{"product_id":"2-5-3-mod-helical-gear-with-step-45-left-spiral-motor-transmission-gear-45-steel","title":"2.5 3 Mod Helical Gear With Step 45°Left Spiral Motor Transmission Gear 45#Steel","description":"\u003cdiv class=\"hdiy-desc\"\u003e\n\n\u003cdiv class=\"hdiy-overview\"\u003e\n\u003ch2\u003eLeft Spiral Helical Gear — Precision 45° Stepped Transmission for CNC \u0026amp; Motor Drives\u003c\/h2\u003e\n\u003cp\u003eWhen your motion-control build demands smooth, low-noise power transfer, a mismatched or poorly machined gear becomes the weakest link in the entire drivetrain. These left-spiral helical gears are engineered for makers, automation integrators, and small-batch manufacturers who need reliable stepped transmission components without sourcing from industrial distributors.\u003c\/p\u003e\n\u003cp\u003eEach gear is machined from 45# medium-carbon steel and features a 45° left-hand helix angle with a precision-cut step bore. Available in Modulus 2.5 and Modulus 3, with tooth counts ranging from 10 to 30 teeth. Outer diameter varies by modulus and tooth count — typically 27.5 mm to 96 mm (approx. 1.08 in to 3.78 in). Face width is typically 20–30 mm (approx. 0.79–1.18 in).\u003c\/p\u003e\n\u003cp\u003eTypical use cases include CNC router Z-axis drives, stepper and servo motor gearboxes, robotic joint transmission assemblies, and custom left-hand helical gear pair replacements in industrial equipment.\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 Designed to mesh with matching right-spiral helical gears of the same modulus (2.5 or 3) and 45° helix angle. Confirm bore diameter and keyway dimensions against your shaft specs before ordering.\n\u003c\/div\u003e\n\n\u003ch2\u003e✅ Key Features of These Left Spiral Helical Gears\u003c\/h2\u003e\n\u003cdiv class=\"hdiy-features\"\u003e\n\n\u003cdiv\u003e\n\u003cdiv class=\"hdiy-icon\"\u003e🔩\u003c\/div\u003e\n\u003cstrong\u003e45# Medium-Carbon Steel Construction\u003c\/strong\u003e\n\u003cp\u003eMachined from 45# steel for a balance of machinability, tensile strength (typically 600–800 MPa), and wear resistance suited to continuous motor transmission loads.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003cdiv\u003e\n\u003cdiv class=\"hdiy-icon\"\u003e🔄\u003c\/div\u003e\n\u003cstrong\u003e45° Left-Hand Helix Angle\u003c\/strong\u003e\n\u003cp\u003eThe 45° left-spiral geometry distributes tooth load across a wider contact area than spur gears, reducing vibration and operating noise in high-speed motor drives.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003cdiv\u003e\n\u003cdiv class=\"hdiy-icon\"\u003e📐\u003c\/div\u003e\n\u003cstrong\u003eDual Modulus Options — 2.5 \u0026amp; 3\u003c\/strong\u003e\n\u003cp\u003eChoose Modulus 2.5 for compact, lighter-duty assemblies or Modulus 3 for higher torque applications. Both series share the same 45° helix for easy pairing.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003cdiv\u003e\n\u003cdiv class=\"hdiy-icon\"\u003e🪜\u003c\/div\u003e\n\u003cstrong\u003ePrecision Step Bore Design\u003c\/strong\u003e\n\u003cp\u003eThe stepped bore profile allows secure shaft seating and simplified axial positioning without additional spacers, saving assembly time in tight gearbox housings.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003cdiv\u003e\n\u003cdiv class=\"hdiy-icon\"\u003e🦷\u003c\/div\u003e\n\u003cstrong\u003eWide Tooth Count Range — 10 to 30 Teeth\u003c\/strong\u003e\n\u003cp\u003eEight tooth-count variants per modulus let you dial in your gear ratio precisely. Pair with a matching right-spiral gear of the same modulus to achieve ratios from 1:1 to 3:1 and beyond.