Square Drive Screws and Drivers
These screw types have a "+" shaped recess on the head and are driven by a cross-head screwdriver, designed originally for use with mass-production mechanical screwing machines. There are a few other recessed drive screws presented that you also want to be aware.
So, why all the confusion? Why all the damaged screw heads and drivers? Why is this screw and driver thing so awkward? Read on and be amazed while I unravel the mystery of screw drives and present some you may have never seen.
For each screw drive type, from ancient Slot through to space-age Lox we present a quick view of the screw head, the drive name, a picture of the appropriate drive bit, followed by an explanation of the type. Also presented are the advantages and disadvantages of each drive type. Slot type are also included because that is where the screw began and a double slot becomes a cross drive, and the Robertson or square drive enter the story with recent combined Phillips/Square drives. The Allan, Spline, Torx etc drives are not included and maybe neither should the Uni-Screw, it is just so darn new and interesting.
This article contains a lot of information and pictures from the Internet. Maybe it will be the definitive guide with your help it could get close. If you disagree with any of the information or if I missed a related drive you know of, please let me know where I can validate the information. Misinformation, incorrect illustrations, screwed up usage of terms on the Internet and elsewhere is rampant and part of the problem created by so many drives.
First a little background:
A screw is really a shaft with a helical groove or thread formed on its surface. Its main uses are as a threaded fastener used to hold objects together, and as a simple machine used to translate torque into linear force. It can also be defined as an inclined plane wrapped around a shaft.
Every threaded fastener needs a way of turning it. Whether a wrench fits a hex-head bolt or a nut, or it may have a shaped and recessed hole into which a driver can be inserted.
Step 1: Early Screws
Metal screws and nuts used to fasten two objects together first appeared in the fifteenth century.
In 1770, English instrument maker, Jesse Ramsden (1735-1800) invented the first satisfactory screw-cutting lathe. Ramsden inspired other inventors. In 1797, Englishmen, Henry Maudslay (1771-1831) invented a large screw-cutting lathe that made it possible to mass-produce accurately sized screws. In 1798, American David Wilkinson also invented machinery for the mass production of threaded metal screws.
The screw on the left (A) was handmade in the late 18th century. Note the flat spot on the shaft, the irregular threads, blunt tip and the off center slot. The screw in the center (B) is machine made around 1830. It has sharp, even threads, a cylindrical shape, blunt end and the slot is still off center. The screw on the right (C) is a modern gimlet screw, post 1848, with tapered shaft, even threads, pointed tip and centered slot.
Step 2: Cut Slot Drive
Advantages and Disadvantages of Slot Screws
The advantages of the slotted head are that: most people have a screwdriver that fits them (sort of); worn drivers are easily reground; a new screwhead slot can easily be cut with a hacksaw. Otherwise the slotted head is the worst screw drive system, and while very common, it is also generally obsolete. Some of its deficiencies include: a screwdriver does not automatically line up with the slot; it is easy to get off center; the user must keep the axis of the screwdriver aligned with the axis of the screw; the driver can engage the head in only two possible positions, at 180 degree to each other. The sides of most slotted screwdriver bits are tapered. When the driver is turned it tends to be pushed up and out of the screw head. This is called camout.
To add to the shortcomings of the slotted head, screwdrivers for slotted screws are usually described by the length of the shaft and the width of the tip; the crucial measurement, the tip's thickness, is not given. Any given tip width is sold in a range of thicknesses; the longer shafts usually have the thicker blades.
Step 3: Crossed-Slot Drive
Advantages and Disadvantages of Crossed- Slot Drive
The advantage of this type of screw head is there are 4 ways to engage the screw. Screw heads need to be thicker and harder to accept the drive. Otherwise all other advantages and disadvantages remain the same as the single Slot Type Drive.
Step 4: Lotus Head Drive
Fellow Instructable contributor further explains ironsmiter says:
The Lotus Head Drive is basically a standard cross-slot screw, as it looks, but the slots are produced by a "much cheaper process". Basically, the head is split by a chisel type tool.
The theory is that, by not removing any material, the head retains the full material strength. This is a similar theory as to how a hole that was been punched and drifted, by a blacksmith, is stronger than one that has been drilled out. The head can also be formed by a machine that costs significantly less to buy and to operate than a recessed head.
The use for these screws is mainly for machine assembly. The constant pressure of the machine driver spindle prevents "skipping" of the bit (that would cause a stripped head, if using hand tools to drive the screw). There is a slightly modified Phillips bit that is used to drive them. It has a matching taper and flat bottom.
