I'd suggest machining the axle shaft about .0015"-.002" larger that the ID of the repair sleeve and either heating the sleeve for a "drop-on" shrink fit, or pressing it on with a little "Never-Seez" as a pressing lubricant. As long as the sleeve isn't heated enough to turn it a different color, the hardness shouldn't be affected. Be sure to put a slight radius at the axle flange end of the machined area to prevent the formation of a stress riser from a squared-off corner. The sleeve pictured in the ad looks like it's got a chamfer on one end of the ID to accommodate a radiused cut on the axle.
Jerry

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