18th c Screw Plate Use

[rich pierce]

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

Pun unintentional?   

[dannybb55]

Jim, How is your forge set up? Side draught, RR Pot, Champion blower or Great bellows?
                           Danny

[James Wilson Everett]

Danny,

You obviously know a lot more than me about the different forges, because I must admit some ignorance of the terms in your question.  For forging the flintlock mechanism and almost all of the small parts I simply clamp an oxy-acetylene torch in my vice with the flame pointing up.  With my anvil within inches of this it is easier to forge the very small parts without burning my knuckles.  I actually do the forging sitting down in a chair.  I can forge a few strokes and reheat several times in a minute quite easily.  For bigger stuff I borrow a  neighbor's forge that uses one of those hand crank things.  The draft blows upwards through what I think is a truck wheel.  Also, some of my pistol barrels are forged by a dear friend, Jymm Hoffman, who uses a trip hammer to forge barrel blanks that are 1,000 times better looking than mine.

Jim Everett

[dannybb55]

Wow! I thought that you would have a Spreading Chestnut tree and everything. My forge is made out of sawmill pine nailed into the form of a 2 foot cube with a 1/8 " sheet iron top. My air comes in from the side through a freight wagon wheel bearing, a side draught forge. The blower is a 19th century Champion Climax, 100 bucks at the flea market and my anvil is a little 100 lb London job, same price. The iron plate is so burned through that I had to fill the holes with concrete but it still works fine.
 What I would like to have is a 200 lb Fisher Norris, a square Rail Road Tuyere in a 3 foot square, bricked in forge with a 6 in deep box full of coal and a 4 foot Great Bellows in an enclosed shop, 5 tons of coal and a ton of steel, like I used to have at the Museum, but i can do all of the work that I require.

[James Wilson Everett]

Guys,

This reply is simply to bring this topic back to life!

[shortbarrel]

James: 40 years ago I got into making a jam tap to make the jam die. If you take a knife blade and a piece of wood dowel and turn the knife blade a few degrees and rotate, you are making a screw. Used this method to make a threaded high carbon (fully annealed) screw thread in a jig I clamped in the vise. Made two sizes. From here it gets kind of deep. If anyone has any questions post them and I,ll try to answer. James THANKS for your time and effort here.

[David R. Pennington]

Ever since this thread started I've been looking for original die plates but so far all the ones I have found were unusable or out of my financial reach.

[Sawatis]

Jim, I don't think this post ever died! 
Do have a question I've been pondering while I've been forging things...tapered reamers...I have a few both 4-square and half round for use in a brace...but their sizes are considerably larger than the screws we use in  locks etc.  Do you have any examples of some that fit in the lock-screw size range..I'm wonder how long, how much taper, how many sizes...it would see that the tapers would have to be less steep with the small diameter holes in thinner metals, otherwise you'd be from good to too large in a hurry across the thickness of the piece...rendering the taps (and screw) useless.  Thoughts?
John

[James Wilson Everett]

Here is a photo of the small tapered reamer that I use for the lock plate screw holes.  I made this one to have about the same taper as the larger originals that I have.  I mounted this reamer in a small wood handle and I simply turn it like a screw driver.  I believe that the survival rate of the really small 18th c tools is very low.



To determine when the hole reaches the correct size, I use a go - no go gauge.  When the hole is the proper size, the gauge will pass into the hole up to the tiny step you see about half way on the pin.

[U

Here is what the gauge looks like when in a hole of the proper size.



All of these sizes are determined by trial & error, there is no manual to find the proper size.

Jim

[hammer]

Just love this topic.
I have some screw plates and also a couple that are adjustable.

There is no doubt in my mind that the old screw threads and holes were tapered.   I have, for instance, an English 1810 f/l fowler and needed a replacement top jaw and screw.  My engineering friend turned up a perfect screw but with a parallel thread.  Sloppy fit, so made a larger one.  Couldn't make it tight.  Tapered female thread.   One day I will have one turned up with a taper.

All male and female screw threads on the fowler are likewise tapered.   And I discovered that the taper has been matched to the hole such that the thread wedges in at just the point the head also tightens against the body.   I assume it must be a careful trial and error process to achieve that fit.    It does mean, however, that the threads on the screw also press outwards against the female threads and hole making for a stronger connection?   I can see how this would make a better interference fit on such as a breech plug.

