Bronze Thru-Hulls

What have others done about the fact that the treads on new thru-hulls are straight cut while those on ball valves are pipe taper and therefor do not thread together properly, only about 3 threads?
On my boat where the wood plank thickness is such that standard flange style thru-hulls will not work the only alternative seems to be this combination even though they are not mechanically compatible.
I thought about chasing the first bit of the thru-hull threads with a pipe die however when you get to 1 1/4 inch size that I need the die is so big it will not go down to the threads before bottoming out.
The parts in question are made by Groco however every combination that I have been able to try is the same.
When questioned, the chandelries just shug and say "that's the way they make them"
What say as a solution?

John Tones* "Penta"
Sidney, BC

The Groco seacocks have NPS (straight thread)for the thru hull connection. I just put ina a new one last spring.
What is not right about the plank thickness...too thin?

The problem with the sea cocks that they have had in stock locally is that they are obviously made for 'glass hulls and are not long enough to penetrate my 2 inch planking with a backing block of any thickness. I have not had any luck in my searching through the catalogs for a longer stem version.
Also, the thru-hull portion of the ones I have looked at seem to be straight thread instead of pipe thread and will not connect with more than about three turns.
There is obviously something wrong with this entire situation however all three major marine supply houses as well as W/M all seem to have the same sort of stock.

Still looking and searching

John

A little confusion it would seem.**The actual thru hull Or could be called the tail piece weather mushroom or flush comes in various lengths you will probubly have to order one.**Any seacock, the thing with the ball valve built into it. Come in sizes from 3/4" to large.* They are also made of Mearlon*( some sort of nylon) as well as bronze. a sea cock will run you a couple of hundred bucks.

.sd

skipperdude - confusion, yes for sure. From what I have been able to gather from two local shipwrights that I have spoken to this AM is that somehow it would seem that the boat supply places all get their stock from one source and that source has started to assemble the "thru-hull" piece to the "sea-cock" and sell them as a unit rather than individual pieces. I have a feeling also that the "thru-hull" parts may not be made by the same company that made the sea-cock.
I called Fisheries Supply in Seattle and they assure me that they have what I need and are shipping it today with the provision that if the parts do not mate they will refund all costs including shipping! I guess they are certain of what they have.
Looks as though my list posting was a bit premature but until about 20 mins ago I was very confused.
Thanks for the input everyone
John

The Fisheries in Seattle down stairs in the commercial/wholes is where I go for all my boating parts as they know their stuff.* Most local marine stores buy their parts stuff from the Fishereis anyway.* I get have an account and get up to 40% discount.*

What I was told at a local boatyard (may be totally wrong, but...):

The through-hull is a straight thread but tapered toward the end so that it will attach to a tapered thread valve.* The straight thread portion is intended to engage the nut that secures it through the hull.*

How to select (or not) thruhulls and how to assemble:


http://www.pbase.com/mainecruising/seacock_primer

http://www.pbase.com/mainecruising/replacing_thruhulls

ON a proper installation the SEACOCK will be bolted to the hull, with at least 2 or better 3,, 3/8 bronze bolts.

The thru hull ONLY keeps water passing thru the hull to the seacock.

It can fall out , and water penetration to an improperly sealed hull would be the only bother.

The thru hull does not hold the valve to the hull, unless its really high , above the healed or partially flooded water line.

Look in a Groco catalog.