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View Full Version : How do I repair stripped screw holes?



John P Lebens
01-26-2010, 12:18 AM
Some of the wood screws on our boat have stripped out their threads. I need to either use larger screws (which would require a lot of countersinking brass fittings) or fill and redrill the holes so I can use the original sized screw.

Any suggestions?

David G
01-26-2010, 12:39 AM
Hi John,

My typical solution is to squirt a little glue in the oversized hole, and jamb it full of round toothpicks. On your boat, in most locations, Titebond III would be fine. Epoxy or resorcinol would be better. If the holes are REALLY big, I might whittle myself an oversized "toothpick" out of some more durable wood. Seat the toothpicks by tapping with a hammer, and slice them off flush with the surface. You can even go right ahead and resink the screw at that point, if you're in a hurry.

G'luck

wizbang 13
01-26-2010, 07:07 AM
Gonna get a real nice paintjob on the end grain of toothpicks,oh ya. How did these buggers get stripped, are you taking them out ,whats doing?

AndreasJordahlRhude
01-26-2010, 11:08 AM
Drill em out, plug 'em with a dowel or wood plug of similar density glued in. Let it dry, cut it off flush, and then redrill for your screw.

Andreas

outofthenorm
01-26-2010, 11:19 AM
Do exactly what Andreas said. I've done dozens and dozens like that and never had a failure of any kind. Use epoxy and never worry about it.

- Norm

John P Lebens
01-26-2010, 11:22 AM
The problem is with both stanchions and with some brass strip windshield surrounds. The brass is countersunk for a #6 screw head and the hole is sized for a number 8. I have a choice of countersinking the brass for a #8 or shrinking the hole somehow.

The stanchion threads are pretty good, but it looks like some really long screws were used on one side - I suspect because the original shorter ones were pulled out by a collision. The threads nearest the deck are gone.

Both of these will be covered when they are done.

Lew Barrett
01-26-2010, 11:34 AM
You can plug as Andreas says (and much as I usually agree with him and Norm this system is OK...sometimes) but I recommend a system such as David suggests but with a variation especially for the stanchions. The problem with filling with a plug is that you will be screwing into end grain. For your stanchions, a more secure method will prove better in the long run.

When I pulled mine (stanchions) I did a lot of research (and had a lot of discussion here) about the best way to accomplish the task and finally came up with the following:

Go get yourself a bag of bamboo skewers. Mix up some epoxy. Dunk the skewers into the epoxy and jam them into the hole. Put in as many skewers as will fit; just shove 'em in and break them off until the hole is stuffed with bamboo and epoxy.

That screw won't spin in the hole, guaranteed. And for fasteners that must attach critical hardware like stanchions, it doesn't matter how they will finish out because nobody will ever see them. If you want, I can show pictures, but using bungs or plugs to repair the holes for an item like a stanchion that takes lateral thrust will not be as secure as filling with the bamboo stakes. For small hardware that doesn't come under pressure, I suppose you can use whatever system you like. But for deck fittings that get used and tugged on, you should think it through.

wizbang 13
01-26-2010, 11:41 AM
overdrill,fill with 407 west,after setting ...carefully drill "nice" holes in the epoxe for new screws of the same size

John P Lebens
01-26-2010, 11:25 PM
Ok - re the bamboo skewers - should I buy them at Sur le Table or Williams Sonoma?

G. Schollmeier
01-27-2010, 12:30 AM
http://westsystem.com/ss/bonding-hardware/
Gary :D

yawldoingood
01-27-2010, 08:41 AM
I highly recommend bamboo skewers as another member mentioned. Bamboo is the "other" hardwood, it is really really tough, does very well in water, it's easy to work with, and is very cheap. Just go to any Asian grocer and get some. Drill the hole to fit the skewer, glue it in with epoxy. cut it off after it's dry, drill it again and your back to a new hole.

Good luck

paladin
01-27-2010, 09:21 AM
The bamboo skewers is good, chopsticks are available at most asian grocers...and are cheap as they are considered disposable. Bamboo is great for other things such as trunnels in blocks etc.

Todd D
01-27-2010, 09:22 AM
I get a piece of the same wood, or at least the same kind of wood and cut bungs from it. At the repair site I use a forstner bit to drill the screw hole out to the diameter of the bungs. Finally I wet the hole and the bungs out with epoxy and tap as many bungs into the hole as it takes to fill the hole. I take pains to make sure the bung grain is aligned with the grain of the surrounding wood.