The example shown is a "quickthread" allowing it to be driven at twice the depth per turn, as compared to a normal screw. It is also a self-drilling model. Primarily designed for use in plastics. You will find similar threads holding almost any cheap plastic radio, light fixture, toy, together.
These are all "improvements" to speed up manufacture, and use of the screw. How successful it is at that, I do not know. Just hope you never have to remove one of these. Trying to get a standard Phillips bit, even if you modify it for the flat bottom profile, to grip on these screws is a Royal Pain (frowning) See end-load in appendix.
Step 5: Robertson® Drive
In 1908, square drive screws were invented by Canadian Peter L. Robertson. Twenty-eight years before Henry Phillips patented his Phillips head screws. The Robertson screw is considered the "first recess-drive type fastener practical for production usage." The design became a North American standard.
Henry Ford used Robertson screws in the Model A car made by the Ford Motor Company (one of Robertson's first customers). The Model T used over seven hundred Robertson screws. Ford dropped these screws when Robertson refused to give him exclusive rights to its use. Robertson also refused to license other fastener manufacturers, so the design spread very slowly. Many recreational vehicles built in the 1950s use these screws. In Canada, most wood and electrical screws have Robertson recess heads.
Advantages and Disadvantages of Robertson Screws
A square recess drive allowed the screw to be placed on the driver prior to the screw being placed in position, so for the first time ever you could start a screw overhead or in a tight spot without an extra hand holding the screw onto the driver. A Robertson head on a screw is much better than a slot head because the screwdriver has great resistance to camout of the screw's head during installation and 4 possible positions to insert the driver. The Robertson drive design utilizes a "Morse-like" taper so the screw will stick to the bit even when held straight down. This taper allows the tool bit to insert deeper into the recess for more contact surface and thus less camout. To avoid problems make sure both screw and driver are of the matching type as there are many square drive drivers and screws around today that are not Robertson. See Square Drive (next topic). Robertson screwdrivers are available in 6 standard tip-sizes, none metric. Orange and orange are seldom used. The largest black is quite rare. Each identified usually by the handle color rather than by number.
Thanks Brian J. Cooley, Robertson Inc., Tools Division Product Line Manager for North America, for adding information on the 6th Robertson size and for pointing out ALL true Robertson Inc. power bits and insert bits are of the 2 piece variety, they have never produced one piece bits. (I've changed the reference picture as the original one was not not a true Robertson). An easy way for consumers to tell if any fasteners came from Robertson Inc. They use the ® following Robertson ® on all of the products manufactured.
Step 6: Square Drive
Two methods of fabrication are the machined one piece and the two-piece is a forged steel tip press fitted into a regular steel tip holder part. Several companies each with their own select brand name produce square Drive.
Advantages and Disadvantages of Square Drive
Due to the lack of taper, the hole must be oversize relative to the screwdriver, and is much more likely to camout than the Robertson. It is infuriating that Home Depot and the tool companies like Bosch and Dewalt bring square drive bits into Canada that nearly fit Robertson screws and are marketed as equal and are unmarked. For any Canadian readers that want bits that work, try to buy the bits that are color-coded red, green, black as well check the engraving is an R on the bit. Dont trust the cheaper bulk packs. Never trust a Robertson that says "Made in America"; it is likely a Square Drive. A "fresh" US square drive driver with a "real" Robertson screw head sticks so tightly that it can take a significant yank to get them disengaged. This is advertised as a selling point of the US Square drivers here in Canada. Unfortunately, if you have a pop out, the driver is usually means youre damaging the tool and is difficult to use from then on. Real Robertson drivers do not suffer from this with Robertson screws. So, while they don't stick quite so tightly, the drivers really do last a long time, and they're just as good at keeping grip under power. Bit sizes come in only four sizes and application and are rarely color-coded.
Step 7: Recessed Cross Drive Systems
Henry F. Phillips (1890 to 1958), a U.S. businessman from Portland, Oregon, has the honor of having the Phillips head screw and screwdriver named after him.
The cruciform shape can be considered to be a cruciform design with their 90 degree shapes as most have similar physics properties.
Phillips developed Thompsons invention screw into a workable form. Phillips had come up with a recessed cross screw designed for efficiency on an auto assembly line. The idea was that the screwdriver would turn the screw with increasing force until the tip of the driver popped out, called camout. When tightening a Phillips screw with a Phillips screw driver you will notice that when the torque gets to be too strong, the screw driver winds itself out of the screw so the screw head would not be ruined or brake off.
