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Sheared Outboard Head Bolt-- help (?)


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Any help appreciated! Tohatsu 9.8 two-stroke. The brilliant engineers put the thermostat under the head. Sigh. 8 of 10 bolts removed easily, two sheared off but got one of those out. However, the last one has defeated me: several repeated soakings with PB Blaster (over several months), percussive raps with a ball peen, and today drilling and trying an EZ-out, have produced no success.

Help...

TohatsuHeadBolt.jpg

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I have dealt with this many times in automotive applications.  If the bolt sheared because of corrosion/friction on the threads, I have NEVER known an easy-out to work (I have several sets in my toolbox).  If the parent material is cast iron (can't tell from your photo), you can use a welding torch to heat up the area until it glows a dull red, then let it cool for a minute or two, and then vise grips will usually turn it out.  Otherwise you have two choices.  One - take to a machinist as suggested above, who will probably use EDM to blast out the bolt.  Two - being as careful as you know how, drill progressively larger holes down the center of the bolt until the thread roots start to show.  Then use a pick to dig out the remains of the thread tips.  This is ugly and will do some damage to the female threads, but it does work.  Good luck!

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If the bolt sheared because of corrosion/friction on the threads, I have NEVER known an easy-out to work (I have several sets in my toolbox). 

This.

You are a lot more likely to snap the easy-out than to successfully remove a seized bolt.

Then you'll really know the meaning of "Now I'm fucked".

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EDM salvaged a similarly broken bolt in my 1959 Lotus (aluminum block) engine!  Even left the original threads undamaged.  Plus, given the cost (now like $50) for a metric helicoil, and the potential for busting through to the water jacket, go with the EDM. 

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1 hour ago, Son of Hans said:

being as careful as you know how, drill progressively larger holes down the center of the bolt until the thread roots start to show.  Then use a pick to dig out the remains of the thread tips.  This is ugly and will do some damage to the female threads, but it does work. 

The ugly part here is that you need your hole to stay vertical. 

If you own a drill press, make a wood block that bolts in places using a couple of the other threaded holes. Make a vertical hole over the bolt you are trying to drill out and use drill bushings in the wood to keep your drill aligned vertically.

If you do not own a drill press, you can buy a portable drill guide thingie from Home Depot etc for $30-40. It’s a little more wobbly, but will still help compared to doing it freehand.

You only need to drill a 1/8-3/16” pilot hole to start using this method, and can then enlarge freehand. The deeper the hole needs to go the thicker the pilot hole needs to be because the last thing you want to do is to break the drill bit off in the screw.

Use sharp bits, low pressure, lots of lube and take your time and you should be ok.

Lastly, if the threads do get a bit chewed up, helicoil inserts work pretty well and should give you a workable thread.

 

 

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A7BB2A05-C2C2-460C-9982-7B00FF6B7177.jpeg

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Looks like you have a pretty good centered hole going.  On something like that you need to use a fluted easy out.  The tapered ones dont get enough depth and push the bolt into the head as it compresses.  I would drill deeper, try the fluted easy out.  Lots of heat, left hand bits are also good if you are able to drill all the way through the broken bolt.  Going up small sizes it may let go while drilling.

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4 hours ago, Son of Hans said:

 I have NEVER known an easy-out to work (I have several sets in my toolbox).  

I think this (above) will stay with me for a long time...

Thanks, and thanks to others who have chimed in. You know, its not like this is the only problem, er project, I have to work on, and I like this little outboard a lot, so... I think I'll reach out to a machinist I know. If that doesn't work, I'll start drilling (why did I bury my drill press at the BACK of the shop I am packing up to move...?).

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I'll second cyclone above.

Get a steel / stainless nut that's a close fit over the top of the stud.

It doesn't have to thread onto the stud.

Spot weld the nut onto the stud.

The heat from the weld will help removal.

 

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Like others, I have never had success with an easy out on a seized bolt. 
 

I had never heard of EDM before this, but I'm glad I did. I hope I remember it for the next time I'm in the same predicament. It seems the most sensible choice. Either that, or go for the gusto and just drill the whole thing out and use a helicoil. 

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On 9/5/2021 at 9:59 AM, SloopJonB said:

pay a machinist to do it.

EDM or weld a nut on the remaining bit of stud. Usually heat breaks the bond. Might be $100 but you're paying for the skill and machinery not the time to do it.

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2 hours ago, Zonker said:

EDM or weld a nut on the remaining bit of stud. Usually heat breaks the bond. Might be $100 but you're paying for the skill and machinery not the time to do it.

I've tried the welding trick a few times - never worked for me.  YMMV.

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17 hours ago, Son of Hans said:

I've tried the welding trick a few times - never worked for me.  YMMV.

Just back from the welding shop--- didn't work for me either. Broke off most of the portion of the bolt that was protruding from the surface of the head. Was trying to go very easy, back and forth just a bit when it broke off. Will check with the machinist I know as to whether he has an EDM machine. Meanwhile, the welder suggested making a jig to guide my drilling-- gave me a block of steel to drill, using the head gasket as a pattern to drill two holes to hold the guide block in place using "good" holes in the head and a third hole to serve as the drill guide for the problem stud. To be continued...

