Gene, maybe I shouldn't have worked backwards on email catch-up after a fortnight on the farm. (Makes this reply a tad delayed.)
On 25.09.15 00:35, Gene Heskett wrote: > Marching along, adding more global vars so there is only one place to > change when something needs changed, the ER20 let go of the mill and > dropped it into the jig, digging a slot about an inch deep in perfectly > solid white ash. And it was tightened about 1/4 turn from broke when > the spindle was started. Ah, then I hope it isn't busted by now. Still, a new nut wouldn't break the bank. They're dirt cheap on fleabay. > This hex nut on the adapter has an eccentric internal ridge that may not > be properly engaging the groove where the two angles meet on the outside > of a collet, and the only reason I can see to explain its existance at > all is to engage that groove on the collet to forcibly disengage the > collet from the taper when the nut is loosened. Yup. Here's a short reminder note I use to keep myself doing it right: ER Collet Insertion: The collet MUST be mounted in the nut before a cutter is inserted, or it will have little holding capacity, and it or the nut are likely to be damaged. An area of the nut's retaining ring is cut away. When held at an angle, and tipped into the cut-out area, the collet will snap into place. A correctly mounted collet is pulled out of the collet holder taper when the nut is slightly loosened. I find it makes a little click on insertion, and the collet doesn't fall out, when it's in. That's as much "snap" as there is, even with an ER40. > If that is the reasoning, I don't think this nut is working as it was > designed to. Once today I installed a mill and snugged it up pretty > good, only to have the mill display a 1/8" run out at the end of the > mill because this eccentric internal ridge apparently didn't drop > properly into the groove in the collet, but was wedging it crossways. If the tool was inserted in the collet first, then that's part of the trouble which results. > Should I ask for a better nut, or will this one break in given enough > time? With the handling it's receiving, it'll just break, given enough time. ;-) > You fellows are the ER-8/16/20/32 experts. I never saw one of them in > person until about 16:00 yesterday. I didn't see any other related advice on this thread, so I figure the experts missed the problem. I just use 'em a bit, and find that they work like a charm when I follow the holy writ, and don't work worth a damn if I don't. I think the easiest way to wreck the nut is undoing it all the way with the tool still inserted, especially when it's been prematurely inserted. Maybe not necessary with an ER20, but a ball bearing nut is one way to get a bit more grip. Once the collet insertion is right, then applying enough torque is the next issue: http://blog.cnccookbook.com/2010/09/28/getting-the-best-performance-from-er-collet-chucks/ Hope some of that's useful, Gene. (And not too late.) Erik ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
