The short answer: An M20×70 track roller bolt normally indicates a metric bolt with a nominal thread diameter of 20 mm and a nominal length of 70 mm. However, this marking alone does not confirm compatibility with every excavator track roller, track shoe, or undercarriage assembly. I recommend verifying thread pitch, thread form, head dimensions, strength grade, nut type, washer arrangement, installation space, and the original equipment specification before placing a bulk order.
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At Zhonghai Jiuchuan, I treat M20×70 as a starting size rather than a complete part number. This guide explains how I would check the specification, compare application requirements, reduce ordering risk, and prepare the information needed for a reliable quotation.
This reference is intended for excavator parts distributors, undercarriage repair contractors, equipment manufacturers, fleet maintenance teams, and international buyers sourcing track roller bolts and nuts. It is also useful for buyers who have a sample bolt but do not yet have a complete drawing or OEM reference. The goal is to help you distinguish a dimensional match from a genuinely suitable replacement.
The guide focuses on M20×70 track roller bolts and nuts used in heavy equipment fastening applications. It does not replace the equipment manufacturer’s service manual, engineering drawing, or approved fastening procedure. Where the original specification is unavailable, I recommend treating all unverified details as items requiring confirmation.
In common metric designation, “M20” identifies a thread with a nominal outside diameter of 20 mm. “70” generally refers to a nominal bolt length of 70 mm, normally measured from beneath the head to the end of the threaded shank for a standard hex-head bolt. The exact measurement convention should still be confirmed against the drawing or sample because bolt designs can vary.
The designation does not automatically identify the thread pitch, property class, head size, coating, flange design, or nut configuration. For example, an M20 thread may be supplied with different pitches, and a nut must match the selected pitch exactly. A bolt can therefore have the correct diameter and length while still being unsuitable for the mating component.
| Specification item | What to verify | Why it matters |
|---|---|---|
| Nominal diameter | M20, approximately 20 mm nominal thread diameter | Must match the threaded hole or nut |
| Nominal length | 70 mm, measured according to the bolt head design | Controls engagement and clearance |
| Thread pitch | Confirm from drawing, sample, or gauge | Prevents cross-threading and incorrect nut selection |
| Strength grade | Use the required mechanical class or drawing value | Supports the intended joint performance |
| Head and nut form | Hex dimensions, flange, washer, and locking features | Ensures tool access and assembly compatibility |
Diameter and pitch must be checked together. M20 identifies the nominal diameter, but it does not by itself identify the pitch. I recommend comparing the replacement bolt with the original part, using a thread pitch gauge where possible, and confirming that the nut is produced for the same thread specification.
Do not force a nut onto a bolt simply because both parts are marked M20. A mismatch may damage the threads, increase assembly time, or prevent the joint from reaching the required installation condition. For export orders, I ask buyers to state the complete thread requirement rather than relying only on “M20.”
A 70 mm bolt may be correct for one track roller or undercarriage joint and unsuitable for another. The effective length depends on the thickness of the clamped parts, washer thickness, nut height, thread runout, and the clearance available behind the assembly. Excessive length can interfere with adjacent components, while insufficient engagement may prevent proper fastening.
As a practical purchasing check, measure the installed bolt from the underside of the head to the end of the shank, then record the washer and nut arrangement. I also recommend confirming whether the equipment design requires full-thread, partial-thread, or a specific unthreaded shank length.
Track roller fastening areas can have limited tool access, so the head and nut geometry may be as important as the thread. Confirm the head height, across-flats dimension, flange requirements, washer diameter, and any required locking arrangement. A standard nut may not be an acceptable substitute where the original assembly uses a special nut or washer system.
When I review an inquiry, I prefer photographs from several angles, including the bolt head, nut, washer, and installed position. A drawing with dimensional tolerances is even more useful. These details help separate a general metric fastener from a purpose-specific track roller bolt and nut set.
Material and mechanical class should be selected according to the joint design and the equipment manufacturer’s requirement. Buyers should identify the required property class, heat-treatment condition, hardness range, and surface finish where these are specified. I do not recommend selecting a grade only because it looks similar to the removed fastener.
