XH Timing Belt: Sizes, Specifications & Applications (2026)

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An XH timing belt is a classical trapezoidal synchronous belt with a 7/8-inch, or 22.225 mm, tooth pitch. Its large teeth and wide standard sections suit industrial drives that need positive, slip-free speed control at higher loads than smaller classical H, L, or XL belts normally handle.

Selecting one requires more than matching the printed length. The belt pitch, pitch length, width, tooth count, pulley tooth form, pulley size, shaft spacing, speed, load, and environment must all agree. An XH belt will not correctly mesh with an HTD, RPP, or other curvilinear pulley, even when a dimension appears close.

This guide explains XH belt markings, standard sizes, construction, applications, and selection limits using current manufacturer data.

Key Takeaways

XH pitch is 0.875 inch, or 22.225 mm.
Nominal tooth height is 6.36 mm; nominal belt height is 11.4 mm.
Common width codes are 200, 300, 400, and 500.
507XH200 means 50.7-inch pitch length, XH pitch, and 2.00-inch width.
XH belts require matching XH pulleys and application-specific drive calculations.

What Is an XH Timing Belt?

XH is the extra-heavy section in the classical imperial timing-belt family. It sits between H, with a 1/2-inch pitch, and XXH, with a 1-1/4-inch pitch. The large XH tooth form gives each engaged tooth more contact area than smaller classical profiles.

Gates describes its classical PowerGrip range as a maintenance-free alternative to chains and gears. The belts use positive tooth engagement to maintain a constant speed ratio without the slip associated with friction belts (Gates, 2025 Industrial Power Transmission Catalogue).

The XH designation identifies the profile, not a complete belt. Two XH belts can have different lengths, widths, materials, or manufacturer ratings. The pulley must have the corresponding 7/8-inch classical trapezoidal groove profile.

Compared with the profiles discussed in TranBelt’s guide to mechanical power-transmission belt types, XH is intended for synchronous industrial drives rather than automotive timing service or ordinary V-belt pulleys.

What Are the Main XH Dimensions and Specifications?

The defining XH dimension is its 7/8-inch pitch. Pitch is measured between the centers of adjacent teeth along the belt’s pitch line, not across the tooth tips. Gates lists a nominal tooth height of 6.36 mm and nominal total belt height of 11.4 mm for its classical XH section.

Specification	XH Nominal Value
Tooth pitch	0.875 in / 7/8 in
Tooth pitch	22.225 mm
Tooth form	Classical trapezoidal
Tooth height	6.36 mm
Belt height	11.4 mm
Common widths	2, 3, 4, and 5 in
Common width codes	200, 300, 400, and 500
Gates listed pitch-length range	1,289-4,445 mm
Gates temperature range for classical PowerGrip	-30°C to +100°C

These values describe the cited Gates product family. They are useful for identification, but they do not replace a manufacturer’s drawing. Backing thickness, tolerances, cord location, available constructions, and temperature ratings can vary.

Continental lists its CONTI SYNCHROBELT XH range from code length 507.0 through 1750.0. Its construction uses synthetic rubber teeth and backing, glass-cord tension members, and polyamide tooth fabric (Continental, CONTI SYNCHROBELT Product Information).

How Do You Read an XH Belt Size?

Classical XH belt markings usually combine pitch length, profile, and width. Gates uses 507-XH-200 as its catalog example. The numbers are expressed in tenths or hundredths of an inch according to the field.

For 507XH200:

507 means a 50.7-inch pitch length.
XH means a 7/8-inch classical trapezoidal pitch.
200 means a 2.00-inch belt width.

Pitch length is measured on the internal pitch line. It is not the belt’s outside circumference. The tooth count follows this calculation:

Number of teeth = pitch length ÷ 0.875 inch

A 50.75-inch pitch length divided by 0.875 inch gives 58 teeth. Although the commercial code is 507, the cataloged pitch length is 50.75 inches because the tooth count must be a whole number.

Width codes use hundredths of an inch. Therefore, 300 is 3.00 inches, 400 is 4.00 inches, and 500 is 5.00 inches. Always confirm the manufacturer’s actual table when an old marking is incomplete or an OEM uses a private number.

Which XH Timing Belt Lengths and Widths Are Standard?

Gates lists twelve common XH pitch lengths from 50.75 to 175 inches. At a fixed 0.875-inch pitch, these correspond to 58 through 200 teeth. Availability by width or region should still be checked before finalizing a machine design.

