| Re: Any tips for drilling out a broken beam bolt???
[Re: dacarls]
#158766 10/30/08 07:30 PM 10/30/08 07:30 PM |
Joined: Feb 2007 Posts: 266 UK Cheshirecatman
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Posts: 266 UK | www.electroarc.comHere is a serious guaranteed solution. Melt your way through the bolt with an electric arc! Note this may be good if your ship is made of stainless steel. If fiberglass or carbon is nearby-- not so much! WHoooosh! Also known as spark erosion. Great for brake callipers (especially sheared off bleed nipples) but as you say not for cat beam bolts. Cheshirecatman | | | Re: Any tips for drilling out a broken beam bolt???
[Re: Team_Cat_Fever]
#252040 09/06/12 02:39 PM 09/06/12 02:39 PM |
Joined: Mar 2011 Posts: 50 Hawaii timtower
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Posts: 50 Hawaii | I’m a pro at resurrecting dead threads. Anyway, here’s my problem, I broke a bunch of the 3/8” stainless beam bolts in my N20 taking the boat apart and now I’m screwed (no pun intended). Attempt 1) Used a fairly small diameter titanium drill bit to drill into the first broken beam bolt. I was making good progress but then the drill bit broke. Then I proceeded to use larger diameter drill bits to continue to drill into the bolt, but the broken titanium drill bit dulled the new drill bits. I suppose if I just keep going through drill bits, I’ll get to the end eventually. Any thoughts on this problem? Attempt 2) For the second broken beam bolt, I switched out titanium drill bits for carbide drill bits with hope that if I break another drill bit, it’ll be easier to drill through a carbide drill bit. Ended up drilling through the bolt, but realized I wasn’t even close to center on the bottom of the bolt. Now, I don’t want to keep going up in size because I’ll chew into the fiberglass. Maybe I can use a small diamond tip dremel and wear away at the sides of the bolt? Besides the two beam bolts that I’ve already f’d up, I have two more to go. I’m thinking with the next two, I’ll use this product… http://www.quikcenter.com/ Thoughts? If worse comes to worse, my plan would be to cut out the broken beam bolts from the hull and 5200 new inserts into the hull, but that seems sketchy. Tim | | | Re: Any tips for drilling out a broken beam bolt???
[Re: Team_Cat_Fever]
#252049 09/06/12 03:13 PM 09/06/12 03:13 PM |
Joined: Sep 2002 Posts: 3,224 Roanoke Island ,N.C. Team_Cat_Fever OP
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Posts: 3,224 Roanoke Island ,N.C. | All I can offer is what is in this thread. Mugrace72's advice pretty much covers your options. If it all goes to shite and you need to break the plates out just use a punch straight down on them. That is not a great option, sucks really, but it broke out on me while I was working on it so I had no choice. You do have to be able to get in there to put them back and that's a whole 'nother P.I.A.
"I said, now, I said ,pay attention boy!"
The cure for anything is salt water - sweat, tears, or the sea Isak Dinesen If a man is to be obsessed by something.... I suppose a boat is as good as anything... perhaps a bit better than most. E. B. White
| | | Re: Any tips for drilling out a broken beam bolt???
[Re: Team_Cat_Fever]
#252050 09/06/12 03:24 PM 09/06/12 03:24 PM |
Joined: Mar 2011 Posts: 50 Hawaii timtower
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Posts: 50 Hawaii | The two bolts I was working on were the rear beam bolts. I couldn't feel a backing plate. Are they glassed straight into the hull? Also, what do the backing plates do? There's no nut on the other side of them.
Last edited by timtower; 09/06/12 03:25 PM.
| | | Re: Any tips for drilling out a broken beam bolt???
[Re: Team_Cat_Fever]
#252051 09/06/12 03:37 PM 09/06/12 03:37 PM |
Joined: Aug 2011 Posts: 774 Greenville SC bacho
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Posts: 774 Greenville SC | The bolts are threaded into a piece of SS or AL that is glassed into the deck as shown on the first page. Are you able to reach the undersides of your bolts through deck hatches?
Your drill going out the bottom of the bolt can be a problem, but you should not hit glass. If you have not already, start soaking them in a penetrant oil. Because the bolts are seized, your gonna have a really hard time using any sort of extractor until you do something to make the bolts loosen up. Heat and PB blaster normally do the trick for me, but heat is not a option for you.