Wooden Boat Fittings
01-27-2010, 07:16 PM
.
And I've used both methods successfully too. What you don't want to do is drill out and then insert a dowel, as the dowel's end-grain invites water ingress and later rot. (My sundial's stanchion is the main masthead of a ketch whose mast at one stage was repaired in this fashion, and which eventually snapped right off, necessitating replacement of the entire mast....)

Mike

Lew Barrett
01-27-2010, 08:23 PM
.
And I've used both methods successfully too. What you don't want to do is drill out and then insert a dowel, as the dowel's end-grain invites water ingress and later rot.

Mike

You have that right Mike! Dowels suck unless one likes doing things more than once

seo
01-28-2010, 08:05 PM
There are two problems with using dowels:
1) Dowels (and toothpicks) are made of birch. Birch has some good things about it, but it rots like crazy.
2) The grain in dowels runs lengthwise, which means you'll be fastening into endgrain. Not as important as #1, but not ideal.

The best solution is to overdrill the screw hole until you're into good wood. Usually 3/8 or 1/2 will do it. The use a Fuller plug cutter to cut out plugs of the same wood type, and set them in epoxy. Take some care that there isn't an air pocket at the bottom of the hole.
The advantages of this is that the repair material is as rot-resistant as the original, it's not end grain, and if some part of the repair is visible, if you take care to align the grain of the bung with the wood, it won't look terrible.

JimConlin
01-28-2010, 08:57 PM
For the lightly loaded screw whose bite has faded, often just a bit of epoxy and filler will make things OK.

For screws with any load on them, to my simple brain, there are four generic approaches:

Replace the whole part. Not often practical.

Put some wood into the hole vertically. The objections here are that the grain of the inserted material is a good conduit for moisture to the bottom of the hole and that screws don't grip well in end-grain.

Bore out a cylindrical crater and glue in a stack of wood having the same grain orientation as the host material. My concern here is that after you drill out half of it for the new fastener, it's hard to see the shreds of wood that are left as having any structural value.

Bore out something greater than the diameter of the mush or the original fastening and cast an epoxy composite plug to receive the fastening. See the West System link above. Using this approach, you have control over the strength of the connection. When Hodgdon Bros. is hanging the headstay of a 100' sailboat on a potted fastener. I feel a little more confident in this.

potterer
01-30-2010, 06:31 AM
. . . for deck fittings that get used and tugged on, you should think it through.

Shouldn't you also drill it through, insert a bolt, washers and nut(s) with a backing pad?

I think I would prefer no stanchions to stanchions held with screws.

On my boat the window (not windshield like John's) surrounds are through bolted.

John P Lebens
01-30-2010, 09:54 AM
The issue with this vessel is access to install bolts. Otherwise I agree that bolts would be best.

Lew Barrett
01-30-2010, 12:28 PM
Shouldn't you also drill it through, insert a bolt, washers and nut(s) with a backing pad?
.


The issue with this vessel is access to install bolts. Otherwise I agree that bolts would be best.

As John says, you don't always have a choice, In fact, if you can through bolt it all, none of this conversation ever needs to happen.

There are ways to secure deck fittings for years of use without through bolting, especially if the fittings involved take shear loads. But most all agree, through bolted is best for fittings under heavy load. I'm confident John didn't have that option.

KAIROS
02-02-2010, 11:28 AM
I rebedded my teak-plank-on-edge toerail last year. About 120 bunged #14x4" screws. The thread holes were okay, but I knew the toe rail gets really torqued from docks etc. since it is on edge. Some of the SB screws showed corrosion from inside from water ingress. Rails last bedded in 1979. Screws go through teak deck and into edge of sheer plank. I decided just to deal with all of the holes systematically regardless of condition.

Took one of the extracted bronze screws and ground the threads off, leaving the shank. Poked very stiff epoxy w/ woodflower (stiff peanut butter consistency) into the holes. Then tapped the screw shank into each which pushed out the excess and forced the epoxy into any residual space....leaving the shank space clear. Cleaned around the holes. Let epoxy cure.

Tested new screws in a couple of holes to be sure the epoxy had not slumped down inside. Nice tight fit but not too tight. Then rebedded, installed new screws and bungs. Before, if you torqued on the toerail, you could see it move some. Now it is immovable.

