Small Mill very early design stage

[Robin Hewitt]

Robin, Is your round column hollow, if it is you could put a screwed rod down the middle and put the column under tension as I'm sure that would help without adding extra weight.

Hi Peter

The twist is too small, like .005 degrees. Adding extra tension wouldn't help, neither would concrete for that matter but it might make me feel better :heehee:

Robin

[leadinglights]

Status of the project.

Having been disabused of my idea that I could get the kind of accuracy that I want in a desktop sized milling machine, I have settled back to trying to get the best I can with my limited resources. Previously I had the new milling machine all planned out down to the level of suppliers and part numbers, but all of my plans now lying in ruins. So far I have come up with three options which are in varying stages of taking shape in the immagination of my Turbocad program.

The first option has reached the stage where I can show you a graphic of the X and Y axes. Construction is intended to be in one inch thick aluminium tooling plate for frame as well as the table. Frame parts held together with 10mm socket screws with 6mm dowels fitted after it has been trued up. Initial trials with a wooden mock up shows that the geometry is stiffer than you would expect. Cost of tooling plate is quite expensive, but not breathtakingly so - the bed at 520mm by 240mm of 1" plate is $108 from an American company (Onlinemetalstore) - I assume not absurdly different in Blighty. I am awaiting with trepidation some quotes for milling the edges - including four accurate datum faces.

Second option is begining to take shape and is more like a normal milling machine with an XY table. The basic idea is to have two large "L" shaped pieces of 7075 aluminium bolted to separators to form a stout "I" beam structure.

Final option is the same as option 2, but is based on a rusty hulk of a milling machine(?) of unknown make. The vertical beds would be milled and hand-scraped flat to fit the guide rails - simlarly the horizontal beds. A new cross table would be built from scratch. So far this is only a picture in my mind.

Mike