How Much Backlash On An Atlas Mfc Mill X Axis?

Jon,

DUH! Of course, that's the reason for the extension. In that case, the extension was intended to come off of the lead screw. So the only problem is, as someone (Archimedes??) once said, a place to stand.

What I would do is this. It will require a hydraulic pump and jacking cylinder and extensions just a little shorter retracted than the larger diameter part of the lead screw/extension (AKA PortaPower Set). Cut two 2X4's or 2X6's to the same length, a little longer than the length of the larger diameter part of the lead screw/extension. Cut two pieces of for example 4" wide steel channel, length about 10". Assuming that the threads on the ends of the lead screw/extension are 3/8"-24, drill two 7/16" holes through the center point of each of the channels. About 3/4" in from each end of the channels, drill a hole about 3/16" diameter. Nail one of the two channels to one end of each of the two pieces of wood, forming a box open top, bottom and one end. But leave about 1/2" of each nail sticking out. Attach one end of the lead screw to the first channel with a stack of flat washers and either a 3/8"-24 long/coupling nut or three regular hex nuts. Fit the other channel over the other end of the lead screw and nail it to the other end of the wood side pieces, leaving the nails loose as before. Install washers and nut or nuts, and tighten both nuts or sets of nuts snugly.

Position the cylinder along one side of the lead screw, between it and one of the boards. If necessary, shim under the cylinder so that it lies in the same horizontal plane as the lead screw. Jack the cylinder out until there is about 1/4" clearance between the channel and one end of the board. Shim the gap with for example 1/4" plywood with a rough slot cut to clear the nail. Move the cylinder to the other side and repeat, except go to 1/2" gap. Repeat as necessary.
 
I think Jon is right :) I moved from being a Fitter Machinist into I.T. 25 years ago i guess this got swapped around in my head at some stage.
X is Left Right
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Reference http://www.tascione.com/Sherlinemill_ins/millinst.htm
David
I've read on the forum someplace that the Z axis is parallel to the spindle. On a vertical mill, that'd be the knee going up and down. The Atlas is a horizontal mill so I think the purist would call the in/out the Z axis since it's parallel to the spindle. Guess the knee would be the Y and the left/right would be the X?

I scratch my head on the lathe all the time. My DRO is set up with the longitudinal feed as the Z axis since it's parallel to the spindle, cross feed is the X axis. Frankly, I'd prefer the coordinate system to be consistent with the vertical mill; longitudinal feed being X and cross feed being Y.

My MFB has about 0.020" in both the left/right and in/out. It doesn't cause me too much inaccuracy problems, most of those are from operator error, not the machine.

Bruce
 
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I made a bushing to accommodate the slightly longer replacement lead screw and got it all back together. The X (?) axis backlash is much better - about 0.010, which I am very happy with. I will save the old lead screw and nut as a spare. Maybe I'll try to pull the extension off following Robert's directions.

As a lathe and mill owner I am becoming intimate with ways, lead screws, bushings, and sharpening HSS cutters. Oddly, I am loving it.
 
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