Tool · Walk-behind mower blades
Blade center-hole identifier
A mower blade center hole chart: how to measure round holes, how star and bow-tie holes are named, how Oregon's catalog names them, and the blades listed with each.
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Short answer
Pick the center-hole shape on your old blade below: round, 5-, 6- or 7-point star, bow-tie or S-shape. Each page explains how to measure or name that hole, what it mounts to and the blades listed with it. A matching hole name is where the check starts, not where it ends: length, width, thickness and the maker's listing still decide fit.
- Round center hole
- 5-point star center hole
- 6-point star center hole
- 7-point star center hole
- Bow-tie (H-pattern) center hole
- S-shape center hole
Choose your center hole to see the key facts and what fits. Each fact links to its source on the full page.
Measured or named
Some holes are measured and some are named. USA Mower Blades notes that round center holes are measured by inner diameter, rounded-rectangle holes by inner length and height, and star and H-pattern (bow-tie) holes are identified by name rather than measurement.[1] So "5/8 in round" and "5-point star" are both complete hole descriptions, of different kinds.
How catalogs name holes
Oregon's Blades by Length catalog records center holes as round sizes, 5-point star, 7-point star, "Y, 6 pt. star" and bow-tie, so every hole name comes with a part-specific record.[2] Aftermarket names do not always match the shape on the spindle:
- Oregon explains that MTD-built blades with a 6-point star are replaced by Oregon blades with a Y-shaped center hole that fits the 6-point star on the spindle.[3]
- Oregon explains that MTD-built walk-behind blades with a bow-tie hole are replaced by Oregon blades with a rectangular center hole that fits the bow-tie pattern on the blade adapter.[3]
Both are Oregon's statements about MTD-built blades. Do not extend them to other makers.
Where the data comes from
The hole pages draw on Oregon's catalog and product pages, the blade makers' own pages, and USA Mower Blades' measuring guide. We read those sources; we do not measure blades. A field marked "Not confirmed" means no source we could read states it.
If you cannot identify the hole
Look for the part number stamped on the blade and search it in the part-number guide, or find the blade in your mower's parts list with the mower model parts finder. The center-hole shapes guide covers look-alike holes.
Next
- Round center hole
- 5-point star center hole
- 6-point star center hole
- 7-point star center hole
- Bow-tie (H-pattern) center hole
- S-shape center hole
Choose your center hole to see the key facts and what fits. Each fact links to its source on the full page.
Questions
How do I measure a round center hole?
By its inner diameter. USA Mower Blades measures round holes by inner diameter and identifies star and bow-tie holes by name instead.[1]
Why does Oregon list a Y-shaped hole for my 6-point star blade?
Oregon says its blades with a Y-shaped center hole replace MTD-built blades with a 6-point star and fit the 6-point star on the spindle. That is Oregon's statement for MTD-built blades only.[3]
If the hole matches, will the blade fit?
Not on that alone. Oregon's Blades by Length catalog records each hole with a part-specific record that also gives length, width, thickness and offset. Check those and the maker's listing.[2]