Product Guides
Socket Size Chart: Metric, Imperial & Drive Sizes
Socket size is the across-flats (AF) measurement of a fastener head, sized in millimetres (metric) or fractions of an inch (imperial/SAE). A 19mm socket equals 3/4" (19.05mm). The quick-reference table below lists the most-used sizes in both systems; full metric, imperial and drive-size charts are further down. Quick answer — socket conversions Metric → Imperial: 8mm ≈ 5/16" · 10mm ≈ 3/8" · 11mm ≈ 7/16" · 13mm ≈ 1/2" · 14mm ≈ 9/16" · 15mm ≈ 19/32" · 16mm ≈ 5/8" · 17mm ≈ 11/16" · 19mm ≈ 3/4" · 21mm ≈ 13/16" · 22mm ≈ 7/8" · 24mm ≈ 15/16" · 27mm ≈ 1-1/16" · 30mm ≈ 1-3/16" Imperial → Metric: 1/4" ≈ 6.5mm · 5/16" ≈ 8mm · 3/8" ≈ 10mm · 7/16" ≈ 11mm · 1/2" ≈ 13mm · 9/16" ≈ 14mm · 5/8" ≈ 16mm · 3/4" ≈ 19mm · 7/8" ≈ 22mm · 15/16" ≈ 24mm ⚠️ Close ≠ exact. For torqued fasteners always use the correct system to avoid rounding the head. For more engineering reference charts and selection tables, see our Engineering Reference Charts hub — covering fasteners, bearings, lubrication, measuring, welding and Australian standards. Socket Size Selector — Find the Right Socket for the Job This chart is a working socket selector — every chart row links to a stocked AIMS product (Ko-Ken, Stahlwille or Trax) or to the matching range. Use the scenarios below to land on the right drive size + socket size fast, or scroll to the chart tables below. How to use: 1. Match drive size to job type 2. Find the metric or imperial socket size in the chart 3. Click the size to view the stocked product Electronics & Small Screws 1/4" drive — fine work 1/4" View → General Workshop 3/8" drive — most-common 3/8" View → Automotive & Engineering 1/2" drive — bolts to M22 1/2" View → Heavy Truck & Mining 3/4" drive — high-torque 3/4" View → Impact / Air Tools Impact-rated black sockets Impact View → Torx & Hex Drive Bolts Torx & hex bit sockets Torx/Hex View → Browse Socket Sets Multi-piece complete sets Sets View → Ko-Ken / Stahlwille / Trax Top brands stocked Brands View → Quick rule: 1/4" drive for small jobs (electronics, dash trim), 3/8" for general workshop and automotive, 1/2" for chassis and engine bolts (M10-M22), 3/4" for heavy truck and mining (M24+). For impact tools, use black impact-rated sockets only — chrome sockets shatter under hammer load. Need help? Call (02) 9773 0122. Jump to: How Sockets Work Metric 1/4" Metric 3/8" Metric 1/2" Imperial SAE Conversion Deep vs Standard Choosing Drive Size Related Selectors Socket Size Chart — Metric to Imperial Quick Reference The most common metric socket sizes and their closest imperial (SAE) equivalents: Metric Imperial (SAE) Metric Imperial (SAE) 8mm 5/16" 17mm 11/16" 10mm 3/8" 19mm 3/4" 11mm 7/16" 22mm 7/8" 13mm 1/2" 24mm 15/16" 14mm 9/16" 27mm 1-1/16" How Socket Sizes Work Socket sizes refer to the across-flats measurement of the fastener head — the same dimension used for spanners and open-end wrenches. A 19mm socket fits a fastener with 19mm across the flats, regardless of whether the fastener itself is metric or has a metric thread. Drive size is separate from socket size. It refers to the square drive on the ratchet or extension bar that connects to the socket — 1/4", 3/8" or 1/2". A 3/8" drive 13mm socket and a 1/2" drive 13mm socket both fit the same nut, but the larger drive handles more torque. Standard (shallow) sockets work for most fasteners. Deep sockets are needed where the fastener shank protrudes through the nut — common on wheel studs, bolts with long thread engagement, and spark plugs. Metric Socket Size Chart — 1/4" Drive A 1/4" drive is suited to light work: electronics, small engines, interior trim, and torque-sensitive applications. Typical range is 4mm–15mm. Handles up to approximately 35 Nm. Socket Size (mm) Drive Size Typical Use 4 1/4" Small screws, electronics 5 1/4" Small fasteners 5.5 1/4" Small engine components 6 1/4" General light fasteners 7 1/4" General light fasteners 8 1/4" Interior panels, brackets 9 1/4" General use 10 1/4" Most common metric bolt head 11 1/4" General use 12 1/4" General use 13 1/4" M8 bolt head 14 1/4" General use 15 