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Mast Gate Screw Hole Too Big

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CateP
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USA
108 Posts

Initially Posted - 01/28/2013 : 15:04:12

Hi Everyone--Thinking about spring projects as the snow falls up here on Lake Winnipesaukee. The first issue I have is that one of the screw holes for my mast gate has gotten too big and I am not sure if the screw will stay in there much longer. Really loose. The three other screws are okay, but I would rather have 4 good connections.

Any ideas on how to deal with an ever-widening screw hole in my mast?

Thanks in advance.

Edited by - on

jerlim
Master Marine Consultant

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USA
1484 Posts

Response Posted - 01/28/2013 : 18:14:06

Either replace the existing screw with a larger screw, or drill a 5th hole adjacently as a replacement hole. It is possible - in a pinch - to 'pad' the hole w/ slivers of some type of available metal, and TEMPORARILY - reset the current screw. OR, you could get crazy, get a MIG welder, fill the hole and re-drill and tap...

Edited by - on

putzmeister
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100 Posts

Response Posted - 01/28/2013 : 18:28:08

I have never used the product below, but if it does what it says - it looks like a promising choice - as it can be tapped. Also states it can be used for marine apps. I'm sure there are other comparable products out there of course.

http://www.jbweld.com/product/j-b-weld/

Good luck!

Edited by - on

CateP
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108 Posts

Response Posted - 01/28/2013 : 18:49:02

This weld goop might be just the ticket. I need to be able to unscrew the mast gate to get my sail out of the mast slot.

Edited by - on

Davy J
Master Marine Consultant

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USA
1511 Posts

Response Posted - 01/28/2013 : 19:10:06

Marinetex grey? Haven't used it that way, but might work.

Edited by - on

GaryB
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USA
4275 Posts

Response Posted - 01/28/2013 : 19:12:27

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by putzmeister
 I have never used the product below, but if it does what it says - it looks like a promising choice - as it can be tapped. Also states it can be used for marine apps. I'm sure there are other comparable products out there of course.

http://www.jbweld.com/product/j-b-weld/

Good luck!
<hr height="1" noshade id="quote"></blockquote id="quote">
I've used JB Weld for several different repairs and it works great. It is drillable and will work good for your need. Just be sure you clean the area well before applying.

Also works good to repair a leaking radiator.

Edited by - on

Stinkpotter
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Djibouti
9013 Posts

Response Posted - 01/28/2013 : 19:53:41

But if you drill and tap that stuff, you'll probably need to be careful not to over-tighten that one bolt.

Another option (just for that one hole) might be a self-tapping screw, which generally has larger threads designed to grab whatever is there.

Edited by - on

delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Response Posted - 01/28/2013 : 19:58:34

Concur on JB Weld, I've used it for some surprising repairs. It can be drilled and tapped, just make sure to give it plenty of time before you do, especially if it's cold there, since cure time is affected by temperature.

You could also potentially put in a [url="http://www.helicoil.in/"]Heli-coil[/url] in it. I did that once with my Toyota truck when a spark plug worked itself loose & damaged the threads. Worked out great, ran that truck for years & years afterward with no problems.

Edited by - on

binky
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USA
115 Posts

Response Posted - 01/28/2013 : 21:57:45

All of the ideas above sound good...my only suggestion is to add a few drops of Loctite to the screws (all of em) once it is repaired. I would probably use the Loctite Blue threadlocker.

Edited by - on

hewebb
Admiral

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USA
761 Posts

Response Posted - 01/29/2013 : 04:51:20

There is also an item called rivnut that works well. They are aluminum and used in aircraft. They make one that is countersunk that will be flush with the surface of the mast. I have used them a few times to repair threaded holes with very good success.

http://www.aimfasteners.com/about_rivnut.html#.UQe2OWfm6R4

Heli-coils also work well, as suggested earlier.

Both of these would be a permanent fix

Edited by - on

redeye
Master Marine Consultant

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3474 Posts

Response Posted - 01/29/2013 : 05:36:21

I'm not sure the JB weld could work well. Make sure you get the fast cure. It may still drip before it sets up. I've used it a lot and it is certainly hard enough.

I'd be inclined to use the Marine Tex. I've been told it was designed for just such work. Harden up well on aluminium.

I'd also be inclined to simply tap it to a larger screw size. Tap all four.

Edited by - on

vipermagic
1st Mate

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USA
69 Posts

Response Posted - 01/29/2013 : 08:38:12

I had the same problem on 1477, with all four holes. I dealt without a mast gate for a while, and that was miserable, so I drilled and tapped all four to 1/4-20, and had to enlarge the holes on the plates. All in all it took about a half hour and was well worth it.

