How to Convert Hex to Binary and Binary to Hexadecimal

The Hexadecimal Numbering System

The base 16, also known as hexadecimal (abbreviated to hex) numbering system is regularly used in computer coding for conveniently representing a byte or word of data. This guide shows you how to convert from hex to binary and binary to hexadecimal.

© Eugene Brennan

Decimal, the Base 10 Numbering System

Before we learn how to convert hex to binary, let's try and understand how the base 10 system works.

The decimal, also known as the denary or base 10 numbering system that we use in everyday life makes use of ten symbols or numerals: 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9.

So to count you start with 0, then continue 1...2...3...4...5...6...7...8...9

What happens when you get to ten? There's no numeral for ten, so it's represented as

10

Which means 1 ten and no units

Similarly when you get to 99, there's no numeral for one hundred, so you write one hundred as 100.

So writing a number in the base 10 system involves using numerals in a "units", "tens", "hundreds", "thousands" place and so on

So 145 really means "one hundred, 4 tens and 5 units" although we just think of it as the number one hundred and forty five.

Hexadecimal, the Base 16 Numbering System

Hexadecimal or "hex" is a numbering system which uses 16 different numerals. We saw that decimal used ten numerals from 0 to 9. Hex expands on this by adding six more—the capital letters A, B, C, D, E and F.

So to count from 0 to 9 you go 0...1...2...3...4...5...6...7...8...9

But what happens next?

Simply continue with A...B...C...D...E...F which represents 10, 11, 12, 13, 14 and 15 decimal.

So now to count to 15 we go 0...1...2...3...4...5...6...7...8...9...A...B...C...D...E...F

In the decimal system, we saw that when we got to nine, there was no numeral for ten so it was represented as 10 or "one ten and no units".

In the hex system when we get to F which is 15 decimal, we have to represent the next number sixteen as 10 or "one 16 and no units".

Binary, the Base 2 Numbering System

The binary system used by computers is based on 2 numerals; 0 and 1. So you count 0, 1, there is no numeral for 2, so 2 is represented by 10 or "one 2 and no units". In the same way that there is a units, tens, hundreds, thousands place in the decimal system, in the binary system there is a units, twos, fours, eights, sixteens place etc. in the binary system.

Decimal to Hex and Binary Table

Binary, decimal and hex equivalents.

Decimal	Hex	Binary
0	0	0
1	1	1
2	2	10
3	3	11
4	4	100
5	5	101
6	6	110
7	7	111
8	8	1000
9	9	1001
10	A	1010
11	B	1011
12	C	1100
13	D	1101
14	E	1110
15	F	1111
16	10	10000
17	11	10001
18	12	10010
19	13	10011
20	14	10100
...	...	...
25	19	11001
26	1A	11010
27	1B	11011
28	1C	11100
29	1D	11101
30	1E	11110
31	1F	11111
32	20	100000
33	21	100001
34	22	100010

Indicating the Base of a Number

If a number isn't decimal (base 10), the base can be explicitly indicated by a subscript to avoid confusion. Sometimes the subscript is omitted to avoid excessive detail if the base has been specified earlier in a discussion or if numbers are listed in a table (e.g. numbers may be indicated as hex in the title of the table).

So for instance 1F hex (31 decimal) can be written 1F₁₆

Steps to Convert Hex to Binary

Hex is very easy to convert to binary.

1. Write down the hex number and represent each hex digit by its binary equivalent number from the table above.
2. Use 4 digits and add insignificant leading zeros if the binary number has less than 4 digits. E.g. Write 10₂ (2 decimal) as 0010_2.
3. Then concatenate or string all the digits together.
4. Discard any leading zeros at the left of the binary number.

© Eugene Brennan

Most Significant Bit (MSB) and Least Significant Bit (LSB)

For a binary number, the most significant bit (MSB) is the digit furthermost to the left of the number and the least significant bit (LSB) is the rightmost digit.

© Eugene Brennan

Steps to Convert Binary to Hex

Binary is also easy to convert to hex.

1. Start from the least significant bit (LSB) at the right of the binary number and divide it up into groups of 4 digits. (4 digital bits is called a "nibble").
2. Convert each group of 4 binary digits to its equivalent hex value (see table above).
3. Concatenate the results together, giving the total hex number.