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003cdiv\u003e\n\u003cdiv class=\"hdiy-icon\"\u003e🛡️\u003c\/div\u003e\n\u003cstrong\u003eSurface Treatment for Extended Service Life\u003c\/strong\u003e\n\u003cp\u003eGear flanks are finished to reduce surface roughness, supporting consistent lubrication film retention and extending service intervals in enclosed gearbox environments.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003c\/div\u003e\n\n\u003ch2\u003e📐 Technical Specifications — Helical Gear\u003c\/h2\u003e\n\u003cdiv class=\"hdiy-table-wrap\"\u003e\n\u003ctable\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003cth\u003eMaterial\u003c\/th\u003e\n\u003ctd\u003e45# Medium-Carbon Steel\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eHelix Angle\u003c\/th\u003e\n\u003ctd\u003e45°\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eSpiral Direction\u003c\/th\u003e\n\u003ctd\u003eLeft Spiral (Left-Hand)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eAvailable Modulus\u003c\/th\u003e\n\u003ctd\u003e2.5 \/ 3\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eTooth Count Options\u003c\/th\u003e\n\u003ctd\u003e10, 12, 13, 15, 18, 20, 26, 30 Teeth\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eBore Type\u003c\/th\u003e\n\u003ctd\u003eStepped Bore\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eOuter 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\u003eTypically 20–30 mm (0.79–1.18 in)\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\u003eSurface Finish\u003c\/th\u003e\n\u003ctd\u003ePrecision-machined, reduced surface roughness\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eHardness\u003c\/th\u003e\n\u003ctd\u003eSee variant options\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eWeight\u003c\/th\u003e\n\u003ctd\u003eSee variant options\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eQuantity\u003c\/th\u003e\n\u003ctd\u003e1 PCS per order (multi-pack options available)\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 between Modulus 2.5 and Modulus 3?\u003c\/summary\u003e\n\u003cdiv class=\"hdiy-faq-body\"\u003e\u003cp\u003eModulus 2.5 gears are smaller and lighter, making them suitable for compact assemblies and lighter torque loads. Modulus 3 gears have larger teeth and a higher load-carrying capacity, making them the better choice for higher-torque motor drives and heavier-duty gearboxes. Both share the same 45° left-hand helix angle, so they can be paired with matching right-spiral gears of the same modulus.\u003c\/p\u003e\u003c\/div\u003e\n\u003c\/details\u003e\n\n\u003cdetails\u003e\n\u003csummary\u003eWhat right-spiral gear do I need to pair with this left-spiral gear?\u003c\/summary\u003e\n\u003cdiv class=\"hdiy-faq-body\"\u003e\u003cp\u003eLeft-spiral helical gears mesh with right-spiral helical gears of the same modulus and helix angle (45°). The mating gear must have the same modulus (2.5 or 3) and a matching tooth profile. Confirm the center distance and gear ratio you need, then select the appropriate tooth count for the driven gear.\u003c\/p\u003e\u003c\/div\u003e\n\u003c\/details\u003e\n\n\u003cdetails\u003e\n\u003csummary\u003eWhat is the bore diameter and keyway size for each variant?\u003c\/summary\u003e\n\u003cdiv class=\"hdiy-faq-body\"\u003e\u003cp\u003eBore diameter and keyway dimensions vary by tooth count and modulus. Please refer to the variant detail images or contact us to confirm the exact bore size before ordering to ensure compatibility with your shaft.\u003c\/p\u003e\u003c\/div\u003e\n\u003c\/details\u003e\n\n\u003cdetails\u003e\n\u003csummary\u003eIs 45# steel strong enough for my application?