JB Weld is brilliant stuff. Can drill, tap and machine it no dramas. Like anything, cleanliness is vital but if everything is clean, it's damn near as strong as the parent metal. I used it to repair a front cover on an engine - with a huge chuck snapped off one corner when someone dropped it - and it's still fine 5 years later. I've used it for repairing threaded holes in non critical applications and never had an issue, built up areas and machined them flat again - it really is worth having around.