On Wednesday, January 11, 2012 02:04:07 PM Jon Elson did opine: > Edward Bernard wrote: > > Here you can read how Phil Moore of PMinMO.com takes care of the > > hold-down problem: > > http://millpcbs.com/index.php?option=com_content&view=article&id=17&I > > temid=46. No need to make it more complicated than necessary. > > I made a fixture plate with a 1" grid of threaded holes, and clamps that > have > a "claw" at the end. When set up properly, only the tip touches the > work. The idea is that if you clamp the PC board a bit in from the > edge, the pressure > of the clamp in from the edge tends to flatten the board. You can > always mill > the edge of the board later to the exact size needed, and that will be > aligned > with the trace milling. > > Jon
I think, if I make another of these, that I will probably make a fixture plate, likely with a hangdown ledge in front to align it with the table with good repeatability. I'll see if I can locate some heavy brass sheet as drilling through the board into that would be far less damaging to the mill/drill than cutting the boards own glass is, and much easier on the tooling than alu is even if flooded with non-oxygen bearing cutting fluids. I have also been tempted to drill & tap my table for 8-32 hold-down screws on about a 1" grid so that both x and y would be repeatable to a couple thou. Or drill the fixture plate as the case may be. First, the fixture plate I think, nearly full table covering. That might keep me out of the bars for a couple days. ;-) And despite my allergy to alu because of the high tool wear, I may have a block of that that is big enough, about 10 lbs IIRC left of that 40 lb block I stumbled over for $1/lb 7 or 8 years ago. But that obviously will need a sacrificial layer under the pcb too. 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> According to my best recollection, I don't remember. -- Vincent "Jimmy Blue Eyes" Alo ------------------------------------------------------------------------------ Ridiculously easy VDI. With Citrix VDI-in-a-Box, you don't need a complex infrastructure or vast IT resources to deliver seamless, secure access to virtual desktops. With this all-in-one solution, easily deploy virtual desktops for less than the cost of PCs and save 60% on VDI infrastructure costs. Try it free! http://p.sf.net/sfu/Citrix-VDIinabox _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