1/4" Upper limit of 1/4" drive Metric Socket Size Chart — 3/8" Drive A 3/8" drive covers the widest general-purpose range — from 8mm up to 24mm in most sets. The right choice for most automotive, machinery, and workshop tasks. Handles up to approximately 100–135 Nm. Socket Size (mm) Drive Size Common Fastener 8 3/8" M5 bolt head 9 3/8" General use 10 3/8" M6 bolt head — most common 11 3/8" General use 12 3/8" M8 bolt head (some) 13 3/8" M8 bolt head (standard) 14 3/8" M9 bolt head 15 3/8" General use 16 3/8" M10 bolt head (some) 17 3/8" M10 bolt head (standard) 18 3/8" M11 bolt head 19 3/8" M12 bolt head / wheel nuts (many) 21 3/8" General use 22 3/8" M14 bolt head 24 3/8" M16 bolt head Metric Socket Size Chart — 1/2" Drive A 1/2" drive is for heavy work: wheel nuts, suspension components, heavy machinery, and high-torque fasteners. Standard range is 17mm–50mm. Handles 200 Nm and above depending on the tool. Socket Size (mm) Drive Size Common Fastener 17 1/2" M10 bolt head 19 1/2" M12 bolt head / most wheel nuts 21 1/2" General heavy use 22 1/2" M14 bolt head 24 1/2" M16 bolt head 27 1/2" M18 bolt head 30 1/2" M20 bolt head 32 1/2" M22 bolt head 33 1/2" Wheel nuts (heavy vehicles) 36 1/2" M24 bolt head 38 1/2" Heavy machinery 41 1/2" Heavy machinery / axle nuts 46 1/2" Axle nuts / heavy plant 50 1/2" Large axle and hub nuts Imperial (SAE) Socket Size Chart Imperial sockets are sized in fractions of an inch and are common on American-manufactured vehicles and equipment, agricultural machinery, and older plant. The sizing convention follows SAE (Society of Automotive Engineers) standards. Available in 1/4", 3/8" and 1/2" drive. Socket Size (inch) Decimal (inch) Metric Equivalent (mm) Typical Drive 3/16" 0.188" 4.8 1/4" 1/4" 0.250" 6.35 1/4" 5/16" 0.313" 7.9 1/4" 3/8" 0.375" 9.5 1/4" / 3/8" 7/16" 0.438" 11.1 3/8" 1/2" 0.500" 12.7 3/8" 9/16" 0.563" 14.3 3/8" 5/8" 0.625" 15.9 3/8" 11/16" 0.688" 17.5 3/8" 3/4" 0.750" 19.1 3/8" / 1/2" 13/16" 0.813" 20.6 3/8" / 1/2" 7/8" 0.875" 22.2 1/2" 15/16" 0.938" 23.8 1/2" 1" 1.000" 25.4 1/2" 1-1/16" 1.063" 27.0 1/2" 1-1/8" 1.125" 28.6 1/2" 1-3/16" 1.188" 30.2 1/2" 1-1/4" 1.250" 31.8 1/2" 1-5/16" 1.313" 33.3 1/2" 1-3/8" 1.375" 34.9 1/2" 1-1/2" 1.500" 38.1 1/2" Metric to Imperial Socket Conversion Chart No exact metric-to-imperial match exists — socket sizes are based on different measurement systems. The table below shows the closest imperial socket to each common metric size. In most cases the fit will be too loose for torquing; use the correct metric socket where precision matters. Metric Size (mm) Closest Imperial Difference 8 5/16" +0.1mm 9 3/8" +0.5mm 10 3/8" -0.5mm 11 7/16" +0.1mm 12 15/32" -0.1mm 13 1/2" -0.3mm 14 9/16" +0.3mm 15 19/32" +0.0mm 16 5/8" -0.1mm 17 11/16" +0.5mm 18 11/16" -0.5mm 19 3/4" +0.1mm 21 13/16" -0.6mm 22 7/8" +0.2mm 24 15/16" -0.2mm 27 1-1/16" +0.0mm 30 1-3/16" +0.2mm 32 1-1/4" -0.2mm Standard vs Deep Socket Guide Standard (shallow) sockets handle the vast majority of work. Deep sockets are needed when the bolt shank extends through the nut, leaving the socket unable to seat properly on a shallow socket. Common applications for deep sockets include wheel studs, exhaust bolts, spark plugs, and any application where thread is exposed above the nut. Socket Type Depth Use When Standard (shallow) ~25–35mm Bolt head or nut flush / minimal thread protrusion Deep ~60–75mm Thread protrudes through nut (wheel studs, spark plugs) Extra deep / pass-through 100mm+ Long studs, threaded rod, specialised applications Choosing the Right Drive Size Drive size determines torque capacity and tool compatibility. Match the drive to the job — using a 1/2" drive on small fasteners risks overtorquing and rounding; using a 1/4" drive on large fasteners risks snapping the drive or the socket. Drive Size Socket Range Torque Range Typical Applications 1/4" 4–15mm / 3/16"–9/16" Up to ~35 Nm Electronics, small engines, interior trim, torque-sensitive work 3/8" 8–24mm / 5/16"–15/16" 35–135 Nm General automotive, machinery, most workshop tasks 1/2" 17–50mm+ / 11/16"–2" 135 Nm+ Wheel nuts, suspension, heavy machinery, high-torque