\u003c\/summary\u003e\n\u003cdiv class=\"hdiy-faq-body\"\u003e\u003cp\u003e45# medium-carbon steel offers a tensile strength typically in the range of 600–800 MPa and is widely used in general-purpose gear manufacturing. It is suitable for moderate-speed, moderate-torque motor transmission applications. For very high-load or high-speed environments, consider whether a heat-treated or alloy steel variant would better suit your requirements.\u003c\/p\u003e\u003c\/div\u003e\n\u003c\/details\u003e\n\n\u003cdetails\u003e\n\u003csummary\u003eAre these gears corrosion-resistant?\u003c\/summary\u003e\n\u003cdiv class=\"hdiy-faq-body\"\u003e\u003cp\u003e45# steel has moderate corrosion resistance. For applications in humid or mildly corrosive environments, we recommend applying a light machine oil or grease coating during installation and maintaining regular lubrication. For highly corrosive environments, a stainless steel or coated gear may be more appropriate.\u003c\/p\u003e\u003c\/div\u003e\n\u003c\/details\u003e\n\n\u003cdetails\u003e\n\u003csummary\u003eCan I use these gears in a CNC router or 3D printer drivetrain?\u003c\/summary\u003e\n\u003cdiv class=\"hdiy-faq-body\"\u003e\u003cp\u003eYes. These left-spiral helical gears are well-suited for CNC router axis drives, stepper motor gearboxes, and similar precision motion-control applications where smooth, low-backlash power transfer is important. Ensure the modulus, tooth count, and bore diameter match your existing drivetrain components.\u003c\/p\u003e\u003c\/div\u003e\n\u003c\/details\u003e\n\n\u003cdetails\u003e\n\u003csummary\u003eWhat tooth count should I choose for a specific gear ratio?\u003c\/summary\u003e\n\u003cdiv class=\"hdiy-faq-body\"\u003e\u003cp\u003eGear ratio is determined by dividing the tooth count of the driven gear by the tooth count of the driving gear. For example, pairing a 10-tooth driving gear with a 20-tooth driven gear gives a 2:1 reduction ratio. Select your tooth counts based on the input\/output speed ratio your application requires.\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 Modulus and Teeth \u0026amp; Amount 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 between Modulus 2.5 and Modulus 3?\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"Modulus 2.5 gears are smaller and lighter, suitable for compact assemblies and lighter torque loads. Modulus 3 gears have larger teeth and higher load capacity for heavier-duty gearboxes. Both share the same 45° left-hand helix angle.\"\n      }\n    },\n    {\n      \"@type\": \"Question\",\n      \"name\": \"What right-spiral gear do I need to pair with this left-spiral gear?\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"Left-spiral helical gears mesh with right-spiral helical gears of the same modulus (2.5 or 3) and 45° helix angle. Confirm center distance and gear ratio, then select the appropriate tooth count.\"\n      }\n    },\n    {\n      \"@type\": \"Question\",\n      \"name\": \"What is the bore diameter and keyway size for each variant?\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"Bore diameter and keyway dimensions vary by tooth count and modulus. Refer to variant detail images or contact us to confirm the exact bore size before ordering.\"\n      }\n    },\n    {\n      \"@type\": \"Question\",\n      \"name\": \"Is 45# steel strong enough for my application?\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"45# medium-carbon steel offers tensile strength typically 600–800 MPa, suitable for moderate-speed, moderate-torque motor transmission. For very high-load environments, consider heat-treated or alloy steel variants.\"\n      }\n    },\n    {\n      \"@type\": \"Question\",\n      \"name\": \"Are these gears corrosion-resistant?