Now you went and did it... After seeing the pics from the Northern Tool grinder, I want one just because of the metal construction.
I have a Harbor Freight grinder and as DOLMARatOs stated, they are cheaply made. BUT, if you have a little patience and some imagination, the Harbor Freight grinder can become something useful.
I found the hinge to be sloppy and would not keep a precise angle on the cutters. The clamp was too wide (for most of my applications) and failed to hold the chain securely in the vise. And the wheel arbor is made of plastic and only pressure fitted onto the motor arbor (which resulted in the wheel sliding away from and off of the motor arbor).
I made some improvements to mine. I tapped the motor arbor and the plastic wheel arbor is now held in place by a washer and bolt. The plastic hinge holes were drilled out and fitted with brass bushings, and the hingle bolt was replaced by a longer 3/8" hex bolt that now is very precise. And lastly, the chain clamp was fitted with thinner washers to make a tighter fit on the chain (that I mostly use).
These improvements are not much, but they have created a totally different breed of machine. The grinder works so much better than when first tested on an old chain. The angles are near perfect and provide an even grind every time now.
Just some food for thought for those with tight budgets. If I had a picture account thingy, I could post some pics. Anyway, I figured if I sharpened 9 chains with it, I got my money back out of it.