Soon nail making really took off, primarily in the USA and also the UK with its captive markets of the British Empire. The cut nail was produced in large numbers and various other shapes were devised to suit different purposes.

The next step in identifying your thread type is to determine the pitch size. A thread’s pitch size is the number of threads per inch or the distance between threads on metric thread types. While a ruler could be used to calculate the pitch size, a pitch gauge is highly recommended as pitch sizes can be very similar. Test a couple different sizes with a pitch gauge to find the best match.

Squarethread angle

Maureen K. Phillips: Mechanic Geniuses and Duckies, A Revision of New England's Cut Nail Chronology Before 1820, APT Bulletin Vol. XXV No. 3-4, and Mechanic Geniuses and Duckies Redux: Nail Makers and Their Machines, APT Bulletin XXVII No. 1-2. Association for Preservation Technology International

Glasgow Steel Nail Co has been involved in many interesting projects that have included providing nails for the Globe Theatre in London, restoration work on Stirling Castle and other castles. The nails are generally used for doors, floors, gates, indeed anywhere a period nail has to be displayed. The company is also prepared to consider special projects, for example, it produced a bronze boat nail for the building of the replica ship the 'Matthew' that in the year 2000 re-traced the 500 year old voyage of John Cabot who discovered New Foundland.

Eventually, in the USA, towards the late 1700's and early 1800's, a nail machine was devised which helped to automate the process. This machine had essentially three parts. Flat metal strips of around two feet (600mm) in length and the width slightly larger than the nail length was presented to the machine. The first lever cut a triangular strip of metal giving the desired width of the nail, the second lever held the nail in place while the third lever formed the head. The strip of metal was then turned through 180° to cut the next equal and opposite nail shape off the strip. These nails are known as cut nails.

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In the heartlands of the industrial revolution, many nail factories had row upon row of these nail machines and the incessant clatter from them created a deafening sound.

As explained earlier, the first cut nail machines replicated the handmade nail - the square tapered nail with a rosehead. Because the process still involves a man (or woman) presenting a strip of metal to a machine, the resulting nail is necessarily imprecise - that is each nail can look a little different to the next one.

A caliper is a useful tool that measures the outside diameter of a male thread and inside diameter of a female thread. Using a caliper will give you the most accurate and precise measurements, but a straight steel ruler is a good alternative. However, if you think you’ll be using one quite often, here’s a digital caliper we found on Amazon for a reasonable price.

Nails have been around for a long time. As soon as man discovered that heating iron ore could form metal, the ideas for shaping it quickly followed.

Thread angle chartmetric

The fact that the nail had a round parallel shank that had up to four times less holding power didn't matter so much. Thinner timbers were being used in construction and other forms of fastening were becoming available if a strong fixing was needed.

In Tudor times, we have evidence that the nail shape had not changed at all as can be seen by the nails found preserved in a barrel of tar on board the 'Mary Rose' - the Tudor flag ship of Henry VIII built in 1509 and recovered from the mud of the Solent in 1982.

The result is that these cut nails are often mistaken for handmade nails. In use, the rosehead is often the only part of the nail that is left visible and this shape of head is now considered vital when a period nail is demanded.

Acmethread angle

For even more detailed information on nail chronology to help determine the age of a building; the shapes of hand made nails; the first cut nails which were then headed in a second process; the fight during the period 1790-1820 to be the first to design the best 'one process' cut nail machine; or you would like to look at the British Army's Nail Standards manual dated 1813, here are the sources for these articles particularly the ones noted below.

In the 21st century, the nail making process through the ages is now being used by the restoration industry to help to establish when a building was built. Hand made nails suggest the building was built before 1800. Cut nails suggest the building was built between 1800 and the early 1900's. Wire nails will be found in a building put up in the period from then to date.

PT thread type is identical and interchangeable with BSPT thread type. However, since the male PT thread does not have a 30-degree flare, it will not mate with the BSPP female swivel with conical seat. Also, we recommended using thread sealant with PT threads to ensure a leak-free seal.

For the restorer, it is vital that the correct raw materials are used in any attempt to preserve an old building. Nails are no exception. The restorer is looking to use similar nails to ensure the authenticity of the restored building.

SAE - Society of Automotive Engineers - straight threads are able to seal because of the 90-durometer Buna-N “O” Ring. This is a highly reliable and reusable thread type. While some thread types require the threads of the male and female end to crush together to form a seal, the O-Ring on this thread type prevents that.

Over the years, the cut nail has faced the problem of competition with its rival the wire nail and its history as the first common nail.

It was not until around 1600 that the first machine for making nails appeared, but that tended really to automate much of the blacksmith's job. The 'Oliver' - a kind of work-bench, equipped with a pair of treadle operated hammers - provided a mechanism for beating the metal into various shapes but the nails were still made one at a time.

