18th c Screw Plate Use

[Bob Roller]

I was told that in flyers jargon,"Buying the Farm" referred to a departure stall at the end of the runway that lands in a housing development. I lost my doctor like that when his V tailed doctor killer crapped out taking him and a daughter with it.
No homes involved but still tragic enough.
Bob Roller

[eddillon]

Bob, you are right about the jargon.  Happy to report that I purchased the farm and that I did not "buy the farm".
Did some unauthorized high speed passes over the farm a couple of time.  Too tempting.  My barn had a shiny metal roof that could be seen from miles away. Managed to cause the early demise of two  my neighbor's turkeys.  Costly lighting of afterburners.  Statisicallyy more doctors "buy the farm" in private aircraft than any other profession. 

[James Wilson Everett]

Guys,

As noted by Riflesmith's comment on 18 Nov., the two side holes seem to be a slightly later development in the manufacture of screwplates.  Please note that I am a tool user, not necessarily a collector and expert on them.  Anyway, here is a screw plate without the side holes, marked P S STUBS and the number 16.  Peter Stubs was a noted English tool maker 1756-1806 although his name was marked on the firm's tools long after his death.  I must assume that this screwplate dates earlier than those shown with the side holes.  By the way, the side holes are used to allow access of a jewler's saw blade to cut through a broken screw shank and to remove it when that oops happens.

Jim Everett

[Acer Saccharum]

What are those little stamped diagonal line, James? is that the sequence you follow to make the screw smaller and smaller?

[Bill-52]

Jim,

Just for reference, roughly how long are the screw plates you've been posting?  Or, what range of lengths?  Just trying to get an idea of size.

Thanks,
Bill

[James Wilson Everett]

Guys,

The little scribed line on the screwplates align the two holes that are for the same thread.  Each of the two holes will make the identical threads with the exception that one thread will be very slightly smaller, usually by about 0.002 inches on the diameter.  The larger thread is for making the tap and the smaller thread is for making the screw.  Really, for everything to fit together properly the tap thread must be a little larger than the screw thread.

The sizes of the screwplates posted are as follows.

The large brown screwplate with the tiny side holes posted first - blade length 6.5 in. and LOA 10.4 in.  It is marked Lewis & Griffith.

The small shiny screwplate with the tiny side holes posted second - blade length 4.3 in. and LOA 7.5 in.  It is marked CB.

The large brown screwplate without side holes posted last - blade length 6.8 in. and LOA 10.7 in.  It is marked Stubs

Jim Everett

[frenchman]

James that is great show and tell now for wood screws how where those baby made

[James Wilson Everett]

Guys,

For the wood screws, look in the tutorial section of the forums under the title "Making 18th c Wood Screws".

Jim

[frenchman]

thanks James
 this is very interesting something to look for you never know maybe old garage sales

[James Wilson Everett]

Guys,

Here are some photos of another screwplate that was not made by a professional tool maker.  The local smith probably borrowed as many taps as he could from his neighbors and made this screwplate from an old file (notice the file handle tang).  Also, to find a screwplate with some of the original mating taps is very unusual.  I don't know the trade of the smith who used this tool, but it looks like he had the screw sizes to make anything from a wagon to a watch.









I do not actually use this one, but it is interesting.

Jim Everett

[Dphariss]

I was told that in flyers jargon,"Buying the Farm" referred to a departure stall at the end of the runway that lands in a housing development. I lost my doctor like that when his V tailed doctor killer crapped out taking him and a daughter with it.
No homes involved but still tragic enough.
Bob Roller

 When I was learning to fly a guy stuck one of these into the plowed field one IFR night while trying to get in on a VOR approach without an instrument rating. 4 on board. His wife crawled from the wreck to a farm house, only survivor. Don't think he was a doctor though.  I had not thought about V tails and doctors in years.... Last one I remember before I quit flying a doc hit Mt McKinley with one.

I don't know where "buying the farm" came from but I always heard it as an aviation term referring to someone who made a "bad landing".
Dan

[James Wilson Everett]

Guys,  Another tool used to make a machine screw prior to threading with the screwplate is a tool called a screw grinder.  This is the tool used to bring the iron to the proper diameter and cylindrical shape.  The screw grinder has a through hole of the proper diameter for the shaft of the screw before threading.  In this case to make a 0.174 - 30 screw thread the shaft starts at 0.157 diameter.  This is not a typo - the threads grow outwards from 0.157 to 0.174 during the thread swage process.  The cutting teeth form both the shaft diameter and the square surface under the screw head.  You clamp the grinder in a vice and twist the iron rod through it allowing the finished shaft to pass into the hole.  It saves time to rough form the shaft using a file until you have an octagon type shape about 0.16 across the flats before using the grinder.

Jim Everett

[James Wilson Everett]

Guys,

Here is a page from the mid 18th c tool catalog by John Wyke showing the array of different size screw plates that were available from England.  Normally the gunsmith would make his own taps from the larger of the mated thread holes in the plate as the taps were an expendable item - just like today, but in the 18th c the gunsmith could not buy a replacement tap that matches the screwplate he has.  Original screw plates that look just like those illustrated are readily available on e-bay or in antique shops.