© Eugene Brennan

Test Yourself!

For each question, choose the best answer. The answer key is below.

1. Convert ABCD hex to binary
   • 10101010
   • 1010101111001101
   • 1111111011001101
   • 1111000011101010
2. What is 10101010 in hex?
   • AA
   • FF
   • FD
   • 1010
3. Convert FFFF to decimal
   • 15151515
   • 255255
   • 65,535
   • 3125

Answer Key

1. 1010101111001101
2. AA
3. 65,535

What is Hex Used For?

Because of the ease of converting from hex to binary and vice versa, it's a convenient shorthand for representing byte values i.e. numbers from 0 to 255. Also it is compact, requiring only 2 digits for a byte and 4 digits for a word.

Typical uses of hex:

• Hex dumps are listings of the bytes in a file in hex format. Because decimal or binary numbers can be displayed compactly as pairs or multiple pairs of digits or characters from A to F, values line up in columns and are easy to trace through.
• Assembly language is written as a series of mnemonic (short, easy to remember word) instructions for a microprocessor. The operand (the data operated on by an opcode) is commonly specified as a hex value. It's also used to indicate the storage location of data

Example of assembly language instruction

In the short code segment below, MOV is the opcode (instruction) and 61 hex is the operand that the opcode acts on. AL is a register that stores a value temporarily so that arithmetic can be done on it before it's moved to memory. A program called an assembler converts the human understandable assembly language to machine code.

MOV AL, 61H ; Load AL register with 61 hex (97 decimal )

Assembly Language Program for an 8 Bit Microprocessor

Original image public domain via Wikimedia Commons

Hex Dump of a File

A "hex dump" or byte value listing of a JPG file as viewed in a file editor. On the left, each byte is displayed as a hex value. On the right, alphanumeric characters corresponding to ASCII values of the bytes are shown. © Eugene Brennan

ASCII Code Table

Two hex numerals also conveniently represent the 255 codes of the extended ASCII character set, used in computing for communication and text storage and display. Yuriy Arabskyy, CC-SA-3.0 via Wikimedia Commons

How to Convert Decimal to Binary

To convert decimal to binary and binary to decimal, see my other guide:
How to Convert Decimal to Binary and Binary to Decimal

What is Binary Used For?

For more details on how binary is used in computer systems and digital electronics, see my other article:

Why is Binary Used In Computers and Electronics?

How to Convert Hex to Decimal

You can convert hex to decimal by simply multiplying each hex numeral by the placeholder's value as a power of 16 and adding the result. (F₁₆ = 15 decimal and A₁₆ = 10 decimal)

Example: What is the decimal equivalent of 52FA₁₆ ?

52FA₁₆ = 5 x 16³ + 2 x 16² + 15 x 16¹ + 10 x 16⁰

= 5 x 4096 + 2 x 256 + 15 x 16 + 10 x 1

= 21,242

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

© 2018 Eugene Brennan

The Andromeda Galaxy: "It's Big, And Also Faaarrr Away"

The apparent size of the Andromeda Galaxy, compared to that of the Moon. AI image created by Grok.

At a distance of 2.5 million light-years, or 24 million trillion km, the Andromeda Galaxy is the most distant object visible to the naked eye. We can see it because space is mostly empty, and light from the stellar object reaches us relatively unchanged, unlike what happens when we view distant objects on the horizon on Earth. Mountains, for instance, sometimes appear bluish and less distinct, or even invisible. That's because moisture in the air scatters and absorbs the light as it makes its way to our eyes.
The Andromeda Galaxy is incredibly distant. To paraphrase Father Ted Crilly, "It's big, and also faaarrr away." So even though it is far away, the fact that it's hundreds of thousands of light years in diameter makes it appear large in the night sky. That's when imaged with a long exposure through a telescope. In fact, it's about six times the apparent width of the Moon, but very faint. You can only see it out of the corner of your eye as a faint, fuzzy patch, and what you are seeing is the bright central bulge. The galaxy appears elliptical because, although it's actually a spiral galaxy with spiral arms, it's tilted at an angle of about 77° to the plane of the Milky Way.
 

Loading Data for the Kilcullen 38 kV Substation.

Loading data for the Kilcullen 38 kV Substation, courtesy ESB Networks.

