Screw Threads in the 17th century

[gwilson]

I made the screw plates by first making taps on a lathe,then using them to thread holes in the forged screw plate blanks. Screws or taps were made by using hand held thread combs often in early times. A person had to become really adept at moving the threading comb at just the right speed along the bar of metal he was threading. If he did not do this correctly,the threads would be totally ruined,or sometimes "drunken threads " could result. These threads were done by specialists.

By the way,the 2 slots you usually see running into the threaded holes in screw plates were NOT cutting edges. They had no relief. What they were for was to provide a way for you to get a jeweler's sawblade into the slot,to saw up a stud that got broken off in the threaded hole. These little slots terminated in small drilled holes on their extremities. That's where the saw blade could be inserted.

There are hash marks between rows of threaded holes on many of these screw plates. The holes within the hash marks had the same thread,but had different diameters to progressively swage the threaded piece down. Hope this makes sense. My dog is distracting me because she hears thunder,and is afraid.

Lids for wooden containers I have read about,made in Tunbridge Wells,England,were threaded with a SINGLE POINT threading tool that was shaped like a "V" carving tool on the end,bent at a right angle so it could enter the lid. The lathe was turned by the turner's WIFE sometimes,and the thread was perfectly cut just by moving the tool along. Not even with a comb of threads to assist by riding in the threads!! That took real skill!! On the wife's part,too!!

These processes are described in the 19th.C. books by Holtzappfel(I never can spell his name).

I'm sure this method was still practiced in the late 19th.C. at least in Europe because years ago I bought some semi finished breech plugs for guns. Some of them were never used because they had the drunken threads on them,and could not have been screwed into a threaded hole. They were late 19th.C.. Drunken threads were only ever made by hand held threading combs.

[Vince]

Larry,

I guess I should have expanded a bit more. "One Good Turn" is not a long book, it should only take a day or two to read. It took me several years, i.e. it did not hold my interest very well. The author looks at the historical information on the screw, and screw driver. The screw appeared long before the screw driver texts if I remember correctly. But since you can not have one without the other, it shows how something can exist without making it into books, so you really don't know how long something has been around.

Vince

[gwilson]

The Romans had nuts and bolts. I don't recall if the Greek Antikethera mechanism has screws or not. I am sure there are many things about the ancient World we know nothing about. In the Bible, FILES for sharpening tools are mentioned!! They had to have files to make the Antikethera mechanism.

[Eric M]

Just making a file for filing metal often required a hammer and chisel to cut the file teeth one at a time.

Actually, until the late 19th century and well into the 20th century, that is EXACTLY how it was done.

Specialized trade. Special chisels and hammers with angled heads (angling towards the user IIRC.)

A good file maker could cut 20 teeth a minute and the entire file might take 10 minutes.

Hand cut files are still held in esteem. Something about the minute irregularities between teeth that make a hand cut file more resistant to vibration and cut smoother. Covered in some detail at "Treatise on Files and Rasps" by Nicholson File Co. ca. 1878.

http://www.amazon.com/Treatise-Files...Nicholson+File

Currently not available but maybe at AbeBooks Official Site - New & Used Books, New & Used Textbooks, Rare & Out of Print Books.

Also descriptive on this in "Modern Machine Shop Practice" by Joshua Rose.

Joe

Joe - I downloaded a .pdf verson of the 1878 edition from Google Books
- A treatise on files and rasps descriptive and illustrated: for the use of ... - William T. Nicholson - Google Books

[99Panhard]

Here is a photo showing the dismantled hilt:



This type is classified as a proto-mortuary sword - a modern term. The approximate date is 1625 to 1635.
The pommel is brass. The grip is especially interesting because it is made of pressed horn, an early plastic. Horn, boiled in oil, becomes plastic and can be pressed in moulds. The technique stayed in use for sword hilts well into the early 19th century and the same technique was used to make the pressed horn buttons on USMC uniforms in WWI.

[S_W_Bausch]

dinosaur's posted link of On ye art and mysterie of turning is a very informative page, other copies exist on the 'net, I cannot say which is the original.