I would use a cobalt drill bit, keep it REALLY lubricated and very centered and keep working up in size until your just slightly smaller than the minor diameter of the threads. Then something like a scribe can make short work of getting the threads out. Normally I do this on a mill and it works great.
Last edited by bacho; 09/06/12 03:39 PM.
| | | Re: Any tips for drilling out a broken beam bolt???
[Re: Team_Cat_Fever]
#252055 09/06/12 04:33 PM 09/06/12 04:33 PM |
Joined: Sep 2002 Posts: 3,224 Roanoke Island ,N.C. Team_Cat_Fever OP
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Posts: 3,224 Roanoke Island ,N.C. | Tim, They are aluminum which is what causes the problem .Galvanic corrosion. Use Tefgel when you re-install. If you are working at the rear you may very well want to build up that spot as a couple of boats had catastrophic hull failure due to the thickness of the laminate under the rear beam.If you are replacing the plates I'd replace it with stainless.
"I said, now, I said ,pay attention boy!"
The cure for anything is salt water - sweat, tears, or the sea Isak Dinesen If a man is to be obsessed by something.... I suppose a boat is as good as anything... perhaps a bit better than most. E. B. White
| | | Re: Any tips for drilling out a broken beam bolt???
[Re: Team_Cat_Fever]
#252059 09/06/12 06:27 PM 09/06/12 06:27 PM |
Joined: May 2006 Posts: 1,383 Kingston SE South Australia JeffS
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Posts: 1,383 Kingston SE South Australia | My mechanic swears by freeze spray you can buy in a can. I think you are supposed to spray it on before you break off the bolt but it works by instantly shrinking the bolt a fraction thereby breaking the rust bond. If you put normal nuts on the back of the backing plates how are you planning to stop them rotating when you tighten your beam bolts in the future?
Jeff Southall Current boats Nacra 5.8 1703 Animal Scanning Services Nacra 5.8 1667 Ram Raider Nacra 18 Square Arrow 1576
| | | Re: Any tips for drilling out a broken beam bolt???
[Re: timtower]
#252063 09/06/12 09:36 PM 09/06/12 09:36 PM |
Joined: Jun 2001 Posts: 12,310 South Carolina Jake
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Posts: 12,310 South Carolina | If it all goes south, I'm considering putting in a big backing plate and just making them thru bolts instead of screw bolts which would be an easier repair. Would you guys recommend against that? Definitely going to use Tefgel. Definitely do this. There is no reason that plate needs to be laminated inside the sandwich construction of the hull. The bond only gets stronger if it's completely on the inside of the hull. Note, however, there is a bulkhead in this location and you may need to work around it. When you set the plate on the inside, make sure it is seated well in some thickened resin so it is making full contact with the fiberglass there.
Last edited by Jake; 09/06/12 09:37 PM.
Jake Kohl | | | Re: Any tips for drilling out a broken beam bolt???
[Re: Team_Cat_Fever]
#252074 09/07/12 10:08 AM 09/07/12 10:08 AM |
Joined: Jun 2001 Posts: 833 St. Louis, MO, Mike Hill
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Posts: 833 St. Louis, MO, | He is going to have to cut a hole in that bulkhead to get to the under side of those bolts. Going to have to be a pretty good size hole to get your whole hand through there.
Mike Hill N20 #1005
| | | Re: Any tips for drilling out a broken beam bolt???
[Re: JeffS]
#252075 09/07/12 10:11 AM 09/07/12 10:11 AM |
Joined: Jun 2001 Posts: 778 Houston carlbohannon
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Posts: 778 Houston | My mechanic swears by freeze spray you can buy in a can. I think you are supposed to spray it on before you break off the bolt but it works by instantly shrinking the bolt a fraction thereby breaking the rust bond. The accepted method of breaking rusty bolts free is to heat them up. There is a reason for this. The expansion or contraction of metal due to heat or cold is proportional to the original size of the hole or the bolt. Since the hole is slightly bigger than the bolt, if the bolt and the backing plate are the same material and you spray the spray the whole thing down so everything is at the same temperature, the hole will shrink more than the bolt and just clamp down on it. In this case the bolt is SS and the plate is AL. The linear rate of expansion for AL is ~4/3 that of SS. If you chill the plate and the bolt the hole will contract 4/3 faster than the bolt and probably make things worse. For a rusty steel nut and bolt(like on a car), using freeze spray can crush the rust and free things up. For a catamaran's beam bolts the "rust" is probably more like a super thick white goo. Chilling can compress the goo into the threads and make things worse. Sorry | | |
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