Professional Tool Reviews for Pros

Makita 5 in. Grinders with SJS 2 Vibration Reduction

Makita GA5042C grinder

Makita has a LOT of angle grinders—dozens if you count all of the corded and cordless variations—and I’m not talking about kitted and non-kitted. They literally have angle grinders for metal grinding, tuckpointing, and surfacing & planing masonry applications. We reviewed the Makita XAG03M 18V brushless grinder and found it powerful and compact. Makita 5-inch grinders with SJS 2 (SJS II) vibration reduction (like the GA5042C) feel like compelling tools.

Makita SJS 2 Technology (SJS II)

Makita GA5042C angle grinder

Makita’s SJS system (Super Joint System) has been out for some time. It’s a mechanical clutch that serves as a gear protection mechanism to keep the grinder from destroying itself (stripping gears and hurting the user) if and when it binds up. It’s basically a large coil spring that’s under constant tension. When binding occurs, however, the coil loosens, allowing one side of the drive shaft to slip. Since it’s a mechanical system and not electronic, it’s nearly fool-proof but limits what Makita could do with respect to the drive system.

To enter into the second phase—SJS 2 (SJS II) was developed. SJS 2 is mostly about vibration reduction. In fact, tools with SJS 2 have an updated electronic clutch system that uses a controller to monitor motor overload and shut down the tool when needed. SJS 2 angle grinders take this and the vibration reduction system and wrap them all into one.

SJS vs SJS 2 Vibration Reduction Technology

Makita SJS 2 technology uses the same basic gearing as SJS grinders. It then upgrades the spiral bevel gear with a longer design. They also added a new leaf spring and cam gear to the drive mechanism. This reduces vibration by leveraging the leaf spring against the cam during rotation. The vibration goes into the leaf spring and not the tool.

Makita SJS II system
Note the leaf spring that engages the cam, transferring vibration energy to the spring instead of to your hands and arms. The vibration reduction is quite tangible.

It’s all topped off with a vibration-reducing handle to further protect against unnecessary vibration during intense heavy duty grinding. Finally, the new Makita GA5042C 5 in. grinder adds a new “labyrinth” air flow system to cool the motor while keeping dust and debris from penetrating the gearbox and front armature bearing. We got to see and use one of these at the Makita 100 year anniversary event.

Makita GA5042C 5 in. Grinder Features

Aside from the SJS 2 technology, electronic motor protection, and updated airflow, the Makita GA5042C Grinder features dust-sealed drive bearings and an enlarged motor fan to increase air flow and keep the motor running cooler, longer. Also, because of that electronic motor control, the Makita GA5042C can now boost power when under load to maintain speed during a particularly difficult cut or grinding application. The result is more consistent work and less stalling. There’s also a nice soft start feature for suppressing that gyroscopic wobble and for extending gear life due to reduced startup stresses.

Makita GA5042C grinder tuckpoint shroud
Both the Makita GA5040X1 and GA5042CX1 5 in. angle grinders include dust shrouds suitable for tuckpointing and other dust collection needs.

Makita currently has four models with SJS II technology. This is the basic breakdown:

Makita GA4542C Angle Grinder

  • Grinder wheel size: 4-1/2 in.
  • Switch: Slide style
  • Tool-less wheel guard
  • Power: 12 amps
  • Speed: 2,800 – 11,000 RPMs
  • Weight: 5.4 lbs
  • Price: $184.99

Makita GA5042C Angle Grinder

  • Grinder wheel size: 5 in.
  • Switch: Slide style
  • Tool-less wheel guard
  • Power: 12 amps
  • Speed: 2,800 – 11,000 RPMs
  • Weight: 5.4 lbs
  • Price: $199

Makita GA5040X1 Angle Grinder w/Tuck Point Guard

  • Grinder wheel size: 5 in.
  • Switch: Slide style
  • Tool-less dust shroud
  • Power: 10 amps
  • Speed: 11,000 RPMs
  • Weight: 7.8 lbs
  • Price: $257.99

Makita GA5042CX1 Angle Grinder

  • Grinder wheel size: 5 in.
  • Switch: Slide style
  • Tool-less dust shroud
  • Power: 10 amps
  • Speed: 2,800 – 11,000 RPMs
  • Weight: 7.8 lbs
  • Price: $317.99

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