Skid Steer Planer: Sizes, Hydraulic Flow and Uses

The short answer

A skid steer planer is a cold milling head that bolts to the quick-attach plate of a skid steer or compact track loader. A drum studded with carbide bits spins inside a steel housing and grinds asphalt or concrete into millings, while two skis riding on the pavement set how deep the drum bites. Common drum widths run from about 14 to 24 inches, with a few 40- and 48-inch heads for loaders that have high-flow or super-flow hydraulics. Most heads cut 5 to 7 inches deep at most.

The key thing to get right before you rent or buy one is hydraulic flow. A planer that needs high flow will not do much on a standard-flow loader, and a big head on a small machine just stalls. The rest of this guide covers how a planer works, how the sizes compare, the jobs it is good at, a worked tonnage example, and what to check at the rental counter.

How a skid steer planer cuts

Bobcat describes the basic mechanism plainly: carbide-tipped bits mounted on a revolving drum cut and pulverize the pavement, the milled material leaves through an opening at the back of the housing, and the operator sets depth and angle by raising or lowering the left and right skis. Depth gauges on each ski can be read from the cab. Because the skis keep contact with the surface, the cut stays steady even when the loader rocks over rough ground.

Three adjustments matter on almost every head:

Depth, side to side. Cat says independent left and right depth control is mechanical on its small PC104 and PC105 planers and hydraulic on the PC305 through PC412 models. Setting one ski lower than the other cuts a slope, which is how crews taper an edge or cut a shallow drainage line.
Tilt. Cat lists about 8 degrees of tilt each way on its PC305 and PC306. Bobcat's newer heads oscillate up to 8 degrees either way, and its oscillating float mode lets the head follow the pavement instead of the loader.
Side shift. A hydraulic side shift slides the drum sideways so you can mill tight to a curb, wall or slab without driving the loader against it. Cat lists 29.5 inches of side shift on the PC306.

Drum choice changes the result too. Bobcat's standard drum is a fast-cut drum. Its smooth-cut drum carries nearly twice as many bits and leaves a smoother surface, which is the one to use when the milled area will stay exposed to traffic. A slot-cut drum, 2.5 or 4 inches wide, cuts a narrow trench for a utility line. If you need a very fine texture over a large area, that is a different process; see our guide to micro milling asphalt.

Skid steer planer sizes compared

The table below pulls published specifications for two common lines. They show how width, depth and hydraulic demand move together. Check the current spec sheet and compatibility chart for the exact head and loader you plan to use, because models and options change.

Model	Cutting width	Max depth	Loader hydraulics	Optimal flow	Weight
Cat PC104	14 in	6 in	Standard flow	16–22 gpm	1,504 lb
Cat PC105	18 in	6 in	Standard flow	21–30 gpm	1,629 lb
Cat PC305	18 in	7 in	High flow	26–33 gpm	1,870 lb
Cat PC306	24 in (23.6)	6.7 in	High flow	26–33 gpm	2,108 lb
Cat PC306 XD	24 in	10 in	High flow XPS	26–33 gpm	3,109 lb
Bobcat 14″	14 in	6 in	Standard flow	see dealer sheet	1,477 lb
Bobcat high flow 18″	18 in	7 in	High flow	see dealer sheet	1,830 lb
Bobcat high flow 24″	24 in	7 in	High flow	see dealer sheet	2,160 lb
Bobcat high/super flow 40″	40 in	5 in	High or super flow	see dealer sheet	2,300 lb
Bobcat super flow 48″	48 in	5 in	Super flow	see dealer sheet	2,524 lb

Cat figures are from its cold planer specalog and the PC306 product page; Bobcat figures are from its North American planer attachment page. Cat lists optimal pressure of 3,050–3,300 psi for the PC104 and PC105 and 3,300–4,000 psi for the high-flow PC305 and PC306.