I wanted to use a Heli-coil, but when the motivation struck, I didn't have any, so it got drilled out!

Edited by - on

redeye
Master Marine Consultant

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3474 Posts

Response Posted - 01/29/2013 : 11:58:21

Just installed mine and the flathead screws bother me. Looking at tapping mine for phillips head screws.

Edited by - redeye on 01/29/2013 12:10:30

islander
Master Marine Consultant

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USA
3992 Posts

Response Posted - 01/29/2013 : 14:28:22

Very easy to strip or enlarge the holes enough to the point that a repair or enlargement of the hole and screw will be necessary. Aluminum is soft and the SS screws will easily cut the threads also the mast extrusion isn't very thick so there aren't many threads in the hole. Hence my suggestion of just snug tight the screws with a dab of silicone or blue loctite. Don't use the red loctite, Way to aggressive for this application.

Edited by - on

BCG-Woodbury
Mainsheet Editor

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USA
396 Posts

Response Posted - 01/29/2013 : 17:18:47

This seems to be a very common problem. Over many seasons of taking the gate off and putting it on will almost always wear the holes out. I think the Rivnuts were suggested but ther are also Pemnuts or Pem Inserts. Some have a knurled diameter that hold them in place. I'm thinking about fixing mine this way and if I have success, I might start selling a kit with instruction. Let me know if anyone would be interested.

Regards,

Edited by - on

putzmeister
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Response Posted - 01/29/2013 : 19:59:24

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Stinkpotter
 . . . Another option (just for that one hole) might be a self-tapping screw . . .
<hr height="1" noshade id="quote"></blockquote id="quote">Mixing machine and sheet-metal threads on the same application? Isn't that unethical . . . especially for sailboats?

Edited by - on

Lee Panza
Captain

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USA
465 Posts

Response Posted - 01/29/2013 : 21:38:14

In a fresh-water environment electrolysis isn't as critical an issue as it is for us in coastal waters, but it still takes place. Stainless steel and aluminum are galvanically incompatible, despite being always used together, and one should use an isolator compound between them if they are exposed to water (even just rainwater). A thread-locker like Loc-Tite can work if it's applied liberally, but Tef-Gel is a popular compound made specifically for this. It's a bit unpleasant to use (quite sticky, so use care not to get your fingers into it), but it works.

Mast gates need to be taken off in order to remove the sail, hence Scott's suggestions above for the blue flavor, but Tef-Gel might be a better choice. I also spread a thin coating onto the surfaces of fittings that are fastened to the mast or boom. When I took my gates off the first time there was a significant amount of corrosion where they overlap the mast (despite the anodizing of the mast extrusion), and I found the same under other fittings.

I'd concur with the recommendations to upsize to larger screws. Resin compounds are hard enough to hold threads, but they're far more brittle. If I were to go to the trouble of tapping new threads I'd much prefer to be doing that directly into the aluminum rather than an intermediary. In some repairs it wouldn't be an option to upsize the screws, but in this case it would work very nicely. In fact, it offers an opportunity to adjust the fit of the gates if you're having any trouble with the slugs getting by: I upsized the screws on mine for that very reason even though they were holding well. It took some work, drilling multiple times with a series of bits of increasing sizes while favoring one side of the holes each time, but the effort has been rewarded many times over each time I raise or lower my mainsail.

BTW, a tapping guide is an invaluable aid for hand-tapping, especially for holes in thin substrates like our spars, and machine screws are superior to self-tappers if speed of production isn't an issue.

Edited by - on

redeye
Master Marine Consultant

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3474 Posts

Response Posted - 01/30/2013 : 04:56:22

<< Aluminum is soft >>

I was surprised at the hardness of the mast aluminum. Added some screws on a cheek block and thought I could drill it out and add a ss screw as if self tapping and it just about broke off the screw.

For what I think of as aluminum, That mast is not a cheep mix of metals..

Edited by - on

Lee Panza
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465 Posts

Response Posted - 01/30/2013 : 21:17:17

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by redeye
 
...thought I could drill it out and add a ss screw as if self tapping and it just about broke off the screw.
<hr height="1" noshade id="quote"></blockquote id="quote">
That's why self-tappers are inadvisable for mounting to our mast or boom anything that might be subject to a significant load. Self-tappers don't remove metal in order to cut threads, as a tap does; they merely push metal aside as they attempt to slice into it. If you drill a large enough hole to get the screw to go in without breaking, it's taking a very shallow bite (the recommended drill bits to use with each tap are sized to allow the threads to engage the substrate to around 50% to 75% of the depth of the threads, depending on the application). On top of that, a self-tapper of the sizes we most commonly use (#8, #10 and 1/4") only engage about a single turn of thread because their pitches are so great compared with the thickness of the metal in our masts and booms.

