"Dumbbells & Dogbones" News Letter
with Helpful Tensile & Tear Test Specimen Die Information
February, 2010- Vol 1, Issue 1
In This Issue
Die Maintenance Questions
Improper Use of Specimen Cutters
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Greetings! 

Welcome to issue #1 of our Dumbbell & Dogbone Die News Letter which is specifically designed to bring meaningful information to those using Tensile and Tear Test Specimen Dies.

 

We invite reader input on problematic issues or helpful suggestions to be discussed in future issues.

We will honor any request to be removed from our emailing list. Likewise, we will be pleased to include any associates you may know who might enjoy receiving future News Letters

Article Headline
 

How often should Tensile & Tear Specimen Dies be Sharpened, Calibrated and Re-Certified?

 

We're often asked that question. Here are some suggestions that may help:

1.       Any die that gives poor quality cuts should be sharpened

2.       A die that has been dropped, but with no visible damage, should be re-calibrated to ensure that it is not out of tolerance

3.       Comply with your company policies

4.       Some ISO guidelines specify annual Certification

5.       Some companies require Certification every six months

6.       In lieu of ISO or specific Company policies notwithstanding, we recommend a two year program for Sharpening, Calibration, and Certification

Properly manufactured Specimen Dies are made from premium, high-grade tool steel, through-hardened and EDM'd with a straight, vertical inside wall all the way to the back. This allows the dies to be ground and sharpened throughout the die life without any change in the dimensional tolerances of the specified cutting edge dimensions. We have sharpened and certified dies that are forty years old and they are perfect in every dimension.

OK, so when should a die be replaced?

1.       Any die suffering from an accident causing damage that is not repairable should be replaced

2.       A die too far out of tolerance to be calibrated should be replaced if the inside walls are not straight; this is common with forged-steel dies

3.       A die that is too short in height may have a stubby outside bevel and should be replaced if the cut parts distort out of specification due to the bevel

How many layers should you cut with a specimen die?

 

This question was posed by a Japanese customer who was experiencing some chipping on the cutting edges of his dies. We asked that he submit some pictures via email so we could evaluate the issues.

 

D624C Gang DieHere's what we found out:

1.       The customer was using a gang of four ASTM D-624-C Tear Test Specimen Dies mounted to a plate with minimal space between the dies so he could get good yield on his material

2.       The dies were used on a "clicker" press; i.e., a swing arm cantilevered head that pushes the dies through the sample material and into a plastic cutting surface

3.       Close examination of the die pictures clearly showed marks on the side wall of the dies indicating the material was pushed nearly �" up the edges of the dies. Pictures of the plastic cutting pad showed deep die penetration into the pad

4.        Subsequent correspondence with the customer to discuss our findings confirmed

a.       They were trying to cut three layers of a fairly dense material

b.      The pressure setting on the press was set too high, causing the dies to drive too deeply into the cutting pad

5.       WE RECOMMENDED that the customer restrict the technician to cutting only ONE LAYER of material because

a.       Multiple plies of material will distort and no two pieces will be exactly the same

b.      Multiple plies may give multiple Tensile and/or Tear Test results/readings

6.       WE RECOMMENDED that the pressure setting on the press be adjusted

a.       To "just" cut the material

b.      Make as little impression on the cutting pad as possible

c.       Maintain the cutting pad in a level and clean condition

Do you have any experiences you'd like to share? Do you have any suggestions for proper die use? Do you have any questions that we might answer and share with other readers?

If you answered yes to any of these questions, please send an email to [email protected]. We promise to keep your name and company information confidential.

 
Sincerely,
 
Jerold Larson
Pioneer-Dietecs Corporation

Member ASTM D11.10 Subcommittee since 1967

[email protected]