From the ESB Networks document 38 kV & 110 kV Station Special Load Readings. 

The table shows summer and winter loads in megawatt (MW) for transformers T41, T42 and T424.

MVA is megavolt-ampere, often seen quoted on generators, although domestic generators are usually rated in kVA (kilovolt-ampere). The base unit, the volt-amp (VA) is a measure of apparent power and is the product of volts and amps sourced or used. In AC equipment, not all of that apparent power is used, and real power is measured in watts (W), which is the product of volts and in-phase current. ESB Networks want us to use in-phase current, and the extent to which current is in-phase with voltage is given by the power factor of a load. Non-in-phase currents waste power in supply cables, so power-factor correction may be implemented. This is normally done for large loads such as motors in industrial settings, although domestic fluorescent lighting may also include power factor correction in the fittings to compensate for the inductive load caused by the ballast coils (known as inductors). The correction can simply be a component called a capacitor wired in parallel with the light, inside the housing.

More information here on how Kilcullen gets its power.

Data courtesy ESB Networks.

It Came From Outer Space....

Nostoc commune (Latin name), also known as "jelly fungus". © Eugene Brennan

 Well not quite. This is probably Nostoc commune (Latin name), also known as "jelly fungus", "star jelly" or "witch's butter". It's not actually a fungus, but a colony of bacteria. There's loads of it in a patch on my yard, but it sometimes grows on lawns. It's extremely slippery on a lawn. Apparently it's eaten as a salad in the Philippines when dried out. I'm a fussy eater so I won't be trying it anytime soon.

More information on jelly fungus here on Wikipedia.

Off-Road Lanes for Cycling in Kildare and Wicklow

Lane from Barretstown to Bishopshill Commons. © Eugene Brennan

I'm always on the lookout for new trails and farm lanes for cycling on. Some are marked with a cul-de-sac sign, and just end up at farmhouses. However, others actually link two roads. Usually, there’s no sign at the junction where they meet a main road, or even a road number, so it can be a mystery where they go. The best way to work out whether there's a through route is to check old maps and Google satellite imagery. (The road layer of Google Maps sometimes only shows sections of a lane). I've found around six of them in the Kildare/Wicklow area. This is one of my favourite trails that runs between the Ballymore Eustace–Barretstown Castle road and the Ballymore–Bishopshill road. (The back road to Blessington which runs at the rear of the Russborough House estate.) It's only really passable in dry weather, as like many of these lanes, it gets flooded at several points and it's  necessary to climb up into the ditch through briars to avoid the floods. Also the ground on such lanes can be hard going as the surfaces are usually untarmacked, potholed and sometimes the surface is churned up by horses' hooves. The screenshot map at the end of this post shows a Google My Map I created. You can zoom into the map when you visit it at this link, or by following the link in the map's caption.

The ground that this trail passes over is hilly and rocky. Looking at the Geological Survey Ireland bedrock map, it appears that the rock in this area is slate and greywacke. The formations here are called the "Glending Formation" and the "Slate Formation". Greywacke is currently quarried north of Blessington near Rathmore and slate was also extracted at least as far back as the early-19th century, resulting in the townland being named "Slate Quarries".

Bedrock geology in the vicinity of Barretstown. Contains Irish Public Sector Data (Geological Survey Ireland) licensed under a Creative Commons Attribution 4.0 International (CC BY 4.0) licence

 

Some nice off-road cycling routes. Image courtesy Google Maps.

Available Substation Capacity in Ireland

Information on substations. Image courtesy ESB Networks.

This interesting interactive map on the ESB Networks website shows transformer capacities. A "substation" indicated on the map could be an actual town substation like the one at Sunnyhill, with 1, 2 or more transformers and associated switchgear and circuit breakers, or a transformer in a cabinet or small building (common in the newer housing estates). A substation could also be a pole transformer. Demand Firm Capacity (DFC) is a measure of a substation's redundancy guaranteed supply available under a "single contingency" (fault). So while named capacity is the total output of a substation, (e.g. 2 MVA for a substation with two, 1 MVA transformers)., DFC is the max output with one of the transformers out of action.

Demand Capacity Available is the amount of spare VA capacity for connections.

In the first image, the popup shows the status for the substation beside Nolan's car park.

