Comparing the hole producted by a 1" hole cutter in a hand drill, to line boring:
Line boring:
+ accurate size to whatever tolerance you want especially if you make guide bushings for the existing holes,
+ round holes
+ both holes concentric / aligned.
+ in the correct place (assuming the existing holes are reasonably round and in the correct place).
+ more controllable, adustable process,
+ safer for the operator. Only torque to be reacted.
- Have to make up the long boring shaft, at least one guide bushing, probably three, if you use a piece of 20mm or 3/4" stock for the boring bar.
Hole cutter (hand held drill, unpiloted - guided by 1/2 plate):
- no control of diameter. Starrett knows a thing or two about metrology, and considers a 25mm and inch hole made with these things as equivelent. That is a strong hint.
- no control of alignment between two sides.
- terrible surface finish in holes
- more danger to operator if it grabs
- have to make the 1/2' guide plate.
Regards,
Mark