fasteners 3/4" 33–75mm+ 700 Nm+ Heavy plant, earthmoving, structural work 1" 50mm+ 2,000 Nm+ Mining, large infrastructure, industrial plant Related AIMS Selectors This selector pairs with AIMS's other fastener & tool guides: Spanner Size Chart — metric AF spanner sizes mapped to bolt size + spanner products. Choosing Socket Drive Size — detailed walkthrough on when to step up or down a drive size. Ratchet Spanner Guide — flex-head vs reversible vs gear count selection. Adjustable Spanner Guide — shifter selection and use. Types of Spanners — open-end / ring / combo / flare / podger reference. Impact Driver vs Impact Wrench — when to use impact sockets vs hand tools. Socket Head Cap Screw Guide — Allen/hex socket fastener reference (paired with socket bits). Metric Bolt Torque Chart — torque values per grade and size (use with torque wrench). Or browse the full sockets range, ratchets & sockets, spanners & wrenches, or by brand: Ko-Ken, Stahlwille, Trax. Next-day Australia-wide dispatch from our Milperra warehouse.Frequently Asked Questions What is 10mm socket in imperial? A 10mm socket is approximately 3/8 inch (9.525mm). The match is close — 10mm is 0.475mm larger — but for torqued fasteners always use the 10mm socket on metric bolts. 10mm fits M6 bolt heads which are extremely common on engines and brackets. Is 3/8 inch socket the same as 10mm? No, they are close but not identical. A 3/8 inch socket measures 9.525mm and a 10mm socket measures 10mm — a 0.475mm difference. A 3/8" socket will fit loosely on a 10mm hex and risks rounding the head under torque. Use the correct system for the fastener. What is 13mm socket in imperial? A 13mm socket is approximately 1/2 inch (12.7mm). The difference is only 0.3mm. 13mm is the standard size for M8 hex bolts — one of the most-used sizes in automotive and machinery work. What is 14mm socket in imperial? A 14mm socket is approximately 9/16 inch (14.29mm). 14mm is commonly used for M10 hex bolts, brake calipers and many engine fasteners. What is 15mm socket in imperial? A 15mm socket is approximately 19/32 inch (15.08mm). 15mm is less common in the standard imperial range — most SAE sets skip from 9/16" (14.29mm) to 5/8" (15.88mm). What is 16mm socket in imperial? A 16mm socket is approximately 5/8 inch (15.88mm). 5/8" is 0.125mm smaller than 16mm — usable on a light fit but always use 16mm for torqued M10 fine-thread fasteners. What is 17mm socket in imperial? A 17mm socket is approximately 11/16 inch (17.46mm). 17mm is one of the most common sizes used on M10 hex bolt heads and brake hardware. What is 19mm socket in imperial? A 19mm socket is equivalent to 3/4 inch (19.05mm) — only 0.05mm difference. This is one of the closest metric/imperial pairs and either socket can usually be used interchangeably on a light fit. What is 21mm socket in imperial? A 21mm socket is approximately 13/16 inch (20.64mm). 21mm is the standard size for many wheel lug nuts on European vehicles. What is 22mm socket in standard? A 22mm socket is approximately 7/8 inch (22.23mm). 22mm is widely used on M14 hex bolts and is a common spark plug socket size. What is 28mm socket in imperial? A 28mm socket is approximately 1-1/8 inch (28.58mm). The difference is 0.58mm — use the correct metric size for axle nuts and large machinery fasteners. What are socket sizes in order? Common metric socket sizes in order: 4, 4.5, 5, 5.5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 27, 30, 32, 36mm. Common imperial (SAE) sizes in order: 5/32, 3/16, 7/32, 1/4, 9/32, 5/16, 11/32, 3/8, 7/16, 1/2, 9/16, 5/8, 11/16, 3/4, 13/16, 7/8, 15/16, 1, 1-1/16, 1-1/8 inch. What is the most common socket size? In metric, 10mm is the most frequently used socket size — it fits M6 bolt heads which appear on engines, brackets and interior components across virtually every vehicle and machine. In imperial, 3/8" and 7/16" are among the most common SAE sizes. Can I use a metric socket on an imperial fastener? In some cases yes — where the metric size is very close to the imperial size. For example, an 11mm socket is almost identical to a 7/16" (11.1mm). However, for