I have used those magnetic drills for drilling safe doors with hardened plates, fitted to protect the lock mechanism, bit like a pillar drill but attached to metal with a bloody strong magnet, they were fine for reasonably small diameter drills, I don’t know the size that is used for drilling RSJs, but I cannot see how you will get the accuracy you will need for a crank pin, I appreciate that you might be able to ream the hole to an accurate diameter (perhaps) but no matter how accurate the diameter of the hole, no good if the hole is in the wrong place to start with.
Vincent, Marcus is right, those pictures won’t open up, not on apple products anyway.