Can’t Remove Screw in Mast

[surfstud31]

Hi all - my Beneteau sailboat is 25 years old and has an in-mast furling system. I am replacing the main sail and furling line. But for the life of me I cannot get the furling line out because the screw that holds the line in the mast is stuck tight. It’s just a large regular screw (not Philips head) and trying to turn it with a large screwdriver is not working. I don’t think this screw has been touched in 25 years. Yet there is no apparent rust visible. It just refuses to budge at all. I’ve tried banging it, vice-grips, PB blaster, a heat gun, and nothing works. I even broke the snake neck of my Dremel trying to grind the screw more square so I could try to get it out with a socket or vice grip.
I can drill it out if I have to but I am trying to keep it intact for future use. Yet I don’t see any other option at this point. I guess I could replace it with a bolt from West Marine but idk if they’ll have the right size & length.
Any advice would be appreciated.

 

[jssailem]

You know what they say about pictures.
Is it stainless screw in aluminum? Is it stainless in stainless?
Sometimes things are galled and have to be drilled. Sometimes an impact driver can free it up. All of this is best guess.

 

[Kings Gambit]

If stainless in aluminum try “basting” it with a 10% or so vinegar in water solution over a few days. Let it soak into the threads if possible. If there is enough penetration, the vinegar & water should eventually dissolve, or at least loosen, the “salt cake” that is jamming the threads. Also, if you decide to drill after the above treatment, use a left-hand bit. As it drills in, it backs out the screw. After half way in or so, the screw might back out entirely, leaving the original threaded hole for the replacement screw, etc. Of course, the screw is destroyed.

 

[Rich Stidger]

I have had good luck when using a battery operated impact driver tool. The hammering and torque in combination works quite often. You must have a tightly fitting bit to engage the screw. My unit is a Ryobi Driver-Drill, but there are many other brands also.

I have also broken screws by just applying torque with a screwdriver, so for a fastener that is stuck, I go for the impact driver.

 

[surfstud31]

Thanks guys - both good ideas. I’m on my way now to buy an impact driver to see if that does the trick. Probably a good idea to have an impact driver in my tool collection anyway. Let’s see if that works.

 

[capta]

At best, spray with a penetrant many times a day for days. It probably won't help, but worth a try.
If it is just not going to come out, then I would suggest you cut the head off at 90 degrees to the shaft so you have a flat surface to begin drilling in. A fractured screw surface is hard to start a center hole in.

 

[Kings Gambit]

If the screw head snaps off, you’ll be able to better apply the vinegar! Also, will make it much easier to drill. Plan A, then Plan B if needed. Good luck.

 

[Kings Gambit]

A fractured screw surface is hard to start a center hole in.

Maybe use a punch if that happens.

 

[BigEasy]

Recently had a struggle trying to remove a toe rail sheave, for my headsail, that was attached to the rail with stainless button head torx screws. After a few days of treating with PB blaster, I finally deformed the torx socket on the screw head. Before attempting to drill out the screw, I had enough access to cut a slot across the face of the button head and used a large straight blade screw driver and a pair of vise grip pliers attached to the shaft of the screwdriver to back out the screw. Using lots of vertical force to engage the slot on the screw head and the mechanical advantage of the vise grips, the screw finally broke loose. Don't know how much clearance you have to work on your application; however, the impact driver may work before you have to start drilling it out. Hopefully, you wont have to tap new threads, however, that may be a necessity. I was able to order replacement 316ss screws from McMaster Carr. They have a great selection of all types of screws in both sae and metric threads. Don't forget to apply Tef Gel or Lanacote to the new screws to prevent them from seizing again. Good luck!

 

[capta]

Maybe use a punch if that happens.

It's tough to use a punch when the surface isn't flat, to get a good center hole. You'd use a punch anyway.

 

[surfstud31]

Well, I got it turn a quarter of a turn with the impact driver and now it won’t move. I can get a pretty good lock on it with the impact driver but I can’t give it full speed. Still, it should give way. This is bizarre. I’ll try the vinegar and more PB blaster, etc but I figured once I got it initially started that it would give way but it hasn’t.

 

[Richard19068]

Well, I got it turn a quarter of a turn with the impact driver and now it won’t move.

I assume you then tried to turn it back in that 1/4 turn and try to work it back and forth?

 

[Brian D]

King's got it. If you keep trying to unscrew it, you will eventually snap off the head. Best bet, don't fight it. Get a hack saw and go at it. Make sure to tape the mast so as not to damage it. Then drill out the rest of the screw with a bit that is a wee bit bigger than the screw. i assume your mast is aluminum, so get some aluminum epoxy putty and fill in the hole. Re-drill and put in a new screw.

JMHO

 

[Rich Stidger]

Excellent that you got it moving. Now the PB Blaster or vinegar (pick your poison) can much more easier penetrate the threads. Apply the liquid and then work the screw as gentle as possible back and forth. Have patience. This is probably a stainless screw and if you have to drill it out it will be a difficult job. Much easier to gently ease it out.

 

[BigEasy]

I assume you then tried to turn it back in that 1/4 turn and try to work it back and forth?

Respray with PB Blaster, let is soak for a while & work screw in and out a patiently. Dont want to break it off at this point, now that you have it moving. Had to do the same with my toe rail sheave. Let the PB Blast do its thing to break down the corrosion products.

 

[DougM]

I want to hijack this thread for a minute: Anybody have a suggestion for extracting a small hardened socket head set screw with a fractured hex socket from an aluminum block? PB blaster and an ez out aren’t working.

 

[surfstud31]

I’m going to try and heat the aluminum mast around the screw. Aluminum heats up faster than steel and this might loosen the screw more. The problem if I try to heat the screw is that it melts the rope that the screw is holding in place. I’m afraid that will just make things worse. But there is no question that I’m dealing with galvanic corrosion and it’s a thought nut to crack.

 

[Kings Gambit]

I’m going to try and heat the aluminum mast around the screw. Aluminum heats up faster than steel and this might loosen the screw more. The problem if I try to heat the screw is that it melts the rope that the screw is holding in place. I’m afraid that will just make things worse. But there is no question that I’m dealing with galvanic corrosion and it’s a thought nut to crack.

Why is there no question? What do you see? Most of the time this is the result of caking & build-up of lime salts/deposits that foul the threads and basically “cement” the two pieces together. One.“fix” is to dissolve/loosen the deposits using acetic acid (vinegar solution), if possible, and then try to work out the screw. I’ve this done a dozen times. Eventually, usually, I get the screw out; but if not, I drill with a left-hand bit. SS fasteners are hard on the outside “skin”, but not internally. Once through the skin drilling is “easy.” But it’s never galvanic that I can tell. BTW. Your mast will absorb a lot of heat and disperse it away from where you apply it, etc. It may or may not work. More likely, you will twist off the head of the screw. Blaster dissolves rusts, not salts. That’s why it is not working.

 

[Tedd]

I’m going to try and heat the aluminum mast around the screw. Aluminum heats up faster than steel and this might loosen the screw more.

It's not that aluminum heats up faster, it's that it has a higher thermal expansion coefficient than the steel. You need to be careful to heat up the aluminum in a large area around the hole. If you heat too small of an area around the hole, then the hole will actually get smaller.

 

[leo310]

I had the same problem and had to drill and tap even after using PB and heat.