Joined: Mar 22, 2017 Posts: 301 Location: Great Mills, MD
Posted: Thu Jun 08, 2017 10:07 pm Post subject: Help needed removing broken bolts
HI Guys,
Looking for some advice on how to remove some broken bolts. Almost all the little No. 8 bolts that hold the vent plate on the top of my fuel tank snapped off when I took the vent plate off. I really don't want to screw up the threaded holes, so I stopped messing with it to see what you guys suggest.
I did file all the broken bolts flat to centerpunch them, as I was planning to start drilling them out. I tried to drill out the first one and the center punch wasn't perfectly centered and I can't remove what's left of the bolt now. Since there's now an off center hole in the center of the bolt I can't put a tap in the hole and cut new threads without messing up the original threads.
I did stop at the hardware store on the way from work today and picked up a real small extractor and a 1/8" left handed drill bit. Before I make a mess out of the rest of the bolts does anyone have any advice on removing these broken bolts successfully?
Bob, there are no secret ways to do this. When you screw one up you weld the hole shut and redrill it. The center punch is not what guarantees a well centered drilled hole. The operator of the drill must practice long periods and learn the fine art of walking the drill to where he wants it. The center punched prick mark is just a starting place for your bit. I use whatever drill is called out in the drill chart for an 8-32" threaded tap.
Joined: May 30, 2014 Posts: 3447 Location: Texas Hill Country
Posted: Fri Jun 09, 2017 5:55 am Post subject:
As Wes says, the center punch is no guarantee. You sure need a very
sharp punch as well. I've done as he suggests walking the bit then enlarging
the hole a couple bit sizes at a time until I get close to the base
metal. Then get a very sharp pin punch and try and get the edge of the
broken screw with it, tapping towards the center. If you've reduced the thickness enough it should be thin enough to begin peeling it back
away from the threads. Work your way all the way around.
If you have a Dremel you might try hand milling the hole back to near center
with one of those burrs.
When using an Easy Out use plenty of Liquid Wrench and let it soak.
You may have to let soak overnight.
Joined: Mar 28, 2008 Posts: 353 Location: BrOoKlYn
Posted: Fri Jun 09, 2017 8:05 am Post subject:
The port of the vent plate is through-hole threaded. After a good soaking with PB blaster or similar, and before you attempt to mechanically extract, you might have some luck using a pair of bent needle nose pliers. Slowly feeding the broken remains from the inside (feed in or out).
Joined: Mar 22, 2017 Posts: 301 Location: Great Mills, MD
Posted: Fri Jun 09, 2017 9:06 am Post subject:
Hi Guys,
Thanks. My problem was I used a drill bit that was too big....meaning I went for the whole ball of wax on the first try......so trying to walk the hole toward center would have caused the bit to hit the threads on the top of the hole as I angled the bit. I need to start smaller and work my way up. I also have enough material on most of the broken bolts sticking up to grind a slot in the bolt and try a screwdriver..........but I got a feeling if they're that stuck that method won't work either.
I saw a cool product online last night (info is on my tablet so I don't have it handy) that I'm going to see if my hardware store carries. I also have a good machinist friend who told me awhile back a sure-fire way to remove broken bolts using heat and cold. I don't remember if it was heat the hole and cool the bolt or vice versa, but it went against intuition and he guaranteed success. I'm not going to rush and screw any more bolts up.........so I'll report back in a bit.
Use the simple chart I posted for you. Start two or three sizes below the bit used to drill a fresh hole for the tap size you are working on. IE for your 8-32 screw start with a #31 drill bit. Then an 1/8 and then a #30 bit. Then put the drill down and start the manual labor system of chipping away screw threads.
Note: you probably are not familiar with numbered and lettered bits so this would be a good time to add a set of each to your shop table!
One of the most fool proof methods used to recover from your situation is to grind the top side smooth, gain access to the threaded stump's back side and attach a pair of vice grips to the stump and continue screwing it down and out (NOT BACK UP THROUGH THE HOLE). _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Mar 22, 2017 Posts: 301 Location: Great Mills, MD
Posted: Fri Jun 09, 2017 10:57 am Post subject:
Thanks Wes. I do have numbered bits.......just not the chart you provided. The backside of the holes are not accessible, as the gas tank seems to have a depression ring that the outer (topside ring) is attached to. I suspect that was to prevent fuel from leaking past the bolt threads. I've got a nice long weekend to figure this out.
Bring's up another issue. If you accidentally drill thru those seal bowls you will have to seal them back up when you are done and RTV doesn't do the job! Use a real fuel system sealer on them. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
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