centering rig for drilling out broken bolt

[ohiofarmer 3,323]

 Most of us have been there. A bolt breaks off below the surface and you need a way to drill it out, but the surface of the bolt makes it difficult to center and using a center punch might not be applicable to all situations.. My special one that had to be done right the first time was a bolt on the end of a motorcycle crankshaft.  If unsuccessful, I was looking at an engine tear down.To get a perfect center, i knew i needed a steadying bushing to perfectly center the drill bit. Sort of like a Vix bit, but easy to make with what you have. Here is a picture of a Vix bit https://www.vixbitsonline.com/

 

 What I did was find a small quarter inch drive socket just a tad bigger than the hole I had to center it in. I chucked the socket in a drill and spun it against a mini grinder until it fit perfectly in the hole. Next, i found a drill bit that fit perfectly the inside of the socket and drilled the hole in the broken bolt. I then enlarged the hole to the correct size for an easy out and it worked perfectly. I also used the type of easy out that was unlikely to break off inside the fastener. Similar to this one. https://www.amazon.com/Alden-8440P-Grabit-Damaged-Extractor/dp/B001A4CWHO/ref=pd_bxgy_469_img_2?ie=UTF8&psc=1&refRID=KHH9Q2YC75ERVVQQYMY6 

 

There are other ways instead of bolt extractors such as left hand drill bits, but this thread is primarily about the centering jig

 

 The most important thing about restoration repairs like this is just to walk away and think about it for a day or so. I have found that solutions will just pop into my head if i stay calm and analyze the problem instead of beating myself up for making a mistake.

 

Edited June 21, 2016 by ohiofarmer

[sorekiwi 761]

Yup, the biggest problem with removing a broken bolt is when you drill the first hole off center.  From then on you are facing a $hit-fight.

[stevasaurus 23,037]

As I get older, I find that walking away for more then a couple of days is becoming the norm.    Great idea.  thanks for the information. 

[Thisguyisnew 114]

Probably cheaper than getting a set of center punches. Hope I'm never in that situation but if it works I'll use it