Well you have stepper motors and the carriage that sticks over the edge by about 12" and if it was me I would want (if you can spare it) at least 24 more inches for you to get around it.
Alot of guys put it up against one wall but you are going to have times when you need to clamp things down on all sides and need to get to all sides.
So the answer is a minimum of 12" and the maximum is "infinity and beyond!"
Words of Wisdom:
“Words that sink into your ears are whispered…… not yelled”
“The biggest trouble maker you’ll probably ever have to deal with, watches you from the mirror every morn’n”
“The only difference between a rut and a grave is the depth”
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Just remember...when it's time for the hearse to pull up..there's no luggage rack on top!
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The beauty of the Second Amendment is that it will not be needed until they try to take it...Thomas Jefferson