torqued fasteners, always use the matching socket to avoid rounding. The closest metric-to-imperial matches are shown in the conversion chart above. When do I need a deep socket? Use a deep socket when the bolt shank protrudes through the nut, preventing a standard socket from seating properly. Common applications include wheel studs (where the thread extends past the wheel nut), spark plugs, and long threaded rod assemblies. If a standard socket rocks or won't engage the full depth of the hex, switch to a deep socket. What is the difference between 6-point and 12-point sockets? A 6-point socket has six internal contact points and grips the flat sides of the hex fastener. It is less likely to round worn or corroded fasteners and is the preferred choice for high-torque work. A 12-point socket has twelve contact points, allowing it to engage the fastener at more angles — useful in tight spaces where swing is limited. For general use, 6-point is the better choice. Ready to get to work? Shop our full range of sockets & socket sets From 1/4" drive metric to 1/2" drive imperial — AIMS Industrial stocks sockets for every drive size and standard, ready to ship Australia-wide. Browse sockets Talk to a specialist People Also Ask — Socket Size Chart: Metric, Imperial & Drive Sizes Q: What is the difference between 3/8" and 1/2" drive sockets? Drive size refers to the square drive that connects the socket to the ratchet — 3/8" is the most versatile for general trade work, while 1/2" drive handles higher torque applications like wheel nuts and structural bolts. 1/4" drive suits tight spaces and small fasteners; 3/4" and 1" drive are for heavy industrial work. Q: Can I use a metric socket on an imperial bolt? In a pinch, a close-fitting metric socket can work on an imperial fastener — for example, a 15 mm socket is nearly identical to 19/32". However, using a slightly oversized socket risks rounding off the fastener corners. Always use the correct size where possible; keep a mixed metric/imperial set for older equipment. Q: What does 6-point vs 12-point socket mean? A 6-point socket has six contact surfaces and grips flat-to-flat on the hex, reducing the risk of rounding fasteners. A 12-point socket engages on corners, making it easier to position in tight spaces but more likely to slip under high torque. Use 6-point sockets for stuck or high-torque fasteners; 12-point for easy access work. Q: Are impact sockets different from standard sockets? Yes — impact sockets are made from thicker, softer chrome-molybdenum steel that absorbs the hammering action of an impact wrench without shattering. Standard chrome-vanadium hand sockets can crack under impact loads. Impact sockets are typically black (not chrome-plated) for easy identification. Never use hand sockets with impact guns.
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How to Identify Synchronous Timing Belts
In an ideal situation, you can identify the belt you have by its markings alone. Typically, those are alphanumeric labels that identify the belt's specifications, often describing the most important dimensions critical to properly identify them. (In another article, we discussed how you can identify a v-belt.) Important: If your pulley has teeth, then you indeed have a synchronous timing belt, which should not be mistaken for cogged belts -- who also appear like they have "teeth" but are just actually cogs (notches) -- such as these banded-narrow, classical and narrow-section cogged belts. For example, in Gates nomenclature, in their PowerGrip range, you’ll see a marking that designates the belt’s pitch length, pitch and tooth profile (the letters), and the width. (Image taken from the Gates Industrial Power Transmission Catalog) Note: This applies to both single-side and double-sided synchronous belts. Nomenclature and order may vary by manufacturer. You may, however, be in a situation where you don’t have access to that information for many reasons, such as: The belt is still installed in the pulley and there’s no way you can see the markings. The belt is already snapped and torn. The markings are too faded or dirtied to be read. In this case, you may have to manually figure out your belt specifications. We hope this article points you in the right direction. Here are the 3 key identifiers you need to determine to order the belt: 1. What is the tooth profile of the belt? 2. What is the length? 