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Automotive Buying Blank Guide:
From Model Identification to Size Matching, Choose Correctly in One Step
Automotive key blanks are the core component for preparing spare keys. Their model and size directly determine compatibility and usability. Many users overlook model differences and confuse size parameters, resulting in purchased key blanks being unusable or damaging the lock cylinder. This guide will help you accurately select a key blank through three core dimensions—model identification, size matching, and purchasing tips—combined with visual references.
I. First, Understand "Model": The "Identity Code" of Key Blanks—A Wrong Choice Renders Everything Useless
Each automotive key blank model corresponds to the lock cylinder structure of a specific vehicle model, serving as the core basis for purchase. Models typically consist of "brand code + lock cylinder type code + tooth profile sequence" and are usually marked on the shank or side of the key blank (some require wiping the surface to read clearly).
1. Model Reference for Mainstream Vehicle Key Blanks (with Compatible Models)
| Key Blank Model | Compatible Brand/Model Series | Core Features (Lock Cylinder/Tooth Profile) | Common Length Range (mm) |
|---|---|---|---|
| HU66 | Volkswagen (Lavida, Sagitar, Magotan), Audi A3/A4L | Internal milling groove structure, symmetrical double-sided tooth profile | 48-52 |
| HU100 | BMW (3 Series, 5 Series, X3/X5) | External milling groove + middle groove, high precision requirement for tooth profile | 50-55 |
| ID48 | Toyota (Corolla, Camry), Lexus | Single-row external teeth, some with chip slot | 45-49 |
| HON66 | Honda (Civic, CR-V, Accord) | Double-row external teeth, dense tooth pitch | 47-51 |
| FO21 | Ford (Focus, Mondeo) | Double-sided milling groove, tooth profile with inclination angle | 49-53 |
| VW33 | Older Volkswagen (Jetta, Santana) | Single-row internal teeth, simple structure | 46-48 |
Note: Vehicles of the same brand but different years may have changed lock cylinder types (e.g., some Volkswagen models after 2019 switched from HU66 to HU162T). Before purchasing, confirm the vehicle's year of manufacture + specific configuration to avoid selecting the model based solely on the brand.
2. 3 Practical Methods to Check the Model
- Method 1: Inspect the original key blank/key: If you have the old key blank, directly check the engraving on the shank (e.g., "HU66", "ID48"). If not, observe the tooth profile structure of the original key (internal/external milling, single-row/double-row) and initially match it with the table above.
- Method 2: Consult the vehicle manual: The "Body Accessories" chapter of the manual will mark the corresponding blank model for the key lock cylinder, and some also include size parameters.
- Method 3: Contact the brand's 4S store/professional locksmith: Provide the vehicle's VIN (Vehicle Identification Number, available on the vehicle license), and the staff can accurately match the key blank model through the manufacturer's system—ideal for beginners unsure of the model.
II. Next, Verify "Size": Length, Width, Thickness—A 1mm Difference Is Unacceptable
The size of the key blank must be identical to the original key; otherwise, it cannot be inserted into the lock cylinder or may jam when turning. There are 3 core size parameters: effective length, shank width, and metal thickness. It is recommended to measure the original key with a vernier caliper or straightedge (if no original key is available, check the vehicle parameter table).
Core Size Reference Table for Automotive Key Blanks (Unit: mm)
| Size Type | Common Range | Allowable Error Range | Measurement Points |
|---|---|---|---|
| Effective Length (Tooth Part) | 45-55 | ≤±0.5 | Straight-line distance from the start to the end of the tooth profile |
| Shank Width | 8-12 | ≤±0.3 | Maximum width at the key grip (compatible with keychains) |
| Metal Thickness | 1.5-2.0 | ≤±0.1 | Thickness of the key blank's metal sheet (excessive thickness jams the lock cylinder) |
| Groove Depth (Internal/External Milling) | 0.8-1.2 | ≤±0.1 | Depth of the milling groove (affects tooth profile matching accuracy) |
III. 3 Key Tips to Avoid Mistakes When Purchasing: Beyond Model and Size, Don’t Overlook These Details
- Prioritize brass material: Key blanks are made of brass, iron, or zinc alloy. Brass has moderate hardness (HRC8-10), is rust-resistant, and easy for tooth milling (more precise during locksmith processing). Iron is prone to rust, and zinc alloy is prone to breakage—both are not recommended.
- Check for a chip slot: For car keys with anti-theft chips (e.g., Volkswagen, BMW), the key blank must have a reserved chip slot (usually on the shank). Blanks without a chip slot cannot accommodate the chip, and the key will fail to start the vehicle after duplication. This is irrelevant for older models without chips (e.g., older Jettas).
- Choose brand-specific models: Avoid "universal key blanks", which require multiple grinding and adjustments, have low precision, and may damage the lock cylinder. Opt for specialized blanks designed for specific brands (e.g., "Volkswagen-specific HU66 blank", "Honda-specific HON66 blank") for better compatibility.
IV. Visual Reference: Automotive Key Blank Structure and Size Measurement Diagram
(Images cannot be directly inserted in the text; please observe the physical object according to the following descriptions)
Structure Diagram:
A key blank consists of three parts:
- Shank: Marked with the model, used for gripping and attaching keychains;
- Transition Part: Connects the shank and the tooth part;
- Tooth Part: Features internal/external milling grooves, the core part compatible with the lock cylinder.
Some blanks have a "chip slot" (rectangular or circular groove) on the side of the shank.
Size Measurement Diagram:
- Effective Length: Align one end of the straightedge with the "start of the tooth part" and the other end with the "end of the tooth part"; the read value is the effective length.
- Shank Width: Clamp the "widest part of the shank" with calipers and read the value.
- Metal Thickness: Measure the thickness of the metal sheet with calipers (avoid tooth grooves, measure the flat area).
By following the above steps—first confirming the model, then matching the size, and finally checking the material and details—you can accurately select the correct automotive key blank. If you are still unsure, it is recommended to bring the original key to a professional lock shop and have the staff match it on-site to avoid purchasing errors due to parameter deviations.