Surface treatment should also be evaluated in relation to the working environment. Excavators may operate in soil, water, mud, abrasive dust, or areas exposed to repeated cleaning, but the correct coating depends on the required corrosion protection, friction behavior, dimensional limits, and installation method. Any coating or plating should be confirmed as compatible with the specified tightening procedure.
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Where a complete material or test requirement is supplied by the buyer, Zhonghai Jiuchuan can review the production specification and discuss available manufacturing arrangements. If no formal requirement is available, I use conservative language in the quotation and identify the points that still need technical approval.
Record the marking on the bolt, the overall length, thread diameter, visible pitch, head style, nut type, washer type, and the number of fasteners required. Take measurements in millimeters and photograph the components before cleaning or disassembly. If the old bolt is damaged, collect an undamaged fastener from the same assembly whenever possible.
Identify the excavator or tracked machine model, undercarriage position, and whether the fastener is used with a track roller, track shoe, carrier roller, idler, or another component. The same nominal size may appear in different assemblies with different grades or head configurations. The machine model and exact installation location provide important context for supplier review.
Inspect the threaded hole or mating nut for damaged threads, contamination, distortion, and excessive wear. Confirm the available clearance for a socket, spanner, washer, and nut. A replacement bolt cannot correct a worn or damaged mating component, so the full joint condition should be considered before ordering.
Use the equipment manual or engineering specification to confirm the required tightening method and torque. I avoid publishing a universal torque value for M20×70 track roller bolts because torque depends on the fastener grade, thread condition, coating, lubrication, washer system, and joint design. The correct installation instruction must come from the approved technical source for that assembly.
Before production, approve the complete description: M20 diameter, 70 mm nominal length, thread pitch, bolt form, mechanical class, material, coating, nut type, washer requirement, packaging, quantity, and inspection documents. If the order is for resale, also confirm labeling and carton requirements. This written approval reduces ambiguity between the quotation, production, inspection, and delivery stages.
The price of an M20×70 track roller bolt and nut set depends on material, mechanical requirements, machining, heat treatment, surface treatment, packaging, order quantity, and inspection scope. A low unit price may not represent the lowest total sourcing cost if the specification is incomplete or if separate nuts and washers must be purchased later. I recommend comparing quotations on an identical technical basis.
Minimum order quantity and lead time should be confirmed for the exact configuration rather than assumed from a standard fastener listing. Custom head dimensions, special nuts, dedicated packaging, or additional inspection may require a different production arrangement. For an accurate quotation from Zhonghai Jiuchuan, please provide the required quantity, destination country, sample or drawing, equipment application, and any quality documentation requirements.
Ask whether the supplier can confirm the complete dimensional description and identify missing information before accepting the order. A capable supplier should be able to discuss thread pitch, length measurement, nut matching, material or grade requirements, surface treatment, and inspection points. The supplier should also distinguish confirmed facts from assumptions.
Review how the supplier manages sample approval, drawing confirmation, batch identification, packaging, and nonconformity communication. Request inspection records or other documentation only when it is relevant to your specification and available for the actual batch. Avoid accepting generic documents as proof that an unverified product is suitable for your equipment.
For international B2B purchasing, confirm carton labeling, packing protection, shipping marks, commercial documents, and replacement communication procedures. Zhonghai Jiuchuan supports buyers by reviewing samples, drawings, and application information for track roller bolts and nuts. Our objective is to help buyers purchase the correct configuration, not simply to quote a nominal size.
M20×70 track roller bolts and nuts are compatible only when the complete dimensional, mechanical, and application requirements match. The size marking provides a useful starting point, but it does not confirm pitch, strength class, head geometry, washer arrangement, or suitability for a specific excavator undercarriage. I recommend verifying these details before placing a production or replacement order.
To request a quotation from Zhonghai Jiuchuan, send the equipment model and fastening position, bolt and nut photographs, sample measurements, required quantity, destination, and any drawing or grade requirement. We can then review the specification, identify open questions, and propose a suitable M20×70 track roller bolt and nut configuration for your sourcing project.
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