{"product_id":"3-mod-spur-gear-15-40-teeth-stepped-45-steel-motor-gear","title":"3 Mod Spur Gear 15-40 Teeth Transmission Gear With Step 45# Steel Motor Gear","description":"\u003cdiv class=\"hdiy-desc\"\u003e\n\n\u003cdiv class=\"hdiy-overview\"\u003e\n\u003ch2\u003e3 Mod Spur Gear with Step — Precision 45# Steel Transmission Gear for Demanding Drive Systems\u003c\/h2\u003e\n\u003cp\u003eWhen a loose gear slips mid-run or a mismatched module throws off your entire drivetrain, the cost is more than downtime — it's a rebuild. Engineers, robotics builders, and CNC hobbyists who need a reliable 3 mod spur gear with a stepped hub design can stop searching: this gear is machined to hold position, transfer torque cleanly, and drop into standard 3M gear trains without shimming or modification.\u003c\/p\u003e\n\u003cp\u003eEach gear is machined from 45# carbon steel — a medium-carbon alloy known for its balance of hardness and machinability — and features a stepped (shouldered) bore hub that seats securely against a shaft shoulder or retaining collar. The tooth range spans 15T to 40T (module 3), with pitch diameters ranging from approximately 45 mm (1.77 in) at 15T to 120 mm (4.72 in) at 40T. Face width and hub step dimensions vary by tooth count; see variant options for exact per-SKU measurements.\u003c\/p\u003e\n\u003cp\u003eTypical use cases include: CNC router axis drives requiring repeatable backlash-free engagement; robotic arm joint gearing where the stepped hub prevents axial creep under cyclic load; and DIY power transmission rigs — conveyor drives, winch mechanisms, and motorized camera sliders — where a standard 3M gear train is the design baseline.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"hdiy-compat\"\u003e\n\u003cspan class=\"hdiy-compat-icon\"\u003e⚙️\u003c\/span\u003e\n\u003cstrong\u003eCompatibility:\u003c\/strong\u003e Module 3 (Mod 3 \/ 3M) gear standard — meshes with any Module 3 spur gear, rack, or pinion of matching pressure angle (typically 20°). Verify shaft diameter against bore size listed in variant options before ordering.\n\u003c\/div\u003e\n\n\u003cdiv class=\"hdiy-features\"\u003e\n\u003ch2\u003e✅ Key Features of These 3 Mod Stepped Spur Gears\u003c\/h2\u003e\n\u003cdiv class=\"hdiy-list\"\u003e\n  \u003cdiv class=\"hdiy-icon\"\u003e🔩\u003c\/div\u003e\n  \u003cdiv\u003e\n\u003cstrong\u003e45# Carbon Steel Construction\u003c\/strong\u003e\u003cbr\u003eMedium-carbon steel delivers the hardness needed for sustained mesh loads while remaining machinable for secondary operations like keyway cutting or bore enlargement.\u003c\/div\u003e\n\n  \u003cdiv class=\"hdiy-icon\"\u003e📐\u003c\/div\u003e\n  \u003cdiv\u003e\n\u003cstrong\u003eStepped Hub Design\u003c\/strong\u003e\u003cbr\u003eThe integrated shoulder hub locates the gear axially on the shaft without relying solely on a set screw, reducing runout and improving concentricity under dynamic loads.\u003c\/div\u003e\n\n  \u003cdiv class=\"hdiy-icon\"\u003e⚙️\u003c\/div\u003e\n  \u003cdiv\u003e\n\u003cstrong\u003eModule 3 Tooth Profile\u003c\/strong\u003e\u003cbr\u003eHobbed to Module 3 standard with a 20° pressure angle, ensuring smooth, low-noise meshing with any compatible 3M gear, rack, or worm wheel in your drivetrain.\u003c\/div\u003e\n\n  \u003cdiv class=\"hdiy-icon\"\u003e📏\u003c\/div\u003e\n  \u003cdiv\u003e\n\u003cstrong\u003eWide Tooth Count Range (15T–40T)\u003c\/strong\u003e\u003cbr\u003eTwenty-six size options from 15 to 40 teeth let you dial in the exact gear ratio your application requires — from high-torque low-speed reductions to faster output stages.