Standard flow or high flow: matching the head to the loader

A planer drum is driven by a hydraulic motor, so cutting power depends on how much oil the loader can push and at what pressure. That is why Cat rates its 14-inch PC104 for 16 to 22 gallons per minute on a standard-flow machine but asks for 26 to 33 gallons per minute, high flow, on the 24-inch PC306. Cat's compatibility chart marks the PC305, PC306 and PC310 as needing the high-flow option, and the XD heads as needing high flow XPS.

Bobcat frames the choice the same way. Its standard-flow planers suit owners who only plane now and then and want a lower purchase price. Its high-flow planers use the extra hydraulic horsepower of a high-flow loader, and its super-flow heads are built for loaders with super-flow hydraulics.

In practice, look up two numbers before you book a head: the loader's auxiliary flow and pressure (on the operator's manual or the machine spec sheet), and the planer's required range. If the loader falls short, choose a narrower standard-flow head and plan on more passes.

Jobs a skid steer planer does well

Cat describes its planers as tools for small residential and commercial paving jobs: milling out imperfections before resurfacing, removing deteriorated pavement, taking off traffic lane stripes, and working where a full-size milling machine is not practical. Bobcat's list of top tasks adds matching uneven pavement surfaces, cleaning up around larger milling machines, cutting drainage in a parking lot, milling around manholes and tapering roadway edges.

For a homeowner or small contractor, the common uses are:

Patch preparation. Milling out a failed area leaves a flat bottom and straight sides, so the new mix sits at full thickness instead of feathering to nothing. Our article on why a pothole patch should be cut square explains why that edge matters.
Tie-ins and transitions. Cutting a wedge where new asphalt meets a garage slab, a sidewalk or an old drive, so the overlay ends flush instead of leaving a lip.
Removing humps and high spots. Grinding down a ridge, a root heave that has been dealt with, or an old speed bump.
Edges and tight spots. Working along curbs and around structures where a big machine cannot reach.

Where it is the wrong tool: milling an entire parking lot or street. A loader-mounted head is narrow and has no conveyor, so millings pile up and must be loaded separately. For large areas, a dedicated cold planer is faster; our guide to the road milling machine shows how those machines work.

Worked example: milling out a driveway edge

Say a 40-foot strip along the edge of a driveway has broken up. The strip is 3 feet wide, and you plan to mill 2 inches and repave it with hot mix. Here are the numbers, step by step.

Step	Calculation	Result
In-place volume removed	40 ft × 3 ft × (2 ÷ 12) ft	20 cubic feet
Weight removed (assumed 145 lb/ft³ compacted asphalt)	20 × 145	2,900 lb, about 1.45 tons
Loose millings volume (FHWA range 120–140 lb/ft³)	2,900 ÷ 140 to 2,900 ÷ 120	about 21 to 24 cubic feet (0.8 to 0.9 cubic yard)
Passes with a 24-inch drum	36 in ÷ 24 in, rounded up	2 passes (second pass overlaps)
Passes with a 14-inch drum	36 in ÷ 14 in, rounded up	3 passes
Hot mix to replace it (same 145 lb/ft³, before waste)	20 × 145 ÷ 2,000	about 1.45 tons

The 145 pounds per cubic foot figure is a planning assumption, the same one our asphalt tonnage calculator uses; your plant ticket is the real weight. The millings range comes from FHWA's user guidelines for reclaimed asphalt pavement, which put milled or processed RAP at 120 to 140 pounds per cubic foot depending on the aggregate and moisture. For more on what loose millings weigh by the yard, see how much a yard of asphalt millings weighs.

Two takeaways from the math. First, even a small strip makes most of a cubic yard of loose millings, so plan where they go: a trailer, a dumpster, or a pile you will spread and compact elsewhere. Second, drum width changes the pass count more than anything else, so a 24-inch head on a high-flow loader can save real time on wider strips.

