CNC Machined Stainless Steel Hinge Block
316L stainless hinge blocks milled from solid with two knuckle bores line bored to H7 and coaxial within 0.02 mm, a mounting face square to the pin bore within 0.02 mm and a knuckle gap controlled to 0.2 mm. Blocks are made as matched pairs so the pin aligns the leaves without a reamer on assembly.
- Knuckle Bores Coaxial 0.02 mm
- Mounting Face Square
- Pin Bore to H7
- Passivated After Boring
*Send the pin diameter and the leaf thickness. The knuckle gap and the bore tolerance have to match the pin and the leaf that goes between the knuckles, and a gap that is 0.1 mm out shows as a sagging door.
Stainless Hinge Block Overview
A hinge block is judged by whether the pin goes in and the leaf swings without play. Both come down to the knuckle bores being coaxial and the mounting face being square to them, which is a boring problem rather than a milling one.
The block is squared on all six faces first, then the mounting holes and the knuckle pocket are milled. The two knuckle bores are cut last with a line boring bar through both walls in one pass, so they share an axis that no re-chucking can disturb.
316L Stainless Block
316L is the default for a hinge in washdown, marine or chemical service, where the pin bore would otherwise rust and seize. It work-hardens, so the bore is cut with a sharp tool and a constant feed rather than a dwell.
304 or 2205 Duplex
304 is used indoors where cost matters. 2205 duplex is chosen for offshore and chloride service, where 316L would pit in the stagnant gap between the knuckles.
The gap between knuckles is where corrosion starts, because it stays wet. In chloride service that gap decides the alloy more than the load does.
Stainless Hinge Block Specifications
Milling and boring data for hinge blocks, with the bore, squareness and gap values that decide whether the pin fits and the leaf swings true.
| Specification | Machining Data | Specification | Machining Data |
|---|---|---|---|
| Product | Hinge Block / Knuckle Block | Machining Process | 3-Axis CNC Milling, Boring, Line Reaming |
| Material | 316L Stainless Block | Block Size | 40 × 40 × 20 to 200 × 120 × 60 mm |
| Pin Bore | Ø 6 – 40 mm, H7 | Knuckle Coaxiality | 0.02 mm |
| Mounting Face Squareness | 0.02 mm to the Pin Bore | Bore Surface Finish | Ra 1.6 µm |
| Knuckle Gap | 0.05 – 0.2 mm Clearance | Mounting Holes | Ø 5 – 14 mm, ±0.05 mm |
| Wall Around Bore | Minimum 1.5 × Bore Diameter | Passivation | ASTM A967 |
| Customization | Grease Groove, Pin Retention Thread, Stop Lug, Weld Prep | Lead Time | 6 – 8 Days Sample, 13 – 17 Days Batch |
| Inspection | Pin Gauge Through Both Knuckles, CMM Squareness, Thread Gauges | Packing | Pair-Matched, VCI Wrap, Carton |
Key Features of Our Hinge Blocks
Line bored through both knuckles, squared before boring.
Knuckles Line Bored Together
Both bores are cut with a line bar in one pass, so they are coaxial to 0.02 mm and the pin slides through from either side without a reamer.
Mounting Face Square to the Bore
The face that bolts to the frame is machined before boring and used as the datum, holding squareness to 0.02 mm so the leaf hangs straight.
Knuckle Gap Controlled
The gap is milled to the leaf thickness plus clearance and checked with a gauge, because a gap that is too tight binds the leaf and one that is too wide lets it sag.
Pairs Matched Before Passivation
Blocks are made as a pair and matched on the pin before coating, so the two leaves that ship together already fit each other.
Hinge that has to swing without play?
Surface Finishes for Hinge Blocks
The pin bore is a fit and the gap between knuckles is a corrosion trap, so both are specified separately.
| Finish | Main Purpose | Finish | Main Purpose |
|---|---|---|---|
| Passivation | Removes free iron from bored holes | Electropolishing | Hygienic finish for food and pharma doors |
| Glass Bead Blasting | Even matte exterior that hides mill marks | Masked Pin Bore | Keeps the bore at H7 where a coating is applied |
| Laser Marking | Pair number and pin size on the block | Dry Film Lubricant | Pin bore that runs without grease |
*Coating inside a pin bore closes the fit. Bores are masked when a coating is required, and the pin is gauged through both knuckles after coating.
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Machining Process for Hinge Blocks
Both knuckles are bored in one pass with a line bar, so the hinge pin slides through from either side without a reamer.
01. Pin and Leaf Review
Check the pin diameter, the leaf thickness and the required swing angle, then set the knuckle gap and the bore tolerance from those three numbers.
02. Square the Block
Machine all six faces square and mark the mounting face, since the bores and the mounting holes are all called from that face.
03. Mill Pockets and Holes
Mill the knuckle pocket, the stop lug and the mounting holes, leaving the bore walls at full thickness until the boring operation.
04. Line Bore the Knuckles
Cut both knuckle bores with a line boring bar in one pass, check coaxiality with a pin through both and record the result before release.
05. Passivate and Match
Deburr the bore entries, passivate, gauge the pin through the pair, mark the pair number and pack them together so they stay a set.
Send the pin and the leaf thickness, and we will quote the hinge block with the knuckles bored on a single axis.
Stainless Hinge Block FAQs
0.02 mm, because both are cut with a line bar in one pass. Bored separately, the same block typically shows 0.08 mm and the pin needs a reamer to go through.
Leaf thickness plus 0.1 mm as standard, controlled to ±0.05 mm. The gap is checked with a gauge before the block is passivated.
Yes, a circumferential groove inside the bore with a cross hole to a grease nipple thread, cut before the bore is finished so the groove does not raise a burr.
Not if the pin and bore are a running fit and the gap is kept clear. In chloride service we recommend 2205 duplex for the block and a matching pin.
Yes, with a weld prep chamfer on the mounting edges. The bore is line bored after welding if the block is supplied as a weldment, which is a separate process.
Blocks are marked with a pair number and packed as a set with the pin, so a mixed crate cannot put two halves of different pairs on one door.
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