I did it this way because it seemed to save lots of time AND the epoxy sealed the wood inside. No re-drilling. I've used the same technique in other cases where spinning screws were more of an issue.

John P Lebens
02-02-2010, 11:42 AM
The wood flower/epoxy sounds like a good way to firm up holes - I like it. The epoxy can seal from water ingress and firm up the surrounding wood. The wood flower can modify the brittleness of the epoxy.

It seems that CPES with flour would provide some additional wood penetration - the combination may be worth considering.

Also, I like the idea of inserting plain CPES into the screw holes to firm them up. As long as the holes are not stripped, this could be an easy way yo add a bit of strength and grip and protect agains water penetration.

Finally, I am thinking about using bees wax on screw threads to make insertion easier and to provide an additional moisture barrier.

Any thoughts on us of beeswax to lube screw threads?

KAIROS
02-02-2010, 11:53 AM
CPES is just a sealer.....I don't think it is robust enough. Never experimented with it with wood flour though. I pre-treated a couple of holes with CPES as a sealer but it was such a mess. Difficult to keep it just in the holes. So, had a priest bless each hole instead.

John P Lebens
02-02-2010, 01:27 PM
Sometimes a hope and a prayer is the best solution!

I hope the priest did not use too much holy water, though.

Tom Robb
02-02-2010, 03:13 PM
Jim Conlin's last example is the hot setup for stanchions or any other highly stressed fastener IMHO.
Toothpicks/skewers and yellow glue are fine where water isn't a consideration.

JimConlin
02-02-2010, 03:53 PM
Jim Conlin's last example is the hot setup for stanchions or any other highly stressed fastener IMHO.
Toothpicks/skewers and yellow glue are fine where water isn't a consideration.
If you're doing stanchions or the like, get the Gougeon book (http://www.woodenboatstore.com/Gougeon-Brothers-on-Boat-Construction/productinfo/300-056/)
http://www.woodenboatstore.com/images/300056.jpg
and understand the engineering.

Lew Barrett
02-02-2010, 09:30 PM
By ignoring the bamboo trick you are dooming yourself to a lifetime of wondering "what if?" :D....and also throwing away the benefits of the toughest material you could use....you think anything you can put in epoxy is gonna be tougher than bamboo?

Soundman67
02-02-2010, 11:16 PM
when repairing stripped wood screws that attach the neck onto a guitar body I have used these before. held up excellent. converted from a wood screw to a machine screw. I imagine something like this epoxied into the stripped hole would give you almost the benefits of a through bolt and none of the water intrusion problems of using a dowel. In essence it is like driving in a much bigger screw without having to change the hole size of your fixture.

http://www.emhart.com/products/helicoil/techtop/tt1.asp

Lew Barrett
02-03-2010, 11:53 AM
Canoeyawl suggested this approach to me and I agree it is superior. You need to be very, very careful regarding registration though, and in a long run such as you have in replacing ten or more stanchions, precision in drilling and installation would be very demanding. If you are up to it, it almost replaces through bolting.
I chose not to do it that way based on the complication of drilling 40 holes in perfect registration across twenty feet......but it was tempting. If my bamboo approach proves unsatisfactory (so far it has been perfect after one year) that't the way I'd go....using inserts.


But I'm tellin' ya John....my recommendation is virtually foolproof, cheap and effective and uses the best qualities of epoxy and the toughest filler available.

Dave B
02-03-2010, 12:27 PM
you think anything you can put in epoxy is gonna be tougher than bamboo?

I've never tried this but it makes sense to me. It's got to be tough stuff because it's darn near impossible to kill once it gets started in your yard!

KAIROS
02-03-2010, 12:57 PM
.....the complication of drilling 40 holes in perfect registration across twenty feet......but it was tempting. If my bamboo approach proves unsatisfactory (so far it has been perfect after one year) that't the way I'd go....using inserts.


But I'm tellin' ya John....my recommendation is virtually foolproof, cheap and effective and uses the best qualities of epoxy and the toughest filler available.

