Impactkut For Precision Notches

A metal impact specimen is a precision part for it must be milled or ground square to tolerances of +.001" (.025mm) and be square withing 1/4º. The bar must be notched to a depth +.001" (.025mm) with a notch radius .010" +.001" (+.025mm). The surface finish of the notch is extremely critical for it must be free of tool marks or induced cold working to achieve accurate impact results.

Limitations are encountered when notches are milled in metals, for milling teeth are used both for roughing and final finishing of the notch. After milling several notches on steel samples, cutter wear occurs and the notch surface finish deteriorates; the severity of induced cold working increases; and the radius of the notch increases, yielding inaccurate test result.

ImpactKuT is a precision broaching machine with a series of teeth similar to a milling cutter, except the 35 teeth are in a straight line. The initial broach teeth are working teeth to remove exactly .0025" (.062mm) of metal per tooth, while the last three teeth are finishing teeth and remove less than .0001 (.0025mm) per tooth. Broaching is the perfect method for machining the critical notch in impact bars - the notches are accurate within .001" (.025mm) in depth and radius configuration with a 10 micro inches surface finish. The notch radius will be essentially free of induced cold working for truly accurate and consistent impact properties.

ImpactKuT is a sturdy compact machine which can be mounted on a metal cabinet and requires minimum floor space. Laboratory personal without previous machining experience can broach a notch in a prepared 10mm square bar in less than one minute. ImpactKuT achieves excellent tool life and can broach up to 10,000 aluminum, 5,000 steel, 2,500 stainless steel or 500 high hardness RC40 specimens within tolerance before broach regrinding is necessary. 

ImpactKuT has a 1 ton capacity and a 24" stroke length to prepare notches in metals ranging from soft lead or aluminum alloys to high hardness steels, titanium, and the tougher nickel and cobalt base alloys. The broaching force is hydraulic and the broaching speed is controlled by a hydraulic check valve. The ImpactKuT holding fixtures is mounted on a rigid steel plate to absorb the broaching forces without deflection. The ram is guided in precision hardened and ground ways to insure rigidity and consistent alignment of the broaching tool in relation to the specimen blank.

Recently, broached notches vs. milled notches was evaluated by a major shipbuilding firm. Milled notches in steel specimens required 100% inspection on a shadowgraph (with 40% rejection), while the ImpactKuT notched specimens were shadowgraphed only every 50th sample for accuracy. This company found the impact results to be more consistent and reliable due to the extreme accuracy of the notch.