Window screws

G

Graham_Wright

Well-Known Member
Joined
30 Dec 2002
Messages
8,187
Location
Gloucestershire
www.mastaclimba.com
Does anybody know the thread on the two part windows commonly used on GRP hulls?

The outside frame has countersunk holes and the inside part is a matching shape in two halves with female threaded inserts. The tpi appears to be 33 which I cannot find in my very comprehensive thread book and the screw diameter is 0.178"/4.52mm. I have tried 2BA and M5 both of which are close but not close enough.

My suspicion is that it is a baastard (misspelling to fool the auto censor) thread to fool the opposition.
 
Graham_Wright said:
Does anybody know the thread on the two part windows commonly used on GRP hulls?

The outside frame has countersunk holes and the inside part is a matching shape in two halves with female threaded inserts. The tpi appears to be 33 which I cannot find in my very comprehensive thread book and the screw diameter is 0.178"/4.52mm. I have tried 2BA and M5 both of which are close but not close enough.

My suspicion is that it is a baastard (misspelling to fool the auto censor) thread to fool the opposition.
Click to expand...
How old are the windows
are we talking Interscrews here
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[TD="class: abovebuttons, align: center"]Machine screws
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[TD="width: 80%"]Interscrews (internally threaded screws or socket nuts) are a neat solution if the situation requires for windows to be fixed by bolting through. Instead of unsightly nuts and screw ends, round the window inside the boat all that can be seen is the head of the interscrew. Not suitable for use directly into acrylic because the splines stress the plastic and cause premature stress crazing and cracking. The solution is to use panhead screws on the acrylic and put the interscrews on the other side. All the interscrews listed below have the same diameter barrel (6.5mm plus splines), they just have different size threads tapped into them.
Please phone or e-mail to check on availability and postage cost.
PRICES DO NOT INCLUDE POSTAGE.
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2BA
M5x6%20interscrew.gif
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2BA
M5x10%20interscrew.gif
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[TD="width: 32%, bgcolor: #006699"]
A4 GRADE STAINLESS STEEL
SMOOTH HEAD
SPLINED BARREL​
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[TD="class: tablehead, width: 34%, bgcolor: #336699, align: center"]THREAD TYPE[/TD]
[TD="class: tablehead, width: 34%, bgcolor: #336699, align: center"]THREAD LENGTH[/TD]
[TD="class: tablehead, width: 32%, bgcolor: #336699, align: center"]PRICE PER 10
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[TD="class: tabletext, align: center"]2BA[/TD]
[TD="class: tabletext, align: center"]7/32" 6mm[/TD]
[TD="class: tabletext, align: center"]£4.50[/TD]
[/TR]
[TR="bgcolor: 99CCFF"]
[TD="class: tabletext2, align: center"]2BA[/TD]
[TD="class: tabletext2, align: center"]3/8" 9.5mm
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£4.50​
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[TD][TABLE="width: 100%"]
[TR="bgcolor: #FFFFCC"]
[TD="width: 34%, bgcolor: #FFFFCC"]
M4 and M5x6mm
M5x6%20interscrew.gif

​
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M4 and M5x10mm
M5x10%20interscrew.gif

​
[/TD]
[TD="class: tablehead, bgcolor: #336699, align: center"]A4 GRADE STAINLESS STEEL
SMOOTH HEAD
SPLINED BARREL
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[TD][TABLE="width: 100%"]
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[TD="class: tablehead, width: 34%, bgcolor: #336699, align: center"]THREAD TYPE[/TD]
[TD="class: tablehead, width: 34%, bgcolor: #336699, align: center"]THREAD LENGTH[/TD]
[TD="class: tablehead, width: 32%, bgcolor: #336699, align: center"]PRICE PER 10
[/TD]
[/TR]
[TR="bgcolor: CCCCFF"]
[TD="class: tabletext, width: 34%, align: center"]M4 Metric[/TD]
[TD="class: tabletext, width: 34%, align: center"]7/32" 6mm[/TD]
[TD="class: tabletext, width: 32%, bgcolor: CCCCFF, align: center"]£4.50[/TD]
[/TR]
[TR="bgcolor: CCCCFF"]
[TD="class: tabletext2, width: 34%, bgcolor: #99CCFF, align: center"]M4 Metric[/TD]
[TD="class: tabletext2, width: 34%, bgcolor: #99CCFF, align: center"]3/8" 9.5mm[/TD]
[TD="class: tabletext2, width: 32%, bgcolor: #99CCFF, align: center"]£4.50[/TD]
[/TR]
[TR="bgcolor: 9999ff"]
[TD="class: tabletext, width: 34%, bgcolor: #CCCCFF, align: center"]M5 Metric[/TD]
[TD="class: tabletext, width: 34%, bgcolor: #CCCCFF, align: center"]7/32" 6mm[/TD]
[TD="class: tabletext, width: 32%, bgcolor: #CCCCFF, align: center"]£4.50[/TD]
[/TR]
[TR="bgcolor: 9999ff"]
[TD="class: tabletext2, width: 34%, bgcolor: #99CCFF, align: center"]M5 Metric[/TD]
[TD="class: tabletext2, width: 34%, bgcolor: #99CCFF, align: center"]3/8" 9.5mm[/TD]
[TD="class: tabletext2, width: 32%, bgcolor: #99CCFF, align: center"]£4.50[/TD]
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[TD="class: tablehead, bgcolor: #336699, align: center"]Washers to fit over interscrews
to increase head size
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[TD][TABLE="width: 100%"]
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[TD="class: tablehead, width: 34%, bgcolor: #336699, align: center"]EXTERNAL DIAMETER[/TD]
[TD="class: tablehead, width: 34%, bgcolor: #336699, align: center"]INTERNAL DIAMETER[/TD]
[TD="class: tablehead, width: 32%, bgcolor: #336699, align: center"]PRICE PER 10
[/TD]
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[TR="bgcolor: CCCCFF"]
[TD="class: tabletext, width: 34%, align: center"]14mm[/TD]
[TD="class: tabletext, width: 34%, align: center"]6.75mm[/TD]
[TD="class: tabletext, width: 32%, bgcolor: CCCCFF, align: center"]£0.50[/TD]
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washer.gif
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http://hadlo-43547-001.dsvr.co.uk/Pages/Interscrews.html
 
theoldsalt said:
I think the interscrews on my elderly Westerly were whitworth.
Click to expand...

At one time Westerly used M3.5 Not exactly non standard, because its a size in the thread tables, but almost un-obtainable. We bought some new ones from Trafalgar Yacht Services... It was good few yeas ago but they still stock them as yellow duck says
 
Last edited:
VicS said:
At one time Westerly used M3.5 Not exactly non standard, because its a size in the thread tables, but almost un-obtainable. We bought some new ones from Trafalgar Yacht Services... It was good few yeas ago but they still stock them as yellow duck says
Click to expand...

I think M3.5 is a standard for electrical socket and switch plates. I had a job requiring this size and the taps and dies were readily available. Those in the electrical world are generally plated brass but come in all sorts of lengths.
 
sailorman said:
#2 was to confirm what you wanted / needed. From that you actually looked further based upon your newly gleaned knowledge
Click to expand...

Assistance was greatly appreciated. My various thread gauges would not fit and my measurements on a 10mm long screw were obviously imprecise. What baffled me was that a 2BA screw I tried (because it looked appropriate) would not start. That could have been a defective screw and threw me.

So the assistance was very helpful suggesting that 2BA was a possibility I later confirmed.

It was the cost of the Interscrew replacements that shocked me.

Once again, apologies if I offended.
 
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