Repairing stripped threaded holes in jugs

[Coolbreeze]

When I removed the cylinders (what sort of jugs did you think I meant?) from my Indian 841, I found that one of the head bolts was larger than the rest. Apparently, a prior owner had stripped the threads in Indian's notoriously soft cast iron and cut threads for a larger bolt. The 1st machinist tried to repair the cylinder by using a helicoil insert. That fix failed when my mechanic tried to torque the head. The cylinder was then sent to another machinist who enlarged the hole (luckily, there was enough material) and cut fine threads in it. He next screwed a bolt of good quality steel into the hole. He then cut the bolt flush and drilled and tapped it for the correct size head bolt. That fix seems to be working. It allows the head to be torqued to the factory specs, and it is holding fast after several miles of road use on the refurbished motor.

I have never heard of this being done before; so, I thought I would share the story.

[Paps]

That is how we used to do strip thread repairs in the commercial machining industry, as long as there was enough wall to allow such a repair. We also weld beveled the outer perimeter of the solid plug and welded it in permanently. If minimal wall was available for such a plug, we welded it up solid, after taking the hole out .010" plus per side oversize. We had great welding skilled people and they could do the job without fear of warpage. Paps

[Ohio-Rider]

Welding the plug in would be the preferred method to hold the plug in but when that isn’t possible to do, there is yet another way to skin that cat. That is, to secure the repair plug into the hole as George’s machinist did, then drill and tap a small hole somewhere along the perimeter of the repair plug and the base metal. Screw a bolt into this new small hole and then grind the head of that bolt off flush. Now you can be sure that repair plug is not coming back out. This method is just another one of many ways of staking in a repair plug.

Your guy did it right George. You can sleep easy now.

[Paps]

Glad you mentioned that staking method Steve ! I plum forgot about that fix. DUH !!

[T. Cotten]

headbolt torque?

George!

Although I have needed to "slug" over-sized bolt holes countless times myself, I still wonder why I have had such great luck with Helicoils when others suffer. They seem stronger than the orginal to me.

Just what are the "factory specs" for headbolt torque on the 841 (assumeably the same for a SS?) anyway? My military literature is lacking...

TIA,

...Cotten

[RichO]

inserts

In aluminum, steel, or cast iron the easiest to use is thread in inserts. They come under different names. Keen-sert being one. They use an oversized outer tap size (unlike helicoils). They thread in and have stainless steel stakes(4) to cross the outside theads so it can never turn back out. I have a large supply in the shop and get they from an industrial supply company. Shovelhead exhaust bolts run in and out with the surrounding heat kills the threads after a while. I drill and tap, run in a keen-sert, install a stud then you nut them on , permanet fix. Work good for bad head bolts on all motors. I have torqued to 150 lbs. no problem. Have used them for 40 years, no failures.

[T. Cotten]

In aluminum, steel, or cast iron the easiest to use is thread in inserts.. They use an oversized outer tap size (unlike helicoils).

Dr. Sprocket!

Convention Helicoils also thread-in, and also require an oversize tap.

Other than when a stainless bolt of similar composition might gall into the insert, 99.9% of all Helicoil failures that I have inspected were either due to improper installation, or excessive use of threadlocking goobers.

And as I live in the land of Caterpillar, I assure you that Keenserts can be screwed up too! (Usually radiating cracks from the four 'pins'.)

...Cotten

[Chris Haynes]

And as I live in the land of Caterpillar,
...Cotten

Hey Cotten,
Do you know where Cataerpillar originated? I do!
Side note that Caterpillar submitted a smaller than usual prototype tank to Uncle Sam during WWI. I was powered by a motorcycle engine. I have never found out what type of motorcycle it was.

[RichO]

Dear Mr. Cotton

When I said oversized I meant a standard size larger tap and not a bastard size non-standard tap like heli-coil. use what you like but screwing in a bolt and drilling and tapping it or God forbid having to weld it in this the hard way. A keen-sert type insert makes a permanet bushing that works way better than a thin heli-coil thread wire. Especially in aluminum or the soft cast iron. Like I said it's just one other way. This isn't my first rodeo by a long ways, pilgrim. Retired now but 45 years as a fleet mechanic, millwright, fabricator, weld shop owner, blah, blah, blah, gives me a little more than the average drover's insight.

