A stud type cam follower is a thick-walled roller on a threaded stud. The outer ring is through-hardened and ground to run directly on a cam profile or a track, and the stud carries the needle bearing inside it — so the part bolts on with one thread instead of needing a shaft and two supports. That makes it the default choice for guide rollers, cam mechanisms and conveyor tracks, provided the stud is short enough not to bend. CF and KR are the same component under two designation systems; the choice between them is a purchasing habit, not an engineering difference. Sealed, crowned and heavy-duty variants cover most positions.

CF & KR Stud Type Cam Followers

A stud type cam follower is a thick-walled roller on a threaded stud. The outer ring is through-hardened and ground so it can run directly on a cam profile or a track, and the stud carries the needle bearing inside it — so the part bolts on with a single thread instead of needing a shaft and two supports. That is what makes it the default choice for guide rollers, cam mechanisms and conveyor tracks, and also what limits it: everything the roller carries has to pass through one cantilevered stud. This page covers the CF and KR designations, the crowned-versus-cylindrical decision, mounting practice and the failure modes that matter.

What a Stud Type Cam Follower Is

Three parts make up the assembly. The outer ring is a thick-walled hardened sleeve, ground on the outside diameter to act as the running surface and on the inside to act as the outer raceway. Inside it sit either needle rollers in a cage or a full complement of cylindrical rollers. The stud is the inner raceway and the mounting element at once: it has a threaded end, a hex socket in the head, and usually a lubrication hole running down its axis to feed the raceway.

The design exists to remove structure. A yoke type track roller needs a shaft, two housing supports and an alignment operation; a stud type bolts into a tapped hole in a plate and is adjusted by turning it. That saves space and assembly time, and it introduces the one weakness the family lives with: the stud is a cantilever, and bending stress at the thread root grows quickly as the overhang increases.

Load direction follows from that. The roller carries radial load from the cam or track; it does not carry meaningful axial load unless it is a flanged variant. If your mechanism pushes sideways against the roller, the stud will not resist it — the flange or a separate guide does.

CF and KR: Two Designations, One Component

CF is the designation used in the Japanese and Asian catalogue tradition; KR is the German equivalent, from Kurvenrolle. Dimensionally the two families overlap so closely that the same position can usually be served by either, and in practice the difference is which standard the buyer's drawing was written to. Where a machine was designed in Europe, the drawing will say KR; where it came from Japan or was copied from a Japanese machine, it will say CF.

Suffixes carry the engineering content, and they differ slightly between the two systems. AUUsuffix indicates contact seals on both sides; an unmarked part is open and relies on the machine for lubrication. A-1suffix typically marks a wider roller within the same stud size, and crowned variants are called out separately or by a distinct suffix depending on the maker.

Because the suffix conventions are not perfectly aligned between CF and KR, the safe practice is to quote the full original designation plus the three key dimensions — outside diameter, roller width and stud thread — whenever a substitution is proposed. A part that matches on diameter and thread but differs in roller width will not fit the same track.

Crowned versus Cylindrical Outside Diameter

This decision is made once and then lived with. A cylindrical OD gives the largest contact area against a flat track and the highest load capacity for a given size, but it tolerates essentially no misalignment: a fraction of a degree of skew moves the contact to the edge and multiplies the stress there.

A crowned OD is ground with a slight spherical profile across the width. It tolerates angular misalignment between the roller and the track — typically up to about half a degree, more in some sizes — at the cost of a smaller contact area and therefore a lower load rating for the same envelope. Crowned rollers are the right answer for cam profiles, for tracks that are not perfectly parallel to the mounting plate, and for any mechanism assembled from welded or fabricated parts where alignment cannot be guaranteed.

The rule of thumb: if the track is machined and the mounting plate is machined, use cylindrical. If either is fabricated, use crowned. Getting this backwards produces either edge loading or unnecessary capacity loss, and both failures look like a bearing problem rather than a design choice.

Stud Thread, Torque and Mounting

The stud is the weak link, and mounting practice decides whether it survives. Thread engagement should be at least one and a half times the stud diameter in steel, more in aluminium or cast iron; a stud threaded only halfway into a soft plate will fatigue at the first thread rather than at the root, and the fracture surface looks different enough to identify afterwards.

Torque the stud to the figure for its size and material, using the hex socket in the head rather than gripping the roller. Gripping the roller to tighten the stud loads the bearing through the cage and can brinell the raceway before the machine ever runs. Where the position allows, add a supporting bracket or a through-bolt on the far side: halving the effective overhang can multiply the permissible radial load several times over.

Check the running clearance after mounting. The roller must not rub the mounting plate, and the seal must not be pinched against a washer. A cam follower that is tight against its support will overheat and destroy its seals within hours, and the symptom — grease weeping from a new part — is often misdiagnosed as a defective seal.

Load, Speed and Lubrication

Radial load ratings for this family are high relative to their size because the outer ring is thick and the rollers are short and stiff. The rating assumes a hardened track: running a cam follower against a soft steel cam will indent the cam, not the roller, and the resulting surface roughness then destroys the roller. Track hardness of roughly 55 HRC or better is the usual requirement for continuous contact.