Belt Length Code	Pitch Length (in)	Pitch Length (mm)	Teeth
507	50.75	1,289.05	58
560	56.00	1,422.40	64
630	63.00	1,600.20	72
700	70.00	1,778.00	80
770	77.00	1,955.80	88
840	84.00	2,133.60	96
980	98.00	2,489.20	112
1120	112.00	2,844.80	128
1260	126.00	3,200.40	144
1400	140.00	3,556.00	160
1540	154.00	3,911.60	176
1750	175.00	4,445.00	200

The common widths are 2, 3, 4, and 5 inches, equal to 50.8, 76.2, 101.6, and 127 mm. Gates notes that other widths may be available on request. Do not assume every length is stocked in every width or construction.

A replacement must match pitch and tooth count before width is considered. Increasing width can raise capacity, but only if the pulleys, guards, shafts, bearings, and alignment can support it. Cutting a wider sleeve to a custom width should be handled by a qualified supplier with suitable tolerance control.

How Does XH Compare with H, XXH, and HTD?

H, XH, and XXH share a classical trapezoidal family, but they have different pitches and pulley geometry. HTD belts use a curvilinear tooth form and are not interchangeable with XH. Similar overall dimensions do not create compatibility.

Profile	Pitch	Pitch (mm)	Tooth Form	Typical Position
H	1/2 in	12.700	Classical trapezoidal	Medium-to-heavy classical drives
XH	7/8 in	22.225	Classical trapezoidal	Extra-heavy classical drives
XXH	1-1/4 in	31.750	Classical trapezoidal	Largest classical section
HTD 14M	14 mm	14.000	Curvilinear	Modern high-torque metric drives

XH can be useful when maintaining an existing machine built around classical pulleys. For a new design, a modern curvilinear profile may offer a more compact drive or different tooth-load distribution. The decision requires manufacturer rating calculations rather than a pitch-only comparison.

Never run XH on an XXH, H, HTD, RPP, or T-profile pulley. Incorrect meshing concentrates load at the tooth edge, creates noise, accelerates fabric wear, and can cause tooth shear. TranBelt’s RPP timing belt guide shows why curvilinear RPP geometry is a separate system.

What Materials and Performance Limits Apply?

A typical rubber XH belt combines a synthetic-rubber body, glass-fiber tensile cords, and nylon or polyamide tooth fabric. The body forms the teeth and backing. Tensile cords control elongation and carry belt tension. Tooth fabric reduces wear during pulley engagement.

Gates publishes broad benefits for its complete classical PowerGrip family, including power transmission up to 150 kW, speeds up to 10,000 rpm, peripheral speed up to 80 m/s, and efficiencies up to 99%. These are family-level limits, not guaranteed ratings for every XH size or drive.

Actual XH capacity depends on:

Driver speed and design power
Service factor and shock load
Small-pulley tooth count
Teeth engaged on the small pulley
Belt width and pitch length
Speed ratio and center distance
Ambient and internal belt temperature
Tension, alignment, and pulley condition
Oil, water, dust, chemicals, and ozone exposure

Gates lists -30°C to +100°C for the cited range. Continental lists -20°C to +100°C depending on application and describes its product as only conditionally resistant to oil. A temperature or chemical limit must be confirmed for the exact belt construction.

Do not apply the catalog’s 150 kW or 10,000 rpm figures directly to an XH selection. Use the manufacturer’s drive-design software or rating tables with the actual pulley diameters, arc of contact, duty cycle, and service factor.

Where Are XH Timing Belts Commonly Used?

XH belts are most relevant to established industrial machinery requiring a wide, positive-drive belt with classical imperial geometry. They are especially common as replacement parts on equipment originally designed around XH pulleys.

Typical applications include:

Large packaging and processing machinery
Printing and paper-converting equipment
Industrial pumps and compressors
Machine tools and production equipment
Textile and woodworking machinery
Conveyors requiring a fixed speed ratio
Mixers, agitators, and material-handling drives
Agricultural and older OEM industrial equipment

Positive engagement makes XH useful where consistent shaft timing matters. However, backlash, tooth clearance, belt elasticity, pulley quality, and structural deflection still affect positioning accuracy. It should not automatically be treated as a zero-backlash motion-control belt.