Metricthread angle

A recognition of the value cut nails offer is needed to ensure that the process is not lost for ever and encourage the handing on of the skills involved. Indeed, the price is not dissimilar to that charged for hand wrought nails in medieval times.

In the UK, early evidence of large scale nail making comes from Roman times 2000 years ago. Any sizeable Roman fortress would have its 'fabrica' or workshop where the blacksmiths would fashion the metal items needed by the army. They left behind 7 tons of nails at the fortress of Inchtuthil in Perthshire.

(this page contains the substance of an article entitled 'Traditional Cut Nails - worth preserving?' written in May 2002 at the request of, and for inclusion in, the RICS Building Conservation Journal)

Buttressthread angle

A pitch gauge measures the threads per inch. For metric threads, this tool measures the distance between the threads. If you’re looking to buy a thread pitch gauge, Grainger has a pretty good selection.

For nail making, iron ore was heated with carbon to form a dense spongy mass of metal which was then fashioned into the shape of square rods and left to cool.  The metal produced was wrought iron. After re-heating the rod in a forge, the blacksmith would cut off a nail length and hammer all four sides of the softened end to form a point. Then the nail maker would insert the hot nail into a hole in a nail header or anvil and with four glancing blows of the hammer would form the rosehead (a shallow pyramid shape).

This is a standard thread type that has been adopted internationally for interconnecting and sealing pipe ends. You’ll find it used all throughout Europe. There are two types of BSP threads, BSPP and BSPT. BSPP refers to parallel or straight threads. Meanwhile, BSPT refers to tapered threads. Sometimes BSPP threads are referred to as G threads and BSPT threads as R threads. Are you confused yet?

Airtac offers a variety of cost-effective replacement pneumatic parts. However, it can be a challenge finding the exact part you need to replace. Luckily our product specialists can guide you through figuring out what part you have on hand. One crucial piece of information our parts specialists need to know is the thread type. With Airtac you have three options: NPT, PT, or G (BSPP). But when you have a machine down, the last thing you want to do is take out your measuring tools and charts to find what threads are on your solenoid valve. Here’s how we can get around all that if you’re in a pinch.

The wire nail quickly became the nail of choice as it is today because of its price and the cut nail's day was numbered.

This shape of nail had the benefit of four sharp edges on the shank which cut deep into timber and the tapered shank provided friction down its full length. The wood fibres would often swell if damp and bind round the nail making an extremely strong fixing.

There is currently an enormous interest in preserving our heritage and much of that heritage is in the shape of the buildings that remain as evidence of a bygone age.

By the start of the 1900's, the first coils of steel round wire were produced and quickly machines were designed to use this new raw material. The first automatically produced wire nails with no human intervention other than to set up the machine immediately showed that this was the way to produce a cheaper nail.

The process is as much part of our heritage as the products produced and it will be necessary for those involved in the restoration industry to change the mindset of trying to compare cut nail and wire nail prices, if the process is to survive.

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Thread angle chartin mm

One aspect of that has been the expectation that because wire nails are cheap, the cut nail should also be cheap. After all, it's just a nail. Attempting to follow that line of thought, no matter how ridiculous as the processes are so different, has meant that many cut nail manufacturers have ceased business over the years because margins were so low.

This thread type is most commonly used in North America. You’ll recognize it by its tapered outer and inner diameter which is self-sealing. When torqued the flanks of the threads compress against each other forming a leak-tight seal. However, it is still recommended to use PTFE tape or another sealant compound to guarantee a completely leak-tight seal.

Because the nail up until then was handmade, the first machines were naturally designed to re-produce the same shape of product - a square tapered nail with a rosehead, but only tapered down two sides of the shank.

History does not record who it was, but the incredible results of that inspirational moment are all around us - in the houses we live in, the bridges we cross, the furniture we sit on.

2. Does your product require fittings? Let’s say you have a pneumatic filter with NPT threads. It may be possible to simply replace these fittings to make them compatible with a PT threaded product.

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After you’ve figured out the pitch size, you’ll need to determine the thread diameter. Using the caliper again, measure the outside diameter on a male thread and inside diameter on a female thread. If you find that your measurements don’t exactly line up with the measurements in the tables below, this is okay. There will inevitably be small variations due to different manufacturers.

The final step in identifying your thread type is to identify the thread type standard. NPT, PT, and G are all examples of thread type standards. Gather the information from the previous steps and compare it with the measurements in the tables below. You can also download all this information in a convenient PDF file.

Thread types can be a little overwhelming to grasp at first. There’s a lot to take in. The types we’ve covered in this guide barely scratch the surface of the many different kinds available. However, having the right tools can a make a world of a difference. We hope this guide is useful and insightful. If you have any questions, feel free to contact us or simply leave a comment below. Lastly, make sure to take all this valuable information with you in our downloadable Thread Identification Guide. It’s packed with all the same useful information and it’s interactive!