The page mentions Maudslay as being given too much credit of origination, that previous lathes had details of Maudslay's lathe. It was mentioned that an inclined knife was used in creating threads.

Like Ramsden before him, Maudslay went to infinite pains to obtain accurate threads for leadscrews. He tried all known methods and finally settled on the inclined knife.

I can easily imagine a bored apprentice in a wood shop forcing a sharp chisel into a turning cylinder and watching the chisel travel along the workpiece.

[dinosaur]

If you go to Google Books and search for Ancient Carpenters Tools it will take you to an interesting book by Henry Chapman Mercer. Page 272 discusses a Roman iron nut about 1-5/8" square from the 1st or 2nd century AD. Apparently, this nut is in a Museum in Bonn Germany. There is mention of a book published in Leipzig in 1914 entitled "Technik der Verzeit" by F.M. Felders where he talks about some wrenches used on some fasteners for armor made by Ramelli in the 1580's.

[richmccarty]

It's all very interesting.
I have worked on a fair number of 17th and 18th cent. clocks. Of the preindustrial clocks like 17th English lantern clocks or real (not English) 18th cent American clocks, the screws are often very coarsly made and act more like 'turn-lock' fasteners than actual screw threads. Especially the square-headed brass screws securing the frets on English lanterns often look like they might have been filed up by hand or maybe cast with a coase thread and then hand filed.

On later English and American Tallcase clocks I've found that BA threads are almost always a perfect fit. I know that many of the clocks I work on predate the BA standard, but I think that the BA standard must be simply a standardization of something already commonly in use, like maybe Stubbs screw plates.

Best,
Rich

http://www.clockconservation.com

[gwilson]

Even if you filed the threads,they would have to go inside a threaded hole. For that,you need a tap. If you must have a tap,easy enough to take that tap and make a screw plate,even if it was just for 1 thread size.

[thermite]

translated by our only engineer U. S. President, Herbert Hoover

Actually one of two in practice, and two others by technicality.

James Earl Carter, adding courses to his basic Annapolis 'unspecified' Bachelor of Science, also qualified as an Engineer (nuke power plant), and served as such. Rather more skilfully than he did as President, actually.

West Point Graduates also have a degree in 'General Engineering' (Hiram Ulysses Grant and David Dwight Eisenhower). Though neither served as such, each arguably left larger footprints than Hoover.

Bill

[dinosaur]

In 1925 Hoover was the Secretary of Commerce under President Coolidge. He warned that the speculation on Wall Street was getting out of control. He was proven correct four years later.

[thermite]

In 1925 Hoover was the Secretary of Commerce under President Coolidge. He warned that the speculation on Wall Street was getting out of control. He was proven correct four years later.

.. while on his watch as President. And it was NOT his fault at all, though he was blamed for it far and wide.

As with any decent Engineer, he had done the best he could with the tools available to limit and correct the damage.

FDR got credit (eventually..) for the salvation - long and painful though it was, but had to 'invent' NEW tools, some of them arguably more problem than solution. With what we know NOW of Mob Economics (still far too little) it isn't even clear which helped and which hindered.

Not to worry. We are being allowed to repeat the course, and the game is again in play... this go with REAL 'Aryan's in the role of the Thousand-Year Reich, Middle East playing the Balkans, China taking Imperial Japan's former role, the US in the 'declining British Empire' seat, and Eurozone states still auditioning for various bit parts. Again.

The more things change ...

Bill

[99Panhard]

gwilson,

Would you say that the tap used to make the screw plate was likely the same one used to make the "nut"? Unfortunately, even though we have photos of three of these swords, this is the only one we've taken apart... as you well know, museums generally don't allow that ... it would be interesting to compare three or four examples but I'd almost bet they were all threaded and tapped with the same tools. Where should I look to find illustrations of the tools?
Thanks,

JV Puleo

[gwilson]

Probably the same tap made the screw plate. Things like threading tools weren't real common hundreds of years ago. A person might make his own to save money he didn't have. It is possible that an initial tap could be filed out,a screw plate made from it,then a more perfect tap made by threading it through the screw plate. This would smooth out the inequities of the filed out tap. Judging from the looks of your sword's threads,the initial tap could have been filed with the corner of a triangular file.

