On Tuesday 04 October 2016 14:25:39 andy pugh wrote: > On 4 October 2016 at 18:55, Gene Heskett <[email protected]> wrote: > > But I went to Home Depot yesterday to find some 3/8-24 > > nuts, but was only able to source them in grade 5, > > Nuts should generally be softer than bolts anyway. > > In the original application they would have been hard, machined bolts > as they were expected to be loosened and tightened thousand of times. > With CNC you almost certainly will never touch then again once > tightened, so the softer nuts will be fine (and will apply a more > tapered force profile to the bolts, good for fatigue)
Good point Andy, but I purposely made that base with an offset top, just so I could loosen it and rotate it to move the QC post around in case I needed to. The offset serves also for additional swing clearance Same idea as the same part on TLM, and I've already rotated it several times now as I like to see the tool tip stay within the saddles foot print on the bed so it doesn't rock against the gibs near as violently. TLM's footprint, saddle to bed, is only a hair over 3" wide. So in that sense, there was a method to my madness. The Sheldon, with its nominally 11" wide saddle footprint, is much less sensitive to those effects as long as the crossfeed gibs are properly adjusted. That also makes up for the crossfeed motion, limited by the ball screw, only having about 4" of radius travel, so I can get the rest of the 11" swing it can supposedly do by rotating the base. With the taper attachment gone, I lost at least 9" of crossfeed motion because the crossfeed anchor point was the taper attachment. So I get a couple inches of that lost motion back this way. Crossfeed thrust anchor is now the bearing boss the old hand crank turned in, converted by adding bearings to it to take the pull of a timing belt & making a new shaft, the one with a socket in the rear end for the ball screw I wrote about which is where I put the long tapered thread on, then edm slit the socket into 6 petals, made a matching tapered nut. Slip the screw in to bottom in the hole, and the screw is locked in place before the nut is even finger tight, but I used wrenches to make a pressure weld. That screw is not going anywhere until I fully loosen that nut again. The screw is now very well protected from swarf, even when cleaning up with an air hose. Panels of sheet metal let into the top of the crossfeed & glued in, and glued into the bottom of the saddle, covering the bottom of that screw from bed rail to bed rail, and a form fitted cover over the rear of the saddle. If those OEM bolts were hardened, I see little evidence of it, but do not own a hardness tester. I'd also say that the wrenching facility of the former setup was incapable of damaging even a grade 3 bolt. I probably have them under more tension right now than they have ever been subjected to in nearly 70 years with a 20 lb pull on an 11/16" box end wrench. Unforch, when I do get my version of the armstrong bolts made, and the other two wrench pockets cut in the base, I'll still have to remove the x screw completely to gain access to the square hole in the bottom of the crossfeed to insert or remove those bolts. TANSTAAFL. Thanks Andy, a bunch. 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> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
