[Lionelgee]

Hello All,

My search for left-handed thread taps and Left-handed M16 bolts was for an experiment. I had bought a truck gearbox and a spare parts motor for a model of International truck that saw both military and civilian use in Australia. On the drive home I wondered why the previous owner had given up on their project. Not long after bringing the goodies home I might have discovered the reason. Since the head was already off the motor and the pistons had a layer of diesel soaking into them, I thought I would grab a large socket and hook up to the crankshaft bolt and turn the motor over.

Crankshaft bolt.... what crankshaft bolt?

Upon closer inspection I found that one of the previous owners must have twisted off the bolt's hex head. What was left was the shaft of the bolt that ended flush with the end of the crankshaft.

To assist in loosening the bolt shaft week in advance of the experiment I had used copious amounts of lanolin-based penetrants, and also used small pneumatic hammer point and rattled the shaft. Then sprayed more penetrant.

I drilled a hole in the bolt shaft and I tried a series of different styles of bolt extractors - the threaded type and the hammer in star type. Also more heat and penetrants were applied. Despite this the bolt dined on both styles of bolt extractor. Round 1: No luck in shifting the bolt shaft from the crankshaft.


Round 2: The experiment: I had heard of people using left-hand drills to remove broken bolts. When the drill bites in it can shock the stiff bolt loose. Having no success with the different types of bolt extractor I wondered if it work if I took that idea to the next level - sort of a form a bolt extractor on steroids. I drilled a series of holes in the bolt shaft up to 14 mm diameter. This was followed by the M16 left-handed thread tap - intermediate and later plug taps. The M16 left-handed bolt was screwed in. More penetrate and some heat and a couple of minutes bouncing around provided by a rattle gun. The aim was to rattle the bolt to possibly shock thing loose, more than an attempt to remove the bolt. More heat... more penetrant. more rattles were applied. Then I tried a 3/4 inch breaker bar on the M16 bolt

With some effort I felt and saw the old original bolt shaft wind two threads out of the crankshaft hole - it had previously been flush to the end of the crankshaft. Then the bolt broke off inside the original bolt shaft.

A trip to the hardware store later and a range of cobalt steel drills were sourced and some specialist cutting compound spray obtained. More drill holes were stepped up inside the left-hand bolt. During each increase of drill diameter I tried the different range of bolt extractors again - with similar results to earlier attempts.

My next step will to move from using an LPG blowtorch for heat to an oxy-acetylene kit instead. Plus I will fall back on welding in a smaller diameter bolt into the hole I had drilled into the left-handed bolt that is inside the original crankshaft bolt. You know a bit like a Russian Babushka Nesting Doll set.

The engine did come with a spare crankshaft so if I do not manage to get the broken bolt shaft out of the original crankshaft all is not lost. I just enjoy the challenge of trying to move on from where another enthusiast sold the project on. Maybe they were just more clever than me and they knew when to stop! I am still out in front because the gearbox was the main motivating factor on that purchase - the spare parts engine is a bonus. I bought more penetrant and I will casually spray the area each afternoon for the next week or so before attempting Round 3.

Kind regards
Lionel