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Jules

Epoxy, Screw Holes and Wood

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When drilling into wood for screw holes that will take wood screws, what's the best way to seal the wood to prevent water penetration? 

  1. Drill larger holes, fill with epoxy, then drill exact size holes for the wood screws?  If so, would you tap the holes first?
  2. Drill exact size holes and soak with penetrating epoxy?  (epoxy diluted with denatured alcohol)
  3. Other?

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#1 - Wet out the oversized hole with unthickened epoxy then fill with thickened and redrill when cured. Self tapping screws work better unless you are using a Fuller or tapered bit to drill for your wood screws. Coat screws with epoxy when driving unless you want the ability to remove them in the future. If you want to use a machine screw or bolt, the cured epoxy can be tapped but it isn't necessary with the self tapping screws and the correct drill bit. Search Epoxyworks at the Gougeon site.

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1 minute ago, Grande Mastere Dreade said:

where are you using wood screws on the deck?

For hinges that hold the extension wings of a cockpit table. 

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Overdoing it IMO.

You aren't preserving core - just coat the screws in sealant when you drive them.

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1 hour ago, Jules said:

For hinges that hold the extension wings of a cockpit table. 

 

yeah, i figured some such...       even if you have a pilot hole, I think the wood screws would still compromise any stuff you put in before hand, I'd do something like getting some 4200 around the threads as you screw it in..  

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Rumor has it that the blades were eventually found some distance away in a farm field among some very nervous cattle.

Must have been Tasmania, N.Z. or Scotland. :D

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1 hour ago, SloopJonB said:

Overdoing it IMO.

You aren't preserving core - just coat the screws in sealant when you drive them.

It's cherry.  Overdoing it is intentional.

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If the width of the board is wide enough to do it... take a forstener bit, and go a 1/4 inch deeper than the screw you are using.  Wet down the inside the hole wih neat resin, then back fill the hole 3-4 diameters larger than the screw with west and milled glass fiber.  The next day, come back, drill and tap the epoxy plug for a machine screw, rather than a wood screw... you can dunk the screws in epoxy and get a better bond if you want.  I power - tap the holes freehand with a tap in a drill small cordless drill.  The epoxy on the screw remakes any issues with the threading.  To remove, take a soldering iron and hold it to the screw head.  Once it's too hot to touch they back right out.  

Works well.  Buddy of mine cats into place mounting bolts for pretty much every piece of hardware they use on the cold molded plywood boats, including the engine mounts, so once you get a system you like it scales up and down readily.  Just don't use a wood screw, machine screw is where it's at...

I agree that if it wasn't cherry, it wouldn't be worth the bother, but that'll hold ya. 

Cheers

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One of the really nice things about Zach's process is that with the tapped holes one can mount deck hardware single handed. The epoxy threads are strong enough to hold even highly leveraged things like lifeline stanchions tightly enough to let you screw them down and then go below and put the nuts and backers on.

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Yup.

If you've got a lot of the same hardware to do... stanchions, etc.  Hardened drill guides in an inch and a 1/2 wood with a piece of carpet tape on the bottom will make your backing plates match too...  A lot of boat stuff is 1/4 inch, and a drill guides are reusable, just make the holes in the block a hammer fit.  Aircraft bits and a pair of bullet levels get close, but a drill guide in a block stuck to the deck means it matches top to bottom.  May not match the bevel of the level on the inner skin if a lot of fairing has been done on top, but the bolts will hit the plate in the same hole up to 2 1/2 inches or so of depth.

Cheers 

  

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21 hours ago, Rasputin22 said:

You just got to get your annulus right!

https://www.epoxyworks.com/index.php/hardware-bonding/

That article get me to thinking...  Rout out the entire area where the hinge will be inset and fill it with thickened epoxy.  Then come back and rout out for the hinge and drill holes for the screws.  One of my concerns has been the poor side loading of screws in wood.  Every time the table wings are open there's side loading that, over time, would be its Achilles heel.  From what I've gleaned from the article, epoxy fill may be the solution.

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My home-built teak table with folding wings was built 12 years ago and on the boat in all weather ever since.  I did nothing special with the screws, including those on the hinges.  No issues.  

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20 hours ago, jamhass said:

My home-built teak table with folding wings was built 12 years ago and on the boat in all weather ever since.  I did nothing special with the screws, including those on the hinges.  No issues.  

Where did you find teak?

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This particular teak came from McBeath in Berkeley CA.  Damnably expensive even 12 years ago, but nice.  I've bought from them more recently also.  Most of their 4/4 is uninspiring, the nicer material is 5/4, but lots of waste.  With care I can resaw and get some thin bits out of the offcuts.  Fortunately, most of my boat woodworking is done, so little need to buy more.

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1 hour ago, Fat Point Jack said:

Try Alva Hardwoods, there just a little bit south of here.

They are closed during the summer.  Also, he thinks his wood is worth more than plutonium, despite what the website says.  He makes up stories about the wood like, "This QS maple came from the Steinway factory.  They were going to burn it but I saved it.  It's piano grade.  I'll let it go for a little over $16 bd/ft."  I can get QS maple for half that price.  And there is no such thing as "piano grade" lumber.

If I went in asking for teak, he'd probably say it came off the Constitution but he'll let it go for $500 bd/ft.  And then it would be plantation teak. 

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