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Pictured here is a homemade base for a Bridgeport mill that runs on casters.
The base is made from 1/4" flat stock (1/4" by 5" steel bar) and 1/4" angle iron. The bars holding casters are 3/16" thick 1.25" steel square tubing.
The casters are something to behold, these are NOT the usual Harbor Freight "heavy duty" casters. I bought them on eBay for $40, Here's the auction screenshot. They are rated for 2,400 lbs each, all swivel, and are made from very heavy plate. (1/2" and 3/8")
The welded-on T-nut with a bolt in it (seen in front) was attached to provide attachment point for an eyebolt in case if the mill needs to be pulled. It is threaded for 1/2"-13 NC. The bolt is there just to show it better, it will be replaced with an eyebolt.
Enjoy the video of this base being gently kicked.
The internal dimensions of my base are 24.5x36.75". Check this pdf. In retrospect, I would like to recommend making internal dimensions of your base to be 24.5x37, a little bigger than I did, as my fit was quite tight -- a little mistake by a couple of mm could create problems. Go to Page 7 of Bridgeport Mill Manual PDF for definitive information.
The base weighs 160 lbs.
The diagonal bar was for welding/tacking rigidity only and has been long removed.
Finally, I lifted the mill with a My Chain Hoist, trying to always keep blocks underneath it, and placed it in the base. The good news is that it fit the base perfectly. The bad news is that I broke the potmetal collet holder while mistakenly applying force to it.
The good news is that the scheme worked, the mill is in the base, everyone is alive, and the base shows no signs of excessive (or any) buckling, etc.
The bad news is that I broke the collet holder.
The mill is neither too easy, nor too hard to move. I am going to remove the front bar holding the casters, and raise the mill by about 1/4" to put it in 2x4s. I will keep rear casters (suspended) because they are not a hindrance.