Jim Everett

[flintriflesmith]

Notice that the #345 is also the tap wrench? That slot near where the handle joins the flat part fits the period taps below.

Gary

[Jim Kibler]

Guys,  Another tool used to make a machine screw prior to threading with the screwplate is a tool called a screw grinder.  This is the tool used to bring the iron to the proper diameter and cylindrical shape.  The screw grinder has a through hole of the proper diameter for the shaft of the screw before threading.  In this case to make a 0.174 - 30 screw thread the shaft starts at 0.157 diameter.  This is not a typo - the threads grow outwards from 0.157 to 0.174 during the thread swage process.  The cutting teeth form both the shaft diameter and the square surface under the screw head.  You clamp the grinder in a vice and twist the iron rod through it allowing the finished shaft to pass into the hole.  It saves time to rough form the shaft using a file until you have an octagon type shape about 0.16 across the flats before using the grinder.

Jim Everett

Jim,

When looking at original screws on 17th and 18th century locks I've not noticed the threads being larger than than the screw shaft diameter.  Perhaps it's just that I've not payed enough attention.  I did take a minute to examine screws on a Andrew Dolep lock from the late 17th century and measured no appreciable difference between thread and shank diameter.  Any thoughts?  I'll look at some other examples I have when I get a chance.

Thanks,
Jim

[James Wilson Everett]

Jim,
Now this is getting somewhat advanced, thanks for the comment.  This does require more explanation.  My screws do not show the threads larger than the shaft, like on the sear screw where the sear pivots on the unthreasded shaft like an axle.  Here the screw blank is formed with two different diameters before threading.  A 0.174 shaft near the head and a 0.157 shaft for the thread.  When the thread is formed and the diameter becomes 0.174 the whole screw is of the same diameter.  Now the sear hole fit will not be sloppy and will not be pivoting on the thresded portion, either.

Jim

[Jim Kibler]

Thanks for the explanation, Jim.  Makes perfect sense.

Jim

[Acer Saccharum]

I suppose you could use a 'thread diameter' screw grinder to cut a nice shoulder on the shank just past the thread. And another size grinder to trim under the head of the screw.

This reminds me, I have some watchmaker taps and dies from the 19th Cent. This topic will get me to dig those out and take a fresh look. And a photo if useful here.

Vewwy twicky business, Mr. Wabbit.

[James Wilson Everett]

Guys,

Actually in making the screws there are several different size grinders for the thread shaft, for the shaft without threads and for the head.  You can thread the shaft for the 0.174 - 30 threads (the ones I use for gunlocks) starting with the shaft at 0.174.  This is just the same way we do the modern die cut threads today.  However, the force required is much higher and the result is often a twisted off shank.  It is much easier to put the 0.174 threads on a 0.157 shaft.  When the threads run to the point where the shaft increases diameter to 0.174 there is often a build up or raised ridge as the swaged material has nowhere to go at this point.  This ridge at the intersection must be filed away for something like the sear or the frizzen hole to fit over the new thread.  I know that this sounds complicated and it is certainly much easier to use the modern Siler style lock kits.  But when you actually make a lock in the 18th c style it give us so much more respect for those period craftsmen.

Jim Everett

[James Wilson Everett]

Gary,

I guess that the black oblong in the #345 may indeed be used for a tap wrench.  It really would make a lot of sense to include such a feature.  However, I have never seen a screwplate with such a tap wrench feature included.  Maybe someone out there has seen one, if so, please let us all know about it.  Here are some photos of a small 18th c tap wrench that was forged from wrought iron.  It is about 8" long.  The tap wrenches that tighten on the tap square by a screw are a lot more easy to use, this one has a lot of slop between the tap and the wrench square.  I am sure you can envision how much more difficult such a tool is to use.  I do not know when the screw adjustable type of wrenches started to be used.

Jim Everett

[dannybb55]

He made that one quick, with a little time and some well made drifts, he would have had some tighter holes.

[James Wilson Everett]

Danny,

Of course your observation is true.  But, I really enjoy looking at some 18th c things that are not exactly perfect.  It helps me to realize that this things were made by a guy who was in many ways just like me, that is imperfect.  Check this out - the copy of the page from the John Wyke catalog was engraved by hand on a copper plate.  Look at the perfection of the straight lines.  If we ever feel proud of our work - try to engrave a truly straight and uniform line as in this example.  I am afraid mine would look a lot like a snake trail.  Boy, did this ever wander off subject!

Happy New Year

Jim Everett

[dannybb55]

And he had to engrave it in reverse! I bet he charged a few shillings for that work.
 HAPPY NEW YEARS y'all.

[David R. Pennington]

Love this stuff! Love being educated on these old tools. This is a large part of the enjoyment for me in building is learning history in a hands-on practical way you can't get any other way. My most recent project hasn't seen a power tool nor will it (except for when Dunlap band sawed out the blank).

[Glenn]

Love this stuff! Love being educated on these old tools. This is a large part of the enjoyment for me in building is learning history in a hands-on practical way you can't get any other way. My most recent project hasn't seen a power tool nor will it (except for when Dunlap band sawed out the blank).

I couldn't agree more; this has got to be one of the best threads I've found on this site to date.  THANKS !!!