Edited by - on

redeye
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3474 Posts

Response Posted - 02/01/2013 : 05:30:00

Interesting... I never thought about the pitch difference giving you much less of an area to hold.

Thanks panza.. so tapping and machine screws are the way to go. I've had a box of taps from my father but I've never used them until one came with the mast gate. New to me, but it seems like it might even work well in fiberglass resin to tap out the holes. I've had the glass crack around the hole using the machine screws as though they were self tapping also.

I've gotta get that box out and learn some more about tapping. I was a little scared I'd grab the wiring in the mast so I really tapped as shallow as I thought I could.

Edited by - redeye on 02/01/2013 05:30:47

CateP
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108 Posts

Response Posted - 02/01/2013 : 07:59:49

Okay-so let me get this straight. Is this the recommendation?
<ul><li> Increase size of screw holes in mast gate and mast</li><li>Use tapping machine screws with blue loctite. (will these come out in the fall?)</li></ul>
My concern with enlarging the screws and holes is that it will just be an ongoing problem and I will have to keep enlarging holes and screws.

Edited by - CateP on 02/01/2013 08:00:03

redeye
Master Marine Consultant

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3474 Posts

Response Posted - 02/01/2013 : 08:30:16

I'm not sure you have the right idea.. I'm no expert on tapping but one recommendation might be worded like this.

1. Purchase a larger size SS machine screw to use.

2. Purchase a tapping bit that sets the threads for the same size and thread.

3. line up and tape down the mast gate.

4. Drill in and out a tapping bit for the correct screw size and threads. This "tapping bit" leaves the correct threads in the mast.

5. Screw in the screws with the blue locktight on them.

I'm new to the terminology so somebody help me out.

Edited by - on

redeye
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Response Posted - 02/01/2013 : 08:37:30

<< a tapping guide is an invaluable aid for hand-tapping >>

Oh ... and apparently ( like I said I'm new to this ) Hand tapping is the way to go. I would guess tapping with a power tool is an easy way to strip out the hole.

So I'm guessing you hafta hand tap and if it gets too difficult you drill out the hole just a bit bigger and try the hand tap again.

Probably drill out the SS mast gate to almost the same size as the screws ( with the gate off the mast ) and the mast hand tapping will go easily into the softer mast metal.

Edited by - redeye on 02/01/2013 08:49:12

islander
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USA
3992 Posts

Response Posted - 02/01/2013 : 08:46:33

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Increase size of screw holes in mast gate and mast<hr height="1" noshade id="quote"></blockquote id="quote">
Probably the best choice
<blockquote id="quote">quote:<hr height="1" noshade id="quote">Use tapping machine screws with blue loctite. (will these come out in the fall?)
<hr height="1" noshade id="quote"></blockquote id="quote">
The blue loctite is a medium strength threadlocker verses the red that is used for a more permanent application. Don't crank down on the screws Just snug them up, The locktite will keep them from loosening.

Edited by - islander on 02/01/2013 08:55:28

CateP
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108 Posts

Response Posted - 02/01/2013 : 08:47:55

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by redeye
 I'm not sure you have the right idea.. I'm no expert on tapping but one recommendation might be worded like this.

1. Purchase a larger size SS machine screw to use.

2. Purchase a tapping bit that sets the threads for the same size and thread.

3. line up and tape down the mast gate.

4. Drill in and out a tapping bit for the correct screw size and threads. This "tapping bit" leaves the correct threads in the mast.

5. Screw in the screws with the blue locktight on them.

I'm new to the terminology so somebody help me out.

<hr height="1" noshade id="quote"></blockquote id="quote">

Terminology aside...I TOTALLY understand this method now. Thank YOU RedEye!!

Edited by - on

Davy J
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1511 Posts

Response Posted - 02/01/2013 : 09:00:55

<blockquote id="quote">quote:<hr height="1" noshade id="quote">So I'm guessing you hafta hand tap and if it gets too difficult you drill out the hole just a bit bigger and try the hand tap again.<hr height="1" noshade id="quote"></blockquote id="quote">
Just use the appropriate sized drill to begin with.

http://en.wikipedia.org/wiki/List_of_drill_and_tap_sizes

I don't have a mast gate, but I have added reefing controls, cleats, a track on the mast and outhaul adjustment equipment on the boom. All drilled and tapped. The most difficult thing about using the handtap, to me, is keeping the tap as perpendicular, to the surface, as possible until you get some threads started in the material. Once you have "bit" into the metal, cut some and then back off to clean out the tap.

Edited by - on

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