On Sunday, February 26, 2012 05:36:38 PM Kirk Wallace did opine: > On Sun, 2012-02-26 at 13:48 -0500, gene heskett wrote: > > You all know by now that I have one of those toy 7x12 lathes, this one > > with a Speedway decal on it. > > > > In looking for a place to put the crossfeed motor, it occurs to me the > > best place is probably on an extension bar (I have a good sized sheet > > of 1/4" alu) that places the motor facing away from the operator and > > extending back and under the bed. A single flat plate on the face of > > the carriage extending downward could serve as the motor mount, and a > > belt cover could be carved to help keep the swarf out of things. > > > > This assumes that a couple of nominally 1" blocks were placed under > > the beds feet to raise it for motor clearance since it sits about > > 1/2" too low to clear as nema 23 motor under it now. > > > > While thinking about that, it occurred to me to ask if it would help > > to add some additional mass to the bed (this whole toy only weighs > > about 79 lbs) by setting those 'feet' on another steel plate, either > > under the splash pan, or in it, that would span the length of the bed > > and possibly help stiffen it? > > > > Is it worth my touring the recycling facilities to look for something > > in the 10" wide by 24" long & an inch thick, in fairly mild steel > > that I could saw the end off to make the 'feet' and use the rest of > > it as a mass and stiffening tabletop? > > > > > > Thanks. > > > > Cheers, Gene > > Based on this picture: > http://coyoteden.dyndns-free.com:85/gene/emc/24.html > > I would try to look at the flex problem this way. Virtually place a > piece of stock in the chuck and grab it with your left hand. Then grab > the tool in the tool post with your right hand. Now push down on the > tool and pull up on the workpiece in the chuck as hard as you can. Then > visualize where any flex or slop can be -- chuck, spindle bearings, > headstock, the connection between the headstock and bed, the portion of > bed between the headstock and carriage, carriage, tool post and tool. > From this I don't see where bolting something to the bed feet will do > much. I suppose pulling the tool towards you and pushing the workpiece > away could cause a twist in the bed between the headstock and carriage. > Without any foot support, the twist is between the headstock and > carriage. If the headstock and tailstock feet where tied together, the > twist might be shared between them. > > Doing this non-virtually might actually reveal some non-virtual flex. I > would look at fits between parts and bearing preloads. I think some > mini-mill owners have been known to lap the axes joints to get a good > fit. The Craftsman AA 6" lathe users have found improvements in changing > the carriage retainer to brass and working on overall fit. > > While I'm at it, I have an opinion on the location for your Z motor > too, ... surprise. I would put it on an extension of the lead screw to > the right. For my Zubal lathe, my plan is to put it on the left where > the change gears used to be. I would get rid of the carriage apron and > mount the lead nut rigidly in its place. Manual mode would need to be > through MPG's.
I hadn't considered getting rid of the apron because I'd like to drive the lead screw and half nut from the left end after removing the change gear stuff that is A: getting sloppy in the left right switching, and never was all that accurate. I can get the lash there down below 10 thou, which leaves about 50 thou in the drive to the change gears, so if I'm cutting threads now, I have to back out the z at least a full turn or the tool mucks the threads up on the back stroke. But, I've been playing this afternoon, having gone out to the shack and picked up enough stuff to cobble up a 36 volt 2amp supply, and having a spare 2M542 driver, not knowing how much current this KE56KM2-009 motor actually needed until I found a link on the web that said this little 52oz/in motor could use 2 amps! So I set the driver for 1.94 & left it sitting on the driver for about 45 minutes and the iron, accordng my IR thermometer, was up from 68F (room) to about 92F, which certainly seems like an acceptable temp rise. At full current and grabbing this motors nylon gear/pulley, it is all these ancient hands can to to make it slip a couple steps, so I believe it will have sufficient power to handle the Z axis duties. And it is small enough it can literally hide behind the toolpost! But the main drive to the existing lead screw will be one of my 425's. Now, if I could find a suitable DC motor to replace that weenie thats in there now for the spindle, they claimed 400 watts, but the nameplate voltage times the nameplate amps isn't even 200! That needs tightened up too, I can see the motor shaft turning several degrees before the gilmer pulley on it moves. As for the carriage, it wasn't even machined for the V at the same angle as the top of the bed, so the carriage wasn't sitting solidly in contact with the bed in my wildest dreams, so the carriage has spent a bit of time in the tiltable vice on the mills table, so that fit, while likely not as precise as it should be yet, is considerably better now that the back edge of the carriage isn't riding 10 thou high off the flatbed back there. I haven't done the brass gib replacement as adjusting it is completely impossible without pulling it out, turning it around and removing the backsplash first. So the cut quality is much improved by that fix I did do, enough that the next 2 problems are the rubber in the QC toolpost, and the -ENOTENOUGHPONIES in the spindle motor, by a factor of 2 or 3. Changing out the pulleys in the headstock so the max rpms at the chuck were reduced to 1000 from 2500 would be one heck of an improvement in that dept. Trying to make a silk purse, I came across some data on the 8x14 and wish now that I had bought that on instead as its about 289 lbs in the crate, 200 lbs heavier, and according to the reviews, 20x as well fitted, its a real lathe! Its also special from HF and about $1000 on the tailgate of the delivery truck. Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> *** PUBLIC flooding detected from erikyyy <lewnie> THAT's an erik, pholx.... ;) -- Seen on #LinuxGER ------------------------------------------------------------------------------ Virtualization & Cloud Management Using Capacity Planning Cloud computing makes use of virtualization - but cloud computing also focuses on allowing computing to be delivered as a service. http://www.accelacomm.com/jaw/sfnl/114/51521223/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