Speed is limited by three things at once — the cage, the seals and the lubrication path. Open versions run faster than sealed ones, and grease reaches the raceway only through the stud hole or from the surrounding machine. In high-cycle cam mechanisms, the roller is often running at a fraction of its rated load but at a high number of revolutions, and the failure is lubrication starvation rather than fatigue.

Relubrication through the stud is the feature to use. Most stud type followers accept a grease nipple in the head, and a small amount of fresh grease at service intervals flushes contamination out through the seals, which is worth more than any grease specification. Where the position is inaccessible, specify a sealed and pre-greased part and accept the shorter life.

Failure Modes and What They Look Like

Stud fracture is the dangerous one. It starts as a fatigue crack at the thread root or at the transition from thread to plain shank, and it usually follows a period of edge loading or an over-long overhang. The fracture face shows a smooth initiation zone and a rough final break — a signature worth recognising, because the customer will often report it as a bearing failure.

Flat spotting on the outside diameter is the second. It comes from impact, from excessive preload against the track, or from a roller that is not turning at all in a high-load position — a condition called skidding. A skidding roller wears a flat in minutes and then hammers the track for the rest of its life.

Spalling is the third: flaking of the hardened surface, usually from a soft or rough track, or from water contamination reaching the raceway. Seal failure is the fourth, showing as grease loss and ingress of coolant or swarf. And loose studs are the fifth — a stud that has backed out of its thread is a mounting problem, but it presents as a noisy, wobbling roller.

Typical Applications

Conveyor and guide systems are the largest group: side guides, accumulation tables and curved tracks, where a row of stud type rollers carries product or holds a belt in line. Cam mechanisms follow — press feeds, packaging machines, labelling heads — where the roller translates a rotating profile into linear motion.

Machine tools use them for linear guidance and for retaining carriages. Agricultural equipment uses heavy-duty versions on planter and harvester mechanisms, where contamination and shock load are constant. Automated storage and lifting equipment uses them as guide rollers in mast sections. And repair work turns up in packaging lines and printing presses, where a single worn roller in a guide rail is enough to misalign a whole web.

The common thread is that none of these positions can be lubricated from the outside once the machine is enclosed. That is why relubrication through the stud, or a sealed part specified from the outset, matters more here than in any other product in the range.

Cross-Reference and Custom Sizes

Because CF and KR overlap, cross-referencing usually succeeds on the three key dimensions plus the thread. Where it does not, the difference is almost always the roller width or the seal arrangement, and both are visible on a photograph of the old part.

We supply non-standard roller widths, alternative stud lengths and threads, crowned profiles in sizes not held in catalogue, and stainless or coated versions for washdown and outdoor positions. For replacement work, send the old designation if it is legible, and the outside diameter, roller width, stud thread and overall length if it is not.

Measure the stud thread rather than assuming it. Metric coarse and fine pitches share the same diameter, and an M10×1.25 will start in an M10×1.5 hole and then bind halfway, which is how a good roller gets a damaged thread and a reputation for poor quality. Check the pitch with a gauge, not by eye, and include it in the enquiry — it takes ten seconds and avoids a rejected shipment.

Ordering, MOQ and Lead Time

Quote the full designation with suffix, the quantity, the track hardness if you know it, and the environment — dust, coolant, washdown or clean. Those last two inputs decide the seal material and the grease, and they are the difference between a part that lasts the life of the machine and one that is replaced twice a year.

Catalogue sizes ship from stock in workshop quantities. Custom stud lengths, special threads and crowned variants outside the standard range are made to order, with lead time confirmed against the drawing. For OEM programmes, state the annual volume as well as the first order, since stud type followers are frequently supplied on a schedule rather than as one-off purchases.

For scheduled supply, tell us whether the parts will be fitted straight from the box or held in stores. Stud followers stored loose in a bin knock against each other and damage the seal lips and the ground running surface, so tray packing is worth specifying for anything that will sit on a shelf.

Frequently Asked Questions

Are CF and KR the same part?

Functionally yes, and dimensionally they overlap heavily — CF is the Japanese and Asian designation, KR the German one. Suffix conventions differ slightly between the systems, so always quote the original designation together with outside diameter, roller width and stud thread when substituting.

Do I need a crowned or a cylindrical roller?

Crowned if the track or the mounting plate is fabricated and alignment cannot be guaranteed. Cylindrical if both are machined and parallel, because it carries more load in the same envelope. Choosing crowned where cylindrical would do costs capacity; choosing cylindrical where crowned is needed produces edge loading and early failure.

How tight should the stud be?

To the catalogue torque for the stud size and the material it threads into, applied through the hex socket in the head rather than by gripping the roller. Aim for thread engagement of at least one and a half times the stud diameter in steel, and more in softer materials.

Why did the stud break?

Almost always bending fatigue from too long an overhang, insufficient thread engagement, or a period of edge loading that raised the stress at the thread root. Shorten the overhang, add a support bracket, and check that the roller is running flat against its track rather than on one edge.