The dealer counter is going away. Farmers are ordering more replacement parts online every year because the pricing is better, the selection is deeper, and the parts show up in 2-4 days instead of "let me see if I can get one in by next Thursday." But there's no counterperson to catch a wrong-spec order. Here's the 7-point checklist to make sure the blade that shows up actually fits.
1. Outside diameter
Measure your existing blade in inches. Not the worn diameter — the new-blade diameter. Blades wear from the outside in, so a 20" measurement on a worn blade might have started as 22". Look for the OEM spec stamped near the axle hole (usually a two-digit number like "24" for 24-inch), or reference the machine's operator manual for the new-blade size.
2. Thickness
Measure the flat body of the blade (away from the sharpened edge) with a caliper. 4-5mm for vertical tillage, 6mm for standard tandem discs, 8mm for heavy offsets. See our thickness guide for detail.
3. Center hole shape (square vs. round)
Look at the axle hole. Is it square or round? Almost every tandem disc uses square. Almost every coulter uses round. Some vertical-tillage machines run round-hole blades on splined axles. Get this right — it's the most common ordering mistake.
4. Center hole size
Measure flat-to-flat on a square hole (not corner-to-corner — corner-to-corner reads about 40% bigger than the flat-to-flat). Common: 1-1/8", 1-1/4", 1-1/2". For round holes, measure diameter. See our axle-size guide.
5. Edge type — notched or smooth
Notched blades have visible scallops around the outer edge; smooth blades are unbroken all the way around. Notched cuts residue aggressively; smooth finishes and levels. Standard tandem harrow setup: notched front, smooth rear. VT tools are usually all notched.
6. Number of notches (for notched blades)
Traditional harrow blades have 6-8 notches around the circumference. Vertical-tillage blades often have 13. Turbo coulters have 8-14 depending on manufacturer. If you're replacing a specific-profile blade (say, a Case IH True-Tandem 13-wave), match the count — a 6-wave blade in the same diameter and thickness won't perform the same at speed.
7. Concavity (dish depth)
Concavity is how much the blade dishes when you set it flat-side-down on a bench. Deeper concavity throws more soil sideways (good for primary tillage), shallower concavity slices more (good for VT). Most product listings state the concavity in inches (say, 2.5" for a standard tandem harrow blade). If the listing doesn't say and your machine is fussy, ask before ordering.
The photo-check shortcut
If any of the above is unclear, text a photo of your existing blade to 515-686-5575 — clear shot showing the outside edge (to see the notches and diameter) and the center hole (to see square vs. round). We'll cross-check against our catalog and confirm the exact SKU that fits before you order. Takes 5 minutes and prevents a wrong-blade return.
What to check when the blade arrives
- Compare the new blade side-by-side with the old blade. Same diameter (new-blade should be a couple inches bigger than a worn blade), same center-hole shape, same edge type.
- Check the edge for shipping damage. Small nicks are fine and will polish out in service. Deep chips or bent edges — call us and we'll exchange.
- Verify the thickness by eyeball or caliper.
Return policy
Standard: 30 days from delivery for unmounted blades. Once a blade goes into service on the machine, we can't take it back. So dry-fit one blade before installing the full gang — if it doesn't fit, stop and call us before you install any others.
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