How Many Disc Blades Do I Need? Gang Counting Guide

The single most common ordering mistake we see is undercounting blades. A customer orders 24 blades for what they call "the front gang" — then discovers there's actually a front and rear gang and each gang has 12 blades on each side. What looked like a 24-blade job was actually a 48-blade job. Here's how to count.

The basic formula

Total blades = (blades per gang) × (number of gangs)

On a tandem disc harrow you have 4 gangs: front-left, front-right, rear-left, rear-right. Each gang has anywhere from 8 to 15 blades depending on the machine's working width and blade spacing.

How to count blades per gang

Walk out to the machine, pick one gang, and count the blades. Include the "half blade" or shorter blade at the end of each gang if there is one — most machines have a short outboard blade that doesn't match the rest but still needs replacement.

Common machine counts

  • Case IH 3900 (25') — 4 gangs × 12 blades = 48 blades total
  • Krause 4900 (22') — 4 gangs × 9 blades = 36 blades total
  • JD 630 (24') — 4 gangs × 11 blades = 44 blades total
  • Sunflower 1435 (24') — 4 gangs × 11 blades = 44 blades total
  • JD 2623 (30') — 4 gangs × 15 blades = 60 blades total
  • Case IH True-Tandem 330 (25') — 4 gangs × 12 blades = 48 blades total
  • Great Plains Turbo-Till (30') — 4 gangs × 15 blades = 60 blades total
  • Wishek 862NT (22') — 2 gangs × 22 blades = 44 blades total (offset design)
  • Case IH 496 (18' offset) — 2 gangs × 18 blades = 36 blades total

These are rough — count your specific machine. Wider machines have more blades; older machines with wider blade spacing have fewer.

Not sure it fits your machine? Text a photo of your old blade to 515-686-5575 — we'll cross-check the diameter, thickness, and axle-hole shape against our catalog before you order. Same-day ship on orders placed by 12pm CT.

Notched vs. smooth per gang

Standard tandem setup: front gangs = notched blades, rear gangs = smooth blades. So on a 48-blade machine, you'd order 24 notched + 24 smooth. Some operators run all notched (more residue cut, less finish); some run all smooth (better finish, weaker residue cut). Order to match what you want, not just what came off.

How many spares to buy

Standard rule: 5-10% extras. On a 48-blade order, buy 4-5 spare blades. Reasons:

  • One or two blades will be damaged during shipping — rare, but happens
  • You'll drop a blade during install and dent an edge on concrete
  • You'll want a couple spares in the shop for mid-season replacement without shutting down for a full re-order

Bearings, spacers, and bolts

When you order a full gang of blades, plan to replace the gang bearings at the same time. Half the reason blades wear unevenly is worn gang bearings that let the axle wobble. Bearings are relatively cheap; if you've got the gang apart to replace blades, the incremental cost to replace bearings is low.

Spacers usually stay in place unless the machine has been through a wreck. Inspect for wear where the spacer meets the blade — deep wear grooves mean the spacer should be replaced too.

Gang bolts get replaced every second or third blade change. They stretch under torque and eventually fatigue.

Bulk pricing kicks in at 20+ blades

Our automatic bulk discount: 5% off orders of 4-19 blades, 10% off orders of 20+ blades. A full-gang order almost always hits the 10% discount. Free shipping on orders $600+ — which is nearly any full-gang order.

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Frequently Asked Questions

How many disc blades does a typical disc harrow have?
Tandem discs typically have 36-60 blades total (4 gangs × 9-15 blades per gang). Offset discs have 30-50 (2 gangs × 15-25 blades). The exact count depends on working width and blade spacing — count your machine to be sure.
Do I need to replace all the blades at once?
Not strictly, but running new blades alongside worn blades causes uneven cut depth and stresses the gang bolts. Best practice: replace gangs at a time. Move front-gang blades that still have life to the back gang, retire the worst blades.
How many extra spares should I buy?
5-10% of your total order. For a 48-blade job, buy 4-5 extras. Shipping damage, drops during install, and mid-season repairs all consume spares.
When should I replace the gang bearings?
When you're replacing blades — you've got the gang apart anyway, and worn bearings are the second-most-common reason blades wear unevenly. Bearings are cheap relative to blades; the labor is the same either way.
How do I count blades on an offset disc?
Offsets have 2 gangs, not 4. Front gang is longer than rear gang (or vice versa depending on the machine). Count each gang separately and add. Some heavy offsets have 20-25 blades per gang.