Any tips for drilling out a broken beam bolt???

It ain't "Drill,baby,drill" but I've gotta get a broken beam bolt out of the hull. Beam is off ,so I've got access. I got about 3/8" into the bolt and now ,my progress has slowed dramatically. Easy outs can't seem to get enough bite and round out,plus I'm deathly afraid of breaking one off in the hull. Any pearls of wisdom would be greatly appreciated.

Tawd

Never used a bolt extractor before but... it should do the job fine if used from the begining, curious if others used bolt extractors.

http://homerepair.about.com/od/interiorhomerepair/ss/screw_extractor.htm
http://en.wikipedia.org/wiki/Drill_bit#Screw_extractor

Regards,

Todd,

Having many years of expience with race cars and mechanical stuff in general....easy-outs usually only work when the bolt is not very tight in its hole.

Keep in mind that the extractor is usually smaller in diameter than the bolt that is stuck and that broke off to start with.

Once the extractor breaks, you are in much deeper s..t!

There are several techniques that might work. All are risky.

My first choice would be to make sure you have brand new drill bits. Try to get a small hole started dead center in the old bolt.

It is best to drill all the way though and then keep drilling larger and larger holes until you get to the minimum diameter of the theaded hole.

Usually by then, you can get a proper tap started and rethread the hole.

Another method that sometime works is to drill a pilot hole and the get a left-hand bit that is slightly smaller than the bolt minimum thead diameter. Often before you get too far the old bolt comes right out.

Left hand drill bits are available from the Snap-On or other tool trucks and certain hardware specialty stores. Also on line.

Once out, if the threads are damaged, you can repair the hole with a HeliCoil insert.

The key is to go slow and keep the drill centered and lubricated.....and SHARP.

We've all been there boy!

Only thing to add is I've always found cobalt steel drill bits to be better with stainless.

Cheshirecatman

Just whatever you do, don't break off the bit halfway through the bolt, it is very difficult to drill through a broken drill bit!

Find yourself a brand new set of good quality left-handed drills. Start with a small diameter, go all the way through the bolt (lubricate! Go slow! Stay centered! Don't break the drill!). Repeat with a slightly larger diameter, and then larger. Do not go larger than half the diameter of the bolt.

At some point the bolt is going to unscrew itself under the action of the drill. If it does not, it's then time to put a bolt extractor in the hole, taping it a few times with a hammer to make it bite and then turning it slowly counter clockwise. Using a bolt extractor is a tricky business, those tools are really strong but brittle, so *go slow*, take your time.

If the bolt extractor doesn't work, continue to drill larger and larger until you can get a tap in to rethread the hole

Thanks for the replies. I tackled it before I got to get back to the post. I must have been on the right track, cuz I did pretty much what everybody advised,especially Jack's(must be the car racin' mindset) including breaking a smaller bit off in the hole. Got it cleaned out and bought some ACE hardware cobalt bits and tried again, the bits were round in about 45 seconds,they suck don't buy them(that's all we have within 30 miles). Eventually with all the frappin' and banging and drillin' and easy outin' the backing plate came loose from the hull. Solved the stuck bolt problem but now I had to pop the foredeck (I-20)lid off. Got that accomplished with a few chips of the gel-coat at the edges. I got out the backing plate, put the bolt stump in a vise and got my backing plate free. Re-tapped it, 5200'ed it in it's former spot and clamped it with a bolt. I'll glass it tomorrow or monday.What a P.I.T.A. Aluminum backing plate and a stainless bolt. I put anti-corrosion spray and never seize on them when installed, but apparently it didn't last. It'll be tef-gel this time around.
Here's a couple of pics.

Here's some pics of forward in the hull, including flotation .

Jeeze...you did good. You don't need no stinkin' advice.

I'm always up for input.
What lubricant should be used for the drill bit, and should you go real slow or medium? Seems like everytime I oil up a drill bit it stops getting any bite and just spins. I was using Kroil.

Every bit and material has an ideal speed and pressure. I know none of them.

Lube is the same way. Some materials cut like butter with a little lube. Others just stop cutting.

It is FM, Todd...F..kin' Majic!

They have books.....

"They have books....."
That'd take too long. But contrary to what alot o' people think I read real good.

p.s. See ya at Steeplechase.

We are the only boat entered.

If you have the tef-gel use that for drill lube. Works great.

yeah, screw extractors / easy out = same thing. That sucks Todd! Good luck with it.

not enough time to read all replies before my laptop battery dies

had similar problem with broken brake caliper bolt on my motorbike

very carefully drilled out bolt stub with various sizes of drills until could just see the threads showing on the side my drill hole was closest too, drilling dead center very tricky

then used a dremel type tool with tiny diamond bits to take out even more material until threads could be seen all round

then after soaking in kero over night, used a sharp point to break out the remaining threads, if they wouldn't come a little more dremel etc etc

best bit was that the diamond bits were bought at the $1 shop!

[quote= should you go real slow or medium? Seems like everytime I oil up a drill bit it stops getting any bite and just spins. I was using Kroil. [/quote]

When I got cobalt drill bits they recommended slow speed for stainless, also they said it's not a good idea to cool them in liquid if they get very hot.

Craftsman GP Cutting Fluid works well.

http://www.sears.com/shc/s/p_10153_12605_00952329000P?vName=Tools&cName=HandTools,GeneralPurpose&sName=Bolt-Out,%20Taps%20&%20Dies&psid=FROOGLE01&sid=IDx20070921x00003a


I regularly have to cut out stainless bolts on the medical equipment I work on. It is bleached daily so corrosion is inevitable.


BUY LEFT HAND THREAD DRILL BITS!

As a rule of thumb the harder the material you are drilling, the slower speed you should use.

www.electroarc.com
Here 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

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

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.

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.

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.

Thanks Bach. Convienently the aft deck plate was pulling up on that side, so I removed it and can feel the bolts from underneath. It would probably behoove me to take a picture of it, the next chance I get. I'll try the PB blaster and quik center and see if that works with the two 'fresh' bolts next time.

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.

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.

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?

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.

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.

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

Actually, the rear beam bolts on my boat are aft of the first bulkhead, so I was able to at least feel them by taking off the aft deck plate. Not sure if they changed the build on later boats though.