In the second image below, the spec is given for Kilcullen 38 kV Station at Sunnyhill. (ESB Networks have it in the wrong place. They haven't fixed it since I let them know). It has two 5 MVA transformers and one 10 MVA transformer. Demand Firm Capacity is 18 MVA. That's based on the larger transformer going off line. That leaves 2 x 5MVA = 10 MVA. The 18 MVA DFC assumes that it takes time for cooling oil to heat up, so a transformer can take higher loads and give overcapacity for a period of several hours until a fault is repaired.

Only 0.6 MVA or 600 kVA Demand Capacity Available is indicated for the town's substation. Also there's a Demand Parent Constraint from the substation's parent at Stratford.

This is a link to the ESB Networks available capacity heatmap.

View the Distribution Network Development Plan.

Information on substations. Image courtesy ESB Networks.

What Is the Ground Wire For?

© Eugene Brennan

What Is a Ground Wire?

The hot and neutral cores in a power cable are used to supply current to the appliances in your home. So what about the green wire? Why is it needed? This is known as the "ground" and is an additional wire that is included for the safety of you and your home.

Note: This article was written for a US audience, so I refer to the protective conductor as "ground". However, it is also called "earth" in other countries. Another difference is that the term "hot" is used, which is also known as "live". The third difference is that a split-phase 120/240 volt supply is provided to most homes in the US, resulting in a 240-volt supply between the two hots in addition to a 120-volt supply. This 240-volt supply is for powering higher powered appliances.

Re-Discovering the Mill Stream Arch

One mill is marked on the OSI c.1837 first-edition six-inch map. Image courtesy the National Library of Scotland, licence CC-BY.

I hadn't seen it since around 1982 or '83. I thought it was covered with scrub and brambles over the decades, but not so. This is a good time of the year to investigate it before the brambles get going. My theory is that it could have been the opening to a culvert/mill race that diverted water to a second mill in the adjoining field beside the cemetery car park or it may have been the return feed to the stream. One mill is marked on the 6-inch, first-edition OSI map and was located just over the wall from where the bins used to be kept in the cemetery. The ruin is still there. There's an arched culvert under the Mile Mill road, south of the lodge, that fed water to this mill.
I think the arched opening into the stream is unlikely to be a latrine outlet or drain as it's too wide. I thought most of the arch was submerged below the waterline, but possibly the bed of the stream has dropped over the last four decades due to erosion. Anyway, I didn't have a camera with me. That's a shame because the arch was nicely lit up by the setting sun.
Will investigate further tomorrow and take some photos.

The map above is a ChatGPT-sharpened version of a screenshot of the c. 1837 first-edition six-inch map available on the National Library of Scotland website. The scans appear to be a bit clearer than those available on Tailte Éireann's Irish Townland and Historical Map viewer.
Map reproduction licence CC-BY, courtesy the National Library of Scotland.

YouTube Requirements and Broadband Speed

Connection speed required for YouTube. Image from Google Help

Unless you have lots of people in your home feeding off  your Internet service and sharing the bandwidth, ultra-high-speed connection promotions such as "Gigabit broadband" are just marketing hype. The table above shows the recommended connection speeds from Google for streaming video from YouTube. Vodafone keeps trying to sell me such a service using a fibre-optic connection that replaces copper wires to the cabinet and which would increase my speed from 100 Mbps to 1 Gbps, but I'm stubbornly refusing as the current speed is perfectly adequate. A faster connection probably increases upload speed (which I think is normally about one tenth of download speed), but most people aren't in a hurry when uploading, unless they can't wait to backup thousands of photos or put their latest video online. Eventually I'll have to give in, because copper lines, which Vodafone rent from Eir, will ultimately be replaced. The process is slow, because there are legacy systems that still require them. 
I ring Vodafone every year, three months before my contract is due for renewal and negotiate a loyalty discount, getting a six-month discount. It's only €5 per month for 6 months, but better than nothing.

A Child Can Push Harder Than a Lawn Mower Blade

AI image generated by Google Gemini.

