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Discussion Starter · #1 ·
My cleats are secured to the deck with machine screw. There's an SS plate embedded in the fibreglass with threads for the screw. I'm thinking of putting a nut to the screw to secure the cleat better. Should I just screw in the nut or drill away the thread on the SS plate and tighten cleat using the nut ?
 

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Leave the threads in the plate. Tighten the bolt and then add the nut to the bottom.
Yep... I'd probably add a flat washer and a lock washer as well
 

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trantor
I was confused at first...did you mean bolt, not screw? A screw won't take a nut on the end. I think you meant bolt
 

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xort: Machine screws will take a nut.

I'd skip the lock washer and use Loctite instead. (And from the top, to protect the threading into the plate, as well.) Keeps weight off the boat, and protects the threads from moisture intrusion and corrosion, too.
 

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Retired and happy
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I would definitely go with the "tighten the screw and add a washer, locking washer and nut" brigade. Belt, braces and piece of string approach. Way to go!

Stuart
 

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Discussion Starter · #8 ·
Yup, its a 1/4" machine screw, screwing into a threaded SS plate. After sever wake-dance the cleats start "moving" thus needing retightening. I added a nut under just so the screw won't be work loose by wake-dancing but not sure if that is the right way, but it now seems that's the way to go by all your account. Thanks for the info.
 

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1/4" machine screw, on a Hunter 326? I'm not sure I'd consider 1/4" screw or bolt, or even a pair of them, large enough to handle the cleats on a boat that size in any kind of chop. Or storm.

Although I suppose upsizing the cleats all around to something that used heavier bolts--and then throughbolting them--would be the usual "not inexpensive!" project.
 

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Discussion Starter · #10 ·
Yah that crosses my mind too. There're 4 screws per cleats.
 

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Discussion Starter · #11 ·
Xort a machine screw is a bolt with a screw type head on it as opposed to a hex head..

These are examples of machine screws:
Looks just like the standing countersunk head but for philips screw driver i.s.o slot one.
 

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Many years ago, when I was a young draftsman aspiring to be a big time machine designer, my mentor taught me a valuable message. He said "Quarter inch bolts are for hanging pictures".

Dick Pluta
AEGEA
Nassau, Bahamas
 

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I would have thought a ¼” screw is a bit on the small size, were the cleats fitted buy the builders? It’s now a bit difficult to do much with them as the threads are glassed in.
It would be difficult, not impossible to drill the threads out and fit bigger threads, possibly with bigger backing plates below, however a lot depends on the condition of what you are fixing through, the deck.

Also with ¼” screw, you don’t have a lot of room for corrosion (i.e. crevice) before the bolt is severely weakened, perhaps they should be pulled fairly regularly.

We have some very nice fabricated stainless steel mooring cleats and fairleads, the cleats are fixed through the deck with 8 No. 16mm countersunk machine screws through a 8” x ¼” steel flat running all the way around the hull.
The fairleads are fixed the same way but with 5 No. 16mm countersunk machine screws.
But then the boat was built in a yard where they build small tugs!!!!, 70 years ago.
When it is blowing hard and she is surging backwards and forwards the only thing that will give away will be the moorings on the quay or pontoon.
Over the years we have towed a few boats, a couple of them were in the 45ft size and again I don’t worry about our fixing point as our cleats are not going anywhere.
We are 48ft in length and around 22 tonnes.
 

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Machine screws are available in many materials, with many head shapes and styles included Roberts (Canadian square drive) Torx, Allen (hex), slotted, and Phillips.

I wouldn't think it worthwhile to drill and tap the existing plates for anything larger--through-bolted is the way to go, less time and effort for a stronger result.
 

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Umm.. even four 1/4-20 machine screws strike me as a bit light for deck cleats, on a 32' boat. IIRC, the deck cleats on my boat, at least the ones at the bow, use four 5/16" machine screws and my boat is a lot lighter than a Hunter 326.
 

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Discussion Starter · #16 ·
Ok, I've gone back to the boat and recheck the machine screws. The screw width is 1/4" and the nut AF is 7/16". So is it 1/4" or 7/16" ?? I've realise there's probably no thread in the backing plate as I unscrew the original screw, it came out bent. When I put in a new screw, it drop straight in. Hmm. I'll see if I can change to a slightly larger screw without enlarging the cleat mounting holes. A question, for same sized screw, should I go for coarser thread (inches) or finer ones (metric) ?
 

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Coarser threads resist corrosion better and are usually harder to strip.
 

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A standard 1/4 nut uses a 7/16 wrench flat ,a 5/16 nut uses a 1/2 wrench flat a 3/8 nut uses a 9/16 wrech flat ,ect


It would be EASY to drill through with a 5/16 bit and tap it to 3/8-16 OR a metric size that would be easy to get there
 

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Discussion Starter · #20 ·
I'll use a flat washer with a spring-washer (split end).
 
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