SILICON BRONZE SCREWS not working....

Designs for inboard or outboard power

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bobinpowayca
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SILICON BRONZE SCREWS not working....

Post by bobinpowayca » Tue Feb 26, 2013 11:44 am

Howdy, I'm building the Geronimo, got most of the frames done using one inch (13/16) sapele and it's been going great - using epoxy and bronze nails on the gussets. However, now I got a problem - plans call to screw the floor timbers on a couple of frames using the same material as the frame - so I'm basically screwing two pieces of one inch sapele together. I posted a question here asking for advice on fasteners and based on that ordered some 1 1/2 inch number 8 silicon bronze screws from Glen-L.
Today I tried using them. I drilled the pilot holes using a number 8 adjustable pilot bit.
Every time I try screwing one in (these are freason screws and I'm using the freason bits I bought and my variable speed drill), as soon as they're almost in, the screw heads get chewed up and I can't tighten them. The screws seem WAY too soft.
I've tried drilling the pilot holes deeper, soaping the screw threads, going slow with force with my drill, etc. I've sunk a lot of screws in my life and I don't think it's my technique. Every attempt, the screw heads disintegrate as they snug up.
Maybe sapele is too hard for Si bronze screws? Maybe I got a batch of screws that are out of spec on the chemistry? I'm thinking of using 1 1/2 inch bronze nails instead - any ideas? These silicon bronze screws seem just too soft for the sapele!
Bob
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ttownshaw
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Re: SILICON BRONZE SCREWS not working....

Post by ttownshaw » Tue Feb 26, 2013 11:47 am

Are you using a tapered countersink? Or at least a stepped countersink?
Bill

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ttownshaw
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Re: SILICON BRONZE SCREWS not working....

Post by ttownshaw » Tue Feb 26, 2013 11:54 am

Standard Countersinks don't really work well with these screws:
Image

Stepped Countersinks are what I use and they work reasonably well:
Image

I have not used Tappered Countersinks but think they would work reasonablly well too:
Image
Bill

I told my wife we needed a three-car garage for my projects...she told me to ask her for permission next time before I buy a house.
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bobinpowayca
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Re: SILICON BRONZE SCREWS not working....

Post by bobinpowayca » Tue Feb 26, 2013 12:00 pm

Thanks Bill - good question, what I'm using is just a simple, adjustable countersink like you can get at the depot; i.e., it has a 7/64 bit in a collar with an allen wrench set screw, and the collar has a bore for a number 8 flathead screw. I don't know if this is what you call a tapered bit. As soon as the screw starts tightening up the slots in the head crumble like butter - like brass, not bronze. What about stainless, or the bronze boat nails?
Bob
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Mr Hot Rod
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Re: SILICON BRONZE SCREWS not working....

Post by Mr Hot Rod » Tue Feb 26, 2013 12:29 pm

Try using regular steel screws with the same thread pitch for initial assembly. This will pre-tap the screw holes. Pull the srews before the epoxy has set, fill the screw hole with epoxy and drive in the silicon bronze screws. It's more work, but makes for faster assembly.

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steveh41
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Re: SILICON BRONZE SCREWS not working....

Post by steveh41 » Tue Feb 26, 2013 12:54 pm

Oops!
Last edited by steveh41 on Tue Feb 26, 2013 1:28 pm, edited 1 time in total.

Tony Hain
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Re: SILICON BRONZE SCREWS not working....

Post by Tony Hain » Tue Feb 26, 2013 1:09 pm

I had the same problem, but now dry fit with steel screws, remove these and then glue and screw with the silicone bronze. Doing this I have had only the occassional stripped head
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jprice
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Re: SILICON BRONZE SCREWS not working....

Post by jprice » Tue Feb 26, 2013 1:36 pm

I agree with the stepped countersinks approach.
I don't have them, but did it manually. First the countersink, then come back with a larger bit (the full shank diameter), and drill down at least 1/4" with that.
You also might want to try bumping up your countersink bit to 1/8".

slug
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Re: SILICON BRONZE SCREWS not working....

Post by slug » Tue Feb 26, 2013 1:40 pm

I always use the tapered bits from Lee Valley.

Doug

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Re: SILICON BRONZE SCREWS not working....

Post by Tony Hain » Tue Feb 26, 2013 1:54 pm

PS
I also recommend using a drill with a adjustable torque setting for driving the screws. Without that, even if you have countersunk properly you will probably strip the head. I put my drill in a clear plastic bag when using to screw up glued parts. Epxoy is a ?#!@ to get off tools as you probably already know
Last edited by Tony Hain on Tue Feb 26, 2013 1:58 pm, edited 1 time in total.
Tony Hain
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John K
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Re: SILICON BRONZE SCREWS not working....

Post by John K » Tue Feb 26, 2013 1:55 pm

Tapered bits work well and I have used them before. You can also try rubbing soap or candle wax on the screw threads before putting them in. You would not have to put steel screws in first. I have used soap on plenty of screws into while oak. Slow down the drill also to let the screw walk into the hole.

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DrBryanJ
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Re: SILICON BRONZE SCREWS not working....

Post by DrBryanJ » Tue Feb 26, 2013 2:07 pm

I was having the same problem. I was also using the type of countersink bit you are. I switched to a stepped bit and also preassembled with steel screws. Had no problem assembling the frames after that
Bryan

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kens
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Re: SILICON BRONZE SCREWS not working....

Post by kens » Tue Feb 26, 2013 4:19 pm

the specie of wood you use can have an effect as well.
Soft woods like white pine would use a smaller pilot drill than something hard like white oak.
I found Sapele to be a bit denser than Mahog, so I used a little bit larger pilot hole.
Oak is over rated, everything about it takes extra time; then it warps, splits or checks !!! :roll:

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Bill Edmundson
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Re: SILICON BRONZE SCREWS not working....

Post by Bill Edmundson » Tue Feb 26, 2013 4:28 pm

Definately a larger pilot hole in oak :!:

Bill
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Ches T
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Re: SILICON BRONZE SCREWS not working....

Post by Ches T » Wed Feb 27, 2013 3:40 pm

I had the same problem. For me it helped to drill the pilot hole deeper and a little larger. I also found it helped to drill a hole as large as the shank of the screw thro the top piece of wood, as I am not using countersinks. I found that sapale is a very hard wood indeed. Nice to work with tho.
Ches

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