On 9/23/2016 9:30 AM, Gene Heskett wrote: > On Friday 23 September 2016 03:47:51 Erik Christiansen wrote: > >> On 23.09.16 01:02, Gene Heskett wrote: >>> So what I am looking for is a bb holder that will work with the >>> smallest QC holder. And will hold it solidly in the face of a 1 >>> horse motor's solid torque. >> My long boring bars have flats top and bottom, so they just go into >> the 4-way toolpost like the square TCT holders, with the 3 hex-socket >> screws squeezing them firmly in place. Only the sides are rounded. >> >> When a small boring bar was needed, I axially drilled a length of >> square Al, cut a slit in one side, pushed in a small end mill, >> squished it all tight under the aforementioned toolpost screws ( with >> slot and one end-mill tooth horizontal), and bored away. (The softer >> Al probably grips better than steel would.) >> >> The cutting tooth is small, and the holding area is proportionally >> enormous. The screws were reasonably tight. The end mill was sharp. >> There was no slip while making several bushes. >> >> Gene, is that Al bar a machinable alloy (i.e. at least a bit of Cu in >> it), or plain toffee? That stuff can be a drag. >> > 6061, so it's not quite as "gummy" as some I've cut. But I've now some > bigger blocks of 7075-T651 to play with also. so the spacer stuffs to > locate the Z screw will be cut from that. I have to get it about as high > as I can so it clears the x motor under it. But the higher I put it is > limited by the nut wanting to hit the swell in the underside of the bed. > That alone assures that the screw is not shielded from swarf by the bed > rail overhang. So I've bought some long bellows that should collapse > enough that the saddle movement isn't restricted. These 6 bolt flanged > nuts are a PITA, but they guarantee everything else will clear if the > nutholder clears. The nut designed for a clearance hole in a piece of > plate with a big nut would have been a much better choice. But they are > hard to find of fleabay. > > At the drive end of the Z screw, its bearing holder will be bolted to the > back of a piece of 1/2" alu plate bolted to the 3 holes the removed QCGB > was, but spaced outward enough that everything clears but just barely. > The big nema 34 motor will be hung on the front face, with two 40 tooth > xl pulleys and a belt, length yet to be determined, connecting the two. > > Swarf protection for the bare x screw is in the form of a 1/8" plate of > rack panel alu let into the top of the long carriage and glued in, and a > similar but much shorter piece of 24 gauge sealing up the bottom of the > saddle between the ways, and the rear of the saddle that used to carry > 60 lbs of taper attachment stuff, will be walled off to prevent swarf > ingress from air hose cleanup activities. All that work on the rear of > the saddle is in the future yet of course, as is fitting and shimming a > full length brass front gib, wide enough to ride the unworn underside of > the bed once I get as much of the paint washed off as I can using enough > acetone I might get raided to find the meth lab. :( None here. > > That pair of steel postage stamp sized plates that served that function > are badly worn and so is the under edge of the bed for the first quarter > inch they rubbed on. If the brass wasn't such a pita to make, I'd > consider makeing a tapered gib. > > I have a block of cast partially machined to replace the junk compound. I > am debating with myself about putting 4 holddown bolts in the base, but > would have to make the other 2 bolts. Belt and suspenders approach to > getting a truly rigid mounting point for that big Phase-II QC tool post. > > Thats another thing I did to TLM, a solid block of cast to replace its > flexible compound, and with the tapered gibs, precision is now limited > by the 2 ball screws moving it. And thats nice!! But the screw is > wearing out its nut from swarf sneaking past the felt seals, so z > backlash was reset a couple weeks ago to 0.163 mm's.:( It's setup to do > metric natively, to train me if for no other reason. :) > > The coffee and morning pills have kicked in about as much as they can, so > I'd best be up the hill & into the shop building in front of TLM making > that special hub I need for the x screw's pulley. > > Thanks Erik. > > Cheers, Gene Heskett
FWIW, I have used Tap Magic Aluminum for turning aluminum with great success. I was turning some Schedule 80 aluminum pipe and it was galling and the surface finish as really bad. I have no idea how it works, but it was better than anything else I had. The improvement in surface finish as amazing... We were using both carbide and hss tools. BTW, the stuff also works well for tapping gummy alum alloys. Dave ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