Did you know that a child can probably produce more torque using their arm, than a lawn mower engine can generate to turn the blade? Surprisingly, the figure for the torque of a 5 hp engine used on a mower is 7 to 10 foot-pounds (ft·lbf) in the imperial system or 11.5 to 13.6 newton-meters (Nm). Applied torque is simply force multiplied by distance, so 1 pound-force applied over a distance of 1 foot from a pivot is 1 foot-pound. In the metric system, the unit of torque is the newton-metre (Nm). A torque of 1 Nm is equivalent to one newton—the SI unit of force—applied over a distance of one metre. The speed of a lawn mower blade is more important than torque, and blades are driven directly by the crankshaft without reduction or overdrive gearing. Blades typically spin at the engine speed of around 3000 RPM, giving a blade tip speed of around 200 mph, or 90 metres per second.

As we saw in the article Interesting Facts - What is Torque?

power = torque x angular rotation speed

So while a child may be able to exert more torque with their arm than a mower engine can exert on a blade, they wouldn't be able to match its power. Another piece of the jigsaw is that the quoted figure of 11 to 13 Nm is for the drive torque from the engine. Since a blade is spinning at around 3000 RPM, it has a lot of inertia. The technical term for this when a rotating body such as a flywheel or blade is involved is moment of inertia. When a blade slows down as it impacts grass, the change in angular momentum creates a force, just like the way a car or any linearly-moving object creates a force as it slows down due to friction, or when it hits something (think of the huge force produced by a hammer, typically many tonnes, when it hits a nail). So the force produced by a blade as it impacts and shears grass is much greater than the force that the engine itself could have generated.

Note: You may be wondering why "newton" in "newton-metres" above isn't capitalised.  The unit is named after the English scientist Isaac Newton. It's not a typo. In the International System of Units (SI), or Système international d'unités, units named after a person are not capitalised. However, the symbol is, N in this case, Units are normally lower case, as are prefixes. However, prefixes over one million are capitalised—so kilometres is km, but gigahertz is GHz.

Cantilevered Boardwalks For Motorway Bridges?

Bridge over M9 Kilcullen Bypass on Sunnyhill Road. Image courtesy Google.

When Kildare County Council, or whoever was responsible, produced the spec for this bridge, (and the one over the M7 at the Bundle of Sticks Roundabout outside Naas), they left out foothpaths. Maybe it was lack of common sense and an attitude of "Sure, only cars go out there". Or perhaps it was due to penny pinching and lack of foresight and a narrow bridge was cheaper than one a couple of metres wider? Anyway, I'm wondering could boardwalks/cantilevered foothpaths be fixed onto the sides, exterior to the parapets?
It would obviously be impractical to install foothpaths on the inside of the parapets due to to both lanes being reduced in width. As it is, cars can't pass pedestrians safely without partially moving into the other lane. An article by Paul MacDonald, Kildare National Roads Office, on the construction of the M7 Newbridge Bypass and M9 Kilcullen Bypass is available on the Kilcullen Diary here.

The section about the earthing of the steelwork of the underbridge for the River Liffey is interesting—High voltage pylons can induce voltages and currents in conductors, potentially leading to different and hazardous potentials between isolated elements of a structure. Bonding them together eliminates these voltages and earthing a structure pulls the voltage down to ground (similar to the equipotential bonding in bathrooms, where metal objects such as drains, radiators, towel rails, water pipes and metal baths are bonded together):

Bridge over M9 Kilcullen Bypass on Sunnyhill Road. Image coiurtesy Google.

How to Calculate Bolt Circle Diameter (BCD) for Chainrings and Bash Guards

Bolt circle diameter (BCD). © Eugene Brennan

What Is a Bolt Circle Diameter (BCD) or Pitch Circle Diameter (PCD)?

As you may be aware, if you've found this guide, a bolt circle is an imaginary circle that passes through the centre of the bolt or screw holes in a round pattern. This is typically a wheel hub on a vehicle, chainring on a bicycle or flange on a pipe. The diameter of this circle is known as the bolt circle diameter (BCD) or pitch circle diameter (PCD).

Typically, BCD is quoted for chainrings on bikes and the bash guards that cover them, and you can calculate it by measuring the distance between the mounting holes of the chainring on the spider. If you need to order a part for a bicycle or check the BCD of a flange and can only measure the bolt hole spacing, you need to know the formula for working it out. Alternatively you can skip to the end of this guide where there are tables for various bolt spacings.

