Makita GA5042C grinder Sander and Grinder Reviews

Makita GA5042C 5 in. Grinder with SJS 2 Vibration Reduction


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, tuck pointing, and surfacing & planing masonry applications. Add up the various sizes, handle & switch options, corded & cordless models (like the Makita XAG03M 18V brushless grinder we reviewed earlier this year), and you get a veritable treasure trove of grinders for every imaginable applications and use. It’s actually a bit overwhelming to be honest… There is some discussion at Makita, in fact, that some simplification of the line might make a lot of sense—particularly when it comes to combining 4-1/2 in. and 5-in. angle grinders—which require very little differentiation in the tool construction itself. That brings me to the new Makita GA5042C 5 in. Grinder with SJS 2 vibration reduction.

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What Makita SJS 2 Technology Does (SJS II)

Makita GA5042C angle grinderMakita’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 2 uses the same basic gearing as SJS grinders, but upgrades the spiral bevel gear to have a longer design. The big deal is that they added a new leaf spring and cam gear to the drive mechanism which reduces vibration by leveraging the leaf spring against the cam during rotation. 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.

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Here’s a video of the new grinder in action:

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 tuck pointing and other dust collection needs.

And here is the High Power Makita GA502CX1 grinder with tuck point guard:

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

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

Makita GA5040X1 Angle Grinder

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

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

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