Sharpening vs. Replacement: When Should You Buy New Shear Blades?

Introduction

In any sheet metal fabrication shop, budget is king. When your hydraulic shearing machine starts leaving burrs or tearing metal, the first question is always: “Can we just sharpen these blades?”
Regrinding (sharpening) is significantly cheaper than buying a new set. However, there is a limit to how many times a blade can be ground before it becomes useless—or worse, dangerous to your machine.

At JSTMT, we want you to get the maximum life out of your tooling. In this guide, we break down the math and mechanics of Sharpening vs. Replacement.

 

1. The Hidden Cost of Sharpening (The Shimming Problem)

Many operators forget that shear blades have precise dimensions (Thickness x Width x Length).
When you sharpen a blade, you are removing material (usually 0.5mm to 1.0mm).

• The Issue: Once the material is removed, the blade is now thinner than the factory specification.
• The Consequence: If you install a thinner blade, the gap between the upper and lower knives will be massive. You will not be able to cut thin sheets.
• The “Band-Aid” Fix: To fix this, you must install Shims (metal spacers) behind the blade to push it back out to the correct position.

Why this is risky:
If the shims are not perfectly flat, or if debris gets behind them, the blade will crack under the tons of hydraulic force. Buying new blades eliminates the need for risky shimming.

 

2. When to Sharpen (The Green Light)

You should sharpen your blades if:

• Rounded Edges: The edge is simply dull (shiny radius), but there are no deep chips or cracks.
• Minimal Material Removal: You only need to remove 0.2mm – 0.5mm to restore the edge.
• Original Hardness: The blade has not been overheated (turned blue) during previous cuts.

 

Pro Tip: After sharpening, you must reset your machine settings. Read our guide on [How to Adjust Shear Blade Gap Clearance] to account for the new blade dimensions.

 

3. When to Replace (The Red Light)

You must stop using the blades and order a replacement set immediately if you see these 3 signs:

A. Deep Cracking or Chipping

If the blade has a crack running vertically or a chip deeper than 2mm, do not grind it.
Grinding deep enough to remove a large chip will remove the “Hardened Zone” of the steel. You will be left with the soft core material, which will dull in 2 days.

B. The “Bow” Effect

If your shear has been cutting short pieces in the center of the bed for years, the blades will wear unevenly (like a banana).
Grinding a bowed blade flat again often requires removing too much material (2mm+). At this point, the blade is too thin to be safely clamped.

C. You Are Cutting Stainless Steel

If you are switching from Mild Steel to Stainless Steel, your old standard blades (likely 6CrW2Si) will fail.
Instead of sharpening the old ones, you should invest in [H13 / 12CrMoV Shear Blades] . These are specifically heat-treated to resist the high tensile strength of stainless steel without chipping.

4. The Economic Verdict: ROI

• Sharpening Cost: $200 – $400 + Downtime + Shimming Labor.
• New Blade Cost: $800 – $1,500 (depending on length).

If you have to shut down your machine for 2 days to figure out the “Shimming” on reground blades, you have already lost more money in production time than the cost of a new set.

Recommendation:
Keep one set of sharpened blades as an emergency backup, but run your daily production on Factory-New Precision Blades to ensure consistent cut quality.

Ready for a Fresh Edge?
Don’t risk your machine’s accuracy with over-ground tools. JSTMT manufactures precision-ground [Replacement Shear Blades]  for Amada, Accurshear, LVD, and custom guillotine machines.