[Sawatis]

OK, thanks for the pics Jim.  Based on these and Mr Hammer's post, it raises another question...screws, taps, reamers all tapered... so how was a hole, like the tumbler shaft hole that should be a precision fit to reduce play handles...are they tapered in the originals?  This would make me think that if the shaft ...which would be concentric based on our tumbler mill discussions, would be rotating in a tapered hole. If so was the large end of the taper on the cock side or tumbler side?? Either way there would be a narrow contact surface where the hole was "just right" and this would undoubtable result in rapid wear...even on a cased lock plate.  Is this evidenced in well worn locks...might be why they are well worn?
John

[rich pierce]

I had the opportunity to study an early Dutch musket lock, very large, with a very curved banana lock plate.   The frizzen was wide as a child's hand. Ok, about 1.5". Anyway I was very surprised to see the tumbler axle was quite noticeably tapered as was the hole in the lock plate.

I have no idea if this was a common feature on very early locks.

[James Wilson Everett]

Guys,

Very good questions, but the answers are elusive indeed.  From all of the 18th c tooling that I have seen, the only way to achieve a tightly controlled diameter small hole is to use an undersized fishtail bit followed by a tapered reamer.  This always results in a very slight or very tiny taper to the hole, probably one or two thousandths of an inch taper in the thickness of a lock plate.  An unknown tool is the "false drill" as used at the Harpers Ferry arsenal.  This tool apparently did result in a cylindrical hole of a controlled diameter.  Unfortunately, I have not been able to discover what a "false drill" looked like or how it was used.  See this topic:   http://americanlongrifles.org/forum/index.php?topic=36020.msg345643#msg345643.

This is now called "primary research" as there is no book or other publication where a researcher can find the answer.  So, anybody out there have any idea what an 18th or19th c "false drill" is?

Jim

[heinz]

Jim, I suspect it is a drill with a false edge on the v bit and sharpened sides like reamer. It could start in the tapered hole and ream it straight

[ShutEyeHunter]

Danny,

You obviously know a lot more than me about the different forges, because I must admit some ignorance of the terms in your question.  For forging the flintlock mechanism and almost all of the small parts I simply clamp an oxy-acetylene torch in my vice with the flame pointing up.  With my anvil within inches of this it is easier to forge the very small parts without burning my knuckles.  I actually do the forging sitting down in a chair.  I can forge a few strokes and reheat several times in a minute quite easily.  For bigger stuff I borrow a  neighbor's forge that uses one of those hand crank things.  The draft blows upwards through what I think is a truck wheel.  Also, some of my pistol barrels are forged by a dear friend, Jymm Hoffman, who uses a trip hammer to forge barrel blanks that are 1,000 times better looking than mine.

Jim Everett

Doh!  Why didn't I think of putting the torch in the vise???

Interested to see if one of these threading devices can be made out of modern materials/tools.

BTW on the  V tail/buying the farm--flew one quite a bit in the 1970s. Didn't kill myself but  I wasn't a Dr (& I understood variable pitch props)

[Mark Elliott]

Danny,

You obviously know a lot more than me about the different forges, because I must admit some ignorance of the terms in your question.  For forging the flintlock mechanism and almost all of the small parts I simply clamp an oxy-acetylene torch in my vice with the flame pointing up.  With my anvil within inches of this it is easier to forge the very small parts without burning my knuckles.  I actually do the forging sitting down in a chair.  I can forge a few strokes and reheat several times in a minute quite easily.  For bigger stuff I borrow a  neighbor's forge that uses one of those hand crank things.  The draft blows upwards through what I think is a truck wheel.  Also, some of my pistol barrels are forged by a dear friend, Jymm Hoffman, who uses a trip hammer to forge barrel blanks that are 1,000 times better looking than mine.

Jim Everett

Doh!  Why didn't I think of putting the torch in the vise???

Interested to see if one of these threading devices can be made out of modern materials/tools.

BTW on the  V tail/buying the farm--flew one quite a bit in the 1970s. Didn't kill myself but  I wasn't a Dr (& I understood variable pitch props)

I have a propane forge and all the accessories capable of doing good size work.   However,  for making springs, final bends in a trigger guard, and similar small bits of work;  I use a rosebud tip on my Smith Little Torch on its magnetic mount.   It puts the flame out horizontally.    That rosebud make more than enough heat for working anything from a mainspring on down.   It is much better than any plain propane or MAPP torch I ever used.   It is one of the best purchases I ever made.  I use it with Propane and it is very clean for indoor use. 

[Bob Roller]

Danny,

You obviously know a lot more than me about the different forges, because I must admit some ignorance of the terms in your question.  For forging the flintlock mechanism and almost all of the small parts I simply clamp an oxy-acetylene torch in my vice with the flame pointing up.  With my anvil within inches of this it is easier to forge the very small parts without burning my knuckles.  I actually do the forging sitting down in a chair.  I can forge a few strokes and reheat several times in a minute quite easily.  For bigger stuff I borrow a  neighbor's forge that uses one of those hand crank things.  The draft blows upwards through what I think is a truck wheel.  Also, some of my pistol barrels are forged by a dear friend, Jymm Hoffman, who uses a trip hammer to forge barrel blanks that are 1,000 times better looking than mine.

