On 23.01.16 14:48, Peter Blodow wrote: > Erik, > the drill sizes you are using are all 0.2 to 0.4 mm too large, > especially with the small values M2 to M6 where it hurts the most.
No, I don't think so. As the note beside the table states: With a nut length of 1.5 * diameter, 50% engagement is stronger than the external thread. Since we don't go below 60% engagement, and are at 70% for M12, there is zero "hurt" there. What would hurt is making the holes smaller, and breaking the tap, due to excessive cutting torque, especially with the small values M2 to M6 where it hurts the most. In Tom's case, M12 is hard to break, so his spindle is giving up, and the hole needs to be larger still. > The resulting threads have got to be too loose, easy to overtighten. The tap & die still cut neatly matching threads, independent of hole size, so a badly undersized hole only makes the tap act as a drill. It does not make the bolt significantly tighter - but it does bind the tap, as Tom is finding. All we are changing with engagement is how much airgap there is at the root of the female thread. By tweaking the dieholder screws with a split die we can adjust the tightness of a thread fit. The tap offers no such variability. Erik ------------------------------------------------------------------------------ Site24x7 APM Insight: Get Deep Visibility into Application Performance APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month Monitor end-to-end web transactions and take corrective actions now Troubleshoot faster and improve end-user experience. Signup Now! http://pubads.g.doubleclick.net/gampad/clk?id=267308311&iu=/4140 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
