On Saturday 03 September 2016 09:58:45 andy pugh wrote: > On 3 September 2016 at 03:52, Gene Heskett <[email protected]> wrote: > > No common sense west of the big pond... > > I have observed that from here :-) > > If you are making a thread for your own use you do not need to stick > to any standard. > My drawbar is held together by an M14.25 x 0.9 thread. Because that is > what gave me a 1:1:1 split between the two parts and the thread. > > Make an oversize nut that will fit over the shaft.
Which has to fully, and tightly, engage a 50 tpi thread cut in that 12.7mm shaft beyond the 12m diameter quasi-smooth shaft where the drive pulley will sit. With ATM a drive or press it on fit, my digital calipers say it is 12.04mm in diameter. So I'll compose a g76 line for the thread, but use a start point a couple mm's off the end of the shaft. If it really chews it up, I'll make the nuts, all 3 of them, one with the tapered thread for the screw grabber compression, and then decide if I need to turn it on down to 10mm's. Pulleys and belts yet to be ordered. I bought a 2505 nut mount block which hasn't arrived yet, but need to hang the screw up with wires to determine how much of a spacer block I need under it to best fit both the tail end bracket to hold its floating bearing, and what I have to cobble up and make for the motor mount and drive belt, where the qcgb used to be. The screw is long enough that its thrust bearing could be on the inside face of a 1/2" thick alu plate, but I suspect I'll have to make spacers to hold the plate out from the bed casting, using longer bolts into those holes, in order to do that. That imply's a spacer block under the nut mount to couple the nut to the apron or possibly to the now unused apron retainer bolts since my new apron is fixed to the front of the saddle with 4 grade 8 1/4" bolts on each side of the x drive bearing. This has to leave room under it for the motor to pass by the screw. With room for the motor mount slider to move and tension the backlash out of the timing belt drive. By the time I find the right bellows for the screws swarf protection, its likely to get crowded anyway. This also will get easier once the x drive is finished because then I'll know where the z screw has to be hung for max bellows clearance all around. Bellows compression room on the right for full travel says the nut will be mounted on the left half of the new apron plate. Tiddly stuff, best done in the proper order, which means get the saddle back on it, with fresh wipers, making a new full length front gib plate, lapped flat on the contact face and shimming if needed. As is turning the rear one over, lapping it flat and adjusting its shims. Time killers... I found, when I built the new Z drive for the toy mill, that I needed 30 or 40 lbs of tension on that belt else the belt was an easily measured source of backlash. I worried about the motors bearing life, but that was 6 or 7 years of heavy use since, no complaints yet. That kevlar corded belt has not stretched that I can detect. But get some coffee on, and see if my lady needs anything. I'm sitting here waiting for the morning pills to kick in, my back was killing me when I tried to roll out of bed 45 minutes ago. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
