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Thread Like Summary
BeezaBryan, D.Bachtel, gavin eisler, Hugh Jörgen, John Healy, Shane in Oz, Stuart Kirk, Tribsauk
Total Likes: 11
Original Post (Thread Starter)
#814403 06/29/2020 5:07 AM
by Shane in Oz
Shane in Oz
This isn't Britbike related without drawing a rather long bow, so the Rod and Tappet seemed a less bad place to post.

I need some advice on removing a broken 1/2" UNC stud from a rather large piece of cast iron.

For my various sins, I have an International A554 diesel tractor which required engine surgery.
Everything was progressing until it came time to torque down the head studs. After running through the sequence 20 lb. ft. at a time, a stud snapped on what should have been the second-last round, at 100 lb. ft.

After the requisite rude words, run through the sequence in reverse and attach the engine crane to remove the head.
There was a beautiful stress fracture just above the deck of the cylinder block, so naturally there was no hope of using any sort of external puller.

All the other studs came out alright with a bit of Inox penetrating oil and using an external stud extractor - probably 60 - 80 lb. ft. to start them. No sign of rust or thread locker, so they're just threaded in tightly.
The broken stud is under the rocker cover, where there is a decent supply of oil, so it's not rusted in. The stud snapped on the first thread, so it shouldn't be jammed from above. It has 1 1/4" of thread into a 1 3/4" deep blind hole. We've drilled through the bottom of the stud with a left-handed drill bit, so it's not jammed in the bottom of the hole, or air locked.

Despite a couple of prolonged soaks with penetrating oil, it doesn't look like moving. I've used a multi-splined Iron stud extractor, but I'm not game to apply above around 50 lb. ft. of torque.

The drill was reasonably well centred, but it's an awkward spot so not drilled as perpendicular to the block as I'd like. That makes me very reluctant to drill out to the tapping diameter, unfortunately.

So, I'm throwing it over to the collected brains trust for suggestions. Even rude ones are fine smile
Liked Replies
#814405 Jun 29th a 05:46 AM
by Stuart Kirk
Stuart Kirk
No rudeness here.
Your dilemma reminds me nasty job I once got. It was a V12 ferrari with 3 broken head studs that came in complaining of a head gasket coolant leak. The studs were somehow broken off sub flush in the aluminum block. After discussing processes like EDM which meant removal and complete disassembly of the engine, my solution was to make a bored out nut with 1/2 of the OD machined to set down in the counterbore of the block, and then weld it to the end of the stud. 2 came out like butter; One fought me.

If I'm understanding your situation, a bit of the stud is sticking up above the deck surface but it has been drilled to use a stud extractor. This makes it much easier. Do you have access to a MIG or TIG welder? If so, this is what you can do.
Step one. find a washer that is a close fit on the stud you want to remove. Set it flat on the deck, around the stud, and carefully weld it to the end of the stud. Let it cool.
Step two. Weld a reasonable sized nut to the washer. Let it cool.
Step three. Turn the nut and see what happens. I bet the broken end will come right out. The heating and cooling helps loosen it. If the weld twists off, just try it again. One of the Ferrari ones took 3 tries. Of course, be sure to protect anything you don't want weld spatter on. Let me know how it works out.
Stuart
2 members like this
by kommando
kommando
Use an end mill in a variable speed drill to flatten off the end of the stud. Then centre punch the centre of the stud, if you get it wrong redo with end mill. Then use a pilot drill to drill a hole and follow up with progressively larger drills until you are at the root of the thread, use a threading tap to remove stud remains from thread. Used to be my last resort but it works so well I go for it much earlier.
2 members like this
#824961 Sep 27th a 09:24 AM
by Shane in Oz
Shane in Oz
The previous 2 weekends were wet, windy or both, so no progress on the Inter.
Yesterday was windy as well, but today came up well.

Like John Cleese and the cricket ball straight, smack, plumb between the eyes, we're getting used to it by now. It didn't take long to lift the head off and fit the jig and drill guide and take it out to 25/64" and then 13/32". The thread was starting to show by then, but the pick couldn't start to lift it. After some more attempts with the pick, we eventually took it out to the tapping size of 27/64". 1/64" extra diameter (1/128" extra depth) isn't much, but still enough to be nervous.
I eventually managed to lift the start of the remains of the stud's thread out of the tapped hole, and it peeled out reasonably readily apart from the last 3 threads. They were eventually persuaded to relinquish their hold as well.
Amazingly, the jig must have been almost dead centre and square, because there is no obvious spot where the drill contacted the thread in the hole.