Thomas McGarry of McGarry's Lane

McGarry's Lane. © Eugene Brennan

I think I may have found the person who lent his name to the lane. 

The Primary Valuation, also known as Griffith's Valuation was a mid-19th property valuation in Ireland. Published between 1847 and 1864, it was the first full-scale survey of its kind, and collected information about the occupiers of land and buildings, their landlords and the amount and value of property held. Griffith's Valuation is searchable here on the Ask About Ireland Website.

In the valuation, a Thomas McGarry appears, with an address in Nicholastown. The Nicholastown townland extends out as far as Yellowbogcommon townland to the south and New Abbey townland to the east. I was aware of the presence of a building, visible on the first edition, c. 1837 6" Ordnance Survey map. This was located across the road from the cottage in McGarry's Lane. By the time the c. 1900 last-edition 25" OSI map was drafted, this building had disappeared. It appears from the map and record below that Thomas McGarry was listed as an occupier of the 8 acres and 3 roods of land on which the building stood, with Robert Brereton as lessor (The owner of New Abbey House). 

Valuation book showing the entry for Thomas McGarry. Image courtesy Ask About Ireland.

Map showing corresponding parcel of land leased by Thomas McGarry (16). Map attribution: Ask About Ireland.

The Tithe Applotment Books, however, show no record of a Thomas McGarry. These books were records of tithes, a form of religious tax paid to the established church in Ireland—the Anglican Church of Ireland. Tithes were extremely unpopular, as the Roman Catholic majority also had to pay them, leading to the Tithe War of the 1830s and eventual repeal of the tax by The Irish Church Act 1869, which disestablished the Church of Ireland. In the records, there are three entries for a John McGarry, and he's recorded as having paid 3/3½  (three shillings, three and a half pence) in one of these records. No information is available on whether John was a brother or father of Thomas. I found a death record for Thomas McGarry on the Irish Genealogy website. He died on 14th March, 1889, with the location indicated as "New Abbey".
It's possible he's buried in New Abbey Cemetery.

Tithe payment by a John McGarry. Image attribution: The National Library of Ireland

The Tithe Applotment database search page is available here.  Image attribution: National library of Ireland

Death record for Thomas McGarry. Image attribution: Irish Genealogy.

The structure shown on the map was located behind this fence. No trace remains.  © Eugene Brennan

Cycle Paths, Moone High Cross and Poor Road Signage

© Eugene Brennan

Yesterday's Sunday cycle took me to the area around Moone, via a more roundabout but pleasant and traffic-free route up Brewel Hill, then through Colbinstown and Timolin. I returned home via Ballitore, Crookstown and Narraghmore Bog, a 30-mile round trip. I wanted to see the infamous Timolin-Moone cycle paths on the R448. As per usual, the path layout includes those ubiquitous grass verges. I'm not sure whether this feature is purely functional to reduce water run-off onto the carriageways or for growing wildflowers in the grass keep to the environmental lobby happy. I dropped in to see the High Cross of Moone. I hadn't been there for a few years. The cross has been protected by a corrugated-Perspex-roofed canopy for over 15 years. Such constructions help to protect carvings on heritage stonework from being eroded by the elements. Perhaps their use could be more widespread, as inevitably more detail will be lost from stonework over the coming centuries?

Missing Clip on My Quick-Release Skewer

Quick-release axle skewer from a bike. © eugene Brennan 

The cam lever fell out of the housing when I took my front wheel off to change a puncture, half-way between Ballymore Eustace and Harristown last Sunday. I hadn't noticed that the retaining clip had disappeared, possibly rusting off over the last 29 years. It's years since I changed a front puncture. I noticed too that I have five patches already on this front tube. 99% of my punctures are caused by whitethorn thorns. Thanks to the people out walking who offered me a lift. Anyway I had a discussion about forces in the axle with ChatGPT:

Eugene:

You know the skewers used on quick release wheels?

 

ChatGPT: 

Yeah, I know exactly the ones you mean—the quick-release skewers on bike wheels.

They’re that rod that runs through the hollow axle, with:

• a cam lever on one side (the bit you flip open/closed), and
• a nut on the other end (to adjust tightness)

When you flip the lever, it tightens via a cam mechanism, clamping the wheel securely into the dropouts—no tools needed.

