Ever heard of Electrical Discharge Machining?

[Gmg31]

So I discovered a fault with my sump at the weekend, there was a damaged thread in the block (despite it being a brand new unused engine).    Initially I was quite annoyed but realised that had I finished the restoration this would have been a much bigger problem.  With no body shell in place it was relatively easy to remove the engine again from the chassis. I inserted a tap to cut a new thread but unfortunately I appear to hit the back of the hole and snapped the tap off in the hole.  although a tap is very brittle and snaps easily they are impossible to drill out because the steel is harder than the drill.  After a few calls I discovered 3D tooling in Stockton who had no hesitation is happily accepting the job and no doubt they could fix it.  Apparently the effected part is submerged in a waxy paraffin solution and an electric arc erodes the tap without marking the aluminium. Sounds like wizardry to me but here's a link to better understand it.

https://en.m.wikipedia.org/wiki/Electrical_discharge_machining

[Bainford]

Yes, I have had some experience with EDM in the past, and it is amazing what can be accomplished with it. The EDM is one of those devices where the imagination is the only limit to the work that can be done with it. Well, that and actual access to a machine. Good luck with the tap removal, but I suspect it will go well.

[StrawberryCheesecake]

I've heard of 'Spark Erosion ' to remove studs from magnesium alloy engine cases (early 911). Might be the same thing?

[Gmg31]

Yes that's the same thing, it has several names.