One way of changing the mindset is to think in terms of the price per nail in comparison with other old artifacts being used and indeed what can be purchased today. Cut nails for the restoration industry can amount to just a few pence each and it only takes a moment to assess their long term value say in comparison with the can of Coca Cola or Mars Bar you might buy for lunch.

However, almost a century after their predicted demise, there are still two cut nail manufacturers worldwide in existence employing the process that is almost 200 years old and using machines that have barely changed in design in that time.

Whether the project involves restoration or the building of a replica, a genuine cut nail made using a process that has not changed in 200 years lends a degree of authenticity to the project.

So you finally found the right solenoid valve to replace your broken one. You call to check stock on the item and the sales rep asks you what thread type you need. You ask, “How do I find out what thread type I need?” Fortunately, we’ve got you covered. Below you’ll find a detailed guide on how to correctly identify the most popular thread types used in industrial components. Plus, learn when it’s okay to use thread seal tape for urgent situations.

Lee H. Nelson: Nail Chronology As An Aid to Dating Old Buildings, Technical Leaflet 48. Nashville: American Association for State and Local History, 1968,

One such company is Glasgow Steel Nail Co which can trace its business roots back to 1870.  In addition to working with these old machines, the process also involves preserving the blacksmith's skills to form cutting and heading tools.

While it is possible to get a blacksmith today to produce a handmade nail from wrought iron, the cost can be prohibitive and the blacksmith is not keen to devote his limited time to making such small products.

The nails are normally made of mild steel and are often used without any further finish and can be clinched (i.e. bent over by 90° to lock the nail in place). A recent expensive project involved nails for studding on large outside doors which would be deliberately left to rust to provide greater authenticity. Nails can also be produced in copper and bronze.

Imagine the limited aspirations of the first pre-bronze age constructor to join two pieces of wood with a sharp implement.

Next, determine if the thread is tapered or parallel. Tapered threads become narrower as they extend outward while parallel threads remain the same diameter. Sometimes this characteristic can be determined through visual inspection, but if not a caliper can come in handy. Use the caliper to measure the first, fourth, and final full thread. If the measurements are all the same, then it’s parallel. If the measurements decrease in size, then it’s tapered.

First, you’ll need to identify whether the thread type is male or female. Take a look at where the threads are located. If they’re on the outside of the thread, it’s a male thread. If they’re on the inside of the thread, it’s a female thread. The gender of the thread doesn’t necessarily have an impact on the functionality of the thread. It simply serves as a way to distinguish between the two connections.

1. Do you know where your equipment was manufactured? If your equipment is originally from China, 9 times out of 10 you’ll need PT threads. If it was manufactured in North America, then you’re safe to go with NPT threads. You may need to reference the user manual to find this information or contact the original equipment manufacturer.

It’s important to identify the specific thread type you need in order for your equipment to function at its best. Pneumatic components such as air cylinders, valves, and air preparation units come equipped with specific port threads. For example, the pneumatic components we offer in our web store are available with either NPT, PT or G port threads. Choosing the correct thread type will ensure optimum compatibility with your equipment. At a glance, threads may look similar. But take a closer look and you’ll notice the very subtle differences that would make them incompatible with one another. For example, G threads are not compatible NPT threads because of their differing angles, shapes, and thread pitches (threads per inch).

NPT/NPTF, BSPT, and Metric Tapered are examples of tapered threads. These threads create a seal through metal-to-metal wedging or slight deformation of the threads. Parallel threads will often require an o-ring or thread tape to ensure a tight seal.

A semi-compatible variant of NPT is NPTF (National Pipe Taper Fuel). It ensures an even more leak-free seal. But it is important to note that using these variants together diminishes their leak-free characteristics. NPT threads should be burr-free and lubricated using lubricating paste or tape. Doing so limits corrosion on the threads which otherwise can make future disassembly nearly impossible.

3. For dire situations, use PFTE thread seal tape. As a last resort, you can use sealant tape to mate PT and NPT threads together. We recommend this as a last resort though.

Metric thread type is most common in Europe. It has a cylindrical inner and outer diameter precise in millimeters. The fine taper of metric tapered thread allows for the best possible force transmission. In writing, you can identify metric threads by a capital “M” plus an indication of their nominal outside diameter (ex. M22 x 1.5). Lastly, when measuring pitch size make sure you’re using a metric pitch gauge.

We have compiled a simple step-by-step guide to help you identify your thread type. In addition, we’ll cover some of the most common port thread types including NPT/NPTF, BSPP (also known as G), BSPT, PT, Metric (M) and SAE. You’ll need a couple tools on hand to make the process easier, but a straight steel ruler may work as well. We also encourage you to download this Thread Identification Guide for future reference because it will certainly come in handy.