A couple of subtle details people often miss:

• The lever doesn’t just “screw tight”—it should leave an imprint on your palm when closing if it’s properly tight.
• The springs on either side (little conical ones) help centre the skewer—narrow ends point inward.
• It’s not the thread that holds the wheel—it’s the cam force when the lever is closed.

Are you thinking about fixing one, replacing it, or did something odd happen with it?

Eugene: 

What type of retaining clip is used to hold on the cam lever? It must have corroded off mine. I haven't changed a front puncture for maybe 10 years, so I didn't notice it missing. It wasn't immediately obvious.

 

ChatGPT: 

Ahh, I know the bit you’re talking about—that tiny piece that quietly disappears over time.

On most quick-release skewers, the cam lever is held onto the skewer shaft with a retaining clip, usually one of these:

• a circlip (snap ring / C-clip) sitting in a groove on the shaft, or
• sometimes a peened-over end (the shaft is slightly mushroomed instead of using a removable clip)

If yours has “vanished,” it was almost certainly a circlip that corroded away or popped off years ago.

A couple of practical points

• Those clips are tiny and fiddly, and not always standardised between brands
• Replacing just the clip can be done if you can match the groove diameter, but…
• In reality, most people just replace the entire skewer—they’re cheap and far more reliable than bodging a new clip onto an old, possibly worn cam

My honest take

If it’s been missing for 10 years, I wouldn’t trust that skewer anyway. The cam faces and shaft could be worn or pitted.

A new skewer costs very little and removes any doubt—especially since that part is literally what keeps your wheel attached 😄

If you want, I can help you identify the exact type/size you need (front vs rear, road vs MTB, etc.).

Eugene: 

But there's a huge force on that cam, so unlikely for the lever to come out (remember limiting force = μRn?)

 

ChatGPT: 

You’re absolutely right to think in terms of friction holding things together—but there’s a subtle mismatch here between what force is doing what.

The clamping force you’re thinking of is captured by:

$F_{\text{friction}} = \mu R N$

That force is between the dropout faces and the hub axle. It’s what stops the wheel from slipping out of the frame.

---

But the clip does a completely different job

The little circlip isn’t resisting that big clamping force at all. It only:

• keeps the cam lever assembly from sliding off the skewer rod
• handles tiny axial forces (basically just gravity, vibration, and handling)

So even though the cam generates a large normal force $N$, that force is internal to the clamping system, not trying to eject the lever.

---

Why yours likely disappeared

Over time:

• corrosion weakens the circlip
• small vibrations + repeated opening/closing
• maybe one partial disengagement

…and eventually it just pops off or disintegrates.

---

A useful way to picture it

Think of it like:

• The cam = a powerful clamp
• The circlip = a tiny “end stop” so the clamp doesn’t fall apart when it’s open

When the lever is closed, everything is compressed together anyway—so the clip isn’t even doing much at that moment.

---

One caution

Even if it feels secure now, without that clip:

• the lever can drift or misalign when open
• you risk losing parts when removing the wheel

So your physics instinct is solid—but it applies to wheel retention, not lever retention.

---

If you want, we can actually estimate the clamping force from a typical cam geometry—that’s a fun little mechanics exercise.

Eugene: 

Yes, but there's an axial load force on the cam that pushes on the cam housing. And that's huge, because you're supposed to wrap your fingers around the lever when squeezing upwards. I probably put 10 kg or maybe 20 kg force or more on the lever with my fingers, and that's magnified by the mechanical advantage. Lever is about 8cm long, so the load can be resolved to midway, say 4 cm. The cam acts at about 5mm, so that's a mechanical advantage of 8 Let's call it 6. So there could be up to 100 kg on the cam, pushing on the axle. a radial force would have to overcome that for the lever to come loose.

 

ChatGPT: 

You’re thinking about it the right way mechanically—but the key is which direction that big force actually acts in.

Your estimate is pretty reasonable:

• ~10–20 kg hand force at ~40 mm
• cam acting at ~5–6 mm
  → mechanical advantage ~6–8
  → axial clamp force easily in the ballpark of 600–1200 N (≈60–120 kgf)

That checks out.

