Why Do Breaker Pistons Crack? 3 Common Causes & Solutions
26 November 2025
The piston is the most strategic part of the breaker, converting hydraulic energy into impact energy and transmitting it to the tool. It is the hardest part to manufacture, with the most precise tolerances (micron level).
HKM Pistons are manufactured from special alloy steel, heat-treated to increase core hardness, and precision ground. However, user errors can crack even this robust part.
1. Why Does a Piston Crack or Break?
90% of damaged pistons arriving at our service center show the following causes:
- Blank Firing: Operating the breaker while the tool is not in contact with the rock. Piston energy strikes the housing.
- Worn Bushings: If the lower bushing is worn, the tool wobbles. The piston strikes the tool off-center, causing the tip to break.
- Dirty Oil: Particles in the hydraulic oil enter between the piston and cylinder, scratching the surface (scoring).
2. Can a Piston Be Repaired?
Since pistons are expensive, customers often ask about repair (chrome plating, grinding). However, HKM warns:
| Process | Risks and Advice |
| Light Polishing | Possible. Can be saved without ruining tolerances. |
| Welding & Grinding | NOT RECOMMENDED. Heat treatment structure is destroyed, it will break again. |
| Chrome Plating | Short-term solution. If plating peels off, it destroys the cylinder. |
3. Compatible Brands
HKM Pistons are manufactured according to the original weight and diameter standards of every brand and model:
- Atlas Copco (Epiroc): SB 202, SB 302, MB 1500, MB 1700, HB 2000, HB 2500.
- Rammer: S 23, S 25, S 27, E 68, G 80, G 100.
- Furukawa (FRD): F 6, F 9, F 22, F 27, F 35, FX 25.
- Soosan: SB 81, SB 100, SB 121, SB 151.
- Others: MSB (Saga), Daemo (DMB), D&A, Okada, Krupp, Indeco, DNB, MTB.