The process of cold-heading allows for the mass production of our screws, bolts, solid rivets, and pins. This unique process plastically deforms raw material like steel and brass under tremendous pressure through specially designed dies which act like molds. It is during this process that the various head drives are formed (Phillips or cross-recess, Allen or socket recess, offset cruciform, sixlobe, Robertson or square-drive, and tri-slot just to name a few). There is no scrap generated during cold-heading, material is simply displaced to form whichever configuration you require to proceed.
Externally threaded fasteners, like screws and bolts, are formed finally using thread-rolling machines where blanks are fed individually into two opposing flat threading dies which force the material into the grooves of the dies. Like the cold-heading process, thread-rolling produces no scrap, but the true advantage to cold-working (as opposed to screw-machining where parts are turned down on a lathe by actually cutting away material to form a component) lies in the strengths achieved.
The hot forging process involves individually heating a pre-determined volume of raw material in an induction heater, then placing in a large vertical press which deforms the slug into the form of the carbide heading die. While cold heading is better suited to mass production of larger quantity runs, hot forging involves a lot of hand work and thus lends itself to smaller lot sizes, typically under 1,000 pieces. The process reduces yield and tensile strengths to improve forming characteristics because the metallurgical structure of the material is often altered. Less pressure is required to make the metal flow plastically since hot forging techniques lower material strength and increase ductility. We routinely produce some of the most complex aerospace screws and bolt in our industry. J-form threads, which have fully formed root radii, are manufactured daily by talented operators trained to produce lap-free parts.
A method of removing material through grinding, this process has a high throughput and allows for a large number of parts to be manufactured in a short time. There are two types of centerless grinding: plunge and throughfeed. In plunge grinding, a part is placed between the wheels on a workblade and a wheel is plunged. In throughfeed grinding, the parts are fed into the machine, grind along the workblade and exit at the rear of the grinding wheels. The benefits of using this process include the ability to grind parts with varying geometries, the ability to remove odd numbered lobing on the shaft of the part, and the ability to maintain size beyond what is capable of a typical grinder.
Drilling Heads & Shanks
Fasteners can be drilled in various ways for many purposes. The most common way is to drill a hole (or holes) through fillister head screws or through the flats of hex head screws, thus allowing two or more screws to be “safety wired" together to prevent loosening. The wire is twisted and connected in such a way that in order for a screw to loosen, the other would tighten. Drilling a screw all the way through lengthwise makes it a vented screw. Its purpose is to maintain constant atmospheric pressure within a device while keeping contaminants out.
Slotting Heads & Shanks
Slots are one of the original drive designs for screws and still readily used. The slots are milled with two saws. The first saw cuts the majority of the slot while the second saw, spinning in the opposite direction, finishes the cut to reduce burrs created in the process. Shank slots use a similar process to cut into the bottom of the screw or through the threads to create a thread-cutting screw.
Milling, Shaving & Pointing
Milling is a process used for complex shaping of metal and other materials. In this process, the cutting tool remains stationary while the work piece moves to custom cut the material. Shaving is often used to remove extruded material that can not be formed in the cold heading process. Pointing is used to make pointed, threaded fasteners by threading, tapering and pointing in thread rolling equipment.
Broaching is normally used to enlarge a circular hole into a non-circular shape, such as a square or triangle.
This process can also be used to cut splines or square keyway on objects such as driveshafts, gears and pulleys.
The amount of material removed depends on the desired outcome, as broaches can chisel anywhere from 0.05 to 0.10 mm.
•.060 to 1.25 inch diameter
• Length: up to 36 inches
• Metric: M1.6 through M25 diameter
Plastic locking elements can be applied to screw threads in the form of a patch, strip or pellet to affix a screw in place, particularly for the initial installation. Locking elements are intended for permanent installation in environments where screws are subjected to vibrations which could cause loosening and possible failures. Pilgrim Screw is proud to partner with the following industry leaders:
Nylok fastener products serve a diverse range of companies in industries such as automotive, aerospace, military and agricultural equipment. The company solves locking problems from the small home appliance industry to NASA applications.
ND Industries supplies user applied, pre-applied fastener locking solutions and a broad range of Automotive and Military Approved processes
IN PROCESS INSPECTION
In an effort to maintain the highest quality, Pilgrim Screw offers the following in process inspections:
• Statistical Process Control – method of monitoring a process though the use of control charts, ensuring that there are no variations in the process that may affect the quality of the end product.
• Johnson Tri-Roll Gages System 22 Gaging – system used to measure round and threaded objects to ensure correct fit and pitch classes.
• TesaScan – process used to measure small and medium sized cylindrical parts to meet the requirements of round part inspections