On 8/15/2013 1:57 AM, Steve Blackmore wrote: > On Thu, 15 Aug 2013 07:25:44 +0200, you wrote: > >> Now would that be a 50% or 75% thread. JT's tables needs both. One for >> softer metals and the other for the harder stuff. > Metric threads are usually specified as .65H In the Machinery's Handbook it has charts about various thread limits based on amount of engagement and some text that says "In general when the engagement length is one and one half times the nominal diameter a 50 or 55 per cent thread is satisfactory." and it goes on to say a twist drill is a roughing tool and if size matters ream the hole. and it also says that while 60% threads is usually all you need 75% is often used.
For example the MH chart shows a 1/4-20 hole size can range from 0.196" to 0.210" depending on the length of engagement. > I've never seen any deviation in percentage diameter specified for > softer or harder materials for drilled and tapped holes, and as most > drills drill oversize anyway it's a moot point. > > You would just use tables or diameter - pitch. What does the next paragraph mean? > For softer or harder materials you just use the appropriate > diameter/pitch faster. This is for tapping holes only... > If you are machining threads on a lathe, it's a different story. Using > the correct form inserts you can get up towards 90%, if you needed > threads that close in tolerance you would be reaming or boring the holes > and tables are of no value. You would use CAM or get the info from > Machinery's Handbook etc. > > Steve Blackmore > -- > > ------------------------------------------------------------------------------ > Get 100% visibility into Java/.NET code with AppDynamics Lite! > It's a free troubleshooting tool designed for production. > Get down to code-level detail for bottlenecks, with <2% overhead. > Download for free and get started troubleshooting in minutes. > http://pubads.g.doubleclick.net/gampad/clk?id=48897031&iu=/4140/ostg.clktrk > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ Get 100% visibility into Java/.NET code with AppDynamics Lite! It's a free troubleshooting tool designed for production. Get down to code-level detail for bottlenecks, with <2% overhead. Download for free and get started troubleshooting in minutes. http://pubads.g.doubleclick.net/gampad/clk?id=48897031&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
