Locating the part and locking down the V-block should be done in a series of steps. Use of a mallet sounds like way too much force needed to adjust the position and isn't good for the rack/gear. Adjust your technique don't use a bigger hammer. I use a small piece of copper round about 2" long x 3/4" for adjusting. Snug the SHCS locking screw and tap the V-block into position, tighten the SHCS a bit more and check position again. If it hasn't moved fully tighten (doesn't take much) and check again. I always set mine on the surface plate before transferring it to the grinder. Usually it was a 5 minute procedure to set-up. Condition of the Harig and fitment of the V-block are everything. If you're getting too much run-out side-to-side then the V-block has too much play and has likely been altered by someone. It's also about how much allowable run-out you're asking for. I used +/-.0002 for general work in die shops for stamping dies with clearance in excess of .005 per side. Excessive fussiness is time wasted. If you do need better results than you're getting, you've not stated what they are, then you can either compensate by shim or simply get another unit that delivers the accuracy you need. There's also the St. Mary style of spinner that doesn't need adjusting if that would work for you. You haven't stated accuracy needed or what you're using it for, it makes a difference. Hope this helped.