U Shape Fork Bracket and Robot Linkage Jaw Bracket with 0.01mm Coaxiality, 0.01mm Jaw Bore Roundness and 0.01mm Jaw End Height Difference
U-Shape Fork Bracket Machining
,Fork Jaw Coaxial Bores
,0.01mm Jaw Width Control
A U-shape fork bracket is an open part, and that is the whole problem. Two jaws stand out from a base, each carrying a pin bore or a bearing seat, and everything depends on those two jaws staying where they were cut. Cut a weight reduction slot into a jaw, unclamp the part, and the jaws can move apart or close by more than the tolerance the drawing asks for. The bracket still measures within tolerance on the bench and still fails to accept the pin on the assembly line.
Dongguan Changxinda Precision Technology Co., Ltd. has machined fork, yoke and clevis geometry to drawing since 2008. The plant runs 4-axis and 5-axis machining centers, turn-mill combined lathes and precision CNC lathes, employs more than 90 people, holds ISO 9001:2015, and exports 50 to 60 percent of output to robot, automation and medical buyers.
- Jaw spread after unclamping: a vise closes the jaws elastically. When released, they open, and the pin bore becomes a press fit at one end and a loose fit at the other.
- Jaw height mismatch: the two jaw end faces end up at different heights, so the pin sits tilted and the linkage binds through its travel.
- Slot-induced spring: a weight reduction slot removes stiffness from one jaw more than the other, and the asymmetry shows up as a twist between the two bores.
- Bore drift from reaming: reaming a long bore through two jaws without support lets the reamer follow the first hole instead of cutting a true line.
| Step | Operation | Why |
|---|---|---|
| 1 | Rough mill the base, both jaws outside and the fork slot | Opens the part early so it can move before precision work |
| 2 | Stress relief, then finish the base and the datum face | The base becomes the reference for both jaws |
| 3 | Mill the weight reduction slots in both jaws, symmetrically | Symmetry keeps the two jaws responding the same way |
| 4 | Finish jaw inner faces and outer faces from the base datum | Sets fork width and jaw parallelism before any bore |
| 5 | Set a controlled spread in the fixture, matching the service preload | The bore is cut in the shape the part will have in use |
| 6 | Bore and ream through both jaws in one pass with a support mandrel between them | One tool path, so the two bores are coaxial by construction |
| 7 | Face both jaw ends in the same setup, then chamfer | Removes jaw height mismatch instead of tolerating it |
| 8 | Deburr, mask bores, anodize, re-check coaxiality | Coating in a bore changes the pin fit |
- Jaw bore diameter 0.01 mm and roundness 0.01 mm, measured at both jaws and at two depths each
- Coaxiality between the two jaw bores 0.01 mm, measured with a mandrel and again on the CMM
- Jaw inner face parallelism 0.01 mm, which sets the fork width and the side clearance of the mating link
- Jaw end face height difference 0.01 mm, measured on both jaws as a pair
- Fork width 0.02 mm, and base-to-bore centre distance 0.01 mm
- Weight reduction slot symmetry: slot to jaw edge within 0.1 mm on both jaws
- Bore roughness Ra 0.8 for pin bores; Ra 0.4 available for bearing seats
- Metrology at 20 °C, CMM resolution 0.001 mm, first article report with jaw pair data
- Fork width 15 mm to 250 mm, jaw height to 300 mm, base footprint to 400 × 400 mm
- Materials: 6061-T6 and 7075-T6 aluminum, 304 and 316L stainless, 40Cr for loaded forks, titanium on request
- Slot patterns: straight, tapered, kidney-shaped or multiple slots, placed to a stated stiffness or mass target
- Bores: plain, stepped, threaded, with bushings, or with a spherical bearing seat
- Fork ends: square, radiused, chamfered or with an insert pocket for a wear pad
- Finishes: clear, black and hard anodizing, nickel plating, with bores and jaw faces masked
- Laser marking of part number, batch and revision on the base — never on a jaw face
- Drawing input in STEP, IGES, X_T, DWG, DXF or PDF, or a sample bracket for measurement
- Prototype quantity from one piece, design feedback within 24 hours
On request, this family runs on confidential terms: mutual NDA before drawings move, restricted file access with named staff, no photographs of the part for marketing, sub-suppliers bound by the same terms, neutral marking and neutral packing, and programs and fixtures reserved to that customer. Mention it at enquiry stage and the quotation is issued under those terms.
- Prototype bracket: 5 to 8 working days including first article inspection
- Batch of 10 to 300 pieces: 10 to 18 working days including anodizing
- Recurring releases: reserved machine capacity with the same spread-control fixture, so jaw width repeats batch to batch
- A named project engineer per account, weekly status update with photographs unless the program is confidential
- Written notice at least 5 working days before the ship date if any step is at risk
- Packing with a spacer inserted between the jaws, so a bracket cannot be squeezed closed in transit
Because a fork is only as good as its jaw spacing, and a carton squeezed in a container can close the jaws enough to change the pin fit. A simple spacer keeps the geometry until the part is unpacked.
After. The slots change the stiffness of the jaws, so the bores are cut last, in the fixture that holds the service spread. Cutting slots after boring is the fastest way to lose coaxiality.
A mandrel through both bores first, then a CMM check that reports each bore's position separately. The mandrel proves it fits today; the CMM data shows how much margin is left.
Yes, on request, including restricted drawings, no marketing photographs, neutral marking and packing, and fixtures and programs reserved to your program.
Machined to drawing in the same plant, with the same tolerance and inspection standard.
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