Big screw broke off inside - Help extract!

A 3-inch hydraulic rod has a 7/8-9 screw broken off about 1/2 inch inside !

The screw is some really hardened tool steel.
They managed to grind a slot in the end of the screw with a die grinder, but our little impact driver was not able to budge it.

BTW, the screw was hard bottomed out with about a 24-inch wrench (hard enough to break it, but it was probably fatigued from thousands of press cycles).
Worse, they had a mild steel spacer inside that they bottomed out on so its probably really gummed on.

While grinding the slot, they may have nicked into the rod, causing an interlocking burr.
They suggested welding to the end of the screw, but I'm afraid to weld it to the inside of the rod, or spatter the remaining screw threads beyond extraction.

We don't want to torch the rod, which would spoil the cylinder packing. I suggested dry ice or liquid nitrogen, but it is facing downward and would be difficult to apply.
I'm willing to try it if I can figure out how to spray LN2 up in there.

Absolute last resort would be, pull the cylinder and saw off an inch of the rod.
There is only about a foot of space in the throat of the press to work on this!

Right now I'm going to the auto parts store for a bigger impact driver!

Torqued with a 2’ wrench...You’re screwed. The rod will turn and kill the impact unless you secure it. Good luck!
Joe

Old school ratchet drill like this Keystone ratchet drill/wrench - to put the pressure on - and drill the broken stud out ;- using guide bushes to get a good start on centre.

Not fast or easy work but more than doable.

Washer on hole, stainless welding rod to build a new bolt shank.

Extra flux of SS rod helps protect threads.

Heat will "tickle things up" and help loosening.

BTDT

I'm gonna say you're going to be screwed also. Time to take it apart so you can either make a new part or get that piece to a real machine tool so the broken piece can be machined out. Welding will probably not work if the broken piece is high carbon. The weld will just break away when you try to apply force. BTDT also. But hey, maybe you'll get lucky.

Is there an EDM shop local to you?

A problem with welding is where do you attach the ground without a chance of an arc ruining the ram? Also, as I understand it, the hole faces down. Is the press still operational? A Milwaukee Hole Hawg drill has a flat opposite the chuck perfect for applying force. Use a small jack if necessary. Using guide bushings drill out the existing stud. If it was bottomed on a mild spacer, drilling the spacer out as well should relieve the pressure on the threads.

digger doug said:

Washer on hole, stainless welding rod to build a new bolt shank.

Extra flux of SS rod helps protect threads.

Heat will "tickle things up" and help loosening.

BTDT

Click to expand...

I've done this many times also with regular rod and a wire machine. The heat seems to do wonders. So many broken bolts, that an impact couldn't get out, spin out with one finger on a hand wrench. Using rod in a deep hole is great, the flux insulates it against the hole threads.

Success. Unbolted the tie rods & pulled the piston out from the top. With the rod on the bench, they tapped the screw out with a punch. Didn't even wreck the packing.

Now... the same people are retightening the tie rods, that broke the tool in the first place...

THANKS TO ALL who read & reply so fast on this forum! You are the knowledge bank, they aren't teaching practical mechanics in school any more (no shop class where I live).
Let's see my kids 3D-print their way out of this! <rant>S.T.E.M.=B.S.</rant>