[okkim]

Hi,

I have a motor which has a crankshaft with broken flywheel bolts. One guy installed flywheel with too long bolts, and flywheel was loose. Then he drove it until only one bolt was holding the flywheel! The others were sheared off. Some quite deep, some on the surface.

I have removed bolts from the aluminum parts by welding a nut with a MIG, but never from the steel.

I think that the ones which are on the surface are easy to remove, but I would need some tips how to remove the ones that are very deep? I'm afraid to weld to the threads. I can also use TIG, but I think that the MIG is better in this case?

[noddybrian]

Welcome to the forum Okkim.

Sure others will chime in that do this more often than I do - my advise is Tig if available is always better than mig as it's far more controllable & you can put more heat in & puddle the end of the broken stud - Mig is hard to aim & the surface fusion is limited though builds up height easily - as usual 309 is the wire of choice & on the deep holes using enough stickout it's still possible - just protect the threads using a piece of copper pipe - if you can't find a good fit use slightly larger plumbing copper pipe - slit it & roll tighter till it fits- alternative is as I have a mill I would probably bore them with an end mill just under tapping size hopefully well centered then gently open out to tapping size & clean the remainder out with a tap - I think TurnWright has some video's of both methods on You Tube.

[ex framie]

Do you have any left hand twist drills? Designed to cut in an anti clockwise direction.
The drilling will wind the theaded bit out if its loose enough.
Probably worth a shot on that diameter bolt.

Cheers

[Poland308]

I use an easy out. I like the square ones not the ones that look like a left hand screw. But I too have used the left hand drill bit.

[rake]

On something like that I'd use some left hand thread shouldered allen head bolts.
Drill to tap size, thread with a left thread tap, bottom the bolts to the shoulder,
a few quick raps on the head with a ball peen and an allen socket on a small impact
tool should spin them puppies out. Avoid "not so easy outs"!
Snap one of them fuggers off and the nightmare gets worse.

[ldbtx]

Here's Keith Fenner's most recent video that has some great closeups of the TIG method:

https://www.youtube.com/watch?v=J8NdQHqKxIU

[rake]

That's a whole lot easier with an aluminum case. Steel or stainless filler doesn't stick to aluminum.
One false move or wandering arc and you've now welded the stud to the crankshaft.

[Otto Nobedder]

On something like that I'd use some left hand thread shouldered allen head bolts.
Drill to tap size, thread with a left thread tap, bottom the bolts to the shoulder,
a few quick raps on the head with a ball peen and an allen socket on a small impact
tool should spin them puppies out. Avoid "not so easy outs"!
Snap one of them fuggers off and the nightmare gets worse.

I happen to like this idea. Those little "hit with a hammer" drivers are very effective. The use of a penetrating oil such as Aerokroil (best in my opinion) or PB Blaster will help, and the hammer impacts increase the effectiveness of the oil.

I also like the copper tube idea, as you could simply fill the tube with weld metal (a little at a time, so as not to melt the copper, as that would be bad), until you're above the surface and can weld a nut on. In this case, the heat into and out of the joint would have the same effect as penetrating oil for breaking the locking forces in the threads.

Steve S

[AKweldshop]

What size bolts?
1/2"?

I'd drill and screw extractor first.

If it don't work, tig welded nuts on would be my next choice.

[AKweldshop]

FORGET mig for this.

[okkim]

The bolt size is M10 x 1mm and those are 12.9 grade, but I could drill those easily with cobalt drills. I don't have left hand bolts or thread tap. That sounds a good idea though. I'm really afraid to damage the threads, since then it makes this project much bigger and more expensive. I have some oll pressure meter adaptors, and one has M10 x 1 mm thread. I was thinking to use that as a drilling guide to get the hole exactly centered. As the bolt head is not straight, and it is hard to get it centered. But first I have to find some left hand bolts and taps.

Today I had some spare time, so I tried to remove the easiest one. But clearly my MIG doesn't make the initial weld so strong, and I didn't have success. I tried to weld a washer and then nut over it, and finally just a nut, but the weld always broke. I have other better MIG, but it has stainless steel wire and I didn't want to use it because the bolt would open easily.

I made some aluminium rolls which I could put inside to protect the threads, but I'm not sure that would it withstand the heat if I would weld the bolt with TIG.

[MosquitoMoto]

Gotta say I think you are very brave trying this with Mig!

Do you have access to a pulse Tig? There's a video of Jody's somewhere (I'll post a link if I can find it) where he uses pulse to build up a pillar of weld on the sheared fastener bit by bit, then grips this and loosens the fastener using this 'extension' of weld.

I am a relative newbie but I have tried this myself with pulse and in my case (sheared motorcycle engine fastener) it worked a treat. Will try to find link for you.

All the best!


Kym

[MosquitoMoto]

https://www.youtube.com/watch?v=ffR2pGVGHbg

Here's that link - I think very apt for what you are doing. Hope this helps!


Kym

[okkim]

Yes I have access to a pulse TIG (Kemppi Mastertig 2800) But it is on my friends garage, and moving the motor there is not that easy. I don't know much about the pulses though, how should it be adjusted? I have welded something with it, but with the default settings.

I have watched that video, it is great! The difference is that those parts are pointing up, but the crank is in normal position. That makes me a nervous because the molten steel could flow downwards and touch the threads. It is difficult to turn the motor so that the crank points upwards. Also the bolts are much deeper than in those videos, maybe 10 mm deep. That complicates thing too.

I bought left hand taps, now I have to find hard M8 left hand thread bolts. I guess I buy Dewalt saw bolts which are 12.9 grade. Those are not sold here in Europe though

[MosquitoMoto]

okkim -

I don't think the challenge would be the position; my main concerns would be depth, and the possibility of oil contamination of the part/fasteners.

