Next message: Mike Maurice: "T&T: Iridium 911 for CONUS"
I agree with most of Larry's comments, however, I sometimes use a joist
brace to drive large screws and always use it to remove them.
It could also have been the use of a tapered bit that caused the
problem. Today's wood screws rarely have the tapered shank. Instead
they have the same straight shank as the sheet metal screws. Perhaps
this is to be able to make both with the same machinery and setups? In
any event, I long ago switched to using a straight drill bit for
drilling the pilot holes for larger wood screws in hard woods. The
plank would be drilled for the screw body diameter and the frame for the
shank. That's the way it looks from here.
Bob Lowe
www.MV-Dreamer.com <http://www.mv-dreamer.com/>
********************************
John and Judy write:
<<
I saw a rather sad occurrence earlier this week when a local chap, who
is also doing a refit on his wooden boat, started to refasten the hull
below the water line with silicon bronze screws that he had imported
from on of the well known eastern US suppliers - about every 3rd screw
would just about come up tight and then the head came off. Now we are
not talking about trying to drive the screw blind into oak or such
hardwood, we are talking about a guy who had the correct tapered drill /
counter bore drill and was driving the screws with an old style brace
and driver bit. In looking at the screws that failed we could not see
anything wrong like cracks or such, they just did not seem to have
enough strength and these were # 12 X 2 1/2 screws not little by any
means.. Sure glad that did not happen to me as I used a cordless drill /
driver set up and drive the screws (same size) until the drill stalled.
In all the screws I used I only damaged about 20 and that was due to the
driver>>
===============
My boat carpenter father-in-law would have been appalled. A brace and
bit can apply enough torque to twist the head off any screw. You have to
learn to be delicate. Using the stall point of a cordless drill to set
the screw is almost as bad for the screw and life shortening for the
drill. Most good drills/drivers have an adjustable clutch that limits
the torque. Each size screw requires a different torque setting.
Screws are designed to be strong in tension and have sufficient thread
area to prevent them from being pulled out of the wood. They are not
intended to pull ill fitting planks together. The proper technique for
driving a screw is to drill and counter sink an appropriate pilot hole,
then LUBRICATE the screw (Ivory Soap works well in wood), and drive it
in until the head bottoms in the countersink. Turn 1/4 rotation more.
Then STOP. Expansion of the wood when wet will provide additional
tension and sufficient friction to prevent the screw from backing out.
And if your wallet can bear the expense, Monel fastenings are better
than silicon bronze or SS.
Larry Z
_______________________________________________
http://lists.samurai.com/mailman/listinfo/trawlers-and-trawlering
To unsubscribe send email to
with the word
UNSUBSCRIBE and nothing else in the subject or body of the message.
Trawlers & Trawlering and T&T are trademarks of Water World
Productions. Unauthorized use is prohibited.