For conveying rather than shaft power transmission, a fabricated polyurethane belt may be more suitable. Covers, cleats, vacuum holes, or profiles add requirements that a standard rubber XH power-transmission belt does not address.

How Do You Select the Correct XH Belt and Pulley?

Start with the driven equipment, not the existing belt marking alone. A successful selection must transmit corrected design power while maintaining enough tooth engagement, acceptable belt speed, suitable pulley diameters, and manageable shaft loads.

Record motor power, speed, starting method, and operating hours.
Identify the driven-machine type and shock-load service factor.
Confirm the required speed ratio and shaft center distance.
Select matching XH driver and driven pulley tooth counts.
Check the minimum recommended small-pulley tooth count.
Calculate pitch length and choose an available tooth count.
Verify teeth in mesh and arc of contact on the small pulley.
Select width from the manufacturer’s corrected-power rating.
Check belt speed, temperature, environment, and bearing load.
Confirm hub, bushing, bore, keyway, guard, and shaft capacity.

The pulley pitch diameter is calculated from tooth count and pitch:

Pitch diameter = number of pulley teeth × 0.875 inch ÷ π

This is the pitch diameter, not the measured outside diameter. Use manufacturer pulley tables for machining or inspection dimensions. XH pulley grooves require the correct tooth angle, root shape, pitch accuracy, and flange arrangement.

When replacing an existing belt, record its complete marking, tooth count, width, pulley tooth counts, center distance, running direction, and failure condition. A broken belt can indicate overload, misalignment, worn grooves, inadequate tension, or seized equipment rather than normal age.

How Should an XH Timing Belt Be Installed and Maintained?

An XH belt should be installed without forcing it over pulley flanges. Loosen the center distance or tensioning mechanism, fit the belt with teeth fully seated, align the pulleys, and apply the belt manufacturer’s calculated installation tension.

Use this checklist:

Isolate and lock out the drive before work.
Inspect pulley teeth for wear, damage, and packed debris.
Check shafts and bearings for play or rough rotation.
Align pulley faces and shafts within manufacturer tolerances.
Never pry, twist, crimp, or sharply bend the belt.
Apply measured tension using the approved method.
Rotate the drive by hand and recheck tooth seating.
Fit a suitable guard before operation.
Reinspect tension and tracking after the specified run-in period.

Too little tension can cause tooth jumping and impact loading. Too much tension increases bearing load and tensile-cord stress. Belt dressing and lubrication are not required because torque is transferred through tooth engagement.

Keep the drive free from oil and abrasive contamination. Replace belts showing tooth fabric wear, missing rubber, edge damage, exposed cords, chemical swelling, or repeated tooth jumping. On multi-belt arrangements, follow the manufacturer’s matching and replacement guidance.

Frequently Asked Questions

What does XH mean on a timing belt?

XH identifies a classical extra-heavy trapezoidal timing-belt profile with a 7/8-inch, or 22.225 mm, tooth pitch. It does not specify length or width, which appear elsewhere in the belt code.

What size is a 507XH200 timing belt?

A 507XH200 has 58 teeth, a cataloged 50.75-inch pitch length, an XH 7/8-inch pitch, and a 2-inch width. The 507 code represents the nominal length in tenths of an inch.

Can an XH belt run on an HTD pulley?

No. XH uses a classical trapezoidal tooth, while HTD uses a curvilinear profile. Their tooth shape, pitch, depth, and pulley grooves differ. Incorrect pairing causes poor contact and premature failure.

What are the standard XH widths?

Common Gates widths are 2, 3, 4, and 5 inches. Their codes are 200, 300, 400, and 500. Availability depends on length, construction, supplier, and region.

How do I calculate the tooth count?

Divide pitch length by 0.875 inch. For example, 70 inches divided by 0.875 equals 80 teeth, producing the length code 700 in a standard XH belt designation.

Conclusion

An XH timing belt is defined by its 7/8-inch trapezoidal pitch, but correct selection also requires the right tooth count, pitch length, width, pulley profile, load rating, speed, tension, and environment.

Use manufacturer calculations rather than family-level maximum figures. For replacements, inspect the entire drive and determine why the old belt failed. For new equipment, compare XH with current curvilinear profiles before fixing the pulley geometry.

TranBelt can manufacture or source matched industrial timing belts and pulleys from your belt code, drawing, tooth count, width, center distance, and duty data.