3. What is the width? Timing Belt Measurement — Quick Reference Synchronous timing belts are identified by three measurements: tooth pitch (distance between adjacent tooth centres in mm or inches), belt length (total circumference in mm or number of teeth), and belt width (across the toothed face in mm). Together these tell you the exact belt — for example "8M-1200-30" means 8mm pitch, 1200mm length, 30mm width. Measurement What it is How to measure Pitch Distance between tooth centres Measure tooth-to-tooth in mm (metric) or 1/inch (imperial) Length Total belt circumference Lay belt flat, measure outside circumference; or count total teeth Width Across the toothed face Measure the belt width perpendicular to the teeth Tooth count Number of teeth around the belt Count all teeth — used in part numbers 1. What is the tooth profile of the belt? This is the most important identifying factor of synchronous belts, so it’s important to get this right. If you get the wrong profile, it may not fit the pulley at all and, if it does, it will wear out very quickly. You can tell the profile of the belt by its pitch and shape. You can also measure the thickness as a cross-check. Pitch This is the “centre-to-centre" distance between two adjacent teeth. To get this number, measure the distance between the middle of one tooth, to the middle of the adjacent tooth. Imperial vs Metric: This is another key factor in finding the type of belt you have, so it’s equally important to get this right. Important: When manually measuring the pitch, please make sure to use the metric system (eg. by millimeters), as we often do here in Australia. Otherwise, let us know that you’re giving us the measurement in imperial, so we can help you work out its metric equivalent. In this sample reference from the Gates PowerGrip range, you’ll see the pitch is indicated in imperial units (eg. 1/5 inch), as it would be typically written. (Image taken from the Gates Industrial Power Transmission Catalog) Here’s another reference from the Gates PowerGrip timing belt range. Note that this range is imperial but, for ease, dimensions are shown in both imperial and metric units. In this illustration, label A is the pitch. (Image taken from the Gates Industrial Power Transmission Catalog) Aside from the belt, don’t forget to check the pulleys for any markings too. The pulley won’t give you everything you need to order the belt but they often have the pitch/profile printed on them. If so, this will make life a lot easier. It also helps a lot because, occasionally, we find that someone has previously fitted the wrong belt, so checking the pulley is a great way of ensuring you’re getting the right belt. Shape This is how the angles of the peaks and valleys in between the teeth look like, as well as the shape of the tooth. Some belts have rounded teeth, whilst others are quite ‘square’ or trapezoidal. Some people refer to this as the tooth form. Metric belts usually have rounded teeth, while imperial belts have trapezoidal ones, but keep in mind that is not always the case. If you’re having trouble and need our help identifying the belt, we won’t need the exact angle of the shape, but as always, it will be helpful if you can send a photo of the actual belt that needs replacing, as well as the pitch as accurately measured as possible. Thickness Aside from the shape, this value will help us get a better understanding of the belt you have. Although it’s more challenging to get this exactly right considering the wear on the belt. Warning: Don’t be confused by the T and AT profiles (eg T10 & AT10). As you can see in the illustration below, the Ts are more trapezoidal, while the ATs are more rounded. Both, of course, have the same Pitch (eg. 10mm) but the shape is very different. If in doubt, send us a photo of