\u003c\/div\u003e\n\n  \u003cdiv class=\"hdiy-icon\"\u003e🛡️\u003c\/div\u003e\n  \u003cdiv\u003e\n\u003cstrong\u003eCorrosion-Resistant Surface Treatment\u003c\/strong\u003e\u003cbr\u003eThe machined steel surface is treated to resist oxidation in typical workshop and light-industrial environments. For high-humidity or outdoor exposure, additional coating is recommended.\u003c\/div\u003e\n\n  \u003cdiv class=\"hdiy-icon\"\u003e🔄\u003c\/div\u003e\n  \u003cdiv\u003e\n\u003cstrong\u003eDrop-In Replacement Geometry\u003c\/strong\u003e\u003cbr\u003eStandard module and pressure angle mean these gears are interchangeable with OEM 3M spur gears in CNC machines, robotic platforms, and motorized DIY builds without custom adaptation.\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"hdiy-table-wrap\"\u003e\n\u003ch2\u003e📐 Technical Specifications — 3 Mod Stepped Spur Gear\u003c\/h2\u003e\n\u003ctable\u003e\n  \u003ctbody\u003e\n    \u003ctr\u003e\n\u003cth\u003eModule\u003c\/th\u003e\n\u003ctd\u003e3 (Mod 3 \/ 3M)\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003ePressure Angle\u003c\/th\u003e\n\u003ctd\u003e20°\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eTooth Count Range\u003c\/th\u003e\n\u003ctd\u003e15T – 40T (26 variants)\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003ePitch Diameter Range\u003c\/th\u003e\n\u003ctd\u003e45 mm – 120 mm (1.77 in – 4.72 in)\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eMaterial\u003c\/th\u003e\n\u003ctd\u003e45# Carbon Steel\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eHub Style\u003c\/th\u003e\n\u003ctd\u003eStepped (shouldered hub)\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eBore Diameter\u003c\/th\u003e\n\u003ctd\u003eSee variant options\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eFace Width\u003c\/th\u003e\n\u003ctd\u003eSee variant options\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eHub Step Diameter\u003c\/th\u003e\n\u003ctd\u003eSee variant options\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eSurface Treatment\u003c\/th\u003e\n\u003ctd\u003eOxidation-resistant machined finish\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eGear Type\u003c\/th\u003e\n\u003ctd\u003eExternal spur gear\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003ePacking Quantity\u003c\/th\u003e\n\u003ctd\u003e1 pc per order\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/div\u003e\n\n\u003cdiv class=\"hdiy-faq\"\u003e\n\u003ch2\u003e❓ Frequently Asked Questions\u003c\/h2\u003e\n\n\u003cdetails\u003e\n  \u003csummary\u003eHow do I choose the right tooth count for my application?\u003c\/summary\u003e\n  \u003cdiv class=\"hdiy-faq-body\"\u003e\u003cp\u003eGear ratio is determined by dividing the driven gear tooth count by the driving gear tooth count. For example, pairing a 15T motor gear with a 30T output gear gives a 2:1 reduction — half the speed, double the torque. Map out your required input\/output RPM and torque, then select the tooth counts that achieve that ratio within your available center distance.\u003c\/p\u003e\u003c\/div\u003e\n\u003c\/details\u003e\n\n\u003cdetails\u003e\n  \u003csummary\u003eWhat shaft diameter does this gear fit?