How best to remove broken & rusted bolt in block

dtfeld

dtfeld

Water Contrails
GOLD Sponsor
Jun 5, 2016
5,590
Milton, GA
Boat Info
410 Sundancer
2001
12" Axiom and 9" Axiom+ MFD
Engines
Cat 3126 V-Drives
Double post, but thought this a better forum to get some options/fixes.

Below is a picture of the mounting bolt for the coolant pump idler pulley on a CAT 3126. Bolt is directly into the block, and in a pretty tight location. Maybe 1/2 a thread above the surrounding metal.

What’s the best way to remove? CAT hardware is typically high strength, hardened bolts and usually take a fair amount of torque to back out. Looks like it’s been in there a while or possibly a former owner/mechanic sheared it off. I don’t think a HD or Lowe’s easy out will get this done.

I’m thinking drilling and running a cutting tap down to remove the remnants, but getting it centered up is going to be tough. Access is not easy.

Maybe try welding a nut on? Not a whole lot of material. Id have to buy a welder. Obviously a little “fire and ice” treatment will always help .

Maybe call in a mobile machinist?


IMG_0288.jpeg
 
dtfeld said:
Double post, but thought this a better forum to get some options/fixes.

Below is a picture of the mounting bolt for the coolant pump idler pulley on a CAT 3126. Bolt is directly into the block, and in a pretty tight location. Maybe 1/2 a thread above the surrounding metal.

What’s the best way to remove? CAT hardware is typically high strength, hardened bolts and usually take a fair amount of torque to back out. Looks like it’s been in there a while or possibly a former owner/mechanic sheared it off. I don’t think a HD or Lowe’s easy out will get this done.

I’m thinking drilling and running a cutting tap down to remove the remnants, but getting it centered up is going to be tough. Access is not easy.

Maybe try welding a nut on? Not a whole lot of material. Id have to buy a welder. Obviously a little “fire and ice” treatment will always help .

Maybe call in a mobile machinist?


View attachment 160488
Click to expand...
I hate that stuff - Carefully grind it flush and flat to the casting.
Get a small (really small) sharp nose punch and locate as humanly possible the center of the bolt where it was ground flat then tap a mark
Get a larger hardened punch and make that mark deeper so a drill bit will stay centered in it.
Now you will need a good set of 135 degree M35 cobalt drill bits (and I don't mean Amazon cobalt drills - Hanson or equal) - with a 1/8" bit and medium speed with WD40 or other cutting fluid drill through the bolt as straight as possible. It will go through like butter. Carbide drill bits will cut better but they are brittle compared to the Cobalt and your chances of snapping are much greater. Then step up to to an 1/4" bit and so on until the casting threads just get touched. As the bits get larger speed goes down. Take your time on the drilling and keep things steady and level - if you break off a cobalt bit in the bolt, just walk away. Now the threads can be cleaned out with a good sharp tap. Those are metric threads BTW.
 
Dave is the bolt broken off in a removable pump or something like that? Can what looks like a bracket be removed to expose the threads? From that picture it looks like that isn't the block?

Tom's method is a tried and true last resort method and does take a lot of patience. But if you can loosen that bracket and use some heat to remove it to expose the bolt you may be able to use some heat and vise grips to remove or on the way to Tom's resolution use an easy out., although chasing the thread's will need to be done any way.
 
I have to do it more than I'd like to admit. As one example, two of the studs that hold the exhaust onto the engine head on my QSM 11's broke - They drilled out just fine - but it was a long haul with several G&T's post event. That sickening, gut-twist of a thought that the cylinder head or worse the engine would need to come out because I just broke off a bolt in the most impossible location to access......
But, I never undertake a project unless it entails the acquisition of new tools. I have that on a placard in my shop....
 
Another thought is there are services with portable EDM's. All they do is remove broken studs in heavy equipment. If you break off a drill bit or tap you'll pretty much have to remove with an EDM machine.
 
Thanks for the replies.

Yup, had a shitty feeling about this all day yesterday. Had this problem running through my brain all night.

Looking at the CAT parts diagram this morning, I did determine that the bolt is stuck in the front housing casting, not the block. If I really screw the pooch, I can at least have a rescue plan that would entail replacing a $1250 casting, not the block. Going to look to see if that could be accomplished in the boat if it comes to it.

IMG_0289.jpeg
 
Got a few other MX items to finish up today, then head home and start acquiring the necessary pcs and parts. What was really bothering me was the “what if” I really screw myself…do I have a 2nd or 3rd alternative.

With issues like this, I always stop and contemplate best way to proceed, and think through a backup plan. I didn’t realize there are mobile EDMs so that good to know.

@ttmott You are correct, these are Metric. First order is to identify the thread. Head was M13.
 
That bolt for anyone that goes looking in the future is an M8x1.25 x 30mm. Drilling that puppy out free hand is going to take a while being so long. All this for a 50 cent bolt. Grrr.

Capture1.PNG


1710540199192.png
 
Parts and tools on hand.

After watching a bunch of bolt removal videos...here's the plan.

1. Penetrant. Douse it let it sit.
2. Heat & Hammer - I have an old oxy MAPP torch that I hope can get some concentrated heat on the bolt,then try loosening with a punch and hammer.
3. Drill and EZ Out
4. Drill and Retap
 
I'm a fan of Kroil brand penetrating oil. It's worked for me when other brands did not. If you have a choice you might want to give it a try.
 
Back years ago when I was working as a tool & die machinist if they had a broken bolt like that on machinery that they couldn't tear down I would carefully use a die grinder with a carbide cutting bit to grind out the bolt until nothing but the threads were left. Then I would use a sharp pick & needle nose pliers to remove the threads. Then all I had to do is chase the threads with a tap & it was ready to go again. It did take a long time but it was much easier than to tear down the equipment to remove a bolt.
If you could find anything close to center you could drill it out by starting small & with many passes using sequentially larger drills until you get out to touch the threads. Then you should be able to pick out the remaining threads & tap to clean the threads.
 
Spent all day alternating between heat and penetrant oil, then working with a chisel. No joy.

Tomorrow I’m going to grind the face flat and attempt to drill it out. I like the idea of a carbide bit as another option.
 
ttmott said:
Kennametal, Sandvik, and Michigan Drill are also very good bits.
If you want a set of bits that will last then these are the ones.
Click to expand...
Kennametal, Sandvik, Chicago Latrobe, Cleveland Twist, New York Twist are all reputable manufacturers. Michigan Drill is a reseller/private labeled product that buys from various sources.
 
Drilled it out and ran a tap thru it to clean it up. That was a 12 hour job all to remove a 50 cent bolt.

New CAT bolts all around and going back with some anti seize on the threads.

20240322_140744.jpg
 
dtfeld said:
Drilled it out and ran a tap thru it to clean it up. That was a 12 hour job all to remove a 50 cent bolt.

New CAT bolts all around and going back with some anti seize on the threads.

View attachment 160923
Click to expand...
Patience is a Virtue! Good job.
 
You must log in or register to reply here.

Forum statistics

Threads
113,183
Messages
1,428,125
Members
61,091
Latest member
dionb
Back
Top