[99Panhard]

Thanks very much. Thats precisely what I had guessed so its gratifying to get a more professional confirmation. The late AVB Norman hypothesized that the treaded tangs were done in order to be able to replace the blades easily but I doubt he had considered the difficulty of making threads and the impossibility of making multiple interchangeable pieces. My theory is that it was done in order to make it easy to tighten the hilt and that the only blades that could be interchanged would be ones made with the identical tools... making them almost impossible to repair unless a large supply of identical blades was available and we have no reason to believe such was the case. These are fairly rare swords - but there are perhaps a dozen or two known. That is a still substantial number for the early 17th century and they constitute a recognizable group. We have at least one with a signed and dated blade so we know who made them and where. They are unquestionably English.

[paul39]

I can easily imagine a bored apprentice in a wood shop forcing a sharp chisel into a turning cylinder and watching the chisel travel along the workpiece.

If you are a beginning wood turner using the accursed skew chisel, the above happens all too often. Even after lots of practice, with a moments inattention, zap, and you have an unintended spiral decoration on your piece.

There are turners who make screw top lidded boxes, doing the threads freehand. There are also many toothed threading tools that make it easier.

Buy Crown Thread Chasing Tool Set 12 TPI at Woodcraft

Paul

[Xunil Ung]

The first thought which came to mind when I saw the photograph, is that the thread on the tang had been generated by twisting whilst hot. A few years ago, I took an evening course in blacksmithing, and one of the first projects was a poker, with the inevitable twisted decoration along its length.

[fciron]

Hot twisting has a very hard time making a single lead thread. Twisting a flat bar has been used to create a augers for drilling and two-lead screws for novelty items like nutcrackers, but both these applications have a very long lead relative to the cross section of the bar. A twist as tight as the one in the screws shown would likely crack at the root of the the 'thread'. Then we get into the variations in the twist resulting from variations in thickness and temperature.

GWilson is an expert on these historical processes and knows what he's talking about. I've never seen even a hint of disagreement with his info in this thread.

[Xunil Ung]

GWilson is an expert on these historical processes and knows what he's talking about. I've never seen even a hint of disagreement with his info in this thread.

That sounds more like an attempt to suppress dissent, than a willingness to embrace open discussion.

[gwilson]

No,fciron is correct. When you twist a piece hot,it makes a spiral,with the number of corners on the iron dictating the number of leads a thread would have. A square would make 4 leads,a triangle would make 3. It would be necessary to have a cross section of the iron looking like an egg with a sharp small end to produce a single lead screw. Then,it would be next to impossible to twist it EVENLY enough to make a reliable thread. And,next to impossible to twist it tight enough to produce a thread that even approached a usable coarse thread. Another problem with twisting iron that tight would be a pronounced tendency for the axis of said thread to become a spiral,rather than staying straight. If you'd gone to the trouble of making a sword blade,you would want a more certain outcome than attempting such a twist.

Lastly,when you got done,you'd have a thread,but no matching tap. It is infinitely more practical if you had only simple tools,to file out the first tap,thread a die with it,and you'd be ready to go.

I've already mentioned the hand turning of screws several posts ago. If the threads were metal,a threading comb would be used. wooden threads,requiring less precision,were sometimes cut with a single "point" tool resembling a "V" parting tool as used for wood carving,but with the cutting edges oriented vertically. This was done at Tunbridge Wells,England(and other places,too.)

I'm pretty certain those antique Chinese ivory chess pieces that have 2 or 3 parts that thread together,were done freehand with a threading comb. Sometimes the threads are somewhat tapered since the tool was run along freehand. They always seem to have used the same thread. If I recall,it was 27 threads per inch. Some years ago,I made myself a thread comb that I use when repairing those chess pieces.

I spent 39 years learning to do things by primitive means in a museum. If a person has a basic understanding of hand metal working,he would quickly abandon the idea of twisting them into shape.