With a very sharply pointed tungsten you could just build a small 'button' on the end of the fastener, stop, let it cool, build it up some more. Search 'rule of 33' for pulse settings. Basically, set your main amps, then set pulse ratio (%) to 33, set your pulse frequency (Hz) to 33, and finally set your base or 'background' amps to 33 percent of what your main amps are. Then maybe find some M6 fasteners and practise building weld onto the ends of them - this will give you confidence before you take on the flywheel fasteners.

I am quite new to TIG welding but using Jody's 'rule of 33' as a basic guide, I quickly came to grips with basic pulse application.

Best of luck - this situation certainly presents a challenge.


Kym

[Artie F. Emm]

Jody's video is also on point:
http://welding-tv.com/?s=broken+bolt

(and 22 minutes shorter)

[Rick_H]

I build performance motors as a side business, I'd be drilling those out, welding them wouldn't even cross my mind.

The issue is most are hardened bolts, usually installed with some type of thread locker and depending on the motor the bolts enter the crank case so pulling oil would be very easy.

I'd use a center punch, starter drill then a 3/32" left hand drill..if they don't come out an easy out. I'd heat the crank a little to help break the thread locker down. Aerokroil is the best product I have ever used, orange can and expensive... But PB Blaster works very well.

Is this a running motor? You'll have to be careful with heat as it will damage any seal in the area (like that rear main) and the bearing won't be very happy either.

If the flywheel was flipping around I am sure it would have done some bearing damage as the motor had to be vibrating from the imbalance.

[okkim]

I changed to the other MIG, and tried to get the bolt with that. I got a better weld, but it didn't open. I have now tried it seven times, time to do some other tricks.

My idea of that oil pressure using as a drilling guide was great I put the adpter to the holes which had threads visible. One had just about 1.5 mm, but that was enough. I got all drilled, and exactly to the center. I have to figure out how to drill that where I can't use the adapter. Maybe I will put a flywheel when the others are removed, and then make some kind of drilling guide and use the bolt hole as a helper. In that crank the bolt holes are closed, no oil will come from the crank case. The bolts are hard and have some kind of blue thread locker, it comes with the bolts from the factory. I guess that doesn't help to remove those. But I will try to drill the holes bigger and then make left hand threads. It just seems difficult (and expensive) to find good ones. I bought 10 from USA, $50 and then the taps included it's close a $100, but still cheaper than a new crank, bolts and stuff


The rear main seal is easy to change, and I will change it. It got pretty hot when I welded there. I don't think that it had much of radial vibrations since it was supported from that center shoulder, sleeve (or what is it called?) Only thing was that it for sure had some rotational vibrations, but those can't hurt the bearings.

[Otto Nobedder]

... Only thing was that it for sure had some rotational vibrations, but those can't hurt the bearings.

Yes, they can. They are rhythmic, and can produce brinneling, and/or false brinneling. Only the rear main bearing "should" show effects, but that depends on how long it ran that way. Harmonics could have travelled and affected more than one bearing.

Don't rule this out based on suspicion or instinct.

Steve S

[Poland308]

Yeah any vibration to a bearing can cause flat spots or dents in the bearing surface. Definite damage to anything high rpm.

[okkim]

Ok, thanks for the info. I didn't think it that way, but you are right. I was hoping that I don't have to open this motor!

I have one broken crank where I'm going to test TIG weldging. I use aluminium as a protect the threads, lets see what happens.

[Otto Nobedder]

okkim,

You can check for brinneling/flat spots with plastigauge. The trick is to lay a couple inches of it along the circumference of the main journal at the centerline, instead of a short strip across it, then torque and remove the cap as normal. You want to see a good straight edge on each side of the plastigauge. Any waviness along the edge indicates irregularities in the bearing that should be investigated further.

If you do crack it open, plastigauge is cheap so I'd suggest doing center bearing back for 5 bearings, or at least the rear two for 4 bearings.

The condition of the rear seal may also be diagnostic, even after heating, if wear patterns can still be discerned.

Just some thoughts...

Steve S

[Cricket]

I'd drill it out. You can take a matching bolt and make an accurate bushing on a lathe for a say 1/4" drill bit. Drill all the way to the bottom with the bushing and second drill with say 8.5mm or so without bushing. The remaining thread usually is easy to pluck out. I would not even try to weld it.

[okkim]

I tested to remove one "snapped" bolt. I cut the bolt with a grinder so it would break when it bottoms out. I tightened it quite tight before it broke. The head was about 7 mm deep.

The I put the aluminum protector inside and started to heat the bolt with a TIG. Well, the aluminum "protector" melted less than a second

I took it away, and used 60 amps to melt the bolt. It was maybe a bit too much. The I just added some material and raised it up. That was dead easy! When it was high enough, I welded a nut and let it cool down. The I just turned it with a wrench, and it opened like it hasn't been tightened at all! Very easy job! No damage to the threads.

So it seems that I could try the TIG welding method to my motor, but It just needs much work to move the motor to my friend garage. I'll leave that as a last option.

[noddybrian]

Glad you are having some success - while aluminum is good for chill blocks if you get the ark near thin / tube pieces as suggested for bolt removal it will vaporize almost instantly - copper will take a lot more heat & just glow / turn black but still protect the threads - also use smallest possible tungsten with sharp point to pin point the heat direction & it will usually work - the best time for removal is when most of the heat has soaked from the bolt into the surrounding material & is still fairly hot- if your going to let it cool before removal try spraying some penetrating oil or use wax while it's all hot & has a chance to leach down the threads - I do this a fair bit with marine parts & have a high success rate.