On Wednesday 06 January 2021 05:28:10 Bruce Layne wrote: > On 1/6/21 4:29 AM, Gene Heskett wrote: > > how does one maintain access to the bed slots for hold down clamps? > > That's the problem with the slotted aluminum table top. Very handy... > until you realize it's not flat and/or level. > > For a small slotted aluminum bed that was flat, I'd probably try to > shim it level. > > If it's not quite flat and the top thickness allowed it, I might > machine the top of the T slot bed flat and level, just like a spoil > board.
That probably would not leave enough meat for the clamp bolt heads to pull against in places. These are off a 16th" or more from previous checks. Very poor extrusions IMNSHO. > If you had convenient access to the edges of the T slots, you could > always use countersunk screws to install a UHMW (cutting board) as a > spoil board and machine it level. Fly cutters are problematic with a > low torque and possibly out of tram spindle that would cause cupping > so I use a 1" or 1.5" diameter router bit on my 2' X 4' CNC router. > You could use an even smaller diameter cutter on your smaller CNC > router. Then drill a series of spaced holes coinciding with the slots > and push in T slot nuts from the side to the location you want when > mounting your workpiece. It's not that fiddly. Push the machine > screws down to stop the nut, lift the screw, and push the nut another > 3/8" until the screw drops into the tapped hole in the nut. You lose > the continuous 1D adjustment range of the entire slot, but there is > already a course spacing between the slots on the other axis. > > Or you could mount the UHMW bed upside down and machine clearance > holes and hexagonal nut pockets an inch apart along the slots, press > in an array of nuts, flip the UHMW over, screw it down and machine the > top level. > > If you really want to impress the chicks, What chicks? At my age, all I see are hungry sharks. > mount an aluminum plate with > countersunk screws, machine the top flat and level, drill or mill an > array of holes and use a thread mill to tap them. That has crossed my mind after seeing a guy put in a steel plate on his 6040 on you-tube. But the cost of that steel plate is an ouch and it will rust. So I'll see about 1/2" alu. And I already have some hardened 6mm black oxide ready thread I can make holdown studs from. > Be sure to use > anti-seize in those holes and use black oxide screws instead of > stainless because aluminum is galling and aluminum and stainless is > bad juju. I am quite fam with that, we use copper bolts for transmission line flanges since the only way to remove a weathered SS bolt is break it and anybody on the ground had damned well be wearing a good hard hat and heavy clothing. A broken 3/8" bolt from 400 feet up is a lethal weapon. > Don't use a cordless impact driver to fixture your work. Aww, gee, why not? :) > Probably twenty eleven other ways to get a flat level bed on your CNC > router... and we haven't even discussed vacuum hold down tables. :-) > Chuckle, mentioning UHMW, I have a cutting board in the kitchen made of that. Its about 1/4" high in the middle after 10 years. Still a usable cutting board, but flat and stable it isn't. I think the dishwasher heat is the main cause. So if I do something like that, I'll probably remove these extrusions and cut it out of a 2x4 sheet of 1/2" alu. And I have a thread mill but its .750" in diameter. I'd need one able to do 6mm holes, pretty small. Pricey too, $85 for 2 in solid carbide single tooth from Hong Kong. So the first step has been taken. Locating the alu sheet is next. But I can have that in 4 or 5 days, the thread mills in around 5 weeks. Spit... 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) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis 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