\u003c\/summary\u003e\n  \u003cdiv class=\"hdiy-faq-body\"\u003e\u003cp\u003eBore diameter varies by tooth count variant. Please check the bore size listed in the variant options before ordering. If your shaft is slightly undersized, the bore can typically be enlarged by a machinist. Do not force-fit a gear onto an oversized shaft as this will crack the hub.\u003c\/p\u003e\u003c\/div\u003e\n\u003c\/details\u003e\n\n\u003cdetails\u003e\n  \u003csummary\u003eWill this gear mesh with my existing Module 3 rack or pinion?\u003c\/summary\u003e\n  \u003cdiv class=\"hdiy-faq-body\"\u003e\u003cp\u003eYes — any Module 3 gear with a matching 20° pressure angle will mesh correctly with this gear. This includes Module 3 racks, pinions, and other spur gears regardless of brand, as long as the module and pressure angle match. Confirm both parameters on your existing components before ordering.\u003c\/p\u003e\u003c\/div\u003e\n\u003c\/details\u003e\n\n\u003cdetails\u003e\n  \u003csummary\u003eHow strong is 45# steel for gear applications?\u003c\/summary\u003e\n  \u003cdiv class=\"hdiy-faq-body\"\u003e\u003cp\u003e45# carbon steel (roughly equivalent to AISI 1045) has a tensile strength of approximately 600–800 MPa in its normalized state, making it well-suited for moderate-to-high torque gear applications. It is commonly used for machine tool gears, conveyor drives, and robotic joints. For extreme shock loads or very high RPM applications, consider heat-treated variants or consult a mechanical engineer.\u003c\/p\u003e\u003c\/div\u003e\n\u003c\/details\u003e\n\n\u003cdetails\u003e\n  \u003csummary\u003eIs this gear corrosion-resistant for outdoor or humid environments?\u003c\/summary\u003e\n  \u003cdiv class=\"hdiy-faq-body\"\u003e\u003cp\u003eThe machined steel surface has a basic oxidation-resistant finish suitable for dry indoor and light workshop environments. For outdoor use, high-humidity enclosures, or washdown environments, we recommend applying a gear lubricant or protective coating (e.g., grease, zinc spray, or black oxide treatment) after installation to extend service life.\u003c\/p\u003e\u003c\/div\u003e\n\u003c\/details\u003e\n\n\u003cdetails\u003e\n  \u003csummary\u003eCan I use this gear in a CNC router or 3D printer build?\u003c\/summary\u003e\n  \u003cdiv class=\"hdiy-faq-body\"\u003e\u003cp\u003eYes. Module 3 spur gears are widely used in CNC router axis drives, laser cutter gantries, and large-format 3D printer extruder\/drive systems. The stepped hub is particularly useful in these builds as it provides a positive axial stop, reducing the chance of the gear walking along the shaft during repeated bidirectional motion.\u003c\/p\u003e\u003c\/div\u003e\n\u003c\/details\u003e\n\n\u003cdetails\u003e\n  \u003csummary\u003eWhat is the difference between this stepped-hub gear and a plain-bore spur gear?\u003c\/summary\u003e\n  \u003cdiv class=\"hdiy-faq-body\"\u003e\u003cp\u003eA plain-bore gear has a straight cylindrical bore and relies entirely on set screws or keys for axial and rotational retention. A stepped-hub gear adds a machined shoulder that seats against a shaft collar, bearing face, or housing wall — providing positive axial location without additional hardware. This reduces assembly complexity and improves positional repeatability in precision drive systems.\u003c\/p\u003e\u003c\/div\u003e\n\u003c\/details\u003e\n\n\u003c\/div\u003e\n\n\u003cdiv class=\"hdiy-cta\"\u003e\n🛒 Select your Size (tooth count) above, then add to cart.