1. Determine that bridge is perfectly fitted with lower side of bridge perpendicular to the top of the bass..With sheet of tagboard (card stock) in between, glue the bridge to piece of 5" x 6" x ¾" plywood or medium density particle board. Be sure feet of bridge are flush to edge of block. I use Tightbond ; let it get tacky; then clamp. Be sure that block is cut at 90 degrees; feet of bridge aligned with edge of block.
2. When glue is dry, cut block and bridge ( be sure of square cut ) 1 1/16" up from bottom of feet.
3. Immediately apply c-clamps the block and feet. This is critical---if the feet and the block become separated at this point, you’ve lost all accuracy! Mark the center of feet on cut side. Using automatic center punch ( if you have one ) indent the center for drilling.
4. Carefully drill 3/16" hole in feet on cut side with drill press, once again being sure that all is at 90 degrees. Be sure block is held or clamped very firmly.
5. Put upper part of bridge and block in vise, bridge out. Keeping feet clamped to block, place feet and bridge together. I use small ( ½" x ½" x 1" ) blocks with a c-clamp on each side for perfect alignment. Be sure ends of block are flush. The feet and bridge will be slightly different due to the width of the saw cut and the inner curve of the bridge.
6. Using a hand drill or electric drill, very carefully, using the feet as guide, drill 2 1/4".
7. Still keeping feet glued to block, drill 3/16" hole in feet out to 1/4". Again perfect 90 degree alignment is all-important.
8. Separate feet an bridge from block and sand off glue residue.
9. Using ¼" x 20 tap, thread upper part of bridge.
10. Lubricate adjusters with paraffin and WD40 and install adjusters. If 90 degree integrity has been carefully maintained throughout, the bridge will fit perfectly and you’re in business. The wheels should be flush to all four sides of the legs and feet.

If you’re using Kolstein’s ebony adjusters, you’ll need different sized drills and tap. Otherwise the procedure will be the same. With ebony adjusters, be sure there’s enough wood to support the thicker shafts. If the bridge is too thin, it may be ncessary to fit a new one.

I’ve experimented with modifying the aluminum adjusters by drilling a 1/8" hole through the shaft and 6 evenly-spaced 3/16" holes in the wheels. I estimate that takes out about 1/4 of the weight resultiung in less muting effect. It made a noticeable difference in my 1955 Morelli. I use a model-makers lathe for the shaft and I’ve set up an indexing arrangement on my drill press to drill out the wheels. I’ve also tried brass adjusters. It was like using a mute !!! They were on the Morelli for no more that ten minutes. Even drilled out, they stifle the sound.

Good Luck !! You might want to try this on an old bridge first.