Avoiding the re-drilling and 'registration' problems for lots of screws (130?) was another reason for the approach I took with the screw shank and thickened epoxy method. Mis-registration in my case would have made the wood toerail split in addition to issues you have with fixed metal stanchions and rails. In most cases, I don't have a lot of faith in [very] thickened epoxy though, for anything but filets. But My method worked well for my 2-1/2" x 3/4" plank-on-edge toerail. If Lew had just come up to me at the dock and told me about this wonderful bamboo method, I'd have been swayed :D. This bamboo method does sound good. And more wholesome.

David G
02-03-2010, 02:06 PM
John,

For your trim pieces, my method is just dandy. Lew's variation is good too, and I use it - when I remember to keep bamboo skewers on hand, or it's worth it to go get some.

For your stanchions - it's too bad you can't through-bolt them. Since you can't, I'd use Lew's method if you're going for the simple version. In that application, though, I think I'd be more inclined to use the West "Advanced Fastener Bonding" method that Mr. Schollmeier linked to. I can envision a time when someone will be glad you did:

http://westsystem.com/ss/bonding-hardware/

BTW - I don't think I raved enough about how lovely your bronze stanchions look when you were by the other day. I agree, though, it's probably best to let them age gracefully... rather than attempt to keep them so pristine.

Lew Barrett
02-03-2010, 03:14 PM
I saw them when he was up here, David, and they are some good looking sticks!
Wait until they get out past Buoy 10 for 15 minutes though! :D

David G
02-03-2010, 03:30 PM
I saw them when he was up here, David, and they are some good looking sticks!
Wait until they get out past Buoy 10 for 15 minutes though! :D

My thought, precisely. They're so gorgeous, though... it is tempting :cool:

John P Lebens
02-06-2010, 11:11 AM
One of our local wood boat guys told me how his beautiful polished bronze (searchlight in this case) went immediately brown when they cruised to Astoria. Still, I can't possibly paint them white again. Clear coating might be OK for the interior, but not for stanchions. We'll have to be happy longer term with the nicely shaped casting and classic bronze color.

Somebody suggested I have a pro photograph the boat when the stanchions are remounted and still shining.

Lew Barrett
02-06-2010, 12:22 PM
There is a chance they will turn an even chocolate brown and that chance is improved when you start out with them evenly polished. Simple exposure to the air is part of that, because it's my theory that it's the sea water that tends to make them go green.

I hear you get the wonderful brown color if you use bamboo stakes to fill the holes! Otherwise, the polishing efforts are wasted!

David G
02-06-2010, 02:39 PM
.
I hear you get the wonderful brown color if you use bamboo stakes to fill the holes! Otherwise, the polishing efforts are wasted!

Lew... I can't believe you divulged such information on a public forum. It's been such a closely held secret amongst us delusionaries for so long! :rolleyes:

JimConlin
02-06-2010, 03:38 PM
If you want an even brown color, paint is OK, too. George Moffett, master of the schooner Brilliant, referred to the dado brown paint on some of her bronze bits as 'Swedish bronze polish'.

floatingkiwi
02-06-2010, 04:30 PM
[QUOTE=

Finally, I am thinking about using bees wax on screw threads to make insertion easier and to provide an additional moisture barrier.

Any thoughts on us of beeswax to lube screw threads?[/QUOTE]

Use grease.

John P Lebens
02-06-2010, 05:24 PM
Lew... I can't believe you divulged such information on a public forum. It's been such a closely held secret amongst us delusionaries for so long! :rolleyes:


Something in the bamboo sap infuses the bronze with the classic color? Wow!

There is something about beeswax that makes sense. I don't think it would add much water proofing, but the idea of (how do I say this with out a double entendre) smoother screw insertion... makes some technical sense. It would be easier to install the screw, there would be less chance of ruining the screw head by slipping the screw driver and the screw ought to me more evenly torqued across it's length. It might slow some corrosion of the metal. Use real beeswax, heat it to a liquid, dip each screw and in they go.

Lew Barrett
02-06-2010, 07:58 PM
Beeswax has anti-fungal properties as well (they say) and may help with removal later.

I think one of the benefits of through bolting (or using a mechanical system such as the inserts we have seen discussed) is that getting the stanchions off in the future will be easier. And taking them off again will be a consideration down the road when they need to be re-bedded as inevitably, they will.

What will you be bedding the stanchions in? That will be more important in preventing water getting under them down the road than if you use beeswax.

John P Lebens
02-06-2010, 08:55 PM
I don't know what I will be using to bed the stanchions. I know I want to use something that will seal well and also enable me to remove them later.