\n\u003c\/div\u003e\n\n\u003c\/div\u003e\n\n\u003cscript type=\"application\/ld+json\"\u003e\n{\n  \"@context\": \"https:\/\/schema.org\",\n  \"@type\": \"FAQPage\",\n  \"mainEntity\": [\n    {\n      \"@type\": \"Question\",\n      \"name\": \"How do I choose the right tooth count for my application?\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"Gear ratio is determined by dividing the driven gear tooth count by the driving gear tooth count. For example, pairing a 15T motor gear with a 30T output gear gives a 2:1 reduction — half the speed, double the torque. Map out your required input\/output RPM and torque, then select the tooth counts that achieve that ratio within your available center distance.\"\n      }\n    },\n    {\n      \"@type\": \"Question\",\n      \"name\": \"What shaft diameter does this gear fit?\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"Bore diameter varies by tooth count variant. Please check the bore size listed in the variant options before ordering. If your shaft is slightly undersized, the bore can typically be enlarged by a machinist.\"\n      }\n    },\n    {\n      \"@type\": \"Question\",\n      \"name\": \"Will this gear mesh with my existing Module 3 rack or pinion?\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"Yes — any Module 3 gear with a matching 20° pressure angle will mesh correctly with this gear, including Module 3 racks, pinions, and other spur gears regardless of brand.\"\n      }\n    },\n    {\n      \"@type\": \"Question\",\n      \"name\": \"How strong is 45# steel for gear applications?\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"45# carbon steel has a tensile strength of approximately 600–800 MPa in its normalized state, making it well-suited for moderate-to-high torque gear applications including machine tool gears, conveyor drives, and robotic joints.\"\n      }\n    },\n    {\n      \"@type\": \"Question\",\n      \"name\": \"Is this gear corrosion-resistant for outdoor or humid environments?\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"The machined steel surface has a basic oxidation-resistant finish suitable for dry indoor and light workshop environments. For outdoor or high-humidity use, apply a gear lubricant or protective coating after installation.\"\n      }\n    },\n    {\n      \"@type\": \"Question\",\n      \"name\": \"Can I use this gear in a CNC router or 3D printer build?\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"Yes. Module 3 spur gears are widely used in CNC router axis drives, laser cutter gantries, and large-format 3D printer drive systems. The stepped hub provides a positive axial stop, reducing gear walk during bidirectional motion.\"\n      }\n    },\n    {\n      \"@type\": \"Question\",\n      \"name\": \"What is the difference between this stepped-hub gear and a plain-bore spur gear?\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"A stepped-hub gear adds a machined shoulder that seats against a shaft collar or bearing face, providing positive axial location without additional hardware. A plain-bore gear relies entirely on set screws or keys for retention.