I reckon that a lot of the difficulty is that the hole is too small. At 12mm, there is quite a lot of force involved, and you are using a semi-bottoming tap, and it's a blind hole, and the tap is a weaker spiral shape.
With a 10.5 hole you are using the tap to drill as well as tap. Use 10.7 as recommended, or even 10.8 if you want to do reduce the chance of breakage. A new tap should easily do the job in one pass. Regards Roland On 22 January 2016 at 19:43, <tom-...@bgp.nu> wrote: > This is the tap I am using: > http://www.mscdirect.com/product/details/58607482?rItem=58607482 > The drill I am using is 10.5mm which is 0.875 of 12mm so I would say that > seems fairly large. The OSG online tool recommends a 27/64” (10.7mm) > drill, so I am very close (0.008” difference). Also, if I was using OSG's > tap they recommend 23.8764 IPM which equates to a spindle speed of 400 > RPM. I can try that (I used 300 RPM), but I suspect I am going to have the > same (torque) issue I had before. And perhaps the answer is I just don’t > have enough torque at low spindle speeds to do it in one pass… > > -Tom > > > On Jan 22, 2016, at 12:00 PM, John Thornton <j...@gnipsel.com> wrote: > > > > What kind of tap did you use? I use only ElectroLube coated taps from > > OSG. OSG has an online tool to select the correct tap and drill for each > > job. I once had to deep hole tap in some 7075 and my normal taps broke > > off. I used the tool and got the right tap and drill so the hole size > > was correct for the job. Tapping charts usually use 75% thread depth > > which is usually OK for a depth = diameter, for deeper depths you need a > > bigger hole. > > > > JT > > > > ------------------------------------------------------------------------------ > 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 > ------------------------------------------------------------------------------ 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
