Thanks Erik, that is the kind of information I have been looking for. Much appreciated.
On 2013/08/18 12:14 PM, Erik Christiansen wrote: > On 15.08.13 06:13, John Thornton wrote: >> 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." > That matches what I've been using, from this table: > > ---------------------------------------------------- > Metric Coarse | BS 4168 Clearance hole: > | | Type of fit: > Size Drill E Core | Close Medium Free > ---------------------------------------------------- > M2 1.70 61% 1.51 | > M2.5 2.15 63% 1.95 | NOTES: > M3 2.60 65% 2.39 | 3.2 3.4 3.6 2.5mm drill -> 82%. > M4 3.40 70% 3.14 | 4.3 4.5 4.8 > M5 4.40 61% 4.02 | 5.3 5.5 5.8 With a nut length of > M6 5.20 65% 4.70 | 6.4 6.6 7.0 1.5 * diameter, 50% > M8 6.90 72% 6.47 | 8.4 9.0 10.0 engagement is stronger > M10 8.70 71% 8.16 | 10.5 11.0 12.0 than the external > thread. > M12 10.50 70% 9.85 | 13.0 14.0 15.0 > M16 14.25 71% 13.55 | For CI and thin sheet, > -------------------------------------------------- stick near 75%. > > E is engagement. Some of those drill sizes are easier to get than others, > so a quick calculation can be made, using: > > # d is full thread depth. > Drill_Size = OD - (E*2d) # E is engagement. > # d = kP , where P is thread pitch. > > Or transposed for E: E = (OD - Drill_Size)/2d > > & k is: ISO Metric 0.613 > UNF/UNC 0.613 > # British Association BA 0.600 > # BSW, BSF, ME (32 & 40 TPI), Whitworth forms 0.640 > # BSB, and BSP parallel. > > Especially with smaller taps, it's also relevant that the torque > required to drive the tap doubles from 60% to 80% thread engagement, > with half the increase occurring between 75% and 80%. Some say: > > To avoid breaking small taps, a guide for Al, brass, and steel is: > < 6 mm: ~ 60% thread engagement > 6 - 10 mm: 70% > > 10 mm: 75% > > and 75% engagement is as high as I'd go, normally. > > The table and equation came from issue 104 of Model Engineering > Workshop, and has worked for me so far. > > Erik > -- Regards / Groete Marius D. Liebenberg MasterCut cc Cel: +27 82 698 3251 Tel: +27 12 743 6064 Fax: +27 86 551 8029 Skype: marius_d.liebenberg --- avast! Antivirus: Outbound message clean. Virus Database (VPS): 130817-1, 2013/08/17 Tested on: 2013/08/18 12:51:14 PM avast! - copyright (c) 1988-2013 AVAST Software. http://www.avast.com ------------------------------------------------------------------------------ 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
