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Drilling out broken bolts in cast iron


MarksA-C

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Working on my 700 wonderboy I went to tighten the bolts on the BGB to the frame. They didn't tighten one bit. Went to remove them and 1 came out but was stripped pretty bad. Go to remove the other one and it snapped. Tried to get out 1 more and SNAP. 1 is left in and I can safely bet that its going to break like the rest. So to save this from becoming a parts tractor to a short-tempered youngin' like myself I am going to attempt drilling out the holes and retapping them. Is there anything I need to know about drilling these out? I know go from small to big and try to keep it centered on the bolt. Any information or help would be greatly appreciated. Mark-
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You could consider taking to it to a muffler shop. Those guys are experts are getting broken studs out. I think a lot of it is that they weld to the broken stud, that takes talent, the heat and cool cycle breaks it free.
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Drilling and using an easy-out is recommended before drilling out the bolt enough and tapping holes, especially in cast iron. The cast iron is a lot softer than the bolt and the frame. Tip #1, center punch the middle of the bolt before drilling, you want to have the center of the bolt drilled, not the threaded hole. Tip #2, don't buy your easy outs from Harbor Freight. Tip #3, use A LOT of penetrating oil. WD-40 PB Blaster etc. Tip #4, BE PATIENT!! Check and see if there is enough meat on the BGB just in case you are forced to drill and tap larger threads.
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I have gotten them out with oil and patience...a week of soaking, tapping with a hammer, maybe some heat, and then a lefthand drill bit spun them out. This has worked on both bgb's and tranny cases. Holds up a project, but sure feels good when it comes out!
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The very best way that is fast, easy, and pretty fool-proof is to use your mig welder to weld onto the end of each bolt. Build up enough to get a vise grips on the end. The heat is focused on the bolt. I've never had a bolt I couldn't get out this way. You can get them out in less than 10 minutes. I hope this helps.
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Orange is right... weld something onto it that you can grab and remove (after soaking with PB Blaster). My luck with EZ-outs is zero. They just break off wasting time and money.
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By far, the easiest I've experienced is welding a nut onto the end. The hole makes a perfect spot to get some heat into the broken bolt while affixing the nut; kills two birds with one stone! Then just use a socket to back the bolt right out. We have all the easy outs and means to drill and tap at work, but the nut method always, always gets the call. dOd
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Every broken bolt I have done has been a little different. But patience is a must. If you do not have much patience, or equipment it might be easier to get another BGB case and swap parts. If I were going to do it: 1. Remove box from tractor put on bench. 2. Strip out all seals gears etc. 3. Turn broken bolt side up. 4. Heat up case around studs with torch. 5. Liberally apply PB Blaster, Kroil, Evaporust. do not waste time with WD-40 6. Repeat. 7. Take small chisel and hammer, and try to tap it loose. If that works clean the treads with tap. Done If that does not work: Now is were many different techniques can be used. The last snapped bolt I fixed I mounted the case in my mini mill. Spot faced the broken bolt to make it flat. Center punched, and left hand drilled out the remaining bolt. Some times they will unscrew themselves. Other times you will need to collapse the bolt "sleeve" with a hammer and small chisel to remove. Clean out threads with tap. It all depends on what equipment you have on hand, or what a buddy may offer. There are many other ways to get them out, your results may vary etc......
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I agree with Orange, Use a mig welder, get a nut that is slightly larger than the broken bolt and weld the broken piece to the nut. I had to do this to 5 of the exhaust bolts in the heads of my 1929 Allis 20-35 model E and it works great. The weld will not attach to the cast part and the heat usually releases the stuck bolt on the first try. I only had to reweld on 1 of the broken bolts but it came out on the second try.
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The bolts are broken off well into the casing, far enough that I can't weld anything onto it. Going to finish tearing it apart this weekend hopefully.
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I am lucky as I have acess to the mill at work.If all else fails I put it in the mill, mill a small hole through the bolt then left hand drill or drill to size and tap.If you need a case I have a few here and can get it down to Brown deer for you . Bob
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