Jøtul 118 - Broken screws, a solution

[hhsixzz]

Howdy!

While restoring a Jøtul 118 I managed to break four screws holding the upper parts of the stove.

Had I known better I would have moved the screws back and forth to break the rust and creosote apart in the threads, instead I forced them after they came loose and the resistance slowly increased until they snapped!

I've had the pleasure of dealing with broken steel screws in the past, I had one in my electric bike which I eventually drilled out with a tungsten carbide bit using an industrial drill press. This is not an option this time around so I have another idea; in the illustration below you can see the part from above, the red represents an angle grinder cut into the cast iron to extract the screw.

This would leave the part with an opening, but I'm thinking I can just use a nut from below to tighten it.

Please advise if you think this is a viable idea, or if you think there is something better I should try let me know.

Sorry for the poor quality pictures.

Cheers!

 

[MongoMongoson]

Are these steel or stainless screws? If they protrude like the one pictured, you can still grab it with vise grips. I would soak it with Kroil or PB Blaster (or the Euro equivalent) maybe hit it with some heat. A propane torch would work. Heat it and spray it with oil. Do this a bunch of times over several hours. Do all four of them and repeat the process on the remaining 3 while you are working on getting the 1st out. Try wiggling it with the vise grips. Apply more penetrating oil and heat. You might get it out. If you can't grab it, get some left hand drill bits. Grind the face of the screw flat. Put a dimple in the center of the screw with a center punch. Start small, drilling a hole in the center of the screw. Turn the drill slowly counter-clockwise (left hand bit) and use pressure. Use cutting oil or some kind of oil (I have used WD 40 when I don't have cutting oil) to help it cut and keep the drill bit tip cool. Work your way up to larger bits. It will probably come out. Worst case, you end up drilling it big enough to put a screw through with a nut. I would do whatever I could to not have to cut that slot.

It will be frustrating and time consuming. Be prepared with some patience and if you get frustrated, walk away for a while. You don't want to break off a drill bit in the screw. Things get worse if you do that. I know. I have done it. Also, I have broken EZ Outs. I hate those things now. There is nothing easy about EZ Outs.

You can still do this if they are stainless, it just is more frustrating and time consuming. If they are mild steel, it shouldn't be terrible.

If you can't get left hand bits, you can still drill it out. The nice thing with left hand bits is eventually when the hole gets big enough, the screw will often turn out with the bit.

 

[hhsixzz]

Thank you I will try your advice and report back, now I know what to do for Christmas!

[EDIT]

Is there a way to tell if the screws are steel or stainless steel?

 

[MongoMongoson]

Magnets will stick to 400-series stainless but not 300-series. If you have a magnet, apply it to a broken off piece of screw or to the end of the long screw still protruding from the cast iron. If there is no attraction, you know it is stainless. If the steel is attracted to the magnet, it is mild steel or 400-series stainless.

400-series stainless will not be attracted as strongly as mild steel. You can use your judgement there. Try a mild steel nut or other screw next to the magnet. Compare it to the pull you feel when it is near the broken screw. If you can't tell the difference, it is probably a carbon steel screw.

If they are stainless, I would make an effort to grab whatever is sticking out with vise grips and work them out that way. The less you have to drill stainless, the better. The good news is if they are stainless you should be able to break them free with penetrating oil easier than rusted-in steel screws.

Good luck, and I hope you have a merry Christmas.

 

[hhsixzz]

I found a kind welder that tried everything but eventually the screws broke so he drilled them out and retapped the threads and kept them M6.

He wanted nothing for the job!

Must have been Father Christmas in disguise I told him

 

[begreen]

Drilling out and retapping it the right way to do it. Once one is set up for the process, it doesn't take too long.

 

[Uschi]

Thank you I will try your advice and report back, now I know what to do for Christmas!

[EDIT]

Is there a way to tell if the screws are steel or stainless steel?

Steel is magnetic, Stainless is not magnetic.
Wire brushing will usually polish a good shine on Stainless and regular stell will be more dull and hard to polish.
The magnet is the best test.