Southbend broken bolt problem please help

[Walter Laich]

I'm totally ignorant on all of this so help me out with a question:
.
why not just drill out to a larger size and retap the hole? Want to learn here, not be a smart-a$$

[oneokie]

The big issue is the broken ezeout and punch that are in the broken bolt at present.

[JSnover]

Generally best to save the existing thread if you can. In this case a larger bolt may not be an option.

[Walter Laich]

could you come in from other side?

[bhop]

no its a blind hole and to drill from other side would mean drilling through about 6" of the bed and thats a no go because that would weaken it way too much

[Walter Laich]

thanks--shows you what I don't know
good luck with this.

[bob208]

two weeks. by now I would have found a place to edm it out.

[bob208]

two weeks. by now I would have found a place to edm it out. some times you have to belly up to the bar and pay the price.

[bhop]

two weeks. by now I would have found a place to edm it out. some times you have to belly up to the bar and pay the price.

well considering i work 11 hours a day 5 days a week i really only have had 4 days to work on it. much less tear the whole thing apart to be able to load it up. today was actually supposed to be my day off but guess where im writing this post at, yep at work.

[bob208]

I was not trying to give you a hard time. just stating from my point of view. to me the lathe being out of service for two weeks would cost me more then paying to get the job done.

[bhop]

Ok my bad. I have another lathe so I can still get stuff done

[Walter Laich]

any up-date?

[bhop]

not yet i havent had a day off in almost a month

[Cap'n Morgan]

Drill & tap a new hole next to the old one. Life is too short to fiddle away on a broken bolt...

[oldlongbeard]

1. Take pencil grinder with carbide flat burr/endmill. Get the top of what is left in there as flat as you can.
2. Make a mild steel tube as thick wall as you can, and still get a welding rod inside..... Just long enough so it is proud of the surface by 1/2-3/4". (Larger bolts we always use black iron pipe, but this looks pretty small.)
3. Place your tube on top, held with vise grip by a partner, FLAT DOWN AGAINST stuck bolt. Stick your rod inside, and fill with weld..... have that beeswax candle mentioned earlier RIGHT there. Melt it in on the outside.
4. While still hot, remove all with pipe wrench/vise grips.
5. If this does not work, you are "screwed" (pun intended)..... and will need to use aforementioned and pictured portable tap burner. If it does work, you can thank the Guru of broken bolts...... don't become one- it ain't a very appealing title.

Greg in West Mitten

[oldred]

1. Take pencil grinder with carbide flat burr/endmill. Get the top of what is left in there as flat as you can.
2. Make a mild steel tube as thick wall as you can, and still get a welding rod inside..... Just long enough so it is proud of the surface by 1/2-3/4". (Larger bolts we always use black iron pipe, but this looks pretty small.)
3. Place your tube on top, held with vise grip by a partner, FLAT DOWN AGAINST stuck bolt. Stick your rod inside, and fill with weld..... have that beeswax candle mentioned earlier RIGHT there. Melt it in on the outside.
4. While still hot, remove all with pipe wrench/vise grips.
5. If this does not work, you are "screwed" (pun intended)..... and will need to use aforementioned and pictured portable tap burner. If it does work, you can thank the Guru of broken bolts...... don't become one- it ain't a very appealing title.

Greg in West Mitten

I have used that method many times on larger bolts (probably dozens of times on a particular job that happened quite often at work) and even some of the size the OP is dealing with, it does work quite well but I would hesitate to recommend that in this case. First it takes a lot of experience to get it right and we don't know the if the OP is an accomplished welder (he may very well be!) and the consequences of making a mistake here could be disaster! Bear in mind this is a precision machined iron casting likely surface hardened and if the arc strays onto the casting and/or the tube burns through or any other scenario occurs where the weld makes contact with the iron the problem will increase by orders of magnitude. Even a tiny area (especially in the thread area) of the steel welded onto the iron casting will present a major problem, this spot of steel/iron casting mix will be much too hard to remove by anything short of grinding. A small spot of steel weld mixed with cast iron is so hard it can't be cut with any normal cutting tool and will strip the teeth right off of a carbide burr, ask me how I learned this!!!! Add to this the possibility of creating stress in the hardened surface that could easily lead to cracking around the weld area.


Also we have a difference of opinion on trying to remove it while still hot, this is ONLY a difference of opinion and I am not saying you are wrong and I am right just that we apparently see this from different angles. While heating a part to remove a bolt is a very common way to successfully accomplish the task the goal is to heat the surrounding metal while keeping the bolt as cool as possible thus expanding the hole while keeping the bolt from expanding as much as is practical. By heating the bolt from welding it will have expanded in the hole while the cooler surrounding metal will remain much as it was thus resulting in an even tighter fit. Once cooled however the bolt will often become looser than before it was welded due to the crushing effect on rust/debris between the threads while still hot/expanded, some of this effect is apparent immediately but becomes even more so as the bolt shrinks from cooling. Hot bolt expanded in the hole vs shrunk cooled bolt, which should be looser?

Mixing scrap cast iron into the weld puddle to form globs of steel mixed with the high carbon cast iron welded onto a high wear surface was once the way hard facing was done and is still today a very economical way of producing a very highly wear resistant surface. That is providing cracking of this surface won't matter because this method is highly prone to cracking, if the cracking does not matter then this method is much cheaper than using the expensive hard facing rods and often works just as good. However it would be the LAST thing the OP would want to happen to his cast iron lathe bed even on a tiny scale and with a bolt that size the risk of this happening could be more than just slight!