\"\n      }\n    }\n  ]\n}\n\u003c\/script\u003e","brand":"HomeDIYer","offers":[{"title":"3M 15T \/ 1 pcs","offer_id":52442768834834,"sku":"GYWYPSHXJZC3388x1","price":35.97,"currency_code":"USD","in_stock":true},{"title":"3M 16T \/ 1 pcs","offer_id":52442768867602,"sku":"GYWYPSHXJZC3389x1","price":43.91,"currency_code":"USD","in_stock":true},{"title":"3M 17T \/ 1 pcs","offer_id":52442768900370,"sku":"GYWYPSHXJZC3390x1","price":49.98,"currency_code":"USD","in_stock":true},{"title":"3M 18T \/ 1 pcs","offer_id":52442768933138,"sku":"GYWYPSHXJZC3391x1","price":55.75,"currency_code":"USD","in_stock":true},{"title":"3M 19T \/ 1 pcs","offer_id":52442768965906,"sku":"GYWYPSHXJZC3392x1","price":62.0,"currency_code":"USD","in_stock":true},{"title":"3M 20T \/ 1 pcs","offer_id":52442768998674,"sku":"GYWYPSHXJZC3393x1","price":68.8,"currency_code":"USD","in_stock":true},{"title":"3M 21T \/ 1 pcs","offer_id":52442769031442,"sku":"GYWYPSHXJZC3394x1","price":76.01,"currency_code":"USD","in_stock":true},{"title":"3M 22T \/ 1 pcs","offer_id":52442769064210,"sku":"GYWYPSHXJZC3395x1","price":83.76,"currency_code":"USD","in_stock":true},{"title":"3M 23T \/ 1 pcs","offer_id":52442769096978,"sku":"GYWYPSHXJZC3396x1","price":90.51,"currency_code":"USD","in_stock":true},{"title":"3M 24T \/ 1 pcs","offer_id":52442769129746,"sku":"GYWYPSHXJZC3397x1","price":98.72,"currency_code":"USD","in_stock":true},{"title":"3M 25T \/ 1 pcs","offer_id":52442769162514,"sku":"GYWYPSHXJZC3398x1","price":107.37,"currency_code":"USD","in_stock":true},{"title":"3M 26T \/ 1 pcs","offer_id":52442769195282,"sku":"GYWYPSHXJZC3399x1","price":115.12,"currency_code":"USD","in_stock":true},{"title":"3M 27T \/ 1 pcs","offer_id":52442769228050,"sku":"GYWYPSHXJZC3434x1","price":123.75,"currency_code":"USD","in_stock":true},{"title":"3M 28T \/ 1 pcs","offer_id":52442769260818,"sku":"GYWYPSHXJZC3435x1","price":132.94,"currency_code":"USD","in_stock":true},{"title":"3M 29T \/ 1 pcs","offer_id":52442769293586,"sku":"GYWYPSHXJZC3436x1","price":143.55,"currency_code":"USD","in_stock":true},{"title":"3M 30T \/ 1 pcs","offer_id":52442769326354,"sku":"GYWYPSHXJZC3437x1","price":154.62,"currency_code":"USD","in_stock":true},{"title":"3M 31T \/ 1 pcs","offer_id":52442769359122,"sku":"GYWYPSHXJZC3438x1","price":164.27,"currency_code":"USD","in_stock":true},{"title":"3M 32T \/ 1 pcs","offer_id":52442769391890,"sku":"GYWYPSHXJZC3439x1","price":175.83,"currency_code":"USD","in_stock":true},{"title":"3M 33T \/ 1 pcs","offer_id":52442769424658,"sku":"GYWYPSHXJZC3440x1","price":187.94,"currency_code":"USD","in_stock":true},{"title":"3M 34T \/ 1 pcs","offer_id":52442769457426,"sku":"GYWYPSHXJZC3441x1","price":199.5,"currency_code":"USD","in_stock":true},{"title":"3M 35T \/ 1 pcs","offer_id":52442769490194,"sku":"GYWYPSHXJZC3442x1","price":210.6,"currency_code":"USD","in_stock":true},{"title":"3M 36T \/ 1 pcs","offer_id":52442769522962,"sku":"GYWYPSHXJZC3443x1","price":221.2,"currency_code":"USD","in_stock":true},{"title":"3M 37T \/ 1 pcs","offer_id":52442769555730,"sku":"GYWYPSHXJZC3444x1","price":234.26,"currency_code":"USD","in_stock":true},{"title":"3M 38T \/ 1 pcs","offer_id":52442769588498,"sku":"GYWYPSHXJZC3445x1","price":246.77,"currency_code":"USD","in_stock":true},{"title":"3M 39T \/ 1 pcs","offer_id":52442769621266,"sku":"GYWYPSHXJZC3446x1","price":261.73,"currency_code":"USD","in_stock":true},{"title":"3M 40T \/ 1 pcs","offer_id":52442769654034,"sku":"GYWYPSHXJZC3447x1","price":275.74,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0884\/8936\/1682\/files\/Picture5of6_4871d872-4a2a-43a6-a0cb-633ff474f1d2.jpg?v=1783591066","url":"https:\/\/homediyer.com\/products\/3-mod-spur-gear-15-40-teeth-stepped-45-steel-motor-gear","provider":"HomeDIYer","version":"1.0","type":"link"}