Hitachi G12SR3 4.5" angle grinder 6.0 amp

[jakeru]

I recently picked up a few 4.5" Hitachi angle grinders (each model number G12SR3, rated 6.0 amp) refurbished. Got them from this vendor:
http://bigskytool.com/Hitachi_G12SR3...d)___i967.aspx





So far, the Hitachi grinders seem to be decent. Compared to the Harbor Freight 4.5 amp "drill master" grinders that I'm most used to (which can be had for $10 with a coupon), the Hitachis run much smoother and quieter.

I think a large part of the smoothness and quietness may be simply because the pinion gear is rigidly fastened/secured to the electric motor shaft (via threaded nut) on the Hitachi design:


In contrast with the above pic, the pinion gear dsign on the Drill Master "floats" on the keyed motor shaft. The floating gear apparently adds considerable rotational backlash, also imprecisely controlled gear clearance. I feel like it may be hard on the nearby bearing (I've already experienced one failure in this bearing in my fleet of Harbor Freight grinders.)

The gear ratios are quite different between the different grinders (3.9 on the Hitachi versus 3.0 for the Harbor Freight), which would seem to help the Hitachi run at a slower, but more consistent speed. I was impressed by how much grease there was in the gearcases of these refurbished Hitachis:


The electric motors between the two different grinders are actually very similar in many respects (same diameter and number of poles, and number of commutator segments) but the Hitachi 6.0 amp motor is significantly longer than the 4.5 amp Drill Master motor. There is no epoxy encapsulation on the motor windings on either.


The cooling fan design seems more sophisticated on the Hitachi (curved vanes with conical air diffuser) than on the Drill Master (straight blades and flat air diffuser), which may contribute to the reduced noise of the Hitachi.


The overall package of the Hitachi feels nice and it doesn't seem overly bulky, long, or cumbersome. However, the 6.0 amp Hitachi unfortunately does add on some significant extra weight compared to the 4.5 amp Harbor Freight.

Specifically, the bare Hitachi weighs 3.3 lbs (versus 2.8 lbs for the bare Drill Master). And when the guard, handle, and disc retaining hardware are included, the weight of the Hitachi goes up to 4.6 lbs (versus 3.5 lbs for the drill master). The guard and disc retaining hardware seem overkill in terms of material thickness on the Hitachi.

Although I don't expect to be able to put extra power to work on most flap wheel jobs that I often do (where the speed is usually limited by rate heat in the work can dissipate), I am looking forward to using it on jobs involving using a cutting wheel or disc grinder on thicker metals where the extra power might come in handy. I can see myself however reaching for the Hitachi most of the time, even if only because of how much quieter and smoother it is.

-edit-
Almost forgot to mention another sign of the Hitachi tool having quality is that the spindle lock button on the Hitachi works very accurately, with little slop. (The Drill Master spindle locking button has tons of slop, and racks sideways like crazy.)