A thread passes the go gage and still won't seat at assembly. A thin stamping flexes the moment the caliper jaws close on it. An optical comparator measures the part's shadow at up to 100x, so you see how far each radius, angle or thread flank sits from the print.
Answer three questions about the part and what you need from the reading. You'll get a starting model and readout.
Start the fit guide →02 / AskDescribe the part, the feature and the tolerance. The Fowler engineer who covers your region replies with a recommendation.
Ask an engineer →03 / Prove itSend a sample and the print. We measure it on the comparator you're considering and send you the results.
Request a part demo →Calipers, micrometers and plug gages each check one feature per setup. Every tool change is another chance for the part to shift and another reading that depends on who's holding the tool. When a lot gets rejected, an attribute gage leaves you with a count of failures and nothing about which feature drifted or by how much.
Load the part once and measure every external feature without moving it to another tool. The stage runs on 0.00002″ (0.5 µm) linear scales, so the number comes from the scale and not from how hard someone turned a thimble.
With the FT2-E FUSION readout you import the .dxf, scan the edge, and the software best-fits the profile to the CAD and marks each feature in or out of tolerance. The output is a dimensioned drawing your customer can read without a phone call.
The comparator measures a shadow, so nothing presses on the part. Thin stampings, plastic extrusions, rubber seals and small medical implants keep the shape they had on the bench while you measure them.
Fowler customers run comparators in aerospace, automotive, medical device, cutting tool, electronics and precision machining shops.
Flank angle, pitch and root form, with the light tilted to the helix.
Turned shoulders, chamfers and tool-nose radii against the print.
Shoulder-to-shoulder lengths on shafts and pins in one setup.
Insert and form-tool profiles, with ±15° stage rotation on the R600.
Gaskets and sheet metal brackets lying flat on the glass stage.
Extrusions, moldings and seals that change shape under caliper jaws.
Watch gears and medical implants, measured with zero contact force.
Counterbores, blind cavities and face features under fiber-optic surface light.
The model comes down to how the part sits and how big it is. The readout comes down to what happens to the number after you take it.
Pick an answer above first.
On a horizontal machine, light crosses the stage sideways, around a part held in V-blocks, a vise or between centers. On a vertical machine, light comes up through a flat glass stage under parts that lie on it.
Built for smaller turned and threaded parts on a workshop bench, with a compact, lightweight chassis. 13.4″ (340 mm) screen, 6.9″ × 3.9″ travel.
Explore R14 configurations →
Built for the shop floor or the standards room, with a bigger screen and a quick-release rapid traverse. 15.8″ (400 mm) screen, 11.8″ × 5.9″ travel.
Explore R400 configurations →
Built for large or heavy turned work in V-blocks and centers, with a powered Y-axis and a hooded screen for bright shops. 23.6″ (600 mm) screen, 17.7″ × 7.9″ travel.
Explore R600 configurations →
Built for small flat parts at the station, with the GMR geometric readout and a built-in printer as standard. 11.8″ (300 mm) screen, 5.9″ × 2.0″ travel.
See the SM300 →
Built for larger flat parts in a production cell or QC room, on a heavy-duty stage with rapid traverse on both axes. 13.8″ (350 mm) screen, 9.8″ × 4.9″ travel.
Explore SM350 configurations →
Built for heavy-duty flat-part inspection standing up, with an angled screen and twin fiber-optic surface lights. 19.7″ (500 mm) screen, 9.8″ × 4.9″ travel.
Ask about the SM20 →| Model | R14 | R400 | R600 | SM300 | SM350 | SM20 |
|---|---|---|---|---|---|---|
| Light path | Horizontal | Horizontal | Horizontal | Vertical | Vertical | Vertical |
| Platform | Benchtop | Benchtop, or floor with optional cabinet stand | Floor-standing, large format | Benchtop | Heavy-duty benchtop | Floor-standing |
| Screen | 13.4″ (340 mm), 90° crosslines, chart clips | 15.8″ (400 mm), 90° crosslines, chart clips | 23.6″ (600 mm), 90° crosslines, hood and curtains | 11.8″ (300 mm) fine ground glass, crosshairs, chart clips | 13.8″ (350 mm) | 19.7″ (500 mm) angled, 90° crosslines, chart clips |
| Stage travel (X × Y) | 6.9″ × 3.9″ (175 × 100 mm) | 11.8″ × 5.9″ (300 × 150 mm) | 17.7″ × 7.9″ (450 × 200 mm) | 5.9″ × 2.0″ (150 × 50 mm) | 9.8″ × 4.9″ (250 × 125 mm) | 9.8″ × 4.9″ (250 × 125 mm) |
| Stage drive | Slotted cast iron stage, one machined slot | Slotted cast iron stage, plain rod drive, quick-release rapid traverse | Heavy-duty stage, two machined slots, powered 7.9″ (200 mm) Y-axis with joystick | Linear scale stage | Heavy-duty stage, plain rod drives, rapid traverse on both axes | Heavy-duty stage, quick-release X and Y clutches |
| Scale resolution | 0.00002″ (0.5 µm) | 0.00002″ (0.5 µm) | 0.00002″ (0.5 µm) | 0.00002″ (0.5 µm) | 0.00002″ (0.5 µm) | 0.00002″ (0.5 µm) |
| Lens magnifications | 10x, 20x, 25x, 50x, 100x | 10x, 20x, 50x, 100x | 10x, 20x, 50x, 100x | 10x, 20x, 50x, 100x | Ask us | 10x, 20x, 50x, 100x |
| Lens mounting | Single mount | Single mount | 4-position rotating turret | Single mount | Single mount or optional 3-lens turret | Single mount or optional 3-lens turret |
| Max part height | Ask us | Ask us | Ask us | 3.1″ (80 mm) | Ask us | Ask us |
| Profile illumination | Halogen with green filter | LED, optional green filter | Halogen with green filter | Built-in | Built-in | Halogen with green filter |
| Surface illumination | Fiber optic | Fiber optic | Fiber optic | Built-in | Included | Twin fiber optic, full color |
| Thread and tool setup | Light source helix ±7° | Light source helix ±7° | Workstage helix rotation ±15° for threads and cutting tools | Ask us | Helix adjustment | Light source helix adjustment |
| Angle readout | Digital, to 1 minute | Digital, to 1 minute | Digital | Through the GMR readout | Digital angle protractor | Digital |
| Edge sensor | With GXL-E or FT2-E | With GXL-E or FT2-E | With GXL-E or FT2-E | Ask us | With GXL-E or FT2-E | Optional automatic edge sensor |
| Readout | XLS, GXL, GXL-E or FT2-E | XLS, GXL, GXL-E or FT2-E | XLS, GXL, GXL-E or FT2-E | GMR with built-in printer, standard | XLS, GXL, GXL-E or FT2-E | Ask us |
All models read to 0.00002″ (0.5 µm). Lenses, fixtures and readouts are configured per order.
Most of what makes a comparator reading trustworthy happens before anyone looks at the number: how the light hits the part, how the edge gets picked up, and how the part sits on the stage.
Every model reads to 0.00002″ (0.5 µm). The readout decides whether that number gets written down, checked against tolerance, or compared to the CAD and charted.
Point-to-point X/Y plus radius and angle. Absolute and incremental modes, inch/metric switch, radius-to-diameter toggle and zero reset.
Full 2D geometric functions for routine profile checks, with a built-in printer for a paper record at the station.
Touch functions for points, lines, circles, distances, angles and skew. Stored routines, tolerance limits, operator prompts and output to a PC or printer.
The sensor logs each point as the shadow edge crosses it, so two operators get the same number off the same part.
2D FUSION software with .dxf import, best-fit to CAD overlay, dimensioned drawings, SPC charts, pass/fail reports and export to Excel. The edge sensor comes with it.
Most comparator questions get answered fastest with the part in hand. If you can't send one yet, describe the job and an application engineer will take it from there.
The print, the features you can't measure well today, the tolerance, and how many you check per shift.
Ship a sample part to Fowler in Canton, Massachusetts, or set up a live video session with the part on the stage.
You get the measurement results from your own part and the model, readout and fixtures we'd quote for it.
Requests go to the Fowler application engineer who covers your state. Prefer the phone? Call (800) 788-2353.
Tell us about the part, the feature that's giving you trouble and how you want to see it measured. An application engineer replies with next steps.
It depends on how the part sits. Horizontal (R-series) machines send light sideways across the stage, which suits turned parts held in V-blocks, a vise or between centers. Vertical (SM-series) machines send light up through a glass stage, which suits flat parts like stampings, gaskets and sheet metal brackets that lie on the glass.
Lining up crosshairs on a shadow edge depends on where each person sees the edge. The edge sensor registers the change from light to dark itself and logs the coordinate, so the reading no longer depends on who took it. It comes with the GXL-E and FT2-E readouts.
Yes, with the FT2-E FUSION readout. You import a .dxf, scan the profile, and the software best-fits the scanned edge to the CAD and shows each feature in or out of tolerance. It can also output a fully dimensioned drawing.
Light shining straight across a thread meets the helix at an angle, so the shadow of the flanks comes out distorted. Tilting the light source to the helix angle gives a true cross-section of the flanks, pitch and root form.
Yes. The profile light shows the silhouette, and the surface light shines onto the face of the part for inspection of counterbores, blind cavities and face details. The SM20 has twin fiber-optic lights for full-color surface work.
A comparator puts the magnified shadow on a screen in front of the operator, which suits profile work like threads, radii and form tools where seeing the whole outline at once helps. A vision system measures from a camera image under a stored program, which suits repeat runs of many features. If your part could go either way, an application engineer can walk you through both.
Yes. Send a sample part and the print, and we'll measure it on the comparator and readout you're considering and send back the results along with a recommended setup.
Send a sample and the print. You get the results from your own part.
Request a demo →AskDescribe the job and get a recommendation from the engineer who covers your region.
Ask an engineer →LearnEvery model, lens, fixture and readout, with full specs.
Open the catalogs →