Helicoils are great things!
We used to wet install helicoils with a poly imide epoxy primer for both
galvanic isolation and as a thread locker building precision guided
munitions. If you can find poly imide epoxy in anything less than
gallon sizes it is very useful anytime you need to install stainless
into aluminum. Tef Gel is great stuff but it is a lubricant.
If you can find locking helicoils, install those. Remember to break the
tangs after installation. If you don't it will gall the fastener very
quickly.
Neil Schiller
1983 C&C 35-3, #028, "Grace"
Whitehall, Michigan
WLYC
Launch on Monday!
On 5/14/2020 10:27 PM, Josh Muckley via CnC-List wrote:
Helicoils are just one option to deal with stripped threads. IMO if
you can go with a larger bolt then it is a better option. Some
applications such as spark plugs have limited "meat" and fixed
diameter threads so staying with original size is really probably the
only option. In other circumstances (SS fasteners in aluminum) you
may actually find a good option is to drill the hole clean and install
a "liner" such as a rivnut (rivet-nut). This way you will have
stainless on stainless. This is really only an option when the
material is relatively thin and has space behind (masts).
As for your furler I imagine that the fasteners failed because of the
aluminum to stainless galvanic corrosion? In this case you probably
have room to increase the diameter but probably not the depth for a
rivnut (or for that matter a Helicoil). I would definitely suggest up
sizing for this situation. You will now find that you have options.
Standard or metric, and how much larger? I would walk the isle of the
hardware store and evaluate availability of fasteners before settling
on anything. Particularly difficult to find may be metric set screws
in stainless. This is your opportunity to "upgrade" to more available
standard sizes in stainless. In the case of set screws, you may want
to consider availability of allen wrench. 9/32nds or 17/64ths is
relatively less available. Stepping up another fraction might put you
in a more conventional size of tool. When you install them, make sure
to use a galvanic isolating material, either a lubricant like tef-gel
or anti-seize, or a thread locker. Blue or green thread locker would
be my choice for 1/8 to 1/4 inch set screws. You'll probably have to
plan on bringing a micro torch when to go to remove the screws.
Josh Muckley
S/V Sea Hawk
1989 C&C 37+
Solomons, MD
On Thu, May 14, 2020, 21:52 David Knecht via CnC-List
<cnc-list@cnc-list.com <mailto:cnc-list@cnc-list.com>> wrote:
I have seen mention of helicoils several times on this list but I
have no experience with them. I have several stripped screws on
my Harken furler and was thinking they might be useful to repair.
What is unclear to me from what I have read is the reason to use
them. I still have threads there, and I thought the idea was to
screw in a helicoil to make the threads grab again. However,
every description I have seen of using them drills out the hole,
taps and then screws in a helicoil. I don’t get the point. If I
am going to drill and tap, why would I use a helicoil instead of
just putting a screw into the newly tapped hole? Is it that you
can use the same size screw as before instead of going to a larger
size? Is that preferable for some reason? Dave
David Knecht
S/V Aries
1990 C&C 34+
New London, CT
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Thanks everyone for supporting this list with your contributions. Each and
every one is greatly appreciated. If you want to support the list - use PayPal
to send contribution -- https://www.paypal.me/stumurray
_______________________________________________
Thanks everyone for supporting this list with your contributions. Each and
every one is greatly appreciated. If you want to support the list - use PayPal
to send contribution -- https://www.paypal.me/stumurray