Phillips also founded the Phillips Screw Company in Oregon in 1933, but never actually made screws. He had called on every established screw manufacturer in the US and was told simply that the screw could not be made. Screw makers of the 1930s dismissed the Phillips concept since it calls for a relatively complex recessed socket shape in the head of the screw; as distinct from the simple milled slot of a slotted type screw.
Phillips then called on the American Screw Company, a newcomer to the industry whose new president, Eugene Clark, personally became interested in the new product, despite the opposition of his engineers, who like others in the industry had insisted it could not be made. According to one printed report, the president of American Screw Company said: "I finally told my head men that I would put on pension all who insisted it could not be done. After that an efficient method was evolved to manufacture the fasteners and now we have licensed all other major companies to use it."
Use of the Phillips screws spread through the automobile industry at a rapid rate. By 1939 it was used by all but two automobile manufacturers. By 1940, Phillips screws were used by the entire automotive industry, although one major manufacturer still would not use them on its passenger cars. Gradually the Phillips screw and screwdriver worked their way into other industrial applications; then consumer products, and eventually showed up in hardware stores.
The American Screw Company spent approximately $500,000 in the 1930s to produce the Phillips screw and obtained patents on the manufacturing methods. It was the sole licenser of the process. By 1940 10 American and 10 foreign companies were licensed to manufacture the screw. Although Henry Phillips received patents for the drive design in 1936 (US Patent #2,046,343, US Patents #2,046,837 to 2,046,840), it was so widely copied that by 1949 Phillips lost his patent.
Phillips' major contribution was in driving the crosshead concept forward to the point where it was adopted by screwmakers and automobile companies. Henry Phillips died in 1958 at the age of sixty-eight.
Step 8: Phillips Drive
Advantages & Disadvantages of Phillips
In all cross drive systems the driver will self-align with the fastener. The tapered design that allows camout can become a problem as the tooling that forges the recess in the head of the screws begins to show signs of wear. The recess becomes more and more shallow, which means the driver will bottomout too soon and will cause the driver to camout early. Another problem is even though the ease to insert, Phillips screws can be tough to get back out. The main disadvantage is the screwdriver pops out too readily, stripping the screw, gouging the work, and in general transferring all the problems that were formerly with the Slot design. Consumers are likely to think that any screw head with a cross drive recess is a Phillips, which can lead to problems.
Step 9: Reed & Prince or Frearson
Advantages and Disadvantages of Frearson
Its advantage over the Phillips drive is that one Frearson driver or bit fits all Frearson screw sizes, although there are 2 sizes available. Improved torque with minimal camout. Unfortunately the screw head recess appears to be a Phillips and so it is too easy to use the wrong tool or screw.
Step 10: JIS - Japanese Industrial Standard
Advantages and Disadvantages of JIS
Most people and companies outside of Japan have absolutely no idea what they are. With the similarity in appearance to the Frearson and the Phillips the screws are often damaged in removing and installing with the wrong tools. JIS tends not to camout like Philips. The JIS driver can be used on Phillips quite easily but not reciprically. Drivers are not easily available in North America, try your local RC Airplane hobby shop. Most RC Helicopters use JIS screws to mount the propeller. JIS-spec cross-head screws are generally marked with a single raised dot or an "X". JIS always fit Phillip fasteners, but because of slight design differences, Phillips drivers may not fit JIS fasteners. (unless the tip is ground down a bit).
Step 11: Sel-O-Fit®
The Sel-O-Fit bit places torque on the strongest and most mechanically advantageous portion of the driver tip. This allows more torque to be applied while minimizing the possibility of breakage and camout.
Step 12: French Recess
Step 13: Posidriv®
Pozidriv is similar in appearance to the classic Phillips crosshead, but in fact is substantially different. On close examination you will notice a second set of cross-blades at the root of the large cross-blades. These added blades are for identification and match the additional makings on the head of Pozidriv screws, known as "tick" marks, single lines at 45 degrees to the cross recess. So, the marks are for identification purpose. Pozidriv also does not have the rounded corners that the Phillips screw drive has. The tip or the driver is blunt which also helps it to seat better into the recess in the screw, unlike the Phillips which comes to a sharper point.
Identified in ANSI standards as type IA. Pozidriv drivers will not turn Phillips screws; but Posidriv screws can be turned by Phillips screwdrivers, although they should not be used as they tend to ride out of the recess and round the corners of both the tool and screw recess.