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13 minutes ago, Anomaly2 said:

Just back from the welding shop--- didn't work for me either. Broke off most of the portion of the bolt that was protruding from the surface of the head. Was trying to go very easy, back and forth just a bit when it broke off. Will check with the machinist I know as to whether he has an EDM machine. Meanwhile, the welder suggested making a jig to guide my drilling-- gave me a block of steel to drill, using the head gasket as a pattern to drill two holes to hold the guide block in place using "good" holes in the head and a third hole to serve at the drill guide for the problem stud. To be continued...

As per SASSAFRASS, left handed drill bits may help, check McMaster-Carr.

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Easy outs are rubbish. Doesn't matter the brand. Buy a left handed regular drill bit. Go at it with the drill on low speed(high torque) putting as much down pressure on the fastener as possible.  Try this in the future on another stuck bolt.

At this point I would hire the muscle to come in and save the day. This could get expensive if you keep going. 

 

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17 hours ago, Anomaly2 said:

Meanwhile, the welder suggested making a jig to guide my drilling-- gave me a block of steel to drill, using the head gasket as a pattern to drill two holes to hold the guide block in place using "good" holes in the head and a third hole to serve as the drill guide for the problem stud. 

A block of steel is good, but IMHO, a hardwood block & drill bushings will work as well and the holes are much easier to drill.

2 pieces of good 3/4” plywood glued together will also work for this. You need just enough precision to get the job done, anything beyond that is useless, just like “altitude above you and runway behind you” (:-)

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Oh eye of little faith...

I appreciate all the helpful suggestions here, others not so much... The left hand bit suggestion(s) was the key, but not in the obvious way. I didn't know where to find such bits and was about to go down the McMaster Carr route when one of the regulars at my shipyard uttered the immortal phrase "have you tried Fuller's?" My god, a miracle in my backyard. Fuller/s has.... everything! And exceedingly helpful and knowledgeable people work there. I bought some cobalt (not available in left hand) and some left-hand bits in graduated diameters and a straight-fluted easy-out and went at it. I confess, I was too impatient to do the 'make a jig' thing and my drillpress was behind a wall of shit stacked up for shipping and.... So, I went at it freehand. Slowly. And with oil. The Fuller bits were a marvel. But the left hand bits did nothing in terms of getting the bolt shaft to back out, and the easy-out didn't result in an easy-out. So, after several iterations, I returned to Fuller and bought a metric 6 tap and the appropriate pilot drill bit, in left hand thread. I got down to a "straw" still threaded in to the cylinder head when I decided to resort to the tap. Proceeding very slow, it worked!

Tomorrow, I'll put the head on. Thanks again to all those who offered helpful suggestions.

PS I was too lazy/impatient to fabricate a jiig (whether of steel or hardwood) and my drillpress was relatively inaccessible (a.k.a. blocked behind too much shit), so I just drilled it out, slowly, incrementally, freehand. Like they say, every once in a while, even a blind squirrel finds a nut...

 

 

cylinder head_tapping.jpg

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I guess you are done, but backing up a bit. If you weld a nut on and it breaks off flush, then you can plug weld a washer onto it, weld a nut onto the washer, and try again. If it is in cast iron, a welder with some skill can burn the bolt out with a cutting torch without hurting the threads. Yeah, you'd think that is impossible but I've seen it done more than once. Finally, if no EDM is available (this is the preferred tool) then you can mill it out, but the best way to do that is to interpolate the hole with a smallish end mill. If you just go for the plunge with a max size mill, as the bits break up they can break the end mill. 

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10 hours ago, Quickstep192 said:

You're obviously smart enough to be sure to clean all that crap out of your cylinders before putting the head back on, but I'm saying it anyway. 

You made me laugh. Thanks. Yeah, I took that photo the moment I finished tapping the threads. There was a LOT of shit (some new, most old) . in the water jacket when I got around to cleaning things up. The cleaning up took longer than the drilling and tapping... The put on a new head gasket and head and ran it in a tank. All good. Will try it in anger soon.

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9 hours ago, DDW said:

I guess you are done, but backing up a bit. If you weld a nut on and it breaks off flush, then you can plug weld a washer onto it, weld a nut onto the washer, and try again. If it is in cast iron, a welder with some skill can burn the bolt out with a cutting torch without hurting the threads. Yeah, you'd think that is impossible but I've seen it done more than once. Finally, if no EDM is available (this is the preferred tool) then you can mill it out, but the best way to do that is to interpolate the hole with a smallish end mill. If you just go for the plunge with a max size mill, as the bits break up they can break the end mill. 

Thanks  DDW. I'll try to remember this the next time. I hope there isn't a next time. But, there always is...

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Congrats on getting that sucker out. Broken studs have to be the most frustrating problems on vehicles or motors. So often things are going well until the last one snaps or just won't budge. 

When you say Fuller are you talking about WL Fuller in Warwick, RI ? They make the best countersinks. Its a shame that Dewalt and others copied their design. The other brands are rubbish.  I've still got a set of their countersinks & plug cutters that I got in the early 90's.

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5 hours ago, CaptainAhab said:

 

When you say Fuller are you talking about WL Fuller in Warwick, RI ? They make the best countersinks. Its a shame that Dewalt and others copied their design. The other brands are rubbish.  I've still got a set of their countersinks & plug cutters that I got in the early 90's.

Yep, that's the place. Just off Jefferson Blvd. about 15 minutes from me and I only just "discovered" them after being here for 20+years. Sheesh! I told them this and they said ""we get about a person a week who comes in and tells us that. We're the best kept secret in Rhode Island.""  Simply the best.

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