On Tuesday 16 January 2018 22:48:59 Tom Easterday wrote: > Well, I hope if G76 is indeed broken it can be fixed? > > Acme taps exist but are expensive. They are usually two stage in > order to get the depth cut. We can do rigid tapping on the Emco but > not sure if we have enough travel for the long tap and not sure we > have enough torque at lower speeds to pull it off. Acme tap example: > (https://www.amazon.com/Alfa-Tools-AT66572-8-8-Acme/dp/B00DYFSH30) > Oh... My... Gawd...
Which leaves the boring head solution, driven by a G33.1 using the single tooth tool you have as the only viable solution. Is this a commercial size whose std measurements are known? And can you accurately center this tool in the hole? For that, I have a piece of teflon stock with a copper wire inserted in it, wired so it can be used with the G38.2 to find the 4 "corners" of the hole, and place the centerline of the tools turn axis within .0005" or better. Once thats established, swap the probe for the boring head, find the dial setting on the head that fits the hole, then run the G33.1 to adequate depth, but don't forget to subtract the overshoot at the bottom of the hole thats used to do the spindle reversal, preventing the tool from hitting the bottom of the hole and destroying the tool. I have code for that which you can add to your hal file, and watch what it says in encoder counts with a halmeter, which you will have to translate into actual distance traveled. At 10 tpi, and controlling the spindle with a vfd whose response is set gently, it can be several turns when 1 turn=.1000" of overshoot. My machine has one of Jon pwm-servo amps driving the pmdc spindle, and I can do a full reverse from 200 revs in about 300 milliseconds. And thats with the turn around being turned into a sine-squared profile so the max accel is at zero speed with a limit3 between the command from motion, and the input to the pid. However. the torque to pull the single tooth should be well within the enco's torque delivery ability. You'll need a back away move in order to have room to get a gage in to check progress as the thread is done. I'd also check the x axis backlash so that it always hits the center of the hole if the head needs advanced. If the hole is blind, how will the swarf be cleared? Hand applied air between strokes of the g33.1 run would seem to be about as "automatic" as I can get on my much simpler machine. Can you put an air/coolant nozzle to do that in the tool turret? If so, write the gcode to bring it to the hole, maybe even into the hole and give it a 1 second hi-pressure shot to clean the hole, then back out of the way and stop the spindle for progress checking. Time consuming, and I don't want to contemplate doing hundreds without an automatic boreing head. The first such threading operation will be "uncharted" territory, so keep notes on the head settings as you progress. That will speed the 2nd and subsequent such "tapping" operations. > > On Jan 16, 2018, at 8:58 PM, Gene Heskett <[email protected]> > > wrote: > > > > I am inclined to agree in that g76 is broken in this regard. My > > feeling is that it should retract to the drive_line, and no further. > > I have in most cases managed a work around with the tools I have by > > jumping in 2 directions, first being from USS threads to SAE, which > > are marginally less deep, and then to the next bigger bolt if there > > is room for it. > > > > But from previous discussions, it appears your bolt size is fixed. > > Given that, I only see one workable solution, which is to make, or > > buy if it can be found, a tap, and use the g33.1, rigid tapping. > > This requires a keyed to the spindle mounting for the tap, and > > adequate torque to turn the tap. I have neither but I have gotten > > away with it by writing a peck tap wrapper, advancing the end point > > only a small fraction of a turn per pass ever deeper into the hole. > > When the tap is 8mm and above, its very difficult to get a std er32 > > collet tight enough that the shank won't slip, and I am talking > > about wrenches 18" long. Ditto the drawbolt of an R-8 collet, with a > > 3/4" bore to hold a TTS toolholder. The TTS, installed in an R8 > > collet, doesn't offer enough traction unless its that proverbial 1/8 > > turn from broke. > > > > I'd call Nook and ask them where they buy the taps for making their > > nuts. I've made carefull note of how proud they are when the asking > > for a 1/2" 10 tpi bronze is right at $50/copy the last time I bought > > 2 of them. Its possible they make their own taps. > > > > Humm, useing the tool you have in a small boring head, driven by > > g33.1 might be workable as that would then back out at the same > > diameter it went in. Put a spindle shut down to adjust the boring > > head, and a click to run the next cycle, to the same depth, but a > > thou or 3 bigger each pass. A boring head like Andy's would be > > ideal as its self incrementing for diameter. > > > > Good luck Tom. > > > > 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 > > ---------------------------------------------------------------------- >-------- 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 Cheers, Gene Heskett The above content, added by Maurice E. Heskett, is Copyright 2018 by Maurice E. 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