Advantages and Disadvantages of Pozidriv
The largest advantage it offers is that, when used with the correct tooling in good condition, it does not cam out, allowing great torque to be applied. The chief disadvantage of Pozidriv screws is that they are visually quite similar to Phillips, thus many people are unaware of the difference or do not own the correct drivers for them, and use incorrect screwdrivers. This results in difficulty in unscrewing the screw and in damage to the slot, rendering any subsequent use of a correct screwdriver unsatisfactory.
Step 14: SupaDriv®
Advantages and Disadvantages of Supadriv
The Supadrivs basic shape is similar to Posidriv and the drive blades are about equal thickness. The main difference is close to a near vertical surface to drive the screws into the drivers. With this superior bite screw driving is more efficient, with less come out.
Step 15: ACR® Phillips®
Advantages and Disadvantages of ACR Phillips
Maintainers prefer the ACR Phillips system because they dont have to push hard on the driver, reducing fatigue and the risk of injury. The results are securely removed screws every time with lowered cost, more productive workers, fewer drill outs, and fewer problems to fix in overhaul. ACR Phillips screws are also compatible with common Phillips drivers allowing emergency modifications and repairs.
Step 16: Phillips Square-Driv®
Advantages and Disadvantages of Phillips Square Drive
This drive system has an increased driver bit cross-section significantly increases the longevity of the driver bit, reducing overall tool costs. Combines positive characteristics of both the Phillips and the Square Drive with few negative characteristics. Not as prone to camout; higher torques than either original drive. Screw damage is minimiied and drive tool life is extended. In addition, there is a consistent stick between the driver and the screw, making hard to reach joints a simple task.
Step 17: ACR® Phillips Square-Driv®
Advantages and Disadvantages of ACR Phillips Square-Driv
All the advantages of the Phillips Square-Driv. ACR is for reduced camout, reliable stick-on and high torque. The screw heads are marked with double ticks as shown.
Step 18: Phillips Square-Driv 2®
Step 19: Phillips II®
Advantages and Disadvantages of Phillips II
The rib-to-rib connection allows for more torque, off-angle driving, heads that will not snap off, and screws that will not strip. You will never have another stripped screw that can not be removed! You can not drive a square drive or a star drive off angle! Proprietary threads means faster drive. Patented anti-camout ribs (ACR), guarantee stick fit, easier drive and less fatigue. Deck Mate screws can be driven with #2 Phillips or #2 square driver bits but for best performance use Deck Mate driver bits with ACR. You will never have a stripped screw that cant be removed.
Step 20: Quadrex®
This controlled radius recess has been designed for optimum driver engagement while providing clearance for wear and plating buildup. Added features include: Universal Application, Increased Productivity, Reduced Inventories, Assembly Line Economics and Universal Acceptance
Step 21: Recex® Drive
Information by Brian J. Cooley, Robertson Inc., Tools Division Product Line Manager for North America
Step 22: Mortorq®
Advantages and Disadvantages of Mortorq
Aerospace designers have had to compromise on fastener performance. Previously, shallow head styles had poor torque transfer and damaged easily while robust drives required thicker material and added weight. The unique shape provides full contact of the driver over the entire recess wing resulting in extremely high torque capability without the risk of damage. Depth of the recess in the fastener head is minimized resulting in true high performance in 100 degree flush head and shear head applications. The open recess concept allows driver to recess misalignment and compensates for paint build-up without degrading torque performance. Workers can easily install and remove panel and structure fasteners at odd angles without high muscle stress or fear of damage to surrounding surfaces. Larger driver cross-sections and curved surfaces provide extended tool life and resistance to tensile fatigue fracture when used with high load pulse tools.
Step 23: Torq-Set®
Step 24: ACR® Torq-Set 2®
Advantages and Disadvantages of ACR Torq-Set
A single driver inserts and removes the fasteners. The interlocking ribs - applied to the removal side of the driver bit and screw surfaces - eases fastener removal, even after a threaded fastener has become corroded, seized, or frozen. Camout is never a problem when driving in either direction with the ACR system. When meeting demands of high torque applications, the ACR Torq-Set drive system delivers ultimate performance while protecting against camout. The offset cruciform shape with interlocking ribs of the ACR Torq-Set design is unmatched for sure steady driving. Additionally, all ACR Torq-Set driver bits and recesses are interchangeable with standard Torq-Set components, thereby eliminating potential difficulties during emergency field maintenance. Available in sizes #0, 1, 2, 3, 4, 5, 6, 8, 10.
