On 10/29/2012 11:26 PM, Sebastian Kuzminsky wrote: > Bone headed error... I am doing a small production run, using three > different drills, each mounted in its own tool holder. I had carefully > measured the length of each tool and recorded them all in the tool > table. I had run about 10 parts, everything was going great, just a few > left to go. > > Then I got distracted and loaded the wrong tool... Unlucky for me, the > tool I loaded was much longer than the tool the machine asked for, and > the machine happily drove a drill chuck with a #39 drill right into the > work. > > The drill shattered and disappeared in a spray of shrapnel (no one was > hit). The jaws of the drill chuck drilled about 0.100 inches down into > the work piece (soft aluminum, fortunately). The Z servo finally > signaled a following error and e-stopped the machine. The work and the > fixture plate absorbed all the damage, the table of the machine is still > unmarked. So it could have been worse. > > But the chuck is completely ruined. It used to be a pretty nice keyless > chuck, 1/32" to 1/2" gripping range, J6 taper. Now it's garbage: the > body (what I would normally turn to tighten and loosen the jaws) turns > very reluctantly, and the jaws don't move at all when i turn it... > > I got it off the J6 tool holder, and the J6 taper on the tool holder has > ~0.001 inches of runout now (measured with a DTI on the taper, while > mounted in the spindle and turning slowly). I don't know what the > runout was before the crash, and I don't know what's acceptable. Does > this seem reasonable, or should I scrap the tool holder too and look for > another? My spindle has a QC-30 taper, which is somewhat unusual - tool > holders like this can be hard to come by. > > In either case I need a new drill chuck. > > The wrecked chuck is of the keyless variety, and while that's convenient > I'm considering replacing it with a keyed chuck because they tend to be > shorter, and my quill is a bit limited in Z travel. Why do CNC machines > usually have keyless chucks? > > What do you all recommend for a good value on a drill chuck, about 1/32" > to 1/2", J6 taper? > > Keyed or keyless? > > Help me emc-users, you're my only hope!
The runout is pretty small, and you could be reading the runout of the bearing in the spindle, unless you know for sure that they are good. However, don't toss that keyless chuck just yet, if it's a Jacobs chuck, here's some rebuilding instructions: http://www.jacobschuck.com/pdf/Precision-Chuck-Repair-Instruction.pdf Other mfg's chucks are similar. I've replaced the jaws on a few Jacobs #36 keyed chucks, with very successful results, and it was cheaper than buying a new chuck. -- MC Cason - Assocaite Developer - Eagle3D Created by: Matthias Weißer http://www.matwei.de/doku.php?id=en:eagle3d:eagle3d http://developer.berlios.de/projects/eagle3d/ ------------------------------------------------------------------------------ Everyone hates slow websites. So do we. Make your web apps faster with AppDynamics Download AppDynamics Lite for free today: http://p.sf.net/sfu/appdyn_sfd2d_oct _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
