A bolt load measuring arrangement 31 has a bolt 4 with a reference pin 10 extending from the root 12 of a hole 11 in the bolt. Shoulder 23 of a bore 22 defines a strainable portion datum shoulder located within the strainable portion 7 of the bolt 4. The strain datum sleeve 32 has a hole 33 to allow it to pass around the reference pin 10 which extends to the end of the strain datum sleeve. The reference datum 15 is on the outer end of the reference pin 10 and the strain datum 16 is on the outer end of the strain datum sleeve 32. The outer end of the strain datum sleeve includes an alignment protrusion 34 over which the measuring tool 40 engages. For the alignment of the measuring tool 40 to be sufficiently accurate, the engagement length 37 is at least 0.9 times the engagement width 38, or diameter of the alignment protrusion.