Saturday, January 29, 2011

The Nano-Xtable

We have now concluded the Christmas presents section of this program and can get back to our regularly scheduled projects.

I have my moto-tool (which is not a Dremel (tm)) mounted in a homemade stand. There are pictures of it all over the blog so I won't repeat. All well and good, but I need a support when I do grinding. I used wooden blocks for a while. They are difficult to clamp, so freehand is just about as good. But an idea came to me, inspired by David Wingrove's books on car modeling. I could make an X-Y table! Then I could do miniature milling with the moto-tool! An X-Y table is a flat piece (the table) that slides on ways in two directions: X and Y. It is turned by screws. So, depending on the accuracy of your srews, you can adjust the table any way you like. I have one, actually, but it is much too big for what I want. Now X-Y movement is what we engineers call "two degrees of freedom." So I thought I would warm up by making a table with but one degree of freedom, an X-table. And I did.
This is the table in its current incarnation, all 85mm of it. Every piece except the ways and bolts was found material from my summer walks. Probably fell off snow machines. Good. The table is a block of aluminum alloy with two grooves cut in it. Providentially the grooves are a perfect fit for the aluminum ways, bought at Lowe's for $1.59 or similiarly low price, and I still have lots left. As you turn the screw, the table moves majestically across the ways. The screw is another objet trouvé -- amazing what people throw away. The white supports are some very dense plastic. I hope it was crucial to the snow machine's operation, said he spitefully. So now on to building it. The first thing I had to do was cut the rabbet (or rebate, a much better word for it) in the plastic supports.
I am using Trusty Taig, the lathe. Thanks to Model Engineering magazine, I find that chucking the end mill right into the 3-jaw chuck gives very nice results. I don't have big enough collets to take 12mm end mills. The plastic, whatever it is, machines beautifully. And note my milling table. This is another find, a right-angle piece of ally alloy that I screwed right down into the primitive vise on the Taig milling attachment. (The Taig atachment is beautiful, but has no vise to speak of. They will sell you one for over fifty bucks. Pah.) I can then clamp to the milling table, as in the picture. I did not make a pass over the bottom of the piece. I will pay for that omission.

The next thing was the feed screw. This is the screw that carries the table (that JRC built). It took some time for me to figure out the obvious. Usually you turn a screw, it moves, right? But this is exactly the opposite. You do not want the screw to move. It has to stay in place. That way, the nut (attached to the table) will move instead. So how do we do this? By removing the thread from the screw where it goes through the support and then securing it with collars. First, a straight turning job to remove threads:
Actually, A groove would be enough, one at each end. But I took off the threads all the way, which leaves lots of room to put in collars. The big-leaguers use circlips, spring-steel circular clips which are guaranteed to reach earth orbit if you don't handle them correctly. Ping! No more circlip. Don't have any. So I cut collars from some of the stiff plastic that came with my brand-new moto-tool packing.
The collars are the white, more-or-less round things at the ends of the screw. Any shape would so, really. Cut them, drill them so's they fit the turned-down section of the screw; split them, force them in. It works! Note the nut attached to the table with JB-Weld, marvellous gunk that sticks to anything. So I can "weld" a steel nut to an aluminum block. Can't do that with your MiG outfit.

I keep looking at this thing and wondering if somewhow I can con it out of another degree of freedom. Then I'd have a true Nano XY-table. Maybe I can. We will see. Not much room left to maneuver. Can't foul the feed screw!

On the net, there is a wonderful article (or was) called "The Fonly Lathe," written by some model railroaders who needed a lathe. They adapted a moto-tool into a lathe. If you google on fonly lathe you should find it. I am slowly working my way up to a Fonly mill. Fonly lathe, of course, is short for "if only I had a lathe."

The ultimate table, Nirvana, is an XYZ-table. Three full degrees of freedom. Hey, maybe I could do X-Z... hmmm. Got to think about this.

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