I've found that cutting off the old acme screw at the rear face of the pinion gear or on a "C" type, the gear blank, then drill the gear blank in a collet or chuck undersize. Bore to 0.010 undersize, then ream to exact size. About an inch deep. This keeps everything concentric to your allowed setup, that means check your collet or chuck at dial in first. Then chuck your Acme replacement rod, center drill and turn down a 1.375 length to 0.001-0.0015 undersize of the reamed hole in the gear. This is important, as it gives clearance for the Loctite 680 film thickness.
Once you have this sliding fit, cut an air groove down this length, about 0.020-0.030 deep. Debur the edges of the cut. re-setup/dial in, the gear/handle blank in the collet and test fit the acme blank with the tailstock center in, do not glue yet. Setup a dial indicator on the acme threads just in front of the gear blank, now rotate the screw assembly including the acme screw. You are checking the run-out of the acme blank to the reamed gear hole. Slowly rotate the acme blank as you read the dial for the lowest run-out between the two parts. Once you have found this, mark the alignment points on both parts at the high point. Remove the acme screw and apply the Loctite 680, twist the acme blank as you re-install in in the gear blank, this will let the air out thru the slot. align your marks and position the aligned marks on the down side. The Loctite expands as it cures, and it will pool slightly on the lower side. This lifts the screw slightly and will help to bring the final center concentric a little closer. If you have less that 0.001 runout, turn on the lathe and run at very low speed for an hour or so, depends on the temp/heat, just enough to keep the Loctite even. If you have more that that, just let it sit with the mark down.
I've found that 0.001 is about the limit it will push up. Let it cure 24hrs before removing from between centers. After 48hrs you can re-chuck and check runout on the far right end of the screw, straighten to best run-out. The extra 3/8 inch on the screw stub length is to match the factory thread relief and get you acme blank length correct. there is no need to pin the glued screw if you use 680 Loctite, after about a week it takes 900-1100 degrees heat to break it's bond, and its rated at close to 3000 lbs shear. To make the air gap cut, take a sharp point turning tool and use it like a shaper blade in the lathe on center, works great. Very Important: After about 30 minutes of work, and you are watching it cure, have a "congratulatory achievement" beer!!