Size a poly edge for a sidewalk machine by measuring the mouldboard’s true cutting width, the existing bolt pattern (pitch, diameter, edge setback), and the machine’s down-pressure and surface mix — then select the poly section thickness and hole layout that matches those three inputs rather than the nominal blade width on the label. The poly edge must sit flush against the mouldboard’s bottom flange and clear the side plates through full trip travel. Everything below works from those measurements.
Start from the mouldboard, not the box
Poly edges are sold by nominal width, but the machine only cares about the bolt line and the mouldboard’s bottom flange. Measure the flange width, the bolt pitch from the centre line outward, and the distance from the front bolt row to the leading edge. A poly edge that overhangs the flange by more than a small margin will curl under load; one that sits short leaves the steel carrier exposed.
- Cutting width: overall mouldboard width minus side-plate clearance, measured at the bottom flange.
- Bolt pitch: centre-to-centre along the row, plus any offset second row.
- Bolt diameter and grade: match the carrier’s existing hardware; do not upsize holes to fit a different bolt.
- Setback: front bolt row to leading edge, which sets how much poly projects past the carrier.
- Thickness: poly sections are commonly supplied in a range of thicknesses; the correct one depends on machine weight and down-pressure.
Match the hole pattern before anything else
Hole layout is the hard constraint. Poly cannot be re-drilled reliably in the field without risking stress risers, so the pattern must match the carrier on the first order. Confirm pitch, hole diameter, countersink or plain bore, and whether the pattern is symmetric or handed.
| Parameter | What to measure | Why it matters |
|---|---|---|
| Bolt pitch | Centre-to-centre along the row | Mismatch prevents assembly; slotting weakens the edge |
| Hole diameter | Bolt shank plus clearance per carrier spec | Oversize holes allow edge movement and bolt loosening |
| Setback | Front bolt row to leading edge | Controls projection and wear pattern |
| Section thickness | Per carrier and machine class | Affects stiffness, trip clearance, and service life |
| Handedness | Symmetric or left/right | Prevents reversed fitment on angled carriers |
Fitment by model is listed in the product page comparison table. Where the machine is older or modified, treat the carrier as the authority and verify against the carbide snow plow blade specification sheet before ordering.
Thickness and down-pressure
Poly edges deflect under load, and the amount depends on section thickness, unsupported projection, and the machine’s down-pressure. A sidewalk unit with light down-pressure and a short projection will run a thinner section than a utility tractor with a heavy carrier. There is no single correct thickness across machine classes; the range that works is set by the carrier and the surface mix.
- Record machine class and typical down-pressure at the edge.
- Measure unsupported projection past the carrier’s front bolt row.
- Note surface mix — brushed concrete, asphalt, pavers, gravel shoulder.
- Select thickness from the range the carrier was designed for; confirm trip clearance at full deflection.
- Verify side-plate clearance through the full trip arc, not just at rest.
Wear life and cost depend on the surface mix
Poly life varies widely with abrasive content, down-pressure, and operator technique. On brushed concrete with light down-pressure, a poly edge can run for a long service interval; on abrasive asphalt or gravel-contaminated pavement, the same section may wear noticeably faster. Cost per hour therefore depends on the route, not just the part price.
Two field checks shorten the feedback loop. First, if one end of the edge is wearing faster, check carrier alignment and bolt torque before changing the specification — see one end of the edge wearing faster. Second, if edges are being flipped or reversed to extend life, confirm the carrier and hole pattern actually permit it; the rules are set out in can you flip a cutting edge. Both checks cost less than a premature reorder.
Confirm clearance and hardware
Before the edge goes on, confirm trip clearance, side-plate gap, and hardware grade. Poly edges are typically fastened with the carrier’s specified bolts and washers; reusing worn or incorrect hardware is a common cause of loosening and edge loss.
- Check full trip travel with the edge fitted — no contact with side plates or frame.
- Confirm bolt grade and torque value against the carrier specification.
- Verify the edge sits flat on the flange with no gap at the front row.
- Record the fitted pattern and thickness for the next order; the product page comparison table is the reference for model fitment.
Quick summary
Size the poly edge from the mouldboard’s cutting width, the carrier’s bolt pattern, and the machine’s down-pressure and surface mix — not from the nominal blade width. Thickness and service life fall within ranges that depend on the route and carrier, so confirm fitment against the model comparison table before ordering.
Sources checked on 2026-11-08: SENTHAI Tools product specification sheet for carbide snow plow blades (dimensions and hole patterns); carrier fitment notes in the product page comparison table; field notes on edge wear and reversible-edge rules from the linked talk pages.
Three more perspectives
Limits
This page is not a fitment chart and does not replace the carrier manufacturer’s specification. It does not cover hydraulic trip systems, steel-edge selection, or pavement-marking compliance. Dimensions and hole patterns must be confirmed against the product page specification for the specific model; where the machine is modified or the carrier is non-standard, measure the carrier directly.