the actual belt and we’ll help you figure it out. (Image taken from the Gates Industrial Power Transmission Catalog) 2. What is the length? Sometimes also referred to as pitch length, this is the total (circumferential) length of the belt, as measured along the pitch line. Put simply, this is the pitch (see #1) multiplied by the number of teeth the belt has. For example, if your belt has a pitch of 10 mm and 32 teeth, then your pitch length is 320 mm. Tip: Mark the tooth where you are going to start counting, and count carefully from there. Some even make subtle marks for every 10th tooth, so it’s easy to go back (and verify) in case you lose count. If possible, get someone else to count as well and then cross-check. We do that with every belt to avoid errors. If you don’t have someone else to check it, then count it yourself 2 or 3 times to ensure you have it right. Special case for imperial belts: Imperial belt pitch lengths are marked in imperial by 1/100 or 1/10 of an inch (in decimal inches). Naturally larger belts are measured in 1/10 and smaller in 1/100. Here is an example from Gates: That means it’s 2.88 inches long and it’s listed this way in the table where you’ll see its metric equivalent of 73.15 mm: 3. What is the width? Measuring this is pretty much straightforward. Just bear in mind that the belt may be a little worn. (Timing belt 3D view illustration courtesy of Pfifer) Special case for imperial belts: Imperial belt widths are identified in decimal inches, as in the previous example by Gates: In this example, the belt width is 0.19 inches. Furthermore, if it were 050, then that would be 0.50 inches. Or 0.75 inches. 100 would be 1 inch and so on. Other factors to consider In addition to those three questions, we may occasionally need to confirm the following: What’s the application? Even when two belts are dimensionally the same, one may be stronger than another and therefore designed to withstand heavier loads (eg. for systems with forced induction mechanisms such as superchargers). Are you sure it’s not a cogged V belt? The 'cog's or notches in cogged V belts make it "look like they have teeth", but they actually go into a pulley with no teeth. To emphasise, if the pulleys have no teeth, then it isn’t a timing belt. It is then typically a cogged V belt or, occasionally, a Variable Speed belt. What is the belt made of? Most are made of rubber, while some are made of aramid, neoprene, carbon fibre, polycarbonate or polyurethane. Some are strong enough they can replace chains, provided they can fit in the proper (or appropriately converted) sprockets. For more information, you can refer to these catalogues by Gates: Gates Belts ID Chart Gates Industrial Power Transmission Catalogue Conclusion Measure your belt pitch. From there, identify your tooth profile. Measure your belt length by counting the number of teeth and multiplying it by the pitch. Measure your belt width. In addition, it’s best if you can identify: The intended application The material of the belt If in doubt, just reach out to us and we’ll help you figure it out. It would be helpful if you can include pictures of the actual belt you want to replace and any measurements you’ve taken. AIMS' Note on Safe Use of Belt-Driven Systems Power down: Before any inspection, maintenance, or adjustment, make sure to completely shut down the power to the machine and apply a lockout/tagout (LOTO) device to prevent accidental restarts. Right belt for the system: Keep in mind that v-belts (especially cogged / notched / wrapped belts) are different from synchronous /timing / ‘toothed’ belts. Some mistake the cogs for teeth but remember that cogged belts run on V-shaped pulleys that do not have teeth. Are you operating where flammable substances are present? Maybe you need fire-resistant anti-static (FRAS) belts – or maybe heat-resistant and oil-resistant belts will do. We compared them in this FAQ. Safe attire: Avoid loose clothing, jewelry and long hair that could get caught in the moving parts. Ensure proper fit of workwear without compromising comfort, dexterity and protection. Tie back