# Bolt circle

> Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Bolt_circle
> Markdown URL: https://mediated.wiki/source/Bolt_circle.md
> Source: https://en.wikipedia.org/wiki/Bolt_circle
> Source revision: 1334216697
> License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/)

Mechanical engineering term

"Pitch circle diameter" redirects here. For the effective distance between gears, see [Pitch circle diameter (gears)](/source/Pitch_circle_diameter_(gears)).

Drawing of 5-hole (left) and 4-hole (right) pitch circles

A **bolt circle diameter** or **pitch circle diameter** (**PCD**), sometimes simply called **bolt circle** or **pitch circle**, is a common term for when a number of [screw](/source/Screw) holes for [bolts](/source/Bolt_(fastener)) are evenly distributed with their centers along an imaginary circle with a given [diameter](/source/Diameter).

An example of use is mounting of car [rims](/source/Rim_(wheel)), where the bolt circle is one of several factors that determine whether a set of rims will fit a car. For example, a bolt circle of 5×130 or 5-130 indicates that a rim is to be attached to the car via 5 screws evenly spaced along a circle with a diameter of 130 millimeters.[1] Other common uses for bolt circles are for indicating mounting for [sim racing](/source/Racing_wheel) and [real-world car steering wheels](/source/Steering_wheel), or in the industry for mounting of [servomotors](/source/Servomotor) or for specifying the bolt pattern of a [flange](/source/Flange). Attachment of chain rings for bicycle [cranksets](/source/Crankset) are also specified by a bolt circle.[2]

## Standards

NEMA ICS 16[3] defines flange patterns that are either defined in millimeters or inches (see collapsible table with comparisons below):

- Metric-based

- Inch-based

NEMA ICS 16:2001 Flange type Bolt circle (M) Square flange max width (BD) Flange min diameter (N) Flange max diameter (P) Number of holes Free holes (S) Tapped holes mm inch mm inch mm inch mm inch mm inch 17 C 43.18 1.7 43.82 1.725 21.999 0.8661 59.94 2.36 4 3.81 0.150 #4-40 17 D 43.18 1.7 50.8 2.000 21.999 0.8661 59.94 2.36 4 4 0.150 #4-40 55 55 2.165 53 2.087 40 1.5748 70 2.756 4 5.8 0.228 M5 23 58.42 2.3 66.675 2.625 38.100 1.5000 59.94 2.36 4 5.21 0.205 #8-32 65 65 2.559 60 2.362 50 1.9685 80 3.150 4 5.8 0.228 M5 70 70 2.756 60 2.362 50 1.9685 80 3.150 4 5.5 0.217 M5 75 75 2.953 70 2.756 60 2.3622 50 1.969 4 5.8 0.228 M5 85 85 3.346 80 3.150 70 2.7559 105 4.134 4 7 0.276 M6 34 86.36 3.4 98.425 3.875 73.025 2.8750 81.53 3.21 4 5.59 0.220 #10-32 100 100 3.937 90 3.543 80 3.1496 120 4.724 4 7 0.276 M6 42 106.68 4.2 125.73 4.950 55.563 2.1875 90.93 3.58 4 7.11 0.280 1/4"-20 115 115 4.528 105 4.134 95 3.7402 140 5.512 4 10 0.394 M8 48 121.92 4.8 95.25 3.750 76.200 3.0000 157.23 6.19 4 7.11 0.280 1/4"-20 130 130 5.118 120 4.724 110 4.3307 160 6.299 4 10 0.394 M8 56 142.24 5.6 149.225 5.875 114.300 4.5000 143.00 5.63 4 10.16 0.400 3/8"-16 145 145 5.709 130 5.118 110 4.3307 165 6.496 4 9 0.354 M8 165 165 6.496 140 5.512 130 5.1181 200 7.874 4 12 0.472 M10 200 200 7.874 174 6.850 114.3 4.5000 225 8.858 4 13.5 0.531 M12 215 215 8.465 190 7.480 180 7.0866 250 9.843 4 14.5 0.571 M12 265 265 10.433 225 8.858 230 9.0551 300 11.811 4 14.5 0.571 M12 300 300 11.811 265 10.433 250 9.8425 350 13.780 4 18.5 0.728 M16 350 350 13.780 300 11.811 300 11.8110 400 15.748 4 18.5 0.728 M16 400 400 15.748 340 13.386 350 13.7795 450 17.717 8 18.5 0.728 M16 500 500 19.685 415 16.339 450 17.7165 550 21.654 8 18.5 0.728 M16 600 600 23.622 495 19.488 550 21.6535 660 25.984 8 24 0.945 M20 740 740 29.134 600 23.622 680 26.7717 800 31.496 8 24 0.945 M20 940 940 37.008 750 29.528 880 34.6457 1000 39.370 8 28 1.102 M24 1080 1080 42.520 865 34.055 1000 39.3701 1150 45.276 8 28 1.102 M24