Step 25: LOX®
Advantages and Disadvantages of LOX
The patented LOX recess easily outperforms every competing drive system on the market, delivering three distinct advantages: 12 points of contact and a near zero degree drive angle, the LOX recess is engineered to accept torque loads many times higher than competing technologies. LOX has vertical sidewalls that transfer forces radially, keeping the bit seated and minimizing end load. The near zero drive angle (4 degrees) optimizes torque transmission and eliminates radial stresses, dramatically increasing bit life. The unique four offset square design four projections that effectively eliminate stripping. These projections maximize bit life while minimizing material waste. Directional stability with multiple, concentric driving surfaces are directionally stable to within less than two degrees which makes this a ideal choice where there is poor access or no direct line of sight to the fastener location. The design also works as a tamper resistant feature and is suitable for high RPM drives (up to 2000 rpm). Because of its precise fit and evenly distributed forces, the LOX bit life is at least 5-10 times longer than competing systems. Even if the material costs are negligible, workers don't like stopping to replace worn bits. It throws off their rhythm and slows their progress. They often wait until bits are completely worn before stopping to changing them.
Step 26: Uni-Screw®
A new design of screw head, the Uni-Screw, has been developed to rival the well-established slotted, Phillips and Pozidriv screws. It is based on a series of hexagonal recesses that avoids camout, which occurs with the other designs when higher torques are applied.
Advantages and Disadvantages of Uni-screw
Website claims Uni-Screw to be the first driver to drive both imperial and metric fasteners, virtually eliminates camout and stripping, positive control with stick fit, and increased productivity. Other benefits include the need for only one driver over a wide range of screw sizes and easy alignment of driver to screw.
Other recess forms can be used including pentagon and heptagon to provide high tamper resistance, and these can be tailored for a single user to give total security.
Step 27: Square Tamperproof
Theft Proof fasteners are virtually impossible to remove without the matching driver.
Step 28: Philips/Cross Tamperproof
Advantages and Disadvantages of Phillips Pin-Head
Theft Proof fasteners are virtually impossible to remove without the matching driver. These screws are easy to drive & remove with matching tool. Also cannot be removed with Phillips Screwdriver. Available in sizes #1, 2, 3.
Step 29: Appendix
Camout (or cam-out) is a process by which a screwdriver slips out of the head of a screw being driven once the torque required to turn the screw exceeds a certain amount. Frequently, camout damages the screw, and possibly also the screwdriver, and should normally be avoided. However, the Phillips head screw and screwdriver combination was designed specifically to cam out, as at the time of its invention torque sensing automatic screwdrivers did not exist.
Phillips is a trademark used for a screw with a head having two intersecting perpendicular slots and for a screwdriver with a tip shaped to fit into these slots.
Recess refers to the shaped socket into which a driver can be inserted
End-Load is the force required to keep the bit to not camout. Low end-load is usually most desirable.
History of Screws and Screwdrivers, by Mary Bellis, About.com
Phillips Screw Company; www.phillips-screw.com
Phillips or Pozidriv? Healey Magazine, Feb 1996
Semblex Corporation; www.semblex.com
Why did this guy Phillips think we needed a new type of screw? by Adams, Nov 24 1989
Assembly Technology Buyer's Guide, Wheeling, IL, Hitchcock Publishing, annual.
Collections Canada; www.collectionscanada.gc.ca/cool/002027-150-e...
A New Design of Screw Head by Brian Rooks, Assembly Automation Vol 21-4, 2001
Furniture screws: primitive to gimlet by Fred Taylor, Discover Mid-America - Aug 2007
S.C.F. Fasteners, Taiwan; www.scffastener.com/main/products/specialS.html
Robertson Screws by Ricketts, www.mysteriesofcanada.com/Ontario/robertson_screws
www.thestuccocompany.com/maintenance/Phillips-vs-roberts-138476- by Chris Lewis
Hands-On: LOX Screws by Chuck Cage; www.toolmonger.com
Uni-Screw Worldwide, Inc; www.uniscrewworld.com
Google Answers Researcher by Tutuzdad ?, Jun 10 2004
Re: star vs square drive; http//forums.jlconline.com/forums dave_k Veteran Contributor
http://boards.fool.co.uk/Message.asp?mid=11161184&sort=whole; Julian F. G. W.
http://www.electronicspoint.com/torx-hex-star-bits-t39076.html; Fred Abse
Instructables feedback of article by contributor ironsmiter
Step 30: What Next? a Sequal! Yipee!!!
Due to input and interest shown by readers, I'm already working on a sequal, or re-write to include combo drives, security drives, and incorporate comments and new pictures.
Remember to Vote when it appears in a contest.