\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"45# steel has moderate corrosion resistance. Apply light machine oil or grease during installation and maintain regular lubrication. For highly corrosive environments, a stainless steel or coated gear may be more appropriate.\"\n      }\n    },\n    {\n      \"@type\": \"Question\",\n      \"name\": \"Can I use these gears in a CNC router or 3D printer drivetrain?\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"Yes. These left-spiral helical gears are well-suited for CNC router axis drives, stepper motor gearboxes, and similar precision motion-control applications. Ensure modulus, tooth count, and bore diameter match your drivetrain components.\"\n      }\n    },\n    {\n      \"@type\": \"Question\",\n      \"name\": \"What tooth count should I choose for a specific gear ratio?\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"Gear ratio equals driven gear teeth divided by driving gear teeth. For example, 10-tooth driving with 20-tooth driven gives a 2:1 reduction. Select tooth counts based on your required input\/output speed ratio.\"\n      }\n    }\n  ]\n}\n\u003c\/script\u003e","brand":"HomeDIYer","offers":[{"title":"Left Spiral \/ 2.5 Modulus \/ 10 Teeth \u0026 1 PCS","offer_id":52439929749778,"sku":"GYJLTHXCDZH3327x1","price":24.45,"currency_code":"USD","in_stock":true},{"title":"Left Spiral \/ 2.5 Modulus \/ 12 Teeth \u0026 1 PCS","offer_id":52439929782546,"sku":"GYJLTHXCDZH3328x1","price":35.5,"currency_code":"USD","in_stock":true},{"title":"Left Spiral \/ 2.5 Modulus \/ 13 Teeth \u0026 1 PCS","offer_id":52439929815314,"sku":"GYJLTHXCDZH3329x1","price":40.94,"currency_code":"USD","in_stock":true},{"title":"Left Spiral \/ 2.5 Modulus \/ 15 Teeth \u0026 1 PCS","offer_id":52439929848082,"sku":"GYJLTHXCDZH3330x1","price":53.72,"currency_code":"USD","in_stock":true},{"title":"Left Spiral \/ 2.5 Modulus \/ 18 Teeth \u0026 1 PCS","offer_id":52439929880850,"sku":"GYJLTHXCDZH3331x1","price":73.85,"currency_code":"USD","in_stock":true},{"title":"Left Spiral \/ 2.5 Modulus \/ 20 Teeth \u0026 1 PCS","offer_id":52439929913618,"sku":"GYJLTHXCDZH3332x1","price":87.99,"currency_code":"USD","in_stock":true},{"title":"Left Spiral \/ 2.5 Modulus \/ 26 Teeth \u0026 1 PCS","offer_id":52439929946386,"sku":"GYJLTHXCDZH3333x1","price":132.33,"currency_code":"USD","in_stock":true},{"title":"Left Spiral \/ 2.5 Modulus \/ 30 Teeth \u0026 1 PCS","offer_id":52439929979154,"sku":"GYJLTHXCDZH3334x1","price":168.61,"currency_code":"USD","in_stock":true},{"title":"Left Spiral \/ 3 Modulus \/ 10 Teeth \u0026 1 PCS","offer_id":52439930011922,"sku":"GYJLTHXCDZH3335x1","price":39.03,"currency_code":"USD","in_stock":true},{"title":"Left Spiral \/ 3 Modulus \/ 13 Teeth \u0026 1 PCS","offer_id":52439930044690,"sku":"GYJLTHXCDZH3336x1","price":61.72,"currency_code":"USD","in_stock":true},{"title":"Left Spiral \/ 3 Modulus \/ 15 Teeth \u0026 1 PCS","offer_id":52439930077458,"sku":"GYJLTHXCDZH3337x1","price":88.64,"currency_code":"USD","in_stock":true},{"title":"Left Spiral \/ 3 Modulus \/ 20 Teeth \u0026 1 PCS","offer_id":52439930110226,"sku":"GYJLTHXCDZH3338x1","price":128.9,"currency_code":"USD","in_stock":true},{"title":"Left Spiral \/ 3 Modulus \/ 26 Teeth \u0026 1 PCS","offer_id":52439930142994,"sku":"GYJLTHXCDZH3339x1","price":210.23,"currency_code":"USD","in_stock":true},{"title":"Left Spiral \/ 3 Modulus \/ 30 Teeth \u0026 1 PCS","offer_id":52439930175762,"sku":"GYJLTHXCDZH3340x1","price":272.79,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0884\/8936\/1682\/files\/Main-07_a5076689-8f26-4de8-9ae1-12d39cf61e5c.jpg?v=1783523444","url":"https:\/\/homediyer.com\/products\/2-5-3-mod-helical-gear-with-step-45-left-spiral-motor-transmission-gear-45-steel","provider":"HomeDIYer","version":"1.0","type":"link"}