long hair and secure loose items. Safeguards in place: Never operate a belt-driven system with the guards removed or bypassed. These guards are there for your protection. Maintenance and replacement: Regularly inspect belts and pulleys for wear and tear. Maintain proper belt tension and alignment as specified by the manufacturer. When replacing the belt, make sure you get the proper fit and measurement of the system. These accessories and maintenance kits (eg alignment tools, belt measurers, pulley gauge sets, spacers, tensioners etc) come in handy. Cleanliness: Keep the area around belt drives free of debris and clutter that could get caught or cause a fire hazard. (Refer to our content library's sub-index of articles about belt-driven systems and electric motors for more information.) Our V-Belt Measurement guide shows how to identify and size every common Australian V-belt profile. People Also Ask — Measuring Synchronous Timing Belts Q: How do I determine the pitch of a synchronous timing belt? Timing belt pitch is the distance from the centre of one tooth to the centre of the next tooth, measured along the belt's pitch line. Measure across several teeth and divide by the number of spaces to get an accurate average. Common metric pitches include 3mm, 5mm, 8mm and 14mm; common imperial pitches include 0.080 inch (XL), 0.125 inch (L) and 0.200 inch (H). Q: How do I measure the length of a synchronous timing belt? Wrap a flexible steel rule or string around both pulleys with the system assembled and under correct tension, then measure the total loop length. For an existing belt, count the number of teeth and multiply by the pitch to get the belt's pitch length, which is the standard way timing belt length is specified. Always compare the tooth count and pitch against the manufacturer's replacement specification. Q: What is belt width and why does it matter? Timing belt width determines how much torque the belt can transmit, as a wider belt carries more load for the same pitch and tooth profile. Belt width must match the pulley face width; if the belt is significantly narrower than the pulley it may track off to one side, and if it is wider it may not be compatible with flanged pulleys. Always replace with the same width unless deliberately upgrading for higher load capacity. Q: Can I replace a timing belt with a different tooth profile? No, the tooth profile of the belt must exactly match the pulley. Mixing tooth profiles, for example installing an HTD belt on a trapezoidal-profile pulley, results in poor tooth engagement, premature wear and possible tooth stripping under load. The belt and pulley must always be the same profile family. For timing pulleys, see our timing pulleys range stocked across Australia.How do I read a synchronous timing belt part number? A synchronous belt code combines the length, the pitch and the width — for example 600-5M-15 is 600mm long, 5M (5mm) pitch and 15mm wide; an imperial code like 150XL037 is 15.0 inches long, XL pitch and 0.375 inch wide. Read the length, then the pitch code, then the width. If the code is worn, measure the pitch and count the teeth. See industrial timing belts. How do I identify a timing belt's tooth profile? Measure the pitch (tooth-to-tooth distance) and look at the tooth shape: trapezoidal teeth are the classic MXL/XL/L/H imperial or T2.5/T5/T10 metric profiles; rounded (curvilinear) teeth are HTD or GT profiles. The profile must match the pulley — a rounded HTD belt won't run correctly on a trapezoidal pulley. Compare against a known belt or a profile gauge. See our synchronous timing belt guide. Should I count teeth or measure length to identify a timing belt? Both help: the pitch length equals the pitch multiplied by the number of teeth, so counting the teeth and knowing the pitch gives the length exactly — more reliable than a tape measure on a flexible belt. On a closed-loop belt, counting teeth is the accurate way to size a replacement. Match the tooth count, pitch and width together. See matched timing pulleys and the Gates range.
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