Thus endeth this part of the saga. If the weather permits, next weekend should see me back to where I thought I was before the stud broke. This should be the world's most expensive A564, with the new sleeves, pistons and big-end bearings, and the high-strength ARP head studs.


Thanks again everybody for the great suggestions. If I'd thought to ask earlier I could have taken advantage of some of them before free-hand drilling the stud to attempt removal with a stud extractor.
It's almost tempting to pick up and old cast-iron block from the wrecker just to practice the techniques.
2 members like this
by Shane in Oz
Shane in Oz
There is some excellent advice so far, which is going straight to the pool room.

It's the weekend here now. I have some free time, but my partner in crime isn't available until tomorrow.
This seemed like a good opportunity to act as a pale imitation of our resident physicist and check just how well various mechanical extractors work, using a scrap piece of cast iron and an old torque wrench.

This morning's exercise covered the extractors currently to hand. These are the sizes recommended for 1/2" or 9/16" bolts

Extract__________Size_______Hole size______________Max torque____________Failure mode

Irwin____________9/32"_______9/32"_________________60 ft. lb.______________splines slipping

Sutton Easy-Out___#5_________7.5 m_________________50 ft. lb.______________extractor snapped

Ridgid___________#5_________11/32"________________80 ft. lb._____________cast iron work piece broke


I used a larger size extractor from the Irwin set a while back to remove a broken 3/4" stud from a tractor axle housing. That worked well, but required a lower torque.

Sutton is a local brand which makes excellent drill bits and other tools. Their Easy-Outs seem to suffer from the same problems as most of their type

The Ridgid handles quite high torque, but is close fit in the hole and has to be whacked in, which doesn't seem like a good idea with a bolt threaded into cast iron.

If nothing else, the comparison of mechanical extractors might prove useful to somebody some time.

P.S.
I managed to dig out a piece of 3/8" mild steel, so had another run with the Irwin extractor.
That got up to 90 lb. ft. before I chickened out.

I was only game to take it to 50 ft. lb. in the broken stud previously, but now I know it can handle 90. If that isn't enough, it's safer to torque to yield in a disposable work piece than the cylinder block.
1 member likes this
#816713 Jul 19th a 01:02 AM
by Stuart Kirk
Stuart Kirk
Originally Posted by Shane in Oz
Perhaps I'll just have ro console myself by working on a BSA instead smile
That works for me. I just got a basket case Goldie up and running that I've had sitting around since the early eighties.
This is it a few weeks ago getting the cush drive nut to go on the end of the crank. The 2x4 is the special tool. I put 4 nails in the other side to engage the notches in the nut. Crude but it worked great.
[Linked Image from i.postimg.cc]
1 member likes this
#821836 Aug 30th a 10:02 PM
by Shane in Oz
Shane in Oz
Well, it's taken a while, but all the materials have turned up and we had a weekend without drizzle or August winds.

We lifted the head off again, sat it on the pair of 400mm x 50mm x 20mm steel bars and transfer punched through the 3 relevant cylinder head holes.
The bar came pre-machined to size, and was within .001" end to end, which is excellent

Just to recap, there are 4 head studs on the pushrod side of the block; 1 at each end and 2 reasonably close together about halfway along.
The broken stud is the second from the rear, so the bar will be drilled to bolt down to the block through the second and rear holes, with a larger hole centred over the broken stud to take replaceable drill guides to work out to size.

There was a certain amount of head scratching after clamping the marked bar down on parallels on the milling table, because the DRO reading for one of the locations didn't look correct. After measuring the head and block multiple times with a steel run (yeah, I know) to prove to myself that I'm not completely mad, it turns out that the spacing between the 2 middle holes is 1 3/4", but the spacing to the rear stud is then 9 5/64".
That just goes to show that no only British engineering has peculiarities.

The final result for the weekend is that the 2 end holes have been drilled to 1/2", the hole for the 3/4" drill guide insert has been drilled to 11/16" in preparation for using the boring head to open it out to a tight slip fit for the drill guide inserts.

