Removing Bolt from Base of Mast

[joker4142]

In the process of purchasing my first sailboat. A 365 Pearson Ketch. Lot of little jobs to be done. One of the first jobs is this. Base plate under mast has one old rusted bolt that needs to be replaced. Now, I will soak it for several days in penetrating oil in hopes that it will turn. Most likely will go at it with a vise grip pliers. Worst-case scenario is the head of the bolt snaps off. Now how am I to get what’s left out with out damaging threads. If the threads get damaged then what? Hire a machinist to re-tap the threads. You’re thought please.

[Zednotzee]

Heat is your friend in this case. I would try without it at first, of course, but if it feels like you're about to turn the corners off the bolt, heat it up with a propane torch.

[brankin]

If you can get an impact driver on the head of the bolt, then gently tighten and then loosen. Also hit the head of the bolt with a hammer. Keep repeating until the vibration has broken rust free and then the bolt will come out. Heat is also a good choice as the heat will expand the metal. I like to heat it very hot and then let it cool for several cycles. The expansion and contraction breaks the grip of the rust on the threads. If you think you will break off the bolt, make sure you have straight access will a drill and bit before you put that much pressure on the bolt. If you break off the bolt, drill out the interior of the bolt using slow RPM's with medium pressure on the bit. If you break off the bit, you are screwed. Use larger drill bits until it is just about the size of the interior of the thread on the bolt. You will need a sample of the bolt to determine the final size of the drill bit. Use a tap and clean the old bolt threads out of the seat. If your bit walks on the bolt and you over size the hole, you can opt for drilling and tapping a new hole slightly larger or perhaps use a helicoil to replace the threads.
If this spooks you, then find someone who has done this before to hold your hand. The first time is always the worst. PS only put vicegrips on a bolt as a last resort.

[capngeo]

Originally Posted by brankin

If you can get an impact driver on the head of the bolt, then gently tighten and then loosen. Also hit the head of the bolt with a hammer. Keep repeating until the vibration has broken rust free and then the bolt will come out. Heat is also a good choice as the heat will expand the metal. I like to heat it very hot and then let it cool for several cycles. The expansion and contraction breaks the grip of the rust on the threads. If you think you will break off the bolt, make sure you have straight access will a drill and bit before you put that much pressure on the bolt. If you break off the bolt, drill out the interior of the bolt using slow RPM's with medium pressure on the bit. If you break off the bit, you are screwed. Use larger drill bits until it is just about the size of the interior of the thread on the bolt. You will need a sample of the bolt to determine the final size of the drill bit. Use a tap and clean the old bolt threads out of the seat. If your bit walks on the bolt and you over size the hole, you can opt for drilling and tapping a new hole slightly larger or perhaps use a helicoil to replace the threads.
If this spooks you, then find someone who has done this before to hold your hand. The first time is always the worst. PS only put vicegrips on a bolt as a last resort.

+1, but get some left-hand bits to do the drilling

[ggray]

If you wring it off and have to drill, a left hand drill bit might help extraction.

[osirissail]

First question is: Is the Bolt threaded into the base plate - or - does it pass through the base plate and have a nut on the other side?

- - If there is a nut on the other side then shearing off; cutting off with a cut-off wheel; or chiseling the head off the bolt is the easiest way. Then punch the remainder of the bolt and its nut out of the bolt hole. Clean everything up and install a new bolt and nut but be sure to use Lan-o-cote or any anhydrous lanolin on the bolt and threads and nut.
- - If the bolt is threaded into the base plate and the head shears off when trying to remove it. Then drill the center of the bolt out using a cobalt drill with cutting oil and low rpm's. Then use a reverse thread extractor to remove the remainder of the bolt. Or, use progressively large drills to remove the maximum amount of the bolt shank from the hole and use taps to get the rest of the bolt out of the base plate threads.

[skipmac]

Not certain about the Pearson 365 but many Pearsons from the eighties were built with a steel mast step on the keel which is incompatible with the aluminum mast, especially sitting in the bilge. If yours is like this it is very likely that the base of the mast is corroded.

I hauled my 1984 Pearson 422 last last year and had the mast pulled. Have to cut about 2 1/2" off the bottom of the mast that is almost completely eaten away. There were three other Pearsons at the same yard when I hauled. Two of them were doing the same thing, the third had already done it. Best long term fix is to off the steel step and replace with aluminum or plastic like UHMWPE.

Not sure where the bolt is you describe. The only bolts at the base of my mast were the four holding the steel step into the keel. How about a picture?

Otherwise, Osirissail's suggestions sound good to me.

[skipmac]

By the way, best penetrating oil PB Blaster. Be careful not to get it on any seals or similar on your engine, pumps etc. It will eat them up.