[T. Cotten]

Chris!

CAT (or 'The Great Yellow Gawd' as we know it in Central Illinois) might have been conceived in California, but it's dying here.

And RichO!
It appears you take this matter so personal!

Don't look now, but a 1/4"-24 Helicoil insert installs perfectly with a common (not 'bastard') 5/16"-24 tap. I imagine that's a hard-to-find Keensert size.

Helicoils require less matrix material and are far less destructive to install than a Keensert, making the best choice when salvaging thin or age-embrittled castings, or holes close to a margin, as they produce an evenly distributed fastener stress when torqued (no pins).

Keenserts have the advantage of withstanding the mindless abuse of factory production workers who install them repetitively in fresh holes in monolithic castings.

There is a time and a place for either, and other designs of inserts as well.

....Cotten

[Chris Haynes]

Chris!

CAT (or 'The Great Yellow Gawd' as we know it in Central Illinois) might have been conceived in California, but it's dying here.

Caterpillar originated in Stockton, CA. It is far from dying. Cat has been buying other companies worldwide. They even now own a railroad.

[Underdoggie]

When I went to Nuclear Weapons Maintenance school back in 65, they taught us all about helicoils because every fastener on a nuke has a helicoil in it. The first thing they taught us was that a helicoil was not designed as a repair proceedure but rathter for "high use" fasteners so the bolt or screw could be installed, torqued and removed often from materials like magnesium, aluminum and other secret light weight alloys.
The ones we would wear out and re install the most were the ones on the rear parachute housing (used for delayed air drops) on Mark 28 Mod 0's
I have no idea of how many of those suckers I installed but I can tell you many people that use them do not install them correctly.
I am also a Caterpillar retiree out of the Engine Divison (right down the road from Cotton's shop actually) and we would use them on finish machined parts rather than welding to keep machined surface profiles from changing. The deal with Engineering was that after installation the fastener would be torqued to 150% for that size fastener without any pulling or distortion, If that requirement was met then it was OK.
It is also not uncommon to see helicoils in Caterpillar Engine Valve cover bases on residual fuel engines (turd burners) where valve lash has to be adjusted at frequent intervals.

[T. Cotten]

Caterpillar originated in Stockton, CA. It is far from dying. Cat has been buying other companies worldwide. They even now own a railroad.

Whew, Chris,

Don't tell that to all my good friends and neighbors looking for work;
The third round of layoffs hit a week ago today, including the fellow across the alley at home....

I have no clue about the tank with a motorcycle motor, but it makes me wonder if Crosley ever made a motorcycle.


...Cotten
PS: Mr. U!
Right down the road? How come I never see you?
Does your '65 have the red 'pilot lamp' on the right and the green on the left,... or t'other way 'round?

[Underdoggie]

Cotten,
I worked right down the road, not live down the road, and I will get there, I am just making sure I have all my issues in order before I come over and well... I guess I'm just getting slow in my old age.
We had this conversation before about the pilot lights and you know both of mine are green and always have been, why would you want different colors when all they do is tell you the turn signals are on. Oh, I get it, your just f___ing with me cause I take everything too serious right?

[Chris Haynes]

[QUOTE=T. Cotten;80157]Whew, Chris,

Don't tell that to all my good friends and neighbors looking for work;
The third round of layoffs hit a week ago today, including the fellow across the alley at home....

I have no clue about the tank with a motorcycle motor, but it makes me wonder if Crosley ever made a motorcycle.


...Cotten

Cotten,
Layoffs in all business is a national catastrophe. That doesn't mean the companies are dying. They don't keep people on payroll when there is no work for them. When orders for the type of equipment made at your local branch come in the workers will be called back to build them. You must remember that Caterpillar is a global company. I operate Caterpillar equipment that is made worldwide. When there is no work for my job I am laid off until they need me. This week I have worked four days for three different employers. Some weeks I don't work at all.
Crosley did indeed make prototype military motorcycles during WWII. Both two and three wheelers.
http://blog.hemmings.com/index.php/2...e-war-machine/