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-   -   Pocket screws in boat building? (http://www.sailnet.com/forums/gear-maintenance/50740-pocket-screws-boat-building.html)

deniseO30 01-22-2009 06:30 PM

Pocket screws in boat building?
 
I asked this on the wooden boat forum too! ( I'm living on the edge! )

Would you use them?

what are the pros and cons of using them?

Would the use of pocket screws be totally immoral?? :D

then the question is are the screws available in SS or Brnz?

Think I'll look around for my flak jacket! :eek:

paulk 01-22-2009 10:12 PM

I'd be concerned about screws being the only thing holding stuff together. Glue - resorcinol or epoxy- would seem to be indicated as well. Steel screws will leave quickly start to leave rust marks. The butt joint used in the pocket screw technique may work well in dry, on-land situations. I wonder how well it would hold up to constant moisture and the attendant swelling and warping of marine situations. The pockets might be a site for rot to begin forming too, unless they were filled in with a putty or compound of some sort. You try it first, and let us know how it holds up!

poopdeckpappy 01-23-2009 12:54 AM

Quote:

Originally Posted by deniseO30 (Post 436357)
I asked this on the wooden boat forum too! ( I'm living on the edge! )

Would you use them?

Yes

what are the pros and cons of using them?

pros;
they're strong, fairly simple jig, eliminates clamping ( except for maybe alignment clamps )

cons;
not very attractive even with plug, so keep out of line of sight

Would the use of pocket screws be totally immoral?? :D

No

then the question is are the screws available in SS or Brnz?

maybe, but they do have non corrosive PH fasteners

Think I'll look around for my flak jacket! :eek:

.............

merc2dogs 01-23-2009 01:09 AM

In addition to the potential rot paulk mentions, the pockets remove material and create weak areas in the wood.
Most broken items I've seen that were built with pocket screws, have failures where the pockets were.

Filling the pocket with tight fitting glued in dowels -may- approach the strength of the original material, but I wouldn't want to rely on it.

Pockets are fine for tables, interior furnishings and any non-critical assemblies. But for anything else the potential risks are too high.
When you consider the added time required to use pocket screws, there is no advantage. Glue or ring shank nails will have far more holding power.


Ken.

poopdeckpappy 01-23-2009 02:54 AM

Quote:

Originally Posted by merc2dogs (Post 436563)
In addition to the potential rot paulk mentions, the pockets remove material and create weak areas in the wood.
Most broken items I've seen that were built with pocket screws, have failures where the pockets were.

When done correctly, using correct pocket depth and properly size PH fastener, (along with some gorilla glue} this is not a issue

Quote:

Filling the pocket with tight fitting glued in dowels -may- approach the strength of the original material, but I wouldn't want to rely on it.
again, not really an issue, but I would use the pocket plug anyhow, you can get them in most all species

Quote:

Pockets are fine for tables, interior furnishings and any non-critical assemblies. But for anything else the potential risks are too high.

I was thinking this is what deniseO30 was talking about

Quote:

When you consider the added time required to use pocket screws, there is no advantage. Glue or ring shank nails will have far more holding power.


Ken.
the time envolved using a PH jig is minute and the advantage over glue and ringshank is enormous, a nail, any nail work by forcing aside material and relying on friction as material compresses back around the nail to hold.

A pocket hole, you're using a stepped bit that creates not only the pocket but also a shoulder, then continues with a pilot hole into the joining material, the pilot hole is smaller dia than the PH screw which is self drilling and only threaded about a 3rd of the screw shank, the remaining shank is smooth.

If done correctly you end up with a clamping force between the screw head sitting on the shouldered pocket and the screw thread that has pass completely though the pocketed stock into the joining material.

This in addition to a good wood binder is very strong

sailingdog 01-23-2009 03:07 AM

I don't see why you couldn't use them for pieces like tables and such. I wouldn't recommend using them for bulkheads and other structural pieces.

Ideally, if you could find them in Magnesium Bronze or 316 Stainless, you'd be best off using them, but even normal steel would work, provided you sealed the wood properly and took steps to prevent the fasteners from getting wet.

However, I wouldn't use pocket screws to fasten laminated materials together, at least I wouldn't recommend putting pockets into laminated materials—like marine plywood—since I think the pockets are better suited to solid wood. For instance, you could use pocket screws to fasten a marine plywood top to a hardwood table base, provided the table base had the pockets in it, not the top.

kaluvic 01-23-2009 07:35 AM

What is a pocket screew...I've been in construction my whole life and never heard that term.

deniseO30 01-23-2009 07:58 AM

there is a company that makes the screws in ss and brnz. I don't see them in any part of a boat below the water line but the clamping type of use they provide is pretty hard to ignore, IF the hole or plugged hole is not visable.

I'm going to use them to set up the forms for my next building project. a 11 or 12 rowing dingy. Cabinetry seems to be the best way to use pocket screws.

I thought this would be a fun and thought provoking thread! ;)

sailingdog 01-23-2009 08:29 AM

Quote:

Originally Posted by kaluvic (Post 436608)
What is a pocket screew...I've been in construction my whole life and never heard that term.

Look HERE

kaluvic 01-23-2009 09:19 AM

So it "toe-nailing" with a self tapping screw!

It looks to have a raised thread like a drywall screw.

It seems to be less about the design of the screw, and more about the jig that makes it easy to drill the counter sink hole.

I would think the question about using this to attach bulk heads would be more about using this method than this particular screw.

As for me those screws have no place on a boat...the idea of "toe-nailing" has its place...if used for attaching bulk heads I'd us a lot of screws, SS or bronze.
However, I would prefer other more robust methods that will be easier to plug the holes.


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