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Apr 29th, 2024
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Joined: Apr 2007
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Sidelock
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Sidelock
Joined: Apr 2007
Posts: 110 |
I had been thinking about posting this question for a long time, holding off only because I was kind of embarrassed to ask, but when a prominent stockmaker asked me the same thing this morning, I decided it was time to take the plunge:
What is the reasoning behind using tapered wood screws in gunmaking? Any rotation from tight will leave no usable engagement in the wood. Thought perhaps some of our friends in the UK could enlighten. Thank you.
Craig Libhart
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Joined: Oct 2006
Posts: 879
Sidelock
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Sidelock
Joined: Oct 2006
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Previous post deleted
Last edited by tudurgs; 01/08/15 05:21 PM.
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Joined: May 2004
Posts: 778 Likes: 36
Sidelock
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Sidelock
Joined: May 2004
Posts: 778 Likes: 36 |
I have never been told the reason for this but I have worked out that it is about the way the screw starts in a virgin wood hole. If you try and screw a parallel pin into a unused hole of the right size it quickly becomes very stiff and needs working in and out several times before it can be safely screwed in all the way without possibly bruising the slot. If you use a tapered screw is starts easily and only gets stiff towards the end of its travel, where it needs to be. Granted that an old screw that has been disturbed a few times usually won't time correctly when tight.
The same problem applies when inserting a new parallel screw into an old threaded hole, they can be very stiff.
A little bit of wax to lube them usually helps or I sometimes cut the required thread with a 1st tap of the right thread. This gives a good start to the thread without cutting it all the way. In a way it duplicates the effect of a tapered screw, giving a nice clear thread to run in for the first 1/3 or 1/2 and a virgin hole beyond.
I have had tapered screws made up for very special jobs but generally I use parallel screws of 3/16 Whitworth and prepare the hole as above.
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Joined: May 2008
Posts: 8,158 Likes: 114
Sidelock
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Sidelock
Joined: May 2008
Posts: 8,158 Likes: 114 |
I have never been told the reason for this but I have worked out that it is about the way the screw starts in a virgin wood hole. If you try and screw a parallel pin into a unused hole of the right size it quickly becomes very stiff and needs working in and out several times before it can be safely screwed in all the way without possibly bruising the slot. If you use a tapered screw is starts easily and only gets stiff towards the end of its travel, where it needs to be. Granted that an old screw that has been disturbed a few times usually won't time correctly when tight.
The same problem applies when inserting a new parallel screw into an old threaded hole, they can be very stiff.
A little bit of wax to lube them usually helps or I sometimes cut the required thread with a 1st tap of the right thread. This gives a good start to the thread without cutting it all the way. In a way it duplicates the effect of a tapered screw, giving a nice clear thread to run in for the first 1/3 or 1/2 and a virgin hole beyond.
I have had tapered screws made up for very special jobs but generally I use parallel screws of 3/16 Whitworth and prepare the hole as above. Are we talking about machine shop standards or sexual experiences. "Old threaded hole" makes me think about some of Ben Franklin's rather sage advice to the young and randy Colonials- what Ho!!
"The field is the touchstone of the man"..
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Joined: Jan 2002
Posts: 5,954 Likes: 12
Sidelock
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Sidelock
Joined: Jan 2002
Posts: 5,954 Likes: 12 |
Per Toby, wood isn't the best of materials for supporting threads. On the other hand, the screw thread remains poster child of fasteners. Therefore, the mechanic does whatever works for threads in wood. And when the wooden threads fail, we fill the hole with something that will support threads much better. Long live epoxy!!!
DDA
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Joined: May 2004
Posts: 778 Likes: 36
Sidelock
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Sidelock
Joined: May 2004
Posts: 778 Likes: 36 |
The original tapered screws are usually a stupid tpi as well, about 22-23, rather than the 24 tpi of the 3/16 Whit. I rarely find tapered screws with 24 tpi so the 22-23 must be some kind of standard.
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Joined: Feb 2006
Posts: 3,733 Likes: 52
Sidelock
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Sidelock
Joined: Feb 2006
Posts: 3,733 Likes: 52 |
Wood screws whether tapered or straight once they are "timed" have to go back into the same hole again. This pertains to butt plate screws and trigger guards that have two screws, and even some for-end screws on the inside iron.
You might get lucky if you don't put them back, but most times when you buy a used gun and they are not "timed" is because they were put in the wrong hole.
Once you try to "time" the wrong screw, now the correct one will be loose.
Most butt plate screws from vintage guns are straight.
David
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Joined: Dec 2001
Posts: 3,553
Sidelock
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Sidelock
Joined: Dec 2001
Posts: 3,553 |
Yes Fox,
they are indeed talking about sex...nice on topic post...as usual, check yourself for any loose screws mate, lol
franc
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Joined: Feb 2009
Posts: 7,463 Likes: 212
Sidelock
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Sidelock
Joined: Feb 2009
Posts: 7,463 Likes: 212 |
I'd guess the furniture industry lead the way in screw design. Might have been thought of as a good trade off between head strength and thread surface area in a shallow hole. The design seems to work well with very quick, accurate and inexpensive hand pilot hole tools. Maybe, less chance of splitting thin inletted spots.
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