On Wednesday 26 September 2018 05:23:42 andy pugh wrote: > On Wed, 26 Sep 2018 at 06:13, Chris Albertson <albertson.ch...@gmail.com> wrote: > > On Tue, Sep 25, 2018 at 1:04 AM andy pugh <bodge...@gmail.com> wrote: > > > I can't help thinking that the way to determine the amount of > > > correction needed is to actually machine a test bar and measure > > > it. > > > > A laser beam is straighter than any bar. and is quicker and costs > > less.
It may be straighter, but the ones I just bought for this, at a combined $85 for the 2of them, have 3 problems: The 1st being that it appears they are multiple emitter devices giveing an upclose beam that integrates to about a .5 by 1mm central image made up of individual beams a few microns apart. And the 2nd is axial alignment, combined with the beam spreading at 30" out, gives a bar of light at full intensity that is around 2mm wide by 4mm long, and describes a nearly 10 mm diameter circle on the target as the spindle rotates. Theres no way a 5mm square working area chip can work with that much off axis a beam. Its going to be clear off the imaging chip. The only way would be to rotate the spindle until the pattern is vertical, and drive the crossfeed to center the beam on the imager. Then rotate the spindle 180 degrees and using the crossfeed drive to recenter the image on the imager then calculate the center, doing this every 1/2 inch near the spindle because thats where the majority of the wear is. The 3rd problem is the general lack of availability of the battery these need, 2 393's-394's I think it was. And the 38 cal model has no switch, you must remove the device from its mounting and remove the batteries by unscrewing the cartridge rim/plug, $14 a pair with an estimated life of less than an hour. The 6.5 Creedmoor version does have a switch of sorts, a nylon button in the rear cap, left handed thread, that screws in and lifts the + end of the battery stack (3 of them in that one) from its ground contact to turn it off. > Yes, but there is more to making straight parts than having perfect > alignment between the unloaded toolpost and the spindle axis. Which is basically what I was doing by dialing the barrel of the tailstock, and pushing the loose tailstock along with the carriage holding the dial. No cutting forces there. I found quite easily, some dings in the inside edge of the front flat the tailstocks front rests on in the bed that had the effect of tipping the tailstock to the rear. Several places along the bed might have light dings, but they were quite obvious in their effect on the dial when the tailstock rode over them at the far end. I'll polish those away with a worn red DMT plate today. After I wash it, its pretty well dirt packed and in need of a good scrubbing. > You seem to be assuming that _I_ am the one under-thinking this :-) That is a Chuckle. We should all know better than that by now, Andy. :-) -- 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 Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
