On Tuesday 18 August 2015 13:37:34 John Kasunich wrote: > On Tue, Aug 18, 2015, at 12:53 PM, Gene Heskett wrote: > > On Tuesday 18 August 2015 12:32:30 Ken Strauss wrote: > > > I haven't closely followed this thread but what is wrong with the > > > traditional method of sweeping a DTI attached to the end of an > > > L-shaped rod secured in the spindle? Simple, time tested and very > > > accurate. > > > > The table is currently occupied by a large holding jig I don't want > > to move without first installing some keys on the ends of it to > > re-align it with the table when I put it back on later. > > > > I wouldn't trust the jigs top plane for absolute square and flat as > > its been a year since I made it. It was machined flat, to that toy > > mills version of flat then, but that 2" thick block of white ash has > > now had another year to dry since. It was 10+ years out of the > > weather seasoned then & should be fairly stable. > > > > I should reflatten the area where the boards get clamped to it, with > > a fresh 2 flute upspiral SC mill, taking off perhaps 10 thou. > > Yes, you should :-)
I took a nominal .005'" cut, no missed spots so I quit. > Since Z won't be used when you flatten that area, any Z errors won't > matter. The newly flattened area will be by definition parallel to > the XY plane of the machine. Which makes it the perfect spot to use > when tramming the spindle perpendicular, using the traditional bent > rod as an indicator holder. > > > But this > > error looks like 5 thou or so just in the 0.760" thickness of the > > board, so a jig level error would have to be truly huge to make that > > big a difference. > > It sounding like you probably do have head tilt. The columns of those > chinese machines are rarely perfectly plumb, but they are also rarely > if ever off that much. I measured the fat part at the bottom of the extended quill housing and found it was less than a thou diff between the bottom dia and several places on up that "cylinder", about 2" high, so I scanned that and found under a thou on the indicator. Front, back, or either side. Thats s/b good enough for the girls I go with. :) > In your shoes, I would flatten the board clamping area of your > fixture, then adjust the head tilt with a spindle mounted indicator > sweeping the largest practical circle on the newly flattened area. > Having done those two steps I bet you'll get nice joints on your > project. Not, so the next thing is a fresh SC bit, and reduce the depth of cut and speed of table to reduce bit flexure. The only thing left has to be bit deflection under that heavy a side load. This is all climb cutting so any deflection would add when the pieces are turned around to mate the joints. It could even disappear with a fresh SC tool. OTOH, I might be the only one with that critical an eye. I just scanned one such pair of joints, so in 5 minutes or so, it will be "test-cut.jpg" in the Mill-stf/pix-scans page at the address in the sig. Cut at a DOC of around .225", 3 passes and a final to cut the thin remaining web at the bottom, and table speed of 50 ipm. It is there now I believe. I can see it. 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