We also tapped the broken stud and fitted a length of threaded 10mm rod to discourage the drill bit from wandering.


The next steps, unless somebody raises the warning flags, are:

Finish boring the hole to size for the drill guides.
Bolt the jig down on the block to check the drill guide location concentric over the broken stud
Fit the 3/8" guide and use a 3/8" end mill to machine a flat surface on the top of the remains of the stud
Fit the 1/4" guide and drill a pilot hole
Swap to the 3/8" guide to enlarge the hole.

That should be getting close to the minor diameter of the thread in the hole without running too great a risk of damaging the thread.
After that, it's a matter of how concentric and square the drilling has been.
The tapping drill size for 1/2" UNC is 27/64", so the 3/8" drill should have taken us to 24/64"

If all is well with the hole and the remains of the stud are still determined to stay put, it might be possible to try to open the hole by 1/64" increments.

It will probably be either raining of windy as all getup next weekend, which will put things on hold again, but we might be lucky. There's always the replacement bearings in the Kubota blade spindles, and dreams of getting back to finishing the B25 fettling...
1 member likes this
by Shane in Oz
Shane in Oz
This stud is certainly determined to fight to the last.

Originally Posted by Shane in Oz
The next steps, unless somebody raises the warning flags, are:

Finish boring the hole to size for the drill guides.
Bolt the jig down on the block to check the drill guide location concentric over the broken stud
Fit the 3/8" guide and use a 3/8" end mill to machine a flat surface on the top of the remains of the stud
Fit the 1/4" guide and drill a pilot hole
Swap to the 3/8" guide to enlarge the hole.

That should be getting close to the minor diameter of the thread in the hole without running too great a risk of damaging the thread.
After that, it's a matter of how concentric and square the drilling has been.
The tapping drill size for 1/2" UNC is 27/64", so the 3/8" drill should have taken us to 24/64"

If all is well with the hole and the remains of the stud are still determined to stay put, it might be possible to try to open the hole by 1/64" increments.
Things went largely according to the agenda above.

This exercise has been slow and frustrating, but also a great learning exercise and good for thinking in new areas.
It's been great for regaining some "feel" with a micrometer and telescoping gauges, and gaining more confidence with the mill before doing battle with BSA parts.


The little column mill not surprisingly isn't particularly rigid, but by taking rather shallow cuts and sneaking up on the last couple of thousandths, the drill guides are a sliding fit.

The drill guide bolted sown on the block, with the front and rear holes positioned as they should be. So, for whatever reason, that 9 5/64" spacing was correct. Visually, the drill guide hole over the broken stud appeared to be off, but that was just an optical illusion (and paranoia) caused by the less than perfect stud surface.

The 3/8" end mill cleaned the surface up well, and the 1/4" pilot hole was a success. with lots of stops to check progress, and clear the hole and drill flutes.

We took the 3/8" hole down about 5/8" - 3/4" with a right-hand bit, then switched to a left-hand bit to see if it might encourage the remains of the stud to budge. Not a chance, but it did unscrew the 8mm "stud" we had used to fill the original misaligned hole. That was quite effective in stopping the 1/4" bit from wandering while drilling the pilot hole.

The 3/8" hole at least appears to be centred and running square, which is a big advance on the original freehand hole.

It was coming over cloudy around 2pm, so we knocked off for lunch and sat the head back on the block.

The pilot guides have now been drilled out to 25/64" and 13/32" for the next round.

It was getting a bit late by then, so we finished the day by battling with Kubota spindles and blade nuts. Ahh, the joys of being on a few acres.
1 member likes this
#825228 Sep 30th a 03:58 AM
by Stuart Kirk
Stuart Kirk
Originally Posted by Shane in Oz
Amazingly, the jig must have been almost dead centre and square, because there is no obvious spot where the drill contacted the thread in the hole.
That, good sir is the golden ring you were after. Not easy to achieve. Well, well done.
Originally Posted by Shane in Oz
I think it's time to finish off the Starlite next.
As in "push it out in the field and torch it"? Because I hear a happily running Starlite isn't easy to achieve either.
But I've never even heard one run so don't listen to me.
1 member likes this
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