Mandrel smangerill. This will likely bring on the nay sayers but it's worked with excellent results for me on 3 hammers......
When I rebuilt this 25 lg last summer I used the shaft itself as the mandrel. With the shaft and cone removed and well prepped simply join them back together (tap the two together with a soft hammer to make sure they stay locked)after filling the grease hole (X) with damming material, remove the grease zerk, damm the space between the cone and clutch shaft with daming material through the holes, set the bull wheel face down supported by blocks (whatever) so the pin is not interfering with keeping it vertical and you're ready to pour. Yes it will come apart after the bearing is poured, simply put a block of lead on the floor, pick up the whole assembly by the bull wheel and drop it hard on the end of the shaft repeatedly till it gives up or you do (it's ok to take a break) but it will come off. Of course it's too tight so you've got to make a scraper which for the 25 lg was just a piece of MS flat stock 3/16 x 1'' bent at one end at about 80* with the radius of the bore ground to fit and sharpened so it shaves the babbit in nice little curls. Work the scraper 360* around the hole methodically from just past center pulling out material then flip the cone and do the same from the other end until the new bore can be coaxed onto the shaft, if it drops on you've blown it... :( so take care to go slowly and evenly removing the material.....Better a little tight than loose because babbit breaks in quickly..... ;) ..........Deflection?? Only slight if any, certianly not enough to inhibit the function of the hammers I've done.
Note: When I did the pour(s) the clutch material was removed, that is it was metal to metal.