How to remove snapped bronze screws ??? (in a hole)

[Rhossydd]

Should accurately go straight down the center (in theory!!!) Then plunge down the bit to the depth of the bottom of the screw.

Nice idea, but give it some thought; You're trying rout out BRONZE.
I think even a solid tungsten bit won't last terribly long.

If you were trying to drill or mill bronze you wouldn't use a router and a woodworking bit.
Maybe a milling bit at a low speed ? possibly, but really how practical is that ?

 

[Cottonwood]

I'm guessing you really want to keep the boards in place as I expect they are precisley scribed to fit the deck shape? Are the teak planks glued down as well as fixed with the bronze screws? If they arent fixed with adhesive, then why not just remove all the plugs, unscrew any screws that will emerge easily, deliberately snap the screw heads off them that wont, then lift the board off, cut off the stumps then replace the teak boards but slightly off set to get new material to screw into? Just a thought.

 

[zak99]

Should accurately go straight down the center (in theory!!!) Then plunge down the bit to the depth of the bottom of the screw.

Nice idea, but give it some thought; You're trying rout out BRONZE.
I think even a solid tungsten bit won't last terribly long.

If you were trying to drill or mill bronze you wouldn't use a router and a woodworking bit.
Maybe a milling bit at a low speed ? possibly, but really how practical is that ?

Thanks for that, yes I guess the router bits will wear quickly, so would drill bits. Drill bits are cheap, router bits are not so but I have to weigh up time against cost and end result. Drilling them out with a twist drill is a major pain. As you say slowing the speed down should help longevity I guess. In boat work we sometimes hit bronze screws and copper nails with the router little impact on the bit. Extended use might be a different story.

 

[zak99]

I'm guessing you really want to keep the boards in place as I expect they are precisley scribed to fit the deck shape? Are the teak planks glued down as well as fixed with the bronze screws? If they arent fixed with adhesive, then why not just remove all the plugs, unscrew any screws that will emerge easily, deliberately snap the screw heads off them that wont, then lift the board off, cut off the stumps then replace the teak boards but slightly off set to get new material to screw into? Just a thought.

The boards cant be lifted at all, they are bonded in place, with either sikaflex or I think most likely epoxy, cant be 100% sure. Why bother replacing the screws I hear you saying, well maybe you would'nt but that was my first thought when they started snapping. Just plug the hole and move on. The customer is not happy with that, and I do sympathize with him although it is going to cost him plenty unfortunately which is a shame as he is a nice guy. With old wooden boats they are made in a certain way for a reason, strength, flexibility, water tightness, serviceability etc. then someone at some point in its life introduces modern techniques like epoxy. It seems like a good and economic idea at the time until some other work needs to be done!!!

This job is all about making the deck watertight and pleasing to the eye. In reality leaving some of the deck screws out may be ok in the long run, but if the customer doesn't want that then that's his call. And also if two years or so down the line in a heavy sea or during crane out (20 + tonnes) the boat moves and the deck starts to move because we left the screws out, it would be my yard (and possibly me) that would get sued. I think I'm talking to myself here !!!!

Thanks again all for all the thought provoking ideas.

 

[bugbear]

a screw extractor may work, which may be what Andrewf was refering to by small hole saw? Personally I'd probably just drill it out :/

How do you drill a metal screw out of wood - the drill bit will just skate off the harder screw into the software wood.

BugBear

 

[nanscombe]

Centre punch it first to make a divot for the tip of the drill to sit in.

I wonder if that whack would be enough to break the seal as well?

 

[Spindle]

Hi

Your proposal with the router will work, router bits are made from the same materials as twist drills / milling bits, (high speed steel / tungsten carbide). The bit must be suitable for plunging - if your router has variable speed, so much the better - slow it down, cutting speed for bronze using carbide tooling is 715 ft/min which if my maths are correct equates to around 17,000 rpm on a 4mm core.

Another option would be to use a milling slot drill in the router

Regards Mick

 

[zak99]

Hi

Your proposal with the router will work, router bits are made from the same materials as twist drills / milling bits, (high speed steel / tungsten carbide). The bit must be suitable for plunging - if your router has variable speed, so much the better - slow it down, cutting speed for bronze using carbide tooling is 715 ft/min which if my maths are correct equates to around 17,000 rpm on a 4mm core.

Another option would be to use a milling slot drill in the router

Regards Mick

Thanks for this, good to get some figures for this approach. Took my Trend 4E in today but found out the variable speed switch had gone kaput (well they are made in china). So tried on a dummy block of wood and bronze screws with an old fixed speed (fast) makita and it worked. Poured some water in the counterbore for a little cooling. Not surprisingly the router bit burned and wont last long but at slower speed when I get the Trend fixed it should work. Only problem with this is the length of the bit is such that the router spindle locking nut hit the back of the 10mm guide bush before I had plunged deep enough.

Also found a milling bit to use as well which is a little longer, but not quite long enough. - I'm getting there.

Did try a drill again but its like trying to do it with your eyes shut. The broken screw is nearly 30mm deep from the top of the deck. The drill just wanders off.

thanks again

 

[Terry - Somerset]

Just a small thought and may be worth a try as low cost and quick - could you make a bush with 10mm outside diameter with a 3mm hole through the centre. This would hold the drill central to the plug hole and (hopefully) allow the remaining screw to be drilled out.

 

[Tony Spear]

As they say - a boat is a hole in the water into which you pour money!

 

[Cottonwood]

Your client seems to want cat skin and all.... :lol:
How essential is it that screws are used? They cant be that good structurally if they snap that easily, and if the deck boards are glued any way, why not just use soild wood pegs epoxed into the screwholes?.
Have you considered just using a small hole saw, drill right through the plug, down around the screws, and deep enough into the rafter (if thats what its called on a ship) so that the screw will snap out and no metal left in. Get some air dried dowel to 10mm or 12 mm whatever diameter and epox into place. If some areas of the deck board is badly worn (exposed screws in places etc) it wouldnt matter as the dowel pegs would go right from the face(?) of the deck right down into the supporting rafter.

 

[Racers]

I would drill at an angle from the original hole with snapped screw in and insert a new screw.

Pete

 

[Sheffield Tony]

They are available here by the look of it.

http://www.jamestowndistributors.com/userportal/show_product.do?pid=437

Is it just me, or does that look remarkably like a roll pin with some teeth dremmeled into the end of it ?

 

[tim burr]

If you could replace the 10mm plugs with 1/2 inch then Fisch do a 6mm plug cutter that leaves a 1/2 inch diameter outer hole, we use them at work for exactly the same problem that you've got (although not on boats!)