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     During heat treatment, many features of machined components
     suffer distortion. If the position or dimensions of a groove are
     critical to the performance of a hardened component. David Richards
     can offer a simple solution to this problem - ‘Hard Grooving’.
     Based on the Top Notch system, David Richards supply grooving
     tools in a wide range of sizes from 0.5 mm width upwards.
     David Richards supply tools for circlip and ‘O’ring grooves with      controlled corners or full radii, either full form for plunging or      undersize for profiling.
     Using such surface speeds typical for turning, grooves are machined
     at low feed rates (0.01/0.05 mm/rev).
     The low feed rate ensures that the swarf is very weak and brittle,
     decreasing the likelihood of it breaking the tool.
     Where there are no interruptions to the cutting path, coolant should
     be used to aid evacuation of the swarf and ensure that the component      remains at a stable temperature for ease of measuring. If the cutting
     path is interrupted, an air blast will serve the same purpose without
     the risk of thermally shocking the PCBN tool.
    If practical, it is better to finish a groove that has been pre-
    formed at the soft stage. This ensures uniform hardness around
    the groove and maintains the structural integrity of the component.
    However, if it is acceptable, satisfactory results are achieved
    grooving through a hardened layer into the core material.



    Successful applications include grooving case hardened (58 / 63 HRc) splined shafts and gear teeth, internal circlip
    grooving hardened EN31 (58 / 60 HRc) bearing components, and producing profiles in the face of D2 tools steel
    tools using Full radii face grooving tools. All operations that would be time consuming and difficult to grind.
    Whilst the Top Notch system offers an ideal base for most grooving tools, other systems have been
     employed with excellent results.
    It naturally follows that, since David Richards can produce tools for ‘Hard Grooving’ full and partial form threading
    tools, both external and internal, are available for ‘Hard Threading’. Where the pitch of the thread is large, or the
    diameter of the component is small, it must be remembered that the feed rate required, at the required surface
    speed for ‘Hard Turning’ will be relatively fast. But, producing a 90 mm diameter internal stub Acme thread 150 mm
    deep, with a 6 mm pitch in 58 HRc Ni-Hard iron, at 120 m/min from blank bore, though somewhat exciting, proved
    a major cost saver.
    David Richards have wide experience in the application of these tools and will be delighted to discuss specific     examples on request.






© David Richards Engineering  2013