cranck case problems

[phillips]

Hi all, a bit of information wanted please. I have just pulled a crank case off the shelf ready for a winter project, and I have found that one of the ¼ whit sump threads has a thread tap or a stud remover snapped just below the surface.
I am finding it hard to even tap a punch mark on the stud; I understand that the “stud” is of hardened steel, so my question is.  Is there some sort of” super” drill bit that I can buy so I can drill it out. Or my second option is to drill and tap a new thread in front, or behind the offending sump thread.    
Many thanks. S&P

[Ruairidh Dunford]

Use a very sharp punch to shatter it.

One careful, but swift, hammer blow is normally sufficient. After it is broken up, you can normally pick it out.

[Chris KC]

Without a photo it's hard to judge but is there not some way you can apply some torque to it, either by grasping it with something or perhaps drifting it around with a punch? If so warming the case will expand the aluminium away from the tap & loosen its grip somewhat. It's not a critical fastening and if you make a mess of the hole it's fairly easily plugged and re-tapped.

[Stuart Giles]

Well worth trying to shatter the tap first, but if that doesn't work, one of these may well allow you to wind the broken tap out. you push the sliding 'fingers' into the tap's flutes. I've bought  them from these people, but there will be other suppliers.

https://www.mscdirect.co.uk/WAL-10253A/S...oduct.html

https://www.mscdirect.co.uk/WAL-10254K/S...oduct.html

I have seen broken taps drilled out with a straight flute carbide drill, needs a very rigid setup and is only doable in a milling machine or a substantial pillar drill with the crankcase bolted or clamped to the table.

[john williams]

Stuart, on my RL original crankcase, my employer a very competent garage owner/engineer; drilled and tapped two 2BA threads either side of a damaged crankcase sump thread, and used the two BA screws to secure the sump. Worked perfectly!!!
John.

[Nick Lettington]

I spent a little time carefully tacking a nut to a broken tap in my crank case... it took two or three attempts...


  Screenshot_20230121-202918_Gallery.jpg (Size: 197.22 KB / Downloads: 516)

[Duncan Grimmond]

That looks like the tip of a very pointed taper tap; very tidy welding , well rescued!

[phillips]

Hi all, and thanks for your suggestions. Food for thought,  will let you know how I get on . S&P

[Stumpi]

https://www.practicalmachinist.com/cutti...the%20hole

More information
Andy

[Nick Lettington]

That looks like the tip of a very pointed taper tap; very tidy welding , well rescued!

Thanks Duncan. I was very pleased when ar the third attempt the weld held. I used MIG and put a few tacks on top of each other to build it up a little proud before welding through the nut.

I didn't have the same success with a broken head stud though.