Jim Everett

Doh!  Why didn't I think of putting the torch in the vise???

Interested to see if one of these threading devices can be made out of modern materials/tools.

BTW on the  V tail/buying the farm--flew one quite a bit in the 1970s. Didn't kill myself but  I wasn't a Dr (& I understood variable pitch props)

I lost my doctor in one of the V tailed Beeches.It also took his beautiful daughter and her fiancé as well.
I have a wee bit of time in one but that was playing around many years ago.

Bob Roller

[James Wilson Everett]

Guys,

In reply to a question from ShutEyeHunter:  Yes, I have made a screwplate that looks a bit like the originals, but has many of the modern screw threads that I would likely encounter when at Show-N-Tells doing 18th c gunsmithing.  With this tool I can make a replacement screw for a modern reproduction just sitting under a shade tree.  Sometimes the re-enactors are rather surprised that a person can actually do an 18th c skill!  The complete discussion of this stuff is found on an old topic "Articifer's Box" http://americanlongrifles.org/forum/index.php?topic=22390.msg214020#msg214020

Here are some photos of the "modern" screw plate.  It is made from 1095 carbon steel, I don't remember the temper.







Jim

[okieboy]

 I am late to this discussion, but it is very good.
 In a modern machine shop the thread grinders would be called hollow mills, they are fairly specialized and a lot of machinists would have never used one.
 The movement of metal in thread forming is interesting. The diameter of stock for a male thread, or the hole for a female thread is close to the pitch diameter of the thread being made. However if one changes the stock diameter by .001", the diameter of the thread will change by .003" because of the geometric nature of the material flow.
 As to "bought the farm", I was given to understand that the phrase started in World War One. A soldier leaving for the war would buy a life insurance policy and the amount was often equal the the family mortgage. If he did not return....

[James Wilson Everett]

Guys,

Recently there have been a couple of mentions of screw plate use.  This comment just resurrects this old topic.

Jim

[David R. Pennington]

Yes I re read all this the other night. I managed to find one old screw plate, (a smaller one) and an adjustable one. Now to make a screw grinder I guess?

[James Wilson Everett]

Guys,

Another update on the use of an 18th c screwplate.  A question often asked is "what is the proper diameter for the shaft prior to forming the threads?"  The answer up to now was to just do a trial & error type of figuring until, at long last, the proper diameter is found.  A much easier, and ingenious, way has been re-discovered.  The proper shaft diameter is that size that will just barely pass through the next larger hole in the screwplate.  It really does seem to work well.  Look at the photo to see what I mean.  This surely does make this tool a lot easier to use and a lot more sophisticated in design.



This information was re-discovered by our own master screwmaker, Mark Elliot, so all thanks go to him alone.  This is another example of the answer being right before our eyes, yet we don't see it.  Thanks again to Mark!

Jim

[Acer Saccharum]

James, would it make sense, if I was a maker (or user) of screw plates, to make all the screw holes the SAME PITCH?

If I were making screws, I can take a blank from one hole to the next to form the threads completely, like move down the plate from a starter size down to a finish size?

[Mark Elliott]

James, would it make sense, if I was a maker (or user) of screw plates, to make all the screw holes the SAME PITCH?

If I were making screws, I can take a blank from one hole to the next to form the threads completely, like move down the plate from a starter size down to a finish size?

The screw plate that I have (18th century) seems to have a couple groups of four holes that have the same pitch with increasingly smaller holes.   The pitches of the eight groups (A-H) are 24, 32, 40, and 48 TPI.   Four of the groups are approxomately 32 TPI and two groups are approximately 24 TPI.

[Mark Elliott]

Guys,

Another update on the use of an 18th c screwplate.  A question often asked is "what is the proper diameter for the shaft prior to forming the threads?"  The answer up to now was to just do a trial & error type of figuring until, at long last, the proper diameter is found.  A much easier, and ingenious, way has been re-discovered.  The proper shaft diameter is that size that will just barely pass through the next larger hole in the screwplate.  It really does seem to work well.  Look at the photo to see what I mean.  This surely does make this tool a lot easier to use and a lot more sophisticated in design.



This information was re-discovered by our own master screwmaker, Mark Elliot, so all thanks go to him alone.  This is another example of the answer being right before our eyes, yet we don't see it.  Thanks again to Mark!

Jim

The relationship also appears to apply to tap drill/reamer size.