[christofer]

Here is a small mill I intend to build. The rectangular tube 8 x 4 inch hot rolled steel with a 3/8" wall. Rails are THK HSR20. Travel is 24" X, 12" Y, and 12" Z. The table is a piece of 1.25" thick MIC-6 aluminum plate. Table size is 22" x 10". 3/8" 16tpi holes will be drilled and taped on 1" centers. The spindle will be a minimill spindle with two angular contact bearings and a custom housing. The motor is a 2.5 HP DC treadmill motor. The spindle will be driven with a timing belt from the motor with a 1:1 ratio. Maximum spindle speed is 4000 rpm. I plan to use 2005 series Chinese ballscrews from LMB2008 on ebay.

The rails are mounted in pairs 5" apart. Do I need more space between the blocks on the X axis? The X axis is 33" wide and weighs about 70 pounds. The outside edges of the blocks are currently 8" apart. Does the head look beefy enough? It is 14" long and made from 1/2" steel plate. I intend to add a counter weight so the ballscrew does not backdrive under the weight of the head.

I plan to weld everything together and then have it ground or milled flat. The joint between the base rectangle tube and the vertical rectangle tube will be filled with epoxy after it is squared. The whole structure will be filled with concrete after is is assembled.

Any thoughts on this design or things I have overlooked?