## Examples

### Racing wheels

On steering wheels for cars utilizing bolt circles, this usually measures 6×70 mm.[4] Some racing wheels attach to the car via a quick release hub,[5] and this hub then usually has a corresponding bolt circle of 6×70 mm. Example of other less used patterns include: 3×1.75 in (44.45 mm), 5×2.75 in (69.85 mm), 6×74 mm and 6×2.75 in (69.85 mm).[4]

### Servomotors

Industrial [servomotors](/source/Servomotor) and gearboxes, with standardised flange mountings for interchangeability.

[Servomotors](/source/Servomotor) in the industry are often mounted via a flange-like coupling to give the shortest possible [leverage](/source/Lever) for high-torque uses. Industrial servomotors often use standardised mounting patterns, of which one example is a bolt circle of 4×130 mm diameter (approximately corresponds to a square pattern of 91.9 mm × 91.9 mm).

### Car rims

A bolt circle with four [wheel nuts](/source/Wheel_nut) on an [Acura](/source/Acura).

The mounting pattern of most car rims are described using bolt patterns, and this pattern is one of many factors which determine whether a rim will fit a given car. Here, the bolt circle indicates the number of [wheel nuts](/source/Wheel_nut) and associated hub bolts (or alternatively just wheel bolts).[6][7]

An example of a bolt circle is 5×100 which indicates 5 nuts placed on a circle with a diameter of 100 mm. Some of the most common bolt circle diameters on modern cars are 100 mm, 112 mm and 114.3 mm.[*[citation needed](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*] The bolt circle of a car is one of several parameters that must be checked before buying new rims to make sure they will fit the car (along with wheel offset, hub diameter, and finally the diameter and width of the rim and tire). Over the years, over 30 different bolt circles patterns have been used by car manufacturers,[8] most of which are not compatible with each other.

## See also

- [Pitch diameter](/source/Screw_thread#Pitch_diameter), a dimension of a screw thread

## References

1. **[^](#cite_ref-1)** ["Wheel Tech: Bolt Pattern"](https://www.tirerack.com/wheels/tech/techpage.jsp?techid=92).

1. **[^](#cite_ref-2)** [Wolf Tooth Tech Help - Measure Bike Chainring BCD Bolt Circle Diameter – Wolf Tooth Components](https://www.wolftoothcomponents.com/blogs/news/how-to-measure-bolt-circle-diameter-bcd)

1. **[^](#cite_ref-3)** ["NEMA Standards Publication ICS 16 | Industrial Control and Systems | Motion/Position Control Motors, Controls, and Feedback Devices (NEMA, 1998, 1999, 2000, 2001)"](https://www.cncitalia.net/file/pdf/nemastandard.pdf) (PDF).

1. ^ [***a***](#cite_ref-nlmotoring_4-0) [***b***](#cite_ref-nlmotoring_4-1) [Steering Wheel Bolt Patterns Explained](https://nlmotoring.com/how-tos/steering-wheel-bolt-patterns-explained/)

1. **[^](#cite_ref-5)** [Quick release hub steering wheel | Raptor Steering Wheels](https://www.raptorsteering.com/blog)

1. **[^](#cite_ref-6)** ["Bolt Circle Diameter (B.C.D.)"](http://www.sheldonbrown.com/gloss_bo-z.html#bcd). Retrieved 3 December 2010.

1. **[^](#cite_ref-7)** ["P.C.D."](http://www.sheldonbrown.com/gloss_p.html#pcd) Retrieved 4 December 2010.

1. **[^](#cite_ref-boltsirkel.no2_8-0)** [Boltsirkel.no](http://www.boltsirkel.no/)

This article about a mechanical engineering topic is a stub. You can help Wikipedia by adding missing information.

- [v](https://en.wikipedia.org/wiki/Template:Mech-engineering-stub)
- [t](/source/Template_talk%3AMech-engineering-stub)
- [e](https://en.wikipedia.org/wiki/Special:EditPage/Template:Mech-engineering-stub)

---
Adapted from the Wikipedia article [Bolt circle](https://en.wikipedia.org/wiki/Bolt_circle) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Bolt_circle?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.