The labels 7.5 mm and 19 mm describe different interfaces, so choosing by the pair alone can produce the wrong gearbox, handle or sash preparation. By the end, you will know how to measure the existing window, verify cam-and-keep alignment, confirm handing and specify a suitable system for Hyderabad conditions.
Key takeaways
- Confirm 7.5mm spindle size and 19mm backset on a dimensioned drawing.
- Measure the existing faceplate, spindle centre, lock length and handle position.
- Match cam geometry, handing, profile groove and handle compatibility before ordering.
- Require batch details, drawings, samples and installation support from the supplier.
What Do 7.5 mm and 19 mm Actually Measure?
7.5 mm normally identifies the square handle spindle measured across its flats. 19 mm normally identifies the backset, measured from the faceplate edge to the spindle centre. Require a dimensioned supplier drawing to confirm this notation because catalogues use “7.5/19” inconsistently.
Measurement diagram, not to scale:
Faceplate edge │←──────── 19 mm backset ────────→│ Spindle centre Lock strip │ Gearbox body │ │ □ 7.5 mm square spindle │ │ ↕ spindle width │ │ ───────────────→ spindle length │ cam ●──────→ cam travel │ faceplate
The spindle length runs from the underside of the handle rose to its tip. The lock strip carries the gearbox and moving locking points along the sash.
- Turn the handle; it rotates the square spindle inside the espagnolette gearbox.
- The central gearbox drives mushroom cams, rollers or shoot bolts along the sash.
- Those locking points enter keeps fixed to the frame and pull the sash against its seals.
The 19 mm backset is a position, not a security rating. A larger backset is not automatically stronger; cam travel, gearbox construction, profile fit and keep engagement determine performance. A 19 mm espag locking system can still be incompatible if its gearbox body, lock strip or routing does not fit the window profile.
How Do You Measure the Existing Window Before Ordering?
Open the sash fully before you measure espag lock hardware. Work through this sequence and record each dimension in millimetres:
1. Remove the handle and any escutcheon or packer. Measure the backset from the centre of the square spindle socket to the nearest edge of the faceplate.
2. Measure the actual spindle across its flats; do not assume 7 mm or 7.5 mm from the catalogue name. Measure spindle length from the underside of the handle rose to the tip, including any escutcheon or packer used in the installation.
3. Record the complete lock strip length and the gearbox length separately. Measure the gearbox body width and depth where it enters the sash groove.
4. Count every locking point, including mushroom cams, rollers and shoot bolts. Measure each cam’s diameter and height, then note its position along the lock strip.
5. Check the faceplate width, shape, thickness and fixing-hole pattern. Record the end-plate dimensions and the handle screw-centre distance rather than assuming the common 43 mm spacing.
6. Photograph the gearbox, end plate, faceplate, cams and exposed sash groove. Include a ruler in each photograph and mark the top, bottom and handle side.
A 19 mm backset confirms only the spindle-to-faceplate distance. The replacement still fails if its gearbox body, total length, cam travel or routing does not fit the aluminium or uPVC profile. Compare your measurements with a dimensioned supplier drawing before ordering, not with “equivalent 7.5/19 mm” wording alone.
Which uPVC or Aluminium Profiles and Handles Will Fit?
Compatibility is a profile-and-hardware check, not a choice between two numbers. Identify the exact uPVC window profiles or aluminium window profiles family, then compare its sash thickness, Euro-groove width and depth, gearbox-body clearance, faceplate shape, screw-hole spacing and end-plate preparation with the supplier drawing. A profile adapter, packer or different faceplate may be necessary.
| Check | What to compare | What failure means |
|---|---|---|
| Profile | Sash thickness, Euro-groove, gearbox clearance, faceplate and end plate | A 19 mm gearbox can fit the spindle position but fail to route into the sash |
| Gearbox | Lock-strip length, fixing holes, cam path and profile orientation | The mechanism binds or locking points stop short |
| Handle | Spindle, rose height, screw centres and handle type | The handle will not clamp, align or operate correctly |
Confirm that the handle has a 7.5 mm square spindle. Measure the required spindle length from the underside of the handle rose to the tip, including an escutcheon or packer, and record handle height and screw centres. Use 43 mm as the fixing-centre dimension only after measurement confirms it.
Check whether the gearbox accepts inline, offset or split-spindle handles. A 7 mm handle is not interchangeable with a 7.5 mm socket: an undersize spindle creates play and can round the socket; an oversize spindle causes stiffness or incomplete return. Do not order an “equivalent 7.5/19 mm” unit until every dimension matches the supplier drawing.
How Do Cam Geometry, Handing and Installation Affect Operation?
Compare every cam with the window keeps already fixed to the frame: record its height, spacing, travel and type, then match those dimensions to the keep’s entry and locking surfaces.
| Feature | Compare against fixed frame | Failure if mismatched |
|---|---|---|
| Cam height | Cam centre and engagement depth against the keep | The cam rides over the keep or engages only its edge |
| Cam spacing | Distance between each cam and the gearbox reference point | One locking point engages while others miss |
| Cam travel and type | Rotation or linear travel, plus mushroom, roller or shoot-bolt shape | The handle appears locked without uniform compression |
Confirm whether the unit is for a left-hand right-hand window, the sash opening direction and the handle’s turning direction. Ask whether the gearbox is reversible on site; some must be ordered for specific handing or profile orientation.
Commission it with the sash open. Operate the gearbox through complete handle travel with light, even resistance. Close the sash only after that test, then correct the keeps, hinges and sash diagonals before applying more force.
Stiffness only when closed, incomplete handle return, flattened gaskets and leakage at the lock side indicate poor locking-point alignment. Check keep position and sash adjustment instead of fitting a stronger handle; force can damage the spindle socket and gearbox.
For an escape route, a lockable espag system is not automatically acceptable. Check key release, clear opening, opening direction and operating force against the applicable fire-safety requirements. A key-dependent or stiff release can defeat escape.
What Should Hyderabad Projects Require from the Supplier?
Require a profile-matched sample and first-article approval before batch supply. A catalogue label such as “equivalent 7.5/19 mm” is not sufficient: reject it unless the supplier provides a dimensional comparison against your existing sash and lock.
1. Ask the espag lock supplier to confirm spindle width and length, 19 mm backset, faceplate width and shape, gearbox length, cam type and travel, locking-point count, handle fixing centres, finish and handing. The drawing must show every measurement, not only the nominal 7.5/19 designation.
2. Check the sample in the actual profile. Confirm that the gearbox fits the sash groove without forcing the extrusion, that each cam reaches its keep, and that the handle completes its travel. A 19 mm backset can still be wrong when the body length, faceplate or cam path does not match.
3. Specify finish for Hyderabad’s intense solar exposure and monsoon moisture, then validate it for the project’s corrosion environment rather than accepting “zinc plated” alone. This is essential when selecting Hyderabad window hardware or monsoon-resistant window hardware.
4. Protect the installation during fabrication and glazing. Keep drainage paths and weep holes open, and exclude plaster, sealant and aluminium swarf from the lock channel. Use only the hardware maker’s specified lubricant; general-purpose oil traps dust and creates abrasive paste.
Aruna Techno Industries can serve as a practical sourcing point when the request includes the profile-matched sample, drawing and compatibility check—not merely a catalogue item.
Frequently asked questions
What do 7.5mm and 19mm measure on an espag locking system?
The 7.5mm measurement normally identifies the square handle spindle across its flats. The 19mm measurement normally identifies the backset from the faceplate edge to the spindle centre. Confirm both on a dimensioned supplier drawing because catalogues use “7.5/19” inconsistently.
How should you measure an existing window before ordering?
Measure the spindle size, backset, faceplate width, lock length, handle position, sash height and the distance between locking points. Record the measurements in millimetres and photograph the existing lock and cams.
Which profiles and handles fit a 7.5mm/19mm espag lock?
Check the lock against the window profile groove, faceplate dimensions, handle spindle length and screw-hole centres. Confirm compatibility with the specific uPVC or aluminium profile and the handle manufacturer’s dimensions before ordering.
How do cam geometry, handing and installation affect operation?
Match the cams to the keep positions, confirm left- or right-hand operation where the lock requires it, and align the lock strip without forcing the handle. Incorrect cam height, handing or installation creates tight operation and incomplete locking.
What should a Hyderabad project require from an espag lock supplier?
Request a dimensioned drawing, material and finish details, batch identification, compatibility information, samples where needed, and installation guidance. Confirm packaging and storage instructions for Hyderabad site conditions before placing the order.
