Plate cam and roller-follower mechanism on a machine camshaft: keeping the pressure angle down and sizing the follower roller against the cam track
Machine camshafts · disc cams with roller followers on rocker arms or slides: pressure angle at the steepest part of the rise, the roller as one half of a bearing whose other half is the cam, and follower speed multiplied by the cam-to-roller diameter ratio
In an automatic machine driven from one camshaft, each disc cam on the shaft is a stored motion program: its profile sets when a follower lever or slide rises, dwells and returns within one shaft revolution. The cam and its roller follower are bought and checked as a pair. The profile has to push the roller without too steep a flank, or the force goes into side load on the follower guide rather than into motion; and the roller has to survive rolling on a cam surface whose hardness limits how much load it can take without denting.
Plate (disc) cams mounted on one camshaft and the roller followers that run on them, on rocker arms or translating slides, as fitted inside automatic production machines: rise-dwell-return profiles, pressure angle and base-circle size, conjugate cam pairs for positive drive, cam-surface hardness against the follower's track capacity, and selection of stud-type follower rollers. Concealed cup hinges for cabinet doors are covered on the Furniture hinge page and eccentric knock-down fittings for panels on the Furniture cam lock connectors page. Cam indexers that step a dial or tool magazine are covered on the Indexing mechanism page; fill-depth cams under tablet press punches on the Lower punch assembly in a rotary tablet press turret page; cam-driven terminal feed on the Terminal feeder of a crimp applicator page; and pressing rolling bearings into housings on the Bearing assembly page.
CNFX editorial research · Sources checked October 13, 2026 · 5 sources
Pressure angle on the rise: base circle, roller radius and the motion law
Chablat and Angeles define the pressure angle of a cam–roller-follower pair as the angle between the normal to both surfaces at the contact point and the direction in which that point of the follower moves; the smaller it is, the better the force transmission. For cams turning faster than 50 rpm they give a recommendation to keep it within 30°. [4]
Iowa State's handout gives the pressure angle of an in-line translating roller follower as the arctangent of the follower velocity divided by the cam angular velocity, over the sum of roller radius, base-circle radius and follower displacement. [5] Editorial calculation with its numbers: the simple harmonic rise reaches its highest velocity at half lift, where the slope is 1.5 × π / (2 × 1.347 rad) ≈ 1.75 in per radian and the radius to the roller centre is 0.5 + 3.5 + 0.75 = 4.75 in, giving about 20°. A cycloidal motion over the same angle peaks at 2 × 1.5 / 1.347 ≈ 2.23 in per radian, about 25°. Both sit inside the 30° recommendation. [4] Holding the same rise in a shorter cam angle, or using a smaller base circle, raises the angle; the editorial calculation shows how quickly, because the slope grows in inverse proportion to the angle allotted to the rise.
The formula above is for a slide moving in line with the cam centre. Rocker-arm followers, like the levers carrying rollers in machine cam boxes, have their own expression and need the profile designer's calculation. Chablat and Angeles assemble more than one cam on the same shaft as conjugate pairs that alternately take over the drive, so that the roller is driven throughout the cycle; in their slide-o-cam study, with at least two lobes, contact is lost once the pressure angle exceeds 20°. [4]
Ask the cam maker for the displacement diagram (rise, dwell and return angles and the motion law for each), the base-circle and roller radii, and the maximum pressure angle and minimum radius of curvature over the cycle at the shaft speed the machine will run.
