I wouldnt recommend this, but needed to extend calipers inorder reach rims. Had a welding shop splice in 1/4" alloy. Had to be very careful with amount of heat since they are cast alluminum alloy and could end up with a pool of metal. One caliper failed immediately and had to be rewelded. Since then no problems. It was my first project so didnt consider all the issues. Here is a pic of the front brake and the bike. The welding shop did a great job of polishing. You would never know they were cut and extended.
