This is, of course, the standard for inexpensive, desktop, square-column, Asian milling machines, the Shanghai Sieg Industrial Co. Model X2. I purchased it new in 2001, and used only sporadically before 2003. It was apparently manufactured in lower-quality control times, because I eventually learned enough to discover that the horizontal way surfaces on the underside of the table were cupped, from end to end, at least .005".

Many owners have published complaints about the machine's lack of rigidity in the column, and the ever-breaking external spindle drive gear. Early in my machining attempts, I also made these complaints, while ignorant of their root cause. I eventually had the good fortune to take two semester's worth of machine tool classes at a community college. That education radically changed my understanding of the mini-mill, and corrected most of the problems I had experienced.

First, tramming in a Bridgeport mill spindle transformed from sketchy concept to solid understanding, and I applied this knowledge to aligning the mini-mill. Of course, the mini-mill doesn't have any built-in adjustment feature to tram the spindle in the y-plane. Or does it? I accomplished an accurate tramming by shimming under the bracket that clamps the column to the base, where the bracket bolts to the mill base. Besides achieving a perpendicular spindle, some of the column flexing that had previously been due to taking a vertically angled cut was eliminated.

Second, I learned how to calculate the correct rpm for a milling cutter. Lacking any specific knowledge of this before taking the class, I had simply assumed that since metal was tough, the end mill had to rotate slowly. Naturally, ignorance is bliss, and I blamed the resulting bouncing column on substandard machine design. I had tremendous problems, even taking a .005" cut. After learning that the correct speed for a .375" end mill to cut mild steel was something like 1300