status & Yet Another Project

 The heat is still kaput in my workshop, so nothing is happening out there. The new inducer for the furnace should arrive this week.  I need to figure out how to get rid of the old van which is parked where I need to put the ladder to get access to the furnace, preferably without taking a bath...

 I've been sick, and banged up, the cat tried to kill me, my hopefully-temporary retail job is kicking my ass, and so on and so forth.  For reasons unknown, November and December are always and forever a terrible time for me.  Loved ones dying.  Home invasion.  Car jacking.  Burglaries.  Breakdowns, losses, illness, death... I don't know why, but if any of those are going to happen to me in any given year, then by god it will happen / has happened in November or December, not any other time of the year.

 Fuck-if-I-know.

 So anyway, I was thinking I should add "vacuum chuck" to my list of tool projects to do. The general idea of a vacuum chuck is that it uses atmospheric air pressure (note that in Denver this is 12.1 PSI, not 14.7 PSI) to clamp think work pieces to a flat plate.

  There are variations, but the simplest to construct for the home shop machinist consists of a flat plate of aluminum with grooves cut into one side, and some pluggable holes as well, the holes being plumbed to a common source of vacuum.

  The grooves are sized and shaped to accept lengths of o-ring material which provide a vacuum seal between the thin work piece and the chuck plate.

  One or a few long lengths of seal can then be laid out in the grid of grooves, to accomodate odd shapes of work.  I think we really only need a single hole in the center of the plate, and not multiple pluggable holes.  The only advantage I can think of for multiple

holes would be to overcome leaks in the seal.

 Now, I no longer have a vacuum pump, since I had to give up trying to do science, so I will purchase a compressed air "vacuum ejector"...

  These are relatively cheap* industrial items which use the venturi effect to create vacuum using a stream of compressed air.  Really good ones have surprisingly low air consumption, and a muffler on the output makes them tolerable to be around. 

 People who engrave plaques (be it with lasers or mills) love vacuum chucks, as you might imagine.  And a vacuum chuck may not achieve as high clamping forces as a magnetic chuck might (since the former is limited by maximum sea level air pressure) but a vacuum chuck works on non-magnetic materials, and it works better than a magnetic chuck on very thin materials.

 As near as I can tell, there are (at least) two ways to create the path from the center of the chuck to the port at the edge where the vacuum is connected:

1) we could drill from the edge using really long drill bits.  I have some, although they are cheap, so I don't know how straight they will drill.  This is fiddly, and becomes REALLY fiddly if you want more than one vacuum port in the working surface of the plate.  It also seems terribly optimistic, and the idea of drilling a .125" hole, say, twelve inches deep, and attempting to intersect another  .125" hole... um... fuck that.

2) we could mill a groove (or multiple grooves, for multiple ports) on the back side of the plate to connect all the dots, and then slap an O-ring sealed plate on the back.  I like this method the best.

3) magic?  Any other ways to do this?  Readers?  Bueller?

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* $10 on eBay for one that fits in your hand - but these things come
in all sizes; there are ginormous ones that run on steam which are
the size of a bus, used for industrial processes... and everything in
between those two scales.  Handy devices.