength without heat treating, plus excellent machinability and tool life.

STRESSPROOF® is electro-magnetically tested using eddy currents. Other benefits include resistance to fatigue and stress, balanced working and minimum warpage and distortion. STRESSPROOF® can also be induction hardened, but should be watched for quench cracks.

It is strongly felt that in our modern computer age, uniformity in machinability of a product has become a key factor in improved productivity, and Niagara LaSalle will continue to be responsive to the needs of its customers.

STRESSPROOF not only meets the minimum properties of ASTM A311, but it also has controlled low stresses, reliable machining, and improved surface quality. Result is longer part life with less manufacturing costs.

FACT: THE GRADE 1144 MODIFIED Grade AISI 1144 was originated by the LaSalle Steel Company in the mid-1930's for the purpose of making STRESSPROOF.

FACT: THE PATENT The original patent for STRESSPROOF, "the steel product and method of manufacture", was based on cold drawing with heavy drafts, i.e., higher-than-normal drafts. This was followed by the highest temperature stress relieving treatment possible to obtain a combination of properties… strength, wear resistance, minimum warpage, and excellent machinability.

FACT: HIGH TEMPERATURE STRESS RELIEVING The importance of high temperature stress relieving to obtain maximum ductility, minimum warpage and excellent machinability is a major part of the original patent. The stress relieving temperature selection is based on 60 years of experience and thorough documentation.

FACT: PATENTED DRAWING DIES Niagara LaSalle's patented drawing dies have always been the most critical part of producing STRESSPROOF. Therefore, a warpage test is always performed on the first bar drawn through either a new or reground die. Warpage tests are also regularly made as part of a standard quality assurance procedure. Niagara LaSalle is the only mill to use a warpage test. The results then become an integral part of the quality assurance program.

FACT: SURFACE QUALITY To assure surface quality, comparitor or roto bar testing for seams on every order is a part of the STRESSPROOF manufacturing process. To further improve quality, Niagara LaSalle reduced the standard seam depth tolerance for STRESSPROOF from 0.0015 per each 1/16" to 0.0010 per each 1/16". This can mean a savings of 3% in material weight purchased.

FACT: ASTM A311 SPECIFICATION This specification was written in an attempt to cover STRESSPROOF properties. This specification is very broad in that it covers eight grades and four conditions of stress relieved cold drawn bars to meet minimum mechanical property requirements.

FACT: MECHANICAL PROPERTY TESTING Mechanical property (tension) testing at Niagara LaSalle uses the largest sampling plan in the industry. A minimum of one test (tensile, yield, elongation, R/A) is made for every 50,000 lbs. or less. Mechanical property testing is always the final production operation after all processing is completed.