A Bevelled Disc Cam is a rotating disc with its working face cut at an angle to the shaft axis, so a follower riding on that face oscillates back and forth along the axis once per revolution. Typical units run 100 to 600 RPM with follower lifts of 2 to 25 mm. We use them where a simple radial cam can't fit — anywhere axial reciprocation must come straight off a rotating shaft, like the thread-guide traverse on a Schärer Schweiter Mettler winder or the needle-bar drive on older Singer industrial machines.
Bevelled Disc Cam Interactive Calculator
Vary bevel angle, contact radius, and speed to see the resulting axial stroke and animated follower motion.
Equation Used
The bevelled disc cam converts shaft rotation into sinusoidal axial follower motion. Stroke is twice the contact radius times tan(theta), with theta converted from degrees for calculation. The amplitude is half the stroke, and one revolution gives one axial cycle.
- Follower remains in contact with the bevelled face.
- Contact radius is measured from shaft center to follower contact point.
- theta is the bevel angle of the cam face.
- One shaft revolution produces one follower cycle.
Inside the Bevelled Disc Cam
The geometry is simple. You take a flat disc, tilt its working face by an angle θ relative to the rotation axis, and let a flat-faced or roller follower ride against that tilted face under spring or gravity preload. As the disc spins, the contact point on the face traces a circle, but because the face is bevelled, the axial position of that contact point rises and falls sinusoidally. One revolution gives you one full rise-fall cycle. That's it — a swashplate cam, a wobble plate, a face cam — different names, same principle.
The lift is set by 2 × R × tan(θ), where R is the contact radius and θ is the bevel angle. So a 30 mm contact radius at 5° gives you about 5.25 mm of follower stroke. Push θ above 15° and the pressure angle on the follower starts driving high side loads into the guide bushing — you'll feel it as accelerated bushing wear and a measurable drop in axial output force. Most production designs stay between 3° and 12°. If you notice the follower chattering or skipping at speed, the usual culprits are insufficient preload spring force (follower lifts off during deceleration), a contact radius that's drifted because the follower tip wore flat, or shaft runout above 0.05 mm that adds a parasitic wobble on top of the intended cam motion.
Unlike a radial disc cam, the bevelled disc cam gives you pure axial follower motion with no need to convert radial-to-axial through a lever or bell crank. That's why you see it on thread guides, oilers, valve actuators, and anywhere you want reciprocation parallel to the drive shaft in a tight envelope.
Key Components
- Bevelled Disc (Cam Face): The hardened steel disc with its working face ground at angle θ to the shaft axis, typically 3° to 12°. Face flatness must hold within 0.01 mm across the contact track or the follower will chatter. Surface hardness sits around 58-62 HRC for a contact pressure of 200-400 MPa.
- Follower: Either a flat-faced plunger or a small roller (5-15 mm diameter) that rides the bevelled face. Roller followers cut friction by 80% versus flat followers but cost more and need a yoke. The follower must be axially constrained in a guide bushing with less than 0.02 mm radial clearance.
- Preload Spring: Holds the follower against the cam face during the falling half of the cycle. Spring force must exceed peak inertia load — for a 50 g follower at 600 RPM with 5 mm stroke, that's about 12 N minimum, with a 1.5× safety factor giving 18 N installed.
- Drive Shaft: Carries the cam disc and runs in two bearings. Shaft runout under load must stay below 0.05 mm TIR or the runout adds onto the intended cam lift and shows up as a vibration tone at shaft frequency.
- Follower Guide Bushing: Bronze or oil-impregnated sintered bushing that constrains the follower to pure axial travel. Length-to-diameter ratio of 1.5-2.0 minimum, otherwise side load from the cam pressure angle cocks the follower and binds it.
Where the Bevelled Disc Cam Is Used
You find Bevelled Disc Cams wherever a rotating shaft needs to drive a short axial reciprocation in a compact package. They are quieter than crank-and-slider mechanisms, simpler than ball-screw reversing drives, and they hold up well at moderate speeds for decades.
- Textile machinery: Thread-guide traverse drive on Schärer Schweiter Mettler precision winders, where the bevelled face oscillates the yarn guide ±10 mm to lay thread evenly across the bobbin.
- Industrial sewing: Vintage Singer 31-15 and Pfaff 145 industrial sewing machines used a wobble-plate-style face cam to drive auxiliary feed-dog lift off the main shaft.
