The jaw interface is already correct. That interface - the slot, the dowel holes and the screw pattern - is where a home-made finger goes wrong, because any error there is multiplied along the finger length and shows up as jaws that no longer close square. Starting from a blank leaves only the workpiece profile to cut.

Enough to change the choice of gripper. Force is rated at a short reference offset from the gripper body, and beyond that the manufacturer's curve falls away because the guide's moment rating, not the piston, becomes the limit. Doubling the finger length can easily halve the usable force, so fingers should be designed before the gripper size is fixed.

Something softer than the workpiece: aluminium, a filled polymer, or a steel finger with a urethane or nitrile pad bonded to the contact face. Hardened steel against a finished surface marks it. Where the part is abrasive - castings, sintered work - the opposite applies and a hardened insert lasts longer.

Rarely. Slot width, dowel spacing and screw size are series-specific even within one brand, and a finger that bolts on but does not locate on the dowels will move under load. Ordering against the gripper's series and size designation is the reliable route.

When the wear has reached the interface rather than the contact face. Re-facing or re-padding a finger restores the grip surface, but a slot that has fretted oval lets the finger rock, and no amount of work on the tip fixes that. Rocking shows as a part that sits at a slightly different angle each cycle.

They carry the load path from the gripper into the arm and fix its angular position. A plain adapter plate takes the bolt pattern from one to the other; a centring ring or dowel pair removes the reliance on bolt friction so the gripper returns to the same angle after any service. Skipping the location feature is why a gripper drifts out of alignment after a finger change.

Yes, because they position the sensor over the piston magnet at the right height and depth. A bracket from another series can hold the sensor in a place where it switches unreliably or only at one end of travel, and the fault presents as an intermittent grip-confirm signal rather than as a mounting problem.