Oops, I was just going by what you said without looking up the sizes. If it's metric coarse, then a M12 x 1.75 thread only needs a 10.2mm hole, so 10.5 should feel easy to tap.
Regards Roland On 23 January 2016 at 13:12, Roland Jollivet <roland.jolli...@gmail.com> wrote: > > 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
