Rex-Cut Blog

    Simple Way of Preventing Stress Cracks on Cast or Machined Parts


    HIGH STRESS? NO PROBLEM:

    Precision parts for high stress applications can cost thousands to manufacture. In aerospace or automotive manufacturing, an hour of production time can be worth $5000-$6000. Hydraulic pump parts in certain applications can cost as high as $25,000 for a single unit. With sky-high manufacturing costs, extending the amount of time these parts can stand up to high stress is important.



     

    Parts in these applications are often made from exotic alloys and machined to exact, precision tolerances. They are engineered for extreme environments using the finest tooling. If a stress crack develops on a part over time, it is ruined and dangerous, which is why putting the perfect “radius” on a part is so important.

    Putting a radius on the edge of a part uses the strength of an age-old shape—the arch—to evenly distribute stress along the entire surface, instead of allowing the stress to be focused on a right-angled edge.


    Close up of rounded edge on turbine blade

    Close up photo of high alloy turbine blade before and after a W163 A80 MTX Mounted Point was used to debur and smooth the edge.

     



    CREATING THE PERFECT RADIUS:

    deburring wheel for titaniummounted points for titanium

    Some manufacturers use a machine tool to attempt to radius a part. But this will tamper or bevel the edge and actually create two smaller edges. While this is an improvement over the original surface, it is still not as effective at reducing stress as the true arch shape.

    Abrasive wheels are effective at putting a radius on the part, but their level of effectiveness depends on the material of the wheel itself. A typical wheel is made from non-woven nylon—an open nylon filament web that has an abrasive grain mounted to it using a bonding agent. The problem is that when the grain is mounted on the surface, an operator can tear the grain right off the wheel while trying to radius a part.

    We recommend a non-woven cotton fiber that’s denser than non-woven nylon. It’s the material used in Rex-Cut wheels and we use it for a reason. Cotton fiber mounted points have a cushion action while in use, and due to their density, will hold up well grinding on an edge. Rex-Cut wheels have a very soft, controllable feel, and an operator can grind as hard, or as soft, as needed to create that perfect, radiused edge without changing the critical geometry of the part.

    Non-woven cotton wheels feature a consistent finish throughout the life of the wheel, and there is no backing that can gouge the surface of the material. Also, these wheels are non-loading on all metals.

     

    SIMPLY STRONGER:

    Rex-Cut wheels also feature the strength and durability of lamination. Cotton inherently has a natural mechanical strength, as the threads of woven cotton reinforce each other, and this bond is only made stronger when combined with lamination. It’s why Rex-Cut wheel typically last twice as long in aerospace, automotive, and other parts finishing applications when compared to non-woven nylon. Each time an operator needs to change a wheel is another delay that can be minimized through a non-woven cotton wheel.

    When each part must absolutely be right the first time, there is simply no better choice than a Rex-Cut wheel to create a perfect radius, and protect your significant part manufacturing investment. Add to that less cost and time spent in replacing wheels, and the bottom line value of a Rex-Cut wheel comes clearly into focus.



     

    Filed under: Aircraft