02
The follower roller rides on the cam: track capacity against cam hardness, and the 50 % dynamic-rating limit
McGill's CAMROL catalogue treats the cam or track as the second component of a two-piece bearing: its material and hardness decide how much load the follower can put on it. McGill defines track capacity as the load a steel track of given tensile strength withstands without plastic deformation or brinelling, rated at 40 HRC (1,242 MPa tensile). [1]
Two caps apply whatever the cam hardness: McGill says dynamic load should not exceed 50 % of the bearing's dynamic rating as a track roller and static load should not exceed its static rating, and a crowned-OD follower is rated at 0.8 times the cylindrical track capacity. [1] McGill's metric table gives 5,340 N track capacity for its 22 mm MCFR-22 follower and 35,500 N for the 62 mm MCFR-62. [1] For SKF's stud-type cam followers of the same diameters, the KR 22 lists a basic dynamic load rating of 3.96 kN, basic static rating 5 kN and limiting speed 5,000 r/min [2], and the KR 62 PP lists 24.2 kN, 44 kN and 2,200 r/min [3]. Editorial calculation applying McGill's 50 % rule to SKF's ratings: about 1.98 kN dynamic on a KR 22 and 12.1 kN on a KR 62 PP.
SKF builds these followers on a needle roller bearing with a threaded solid stud in place of an inner ring and a thick-walled outer ring with a crowned running surface, which takes axial load from skew or tilting. [2] McGill credits the crown with spreading the stress from misalignment due to mounting inaccuracy or stud deflection, and the cylindrical OD with more track capacity through the larger contact area. [1]
On a cam, the follower turns faster than the cam: McGill multiplies cam rev/min by the ratio of cam OD to follower OD, prefers oil lubrication for cams because of the higher speed, and calls for frequent grease replacement where oil is not possible. [1] Editorial calculation: a 200 mm cam at 60 rpm turns a 22 mm follower at about 545 r/min. McGill also warns that a rapid rise produces instantaneous loads that must be kept below the follower's maximum recommended or static load, and that the load reversal in box cams can shock-load the stud. [1]
Cam or track hardness
Tensile strength
McGill track capacity factor
Editorial calculation: 2 in follower, cylindrical OD (7,350 lb at 40 HRC)
Give the follower supplier the cam surface hardness and material, the peak follower load from the cam's acceleration at the fastest rise (not only the static spring or process force), the cam OD and shaft speed, and whether the cam is open with a return spring or a box or conjugate design with load reversal.
03
Data to send with a cam and follower enquiry
Paste it into your enquiry below or into an email to a maker, then replace every bracket.
Motion: [rise, dwell, return angles; lift in mm; motion law per segment]
Shaft: [speed in rpm; number of cams on the shaft; phase between cams]
Follower: [translating slide or rocker arm; lever length; roller diameter]
Load: [process force; spring preload; moving mass on the follower]
Cam: [material; surface hardness HRC; open, box or conjugate pair]
Roller: [stud or yoke type; crowned or cylindrical OD; sealing; lubrication]
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Compiled and source-reviewed by the CNFX editorial team.
Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review
· Page last updated 13 October 2026
Buyer questions
What pressure angle should a plate cam stay within?
Chablat and Angeles give a recommendation of 30° for cams running faster than 50 rpm; the smaller the angle, the better the force transmission. [4]
Does the cam's hardness limit the follower load?
Yes. McGill rates track capacity at 40 HRC and multiplies it by 0.445 for a 26 HRC track and 2.780 for 58 HRC; dynamic load is still capped at 50 % of the follower's dynamic rating. [1]
Why does a cam follower need more lubrication than a track roller?
McGill notes that on a cam the follower speed is the cam rpm multiplied by the ratio of cam OD to follower OD, and prefers oil lubrication for cam applications. [1]
What load ratings does a 22 mm stud-type cam follower have?
SKF's KR 22 lists 3.96 kN basic dynamic load rating, 5 kN basic static rating and a limiting speed of 5,000 r/min. [2]
Sources and what still needs a direct check
Sources checked 2026-10-13. McGill's CAMROL catalogue and SKF's data sheets supply the follower ratings and the cam-hardness factors; a CK2005 paper by Chablat and Angeles gives the pressure-angle recommendation and conjugate-cam arrangement; an Iowa State course handout gives the pressure-angle formula and the worked cam schedule.
