antique bolts and screws

[whitebear]

I don't know if this should be here or where, if it needs to be moved please move it. but, I know that there is machinery now to make all kinds of bolte and screws to a standard size and thread pitch.  My question is did the original makers use a standard size bolt or screw that may also have been used by other makers or did they make the screw threads and make a tap to fit them.  I have never dismantled an original and have had my hand on very few so I have no knowledge on this subject.  I am thinking especially of the breechplugs.

[Acer Saccharum]

Look up James Wilson Everett's posts on screw plates. Threads were 'formed' rather than cut, and you needed the tool to do it with. In the early 19th century and before, standardized threads were non-existent.

[Mark Elliott]

Individual tool manufacturers had standards, but there were no industry standards.   You would have to buy your taps and dies or screw plates from the same manufacturer; or make your taps from your screw plate/die/swage.

[whitebear]

Thanks that's what I thought but wasn't sure.  So if you lost or broke an internal lock screw you needed to go back to the maker or find someone with a screw that fit.  Is this correct?

[jerrywh]

 White bear.
  In my opinion both of the options were used. Some used commercially made screw plates and some made their own.
 I have dismantled antique guns and found that no existing thread would match them. Some were metric and some guns had a combo of both on them. I just un breeched a set of 18th century shotgun barrels and the breech plug threads did not appear to be cut. They appeared to be swaged . Sort of a force fit. They were rounded looking threads and the plugs were about 1 1/4" long. The touch holes go through the side of the plugs.  

[Acer Saccharum]

Thread profiles took ages to standardize. The rounded thread Jerry refers to is an old one, similar to the thread on a lightbulb base.

Many early threads are 90 Vee, with rounded tops and gullets. This profile is quite suited to forming, rather than cutting.

The 60 degree Vee thread is standard in the US for threads. Whitworth, BSA, Metric, buttress, Acme, etc. Enough styles to make your head spin. Very hard to determine what thread you have when a fastener is small, or all you have is an internal thread and you need to make the bolt/screw to go in it.

[James Wilson Everett]

Guys,

Here is a somewhat older topic on making the breech plug threads using only 18th c type tools and techniques.  Really quite a bit different than what is done today.

http://americanlongrifles.org/forum/index.php?topic=33217.msg318587#msg318587

Yes, the older threads did tend to look a lot like lightbulb threads.  The male part of the breechplug was made using an adjustable split die tool.  In this way a great variety of sizes could be made.  Also, when using the original 18th c tools & techniques a dedicated gunsmith could make the breechplug threads with a lot less "slop" in the threads than we see today with a standard UNF/UNC tap & die.

Jim