Running a planer: setup and good habits

Measure and mark the cut. Lay out the area with a measuring wheel and paint straight lines with inverted marking paint. Take the cut back to sound pavement, not just the visible hole.
Call before you cut. Shallow utilities and irrigation lines can sit close to the surface at driveway edges. Use your state's 811 service before any milling that might reach the base.
Set both skis. Zero the gauges on the existing surface, then set the depth you want on each side. Use a deliberate ski difference only when you want a slope.
Run the drum, then lower. Bring the drum up to speed before it touches the pavement, and creep forward slowly. Pushing too fast lugs the motor and wears bits.
Overlap passes. Overlap each pass slightly so no ridge is left between them, and use the side shift instead of steering into curbs.
Check the bits. Worn or missing bits leave grooves and slow the cut. Rental heads should come with bits in good shape; ask.
Clean the cut. Sweep and blow out loose millings and dust before tack and new mix go down, so the patch can bond.

Dust, silica and noise

Milling throws dust, and both asphalt aggregate and concrete can contain crystalline silica. OSHA's construction silica standard, 29 CFR 1926.1153, includes a Table 1 of task-based controls. It lists walk-behind milling machines and drivable milling machines and calls for water delivery or dust collection. A skid steer planer attachment is not named in Table 1. For tasks not listed, an employer has to keep each worker's exposure at or below the permissible exposure limit of 50 micrograms per cubic meter as an 8-hour time-weighted average and assess exposure under the standard.

The practical answer is water. Bobcat offers an integrated water kit on several heads, and says it suppresses dust and lubricates the bits to extend their life. Cat also lists a PC306 variant with a water tank. For a weekend job at home, wet the surface, keep people and pets out of the dust, and wear eye protection. A loader running a planer is loud, so hearing protection such as 3M Peltor Optime 105 earmuffs is worth wearing.

Renting a skid steer planer: what to ask

Rental yards often stock a planer head or two next to their loaders. Prices vary a lot by region, so get a quote and ask:

What drum width is it, and what is its maximum depth?
Does it need standard flow or high flow, and will it work with the loader I am renting or already own?
Are the bits fresh, and is bit wear billed separately?
Does it have a water kit, and how do I fill it?
Is a fast-cut or smooth-cut drum fitted, or can I get a slot-cut drum for a trench?
Can I dump millings at your yard, or do I need my own disposal plan?

If the job covers more than a few hundred square feet, also get a price from a paving contractor with a dedicated milling machine. Paying a crew for an hour can beat a full-day attachment rental plus loading the millings yourself.

Skid steer planer FAQ

What size skid steer do I need for a planer?

Match the planer to the loader's hydraulic flow rather than its size. Cat rates its 14-inch PC104 for 16 to 22 gpm on standard flow, while its 24-inch PC306 needs high flow at 26 to 33 gpm. Check the attachment's compatibility list for your loader model.

How deep can a skid steer planer cut?

Most heads cut 5 to 7 inches at most. Bobcat lists 6 inches for its 14-inch planer, 7 inches for its high-flow 18- and 24-inch heads and 5 inches for its 40- and 48-inch heads. Cat's PC306 XD reaches 10 inches on high flow XPS loaders.

Can a skid steer planer cut concrete?

Yes. Both Cat and Bobcat describe their planers as tools for milling asphalt and concrete. Expect more bit wear in concrete, and control the dust with water.

Is a skid steer planer the same as a milling machine?

It does the same kind of cut with a toothed drum, but it is much narrower and has no conveyor. It suits patches, edges and tie-ins, while dedicated cold planers handle whole streets and lots.

Do I need water when using a planer?

Water is strongly recommended. Bobcat says its integrated water kit suppresses dust and lubricates the bits, and OSHA's silica rule for construction expects dust controls on milling work.

The bottom line

A skid steer planer turns a loader into a small cold milling machine for patches, tie-ins, high spots and edges. Pick the head by the loader's hydraulics first: standard-flow heads around 14 to 18 inches wide, high-flow heads up to 24 inches, and super-flow heads up to 48 inches. Most cut 5 to 7 inches deep. Mark the area, overlap your passes, use water against dust, and plan for the millings, which come to almost a cubic yard even on a modest 40-foot strip.

Sources checked for this article

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