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The subtle bit: where that force goes

That large force is almost entirely:

• axial along the skewer, and
• compressing the cam faces and dropouts together

It’s not trying to push the lever off the end of the shaft.

When the lever is closed:

• the cam is wedged hard against its mating surface
• everything is in compression
• the system is actually self-locking (that’s the cam design doing its job)

So in that state, the circlip is basically doing nothing at all.

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When the clip actually matters

The circlip only earns its keep when the lever is:

• open, or
• somewhere mid-travel

In that position:

• there’s little to no clamp force
• the cam isn’t wedged
• the lever assembly can slide axially along the shaft

And the forces there are tiny:

• vibration
• gravity
• a bit of handling

That’s why a flimsy little circlip is enough.

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Why your “it shouldn’t come off” intuition still makes sense

You’re right in a practical sense:

• If the skewer is closed, the lever is very unlikely to just fall off
• The geometry + friction + compression all help keep it together

But:

• once you open it, there’s nothing preventing the lever from sliding off the end
• over years, that’s when parts go missing

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One more nuance (you’ll like this)

Cam quick-releases are designed so that:

• the cam passes slightly over-centre
• which means the reaction force actually helps keep it closed, not open

So even that big force you calculated is stabilising, not ejecting anything.

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Bottom line

• Your force estimate → solid
• Your conclusion → slightly misapplied direction-wise
• The circlip → only a retainer for the loose state, not a load-bearing component

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If yours has survived 10 years without the clip, that’s actually kind of impressive 😄
…but it also means you’ve probably just been lucky not to lose the lever while the wheel was off.

Want to go one level deeper and sketch the force directions? It’s a nice little statics problem.

Eugene: 

Now possibly radial shock forces could loosen it?

 

ChatGPT: 

Yeah—that’s the right line of thinking now 👍

Radial shocks (bumps, vibration, wheel chatter) can definitely contribute to the lever working loose—but not in the way your earlier force model was pointing.

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What radial shocks actually do

They don’t overcome that big axial clamp force directly. Instead they:

• create small oscillating forces and micro-movements in the mechanism
• introduce slight lateral and axial play when the lever isn’t perfectly loaded
• cause fretting + wear + tiny shifts over time

Think of it less like a single big force and more like:

thousands of tiny nudges gradually walking the part outward

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When this matters most

Radial shock becomes relevant when:

• the lever is open (no clamp force → nothing “locking” it)
• the cam surfaces are worn or dry
• there’s clearance in the fit between parts
• corrosion has already weakened things

In that state, vibration can:

• rotate the nut slightly
• shift the cam position
• and crucially… let the lever creep along the shaft

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Why the clip still matters

Even with shocks:

• there’s still no strong continuous axial force pushing the lever off
• but shocks can give it just enough intermittent movement to eventually:
  • reach the end of the shaft
  • and slip off if there’s no circlip to stop it

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Analogy (closest real-world feel)

It’s like a bolt that doesn’t unscrew from one big force—but from:

• vibration
• tiny cyclic loads
• gradual loss of friction

Same idea here—just linear instead of rotational.

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So your revised model is basically spot-on

• Big clamp force → not the issue
• Shock/vibration → slow migration mechanism
• Missing clip → nothing to stop the final exit

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If you’re half tempted to keep running it as-is… I’d still swap the skewer. It’s one of those parts where failure is very “all at once,” and usually at the worst possible moment.

what is the piece called that the cam lever fits into?

That part is usually called the cam body (or sometimes the cam housing).

On a typical quick-release skewer you’ve got:

• the skewer rod (the long shaft)
• the cam lever (the flip handle)
• the cam body / housing ← the bit you’re asking about
• the adjusting nut on the other side

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What it actually does

The cam lever pivots against this cam body, which has:

• a curved cam surface
• a seat for the lever to press into

When you close the lever, it rolls/wedges against that surface and generates the clamping force.

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Other names you might see

Depending on brand or context, it can also be called:

• cam assembly (when grouped with the lever)
• lever seat (less common)
• cam mechanism

But “cam body” is the clearest, most widely understood term.

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If you’re trying to source parts individually, that’s where it gets annoying—most manufacturers don’t sell the cam body separately. They expect you to replace the whole skewer.

Are you trying to rebuild it piece-by-piece, or just figuring out what went missing?