--- title: "What Are Parallel Keys Used For?" description: "Parallel Keys (DIN 6885 / ISO 773) are used for transmitting torque between a shaft and a hub. Catalogued 6~8 to 440~500." url: https://engineeringhardware.com/applications/parallel-keys/ source: Engineering Hardware & Fasteners --- # What Are Parallel Keys Used For? Keys · DIN 6885 / ISO 773 · Application guide Typical applications, the industries that specify parallel keys, and how to choose the right size, material and finish for the joint. Parallel Keys are used for transmitting torque between a shaft and a hub. They are manufactured to DIN 6885 / ISO 773, and selection is driven by the key section, the fit and tolerance the assembly requires, and the service environment. - **Primary duty:** Transmitting torque between a shaft and a hub - **Governing standard:** DIN 6885 / ISO 773 - **Key section range:** 6~8 to 440~500 - **Category:** Keys Application notes are general engineering guidance. Verify the property class and any approval requirement against your own design calculation. ![What Are Parallel Keys Used For? application image](https://engineeringhardware.com/wp-content/uploads/2026/06/Parallel-Keys-—-DIN-6885-／-ISO-773.webp) Parallel Keys are selected when an assembly calls for transmitting torque between a shaft and a hub. This application guide to the DIN 6885 / ISO 773 type covers concrete end-uses, the specification checklist, correct installation, and where an alternative fastener performs better. Stocked across roughly 6 mm to 440 mm, they cover general to heavy-duty work. ## Typical Applications for Parallel Keys The most common settings where these are specified: - **Gearboxes & motors:** transmitting torque from a shaft to a hub. - **Pumps & fans:** driving rotating components without slip. - **General machine building:** fastening covers, brackets, motors and sub-assemblies on production equipment. - **Maintenance & repair (MRO):** a stocked size for servicing existing plant where the original fastener spec must be matched. - **Fabrication & metalwork:** bench and on-site assembly of steel frames, enclosures and weldments. ## How to Specify Parallel Keys for Your Application - **Size:** Select on key section, and confirm it against the mating feature in the assembly. This product spans 6 mm–440 mm; check the full table below for the exact dimensions of each size. - **Material:** Choose the material and finish for the service environment — plated steel for general use, stainless for corrosion resistance. - **Environment:** For damp, coastal or chemical exposure prefer A4/316 stainless or a suitable coating; indoors, plated steel or A2 is usually sufficient. - **Standard:** This product is supplied to DIN 6885 / ISO 773. Quoting the standard on your order guarantees interchangeable dimensions between suppliers. ## Where Parallel Keys Are Not the Right Choice Not for very high reversing torque without an interference fit, and not as an axial retainer. Custom manufacturing · Made to drawing ## Need a parallel keys outside the standard range? Width, height, length, taper and material are specifiable, and the keyway drawing matters as much as the key itself. Made by milling or broaching & serration. Minimum order from 2,000 pieces; samples within 7 days of drawing approval. [Custom machine key manufacturing](https://engineeringhardware.com/custom/keys/)[Send a drawing](https://engineeringhardware.com/custom/keys/#rfq) ## Technical Drawing Dimensioned line drawing of 6~8 Parallel Keys to DIN 6885 / ISO 773. Side view and top view, drawn to the dimensions in the table below and redrawn for any size selected. - **Key width b (mm):** 2 - **Key height h (mm):** 2 - **Key length range (mm):** 6~20 - **Shaft groove depth t1 (mm):** 1.2 - **Hub groove depth t2 (mm):** 1.0 - **Notes:** Type A round ends; B square ends; C one round one square ## Dimensions & Specifications (DIN 6885 / ISO 773) | Shaft diameter range (mm) | Key width b (mm) | Key height h (mm) | Key length range (mm) | Shaft groove depth t1 (mm) | Hub groove depth t2 (mm) | Reference standard | Notes | | --- | --- | --- | --- | --- | --- | --- | --- | | 6~8 | 2 | 2 | 6~20 | 1.2 | 1.0 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square | | 8~10 | 3 | 3 | 6~36 | 1.8 | 1.4 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square | | 10~12 | 4 | 4 | 8~45 | 2.5 | 1.8 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square | | 12~17 | 5 | 5 | 10~56 | 3.0 | 2.3 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square | | 17~22 | 6 | 6 | 14~70 | 3.5 | 2.8 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square | | 22~30 | 8 | 7 | 18~90 | 4.0 | 3.3 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square | | 30~38 | 10 | 8 | 22~110 | 5.0 | 3.3 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square | | 38~44 | 12 | 8 | 28~140 | 5.0 | 3.3 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square | | 44~50 | 14 | 9 | 36~160 | 5.5 | 3.8 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square | | 50~58 | 16 | 10 | 45~180 | 6.0 | 4.3 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square | | 58~65 | 18 | 11 | 50~200 | 7.0 | 4.4 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square | | 65~75 | 20 | 12 | 56~220 | 7.5 | 4.9 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square | | 75~85 | 22 | 14 | 63~250 | 9.0 | 5.4 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square | | 85~95 | 25 | 14 | 70~280 | 9.0 | 5.4 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square | | 95~110 | 28 | 16 | 80~320 | 10.0 | 6.4 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square | | 110~130 | 32 | 18 | 90~360 | 11.0 | 7.4 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square | | 130~150 | 36 | 20 | 100~400 | 12.0 | 8.4 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square | | 150~170 | 40 | 22 | 100~400 | 13.0 | 9.4 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square | | 170~200 | 45 | 25 | 110~450 | 15.0 | 10.4 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square | | 200~230 | 50 | 28 | 125~500 | 17.0 | 11.4 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square | | 230~260 | 56 | 32 | 140~500 | 20.0 | 12.4 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square | | 260~290 | 63 | 32 | 160~500 | 20.0 | 12.4 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square | | 290~330 | 70 | 36 | 180~500 | 22.0 | 14.4 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square | | 330~380 | 80 | 40 | 200~500 | 25.0 | 15.4 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square | | 380~440 | 90 | 45 | 220~500 | 28.0 | 17.4 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square | | 440~500 | 100 | 50 | 250~500 | 31.0 | 19.5 | DIN 6885 type A / ISO 773 | Type A round ends; B square ends; C one round one square | Inside the plant ## Manufactured in our own plant This part is cold-formed, threaded, heat-treated and finished in-house. The stages below are where its class and finish are actually decided. 1. ![Wire rod feeding into a cold heading machine](https://engineeringhardware.com/wp-content/uploads/2026/08/09-wire-rod-feed-cold-heading-machine.webp) 01 **Cold heading** Wire rod is drawn to size and cold-formed into blanks. Forming rather than cutting keeps the grain flow continuous around the head, which is where a bolt is most likely to fail. Head dimensions and under-head radius checked at set-up and per shift. 2. ![Thread rolling machine producing bolt threads](https://engineeringhardware.com/wp-content/uploads/2026/08/03-thread-rolling-machine-bolt-production.webp) 02 **Thread rolling** Threads are rolled between hardened dies rather than cut. Rolled threads are stronger in fatigue than cut threads and hold pitch and flank angle far more consistently across a batch. Go / no-go ring gauges to ISO 965 tolerance class 6g. 3. ![Baskets of bolts staged for heat treatment](https://engineeringhardware.com/wp-content/uploads/2026/08/05-heat-treatment-baskets-black-bolts.webp) 03 **Heat treatment** Quench-and-temper brings carbon and alloy steel to the property class ordered — 8.8, 10.9 or 12.9 — with the furnace charge tracked so a finished lot can be traced back to it. Core hardness and tensile tested per lot to ISO 898-1. 4. ![Zinc plated bolts in a treatment basket](https://engineeringhardware.com/wp-content/uploads/2026/08/23-zinc-plated-bolts-treatment-basket.webp) 04 **Surface treatment** Zinc, zinc-nickel, hot-dip galvanizing, black oxide, phosphate and Dacromet, selected against the service environment rather than against the price list. Coating thickness and neutral salt spray hours to ISO 9227. ## Frequently Asked Questions ### What material should Parallel Keys be for outdoor use? For damp, coastal or chemical environments specify A4 (316) stainless or a suitably coated steel. For indoor or dry use, A2 (304) stainless or zinc-plated steel is normally adequate. ### Are Parallel Keys made to a recognized standard? Yes — they are manufactured to DIN 6885 / ISO 773, so dimensions are interchangeable between suppliers when you quote the standard on your order. ### What are Parallel Keys used for? Transmitting torque between a shaft and a hub. They are supplied to DIN 6885 / ISO 773. ### Which industries use Parallel Keys? They are commonly specified in general machine building, maintenance & repair (mro) and fabrication & metalwork, among other sectors. ### Can I get a quote for Parallel Keys in the size and material I need? Yes. Use the technical drawing and quote form on this page to set the size and options, then send the exact configuration to our team for pricing and lead time. ## Related Pages Product page: [Parallel Keys — specifications & sizes](https://engineeringhardware.com/fastener/parallel-keys/) ### Parallel Keys Specification Guides ### Related Fastener Applications