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Sheared screws in mast step

Printed From: Yachts and Yachting Online
Category: General
Forum Name: Repair & maintenance
Forum Discription: Questions & tips on the subject
URL: http://www.yachtsandyachting.com/forum/forum_posts.asp?TID=13361
Printed Date: 26 Sep 20 at 12:42pm
Software Version: Web Wiz Forums 9.665y - http://www.webwizforums.com


Topic: Sheared screws in mast step
Posted By: Wobble
Subject: Sheared screws in mast step
Date Posted: 15 Jul 19 at 11:40am
The mast step in my Flying Fifteen has worked loose. When I tried to remove it, two of the forward fixing screws sheared off rather than screwed out, creating even more movement, as it is now held in by just two screws aft.
Would anyone have any tips for removing the screw stubs left within the deck, doing the least damage possible? I'm thinking drill out and fill with epoxy, but wondering if there are better methods.
Thanks in advance!



Replies:
Posted By: Sam.Spoons
Date Posted: 15 Jul 19 at 12:02pm
The broken screws will be brass, bronze or stainless steel and much harder than the wood or GRP they are fixed into. This will make them incredibly difficult to drill out as the drill will constantly try to wander into the surrounding material. Try heating the screws with a large soldering iron before gripping the end with a mole grip (same for the remaining two, heat before trying to remove). It'll leave a divot around the top of the screw hole but might leave the most of the depth still functional.

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Spice 346 "Flat Broke"
Blaze 671 "supersonic soap dish"


Posted By: Wobble
Date Posted: 15 Jul 19 at 12:58pm
Thanks for your very quick response Sam.

The problem is that the screws (they look like low-grade stainless, and much lighter than I would have expected) are broken beneath the surface, so I have no way to grip them externally.

The other two have already been removed and replaced with new stainless screws, up one size.



Posted By: Sam.Spoons
Date Posted: 15 Jul 19 at 1:11pm
Tis a tricky one, and it's a while since I had to do it. Can you get a drummer* and put a slot in the top then apply heat? What's probably happened is that the screws were coated in varnish or something when they were fitted and heat will soften that, also expansion may break the grip the wood has on them. Failing all else drilling them will probably result in a much larger hole which you could fill with epoxy and microfibres as you originally suggested. Good luck.

Edit :- * Yup, Dremmel obviously though I know a drummer who might do it...........


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Spice 346 "Flat Broke"
Blaze 671 "supersonic soap dish"


Posted By: Wobble
Date Posted: 15 Jul 19 at 2:45pm
What's a drummer?

Apart from that, looks like a drill and fill!


Posted By: Noah
Date Posted: 15 Jul 19 at 3:34pm
I think drummer may be an auto-correct from Dremel...

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Nick
https://www.fireballsailing.org.uk/index.asp?selection=boat-register&subsel=14821" rel="nofollow - GBR 14821 Sijambo



Posted By: didlydon
Date Posted: 16 Jul 19 at 10:15am
If you can get in there to use a Dremel,  use a small diamond burr to "spot" it then gradually enlarge the burr keeping it on course till its gone. Patience & perseverance needed here!

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Vareo 365



Posted By: Wobble
Date Posted: 16 Jul 19 at 11:33am
Thanks Sam and didlydon both. All a bit scary.

I'm thinking of taking a swerve and drilling two new holes in the mast step. It'll be a bit weaker, but the attachment to the boat a bit stronger, I reckon.


Posted By: jharvey
Date Posted: 16 Jul 19 at 5:27pm
Is there any room to move the mast step forwards or backwards an inch and have 4 new holes?


Posted By: Wobble
Date Posted: 16 Jul 19 at 6:11pm
Good idea, thanks! I'll check to see if there's room for manoeuvre.


Posted By: Gordon 1430
Date Posted: 17 Jul 19 at 7:57am
Hi Wobble
Sorry don't know FF very well can you bolt it down instead of screws?


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Gordon
Phantom 1430


Posted By: craiggo
Date Posted: 17 Jul 19 at 7:57am
Get hold of a thread extractor. They are a tapered drill with a reverse thread. You start a small hole in the top of the broken screw and then drive the extractor in. At some point it will bite and wind the remnants of the screw out.

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OK 2129
RS200 411


Posted By: Sam.Spoons
Date Posted: 17 Jul 19 at 9:08am
Do not buy one off facebook, the set I bought was not very expensive (under a tenner) and totally useless, the drill end blunted in a second and the reverse thread smoothed off even faster. Test with a file to see if it's properly hardened , if it bites send it/them back.

Also remember that the odds of it working on the shaft of a screw is slim at best even if you get a decent one. If the screw is well enough stuck to shear then it'll need a fair bit of grip to remove it so go in with plenty of heat before attempting.


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Spice 346 "Flat Broke"
Blaze 671 "supersonic soap dish"


Posted By: Wobble
Date Posted: 17 Jul 19 at 9:45am
Gordon, nowhere to bolt to, as there's no opposing face to tighten against. These screws go into the meat of the hull spine.
I've used a thread extractor on an engine bolt before, but never on a screw. I have my doubts that they would work, given how fast the screw stumps are.
I'm going to take some time next week to look at the boat more closely, and decide what to do then. I don't think it's a killer problem -- just want to do the best job possible.


Posted By: mole
Date Posted: 17 Jul 19 at 10:33am
Hi
the hardest part is drilling the stainless screw. Ideally you need to flatten the top of the screw and use a centre punch before starting to drill.
A small drill will be required to start, with stainless use constant pressure and fairly low rpm and some form of lubrication. If you don't the metal will work harden and the drill bit will soon become blunt. Obviously be careful of too much pressure and breaking the drill
It maybe the full removal, and repositioning would be the best bet. Maybe consider using another suppliers mast step with different hole positions?
Hope you get it sorted
cheers


Posted By: Sam.Spoons
Date Posted: 17 Jul 19 at 3:09pm
What might help is a left handed drill bit.
  


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Spice 346 "Flat Broke"
Blaze 671 "supersonic soap dish"


Posted By: yottiemad
Date Posted: 17 Jul 19 at 3:16pm
I had the same issue in an FF, no one to blame but myself as I fitted the hull out from new.
I never tried to get the broken screws out, my screws had been installed with epoxy as lube/sealant from new so no extract tool would get them out. Just re drill the the alloy mast heel when it is removed, counter sink holes and put screws a size larger in different positions. It is an FF, a couple of grams in the hog will not make the boat over weight.


Posted By: Moomin.W
Date Posted: 17 Jul 19 at 3:42pm
Just a different approach for removal which is easier than drilling out. Use a small cutting disk in a dremmel to cut a slot on the top of the screw shank. You'll cut into the surrounding wood but only a slot and it helps stabilise the cut on the screw. Then use a flat head driver to unscrew.


Posted By: Sam.Spoons
Date Posted: 17 Jul 19 at 3:46pm
Or use a 'drummer' Wink

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Spice 346 "Flat Broke"
Blaze 671 "supersonic soap dish"


Posted By: Chris Robinson
Date Posted: 18 Jul 19 at 8:37am
http://youtu.be/dJfkCj3FWBs" rel="nofollow - https://youtu.be/dJfkCj3FWBs

This guy looks like he may have the answer. You may have to search to find the right tools though.



Posted By: Sam.Spoons
Date Posted: 18 Jul 19 at 9:10am
The hardest thing to find will be the left handed drills (well, a lathe to drill the guide bolts, but I guess that's not relevant in this case), Amazon is you friend. Much easier with larger, and clean, un-corroded, bolts though Embarrassed

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Spice 346 "Flat Broke"
Blaze 671 "supersonic soap dish"


Posted By: JimC
Date Posted: 18 Jul 19 at 9:11am
The big trouble with these techniques is that they require skill, experience and practice. So if someone like me without those three attributes has a go the first few attempts tend to end badly. So in the trade you might give a youngster a scrap cylinder head to practice with. If the OP boat is wood I'd be thinking that my fallback would be to drill all round the screw to extract, then drill a large hole and plug it. New screw could then go in the plug.


Posted By: 423zero
Date Posted: 18 Jul 19 at 12:00pm
One inch hole saw, drill down side of screw, then glue in one inch Dowell, prefix mast foot in same place.


Posted By: Sam.Spoons
Date Posted: 18 Jul 19 at 3:51pm
Originally posted by JimC

The big trouble with these techniques is that they require skill, experience and practice. So if someone like me without those three attributes has a go the first few attempts tend to end badly. So in the trade you might give a youngster a scrap cylinder head to practice with. If the OP boat is wood I'd be thinking that my fallback would be to drill all round the screw to extract, then drill a large hole and plug it. New screw could then go in the plug.

Exactly. The guy in the (excellent BTW) video had it easy with all the tools including access to a lathe to make his drill guides, and sheared bolts with not a sign of corrosion. Not saying he was not skilled and a video of him waiting for penetrating oil penetrating would be worse than one of paint drying but.......

If other methods fail then I too would drill oversize and use a plug of new wood too.


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Spice 346 "Flat Broke"
Blaze 671 "supersonic soap dish"


Posted By: Chris Robinson
Date Posted: 19 Jul 19 at 8:12am
I agree that the techniques shown in the video are above average boat bimbling level but the purpose of linking it was to show the methods for overcoming problems that others had mentioned. I would imagine that it would not be too hard to make a pre drilled plate which could be screwed into place and would then act as a jig to drill the sheared screws out.

Personally, I like the hole saw suggestion. Simple and effective.Smile


Posted By: Sam.Spoons
Date Posted: 19 Jul 19 at 9:14am
That video is excellent, I didn't want to suggest otherwise.

I agree WRT the hole saw technique if all else fails, an elegant solution. Thumbs Up


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Spice 346 "Flat Broke"
Blaze 671 "supersonic soap dish"



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