- Lubrication systems: Bijur Delimon centralised oilers use a small bevelled face cam to drive the metering plunger once per shaft revolution, delivering a precise oil shot of 0.03-0.10 cc.
- Packaging machinery: Glue-applicator nozzles on Bosch and Krones labelling lines use a 6° bevelled disc cam to lift and lower the nozzle in sync with bottle pitch at 200-400 BPM.
- Small-engine fuel pumps: Mechanical diaphragm fuel pumps on older Briggs & Stratton engines drove the pump lever from a small bevelled cam ground onto the camshaft, giving 2-3 mm diaphragm stroke.
- Indexing tables: Camco low-cost rotary indexers use a bevelled face section combined with a Geneva-style drop section to give controlled axial pin engagement during index transfer.
The Formula Behind the Bevelled Disc Cam
The follower's instantaneous axial position is what you actually need to design around — peak lift sets the stroke, peak velocity sets the spring preload, and peak acceleration sets the contact stress on the face. At the low end of the typical bevel range (3°) you get gentle motion and long life but limited stroke. At the high end (12°+) you get usable stroke from a small disc but pressure angle climbs and side load on the follower bushing dominates. The sweet spot for most production designs sits between 5° and 8°.
Variables
| Symbol | Meaning | Unit (SI) | Unit (Imperial) |
|---|---|---|---|
| x(φ) | Axial follower position from the mean | mm | in |
| R | Contact radius from shaft centreline to follower tip | mm | in |
| θ | Bevel angle of the cam face relative to a plane perpendicular to the shaft | degrees | degrees |
| φ | Shaft angular position | radians | radians |
| S | Total peak-to-peak follower stroke = 2 × R × tan(θ) | mm | in |
Worked Example: Bevelled Disc Cam in a precision yarn-winder traverse
You are designing the traverse drive for a precision yarn winder that lays 40-denier polyester onto a 70 mm bobbin at 300 RPM. The thread guide must reciprocate ±4 mm peak from centre, total stroke 8 mm. Contact radius is set at 30 mm to clear the surrounding bearing housing. You need to pick the bevel angle, then check what happens at the slow-start condition (100 RPM) and the high-speed finishing pass (600 RPM).
Given
- S = 8 mm
- R = 30 mm
- Nnom = 300 RPM
- mfollower = 40 g
Solution
Step 1 — solve for the bevel angle θ that gives the required 8 mm peak-to-peak stroke at 30 mm contact radius:
That sits comfortably inside the 5°-8° production sweet spot. Pressure angle is moderate, side load on the bushing is manageable, and the disc face can be ground without special fixtures.
Step 2 — at the nominal 300 RPM operating point, peak follower velocity is:
That's a smooth, controlled traverse that lays thread cleanly without overlap or gapping — exactly the feel you want on a precision winder.
Step 3 — at the low-end start condition of 100 RPM:
The traverse is slow enough that you can watch the guide creep back and forth — useful during thread-up and bobbin-change diagnostics. Spring preload requirements are minimal because peak inertia force scales with ω².
Step 4 — at the high-end finishing pass of 600 RPM, peak acceleration becomes the design driver:
At 600 RPM the follower starts to fight the spring. Push much past 700 RPM with this stroke and contact radius and the follower will lift off the cam face during the deceleration phase, and you'll hear it as a clicking tone synchronised with shaft speed.
Result
Pick a 7. 6° bevel on a 30 mm contact radius, install a preload spring giving at least 1.0 N seated force, and you'll get a clean 8 mm traverse stroke at 300 RPM with peak follower velocity around 0.126 m/s. At 100 RPM the motion is gentle and visibly traceable; at 600 RPM you're near the practical ceiling for this geometry — peak acceleration jumps from 1.75 m/s² at start-up to 15.8 m/s² at full speed because acceleration scales with the square of shaft speed, not linearly. If your measured stroke comes in short of 8 mm, check three things in order: (1) contact radius drift — a worn flat-faced follower tip moves the effective R inward by 1-2 mm and shrinks stroke proportionally; (2) bevel-face wear on the disc, which flattens θ over time and shows up as a bright ring on the contact track; (3) follower-bushing cocking from a length-to-diameter ratio under 1.5, which lets the follower tilt and lose effective stroke under load.
Bevelled Disc Cam vs Alternatives
Bevelled Disc Cams compete with a few other ways to get short axial reciprocation off a rotating shaft. Each option has a clear sweet spot — here is how they line up on the dimensions that actually matter when you are choosing between them.
| Property | Bevelled Disc Cam | Crank-and-Slider | Cylindrical (Drum) Cam |
|---|---|---|---|
| Typical operating speed | 100-600 RPM | 100-3000 RPM | 50-400 RPM |
| Practical stroke range | 2-25 mm | 10-200 mm | 5-150 mm |
| Motion profile flexibility | Sinusoidal only | Near-sinusoidal, fixed by geometry | Any profile — rise/dwell/fall fully programmable |
| Axial envelope | Compact — disc thickness only | Long — needs crank throw + conrod length | Medium — drum length sets stroke |
| Side-load on follower | Moderate, climbs with bevel angle | Low — pin joints carry load | Low — groove constrains follower both ways |
| Manufacturing cost | Low — single ground face | Medium — multiple precision parts | High - 3-axis profiled groove |
| Lifespan at rated load | 10⁸-10⁹ cycles | 10⁷-10⁸ cycles | 10⁸-10⁹ cycles |
| Best application fit | Short-stroke axial oscillation off a running shaft | Long-stroke pumps, compressors, presses | Indexing, complex timed motion, packaging |
Frequently Asked Questions About Bevelled Disc Cam
Stroke does keep growing with tan(θ), but pressure angle on the follower grows with it. Above roughly 12° the side-load component on the follower bushing starts to exceed the axial driving force, so a large fraction of the cam's torque goes into squeezing the follower sideways against its bushing instead of moving it axially.
You'll see this as accelerated bushing wear, a measurable drop in delivered axial force, and on flat followers, edge-loading marks on the cam face. If you need more stroke than 12° gives you at your contact radius, increase R instead — moving the follower outward gains stroke without increasing pressure angle.
The static preload calculation only covers rigid-body inertia. What's almost always missing is spring surge — at high cam speeds the spring's own natural frequency couples with the cam excitation and the spring coils start oscillating internally, momentarily dropping seated force to zero even though average preload is fine.
Quick check: calculate the spring's natural frequency and compare to your cam frequency. If cam frequency is within 20% of spring fn or any harmonic up to the 5th, you're surging. Fix is either a stiffer spring with higher fn, a damper coil, or a dual-spring nest with different rates.
At 15 mm stroke and 200 RPM either will work, so the decision comes down to motion profile and envelope. If you can live with sinusoidal motion — equal rise and fall, no dwell — the bevelled disc is half the cost and a quarter the size. If you need a dwell, an asymmetric rise, or any kind of programmed profile, you need the drum cam.
Rule of thumb in our shop: under 20 mm stroke, sinusoidal motion acceptable, axial space tight → bevelled disc. Anything that says "dwell" in the spec → drum cam, full stop.
The formula assumes the follower contacts the cam at exactly radius R throughout the cycle. In reality, a flat-faced follower contacts the bevelled face at a point that wanders radially as the disc rotates, because the highest point of the tilted face shifts azimuthally with shaft angle. Effective R can be 5-10% smaller than the nominal follower-tip radius.
The other 5-10% usually comes from elastic deflection in the follower stem and bushing clearance taking up slack on each direction reversal. A roller follower with a precise contact line eliminates the wandering-contact error and typically brings measured velocity within 3% of prediction.
The kinematics are perfectly symmetric — reversing shaft direction gives you an identical sinusoidal lift profile, just phase-shifted by 180°. So mechanically, yes, it runs in reverse with no penalty.
Where direction does matter is wear-pattern conditioning. After a few hundred hours of one-direction operation the cam face develops a microscopic asymmetric wear pattern aligned with the sliding velocity vector. Suddenly reversing direction on a worn cam gives you a brief spike in friction and noise until the face re-conditions. On a new cam, run either way you like.
That's a classic symptom of shaft misalignment or disc-face runout. The follower is contacting the high side of the bevel harder than the low side because the disc isn't spinning truly perpendicular to the follower's axis of travel — there's an additional small wobble on top of the intended bevel.
Check disc face runout with a dial indicator at the contact radius. Anything above 0.02 mm TIR will produce visible asymmetric wear within a few hundred hours. Common causes are a burr under the disc on the shaft shoulder, a bent shaft, or the cam being clamped against a non-perpendicular shoulder face.
References & Further Reading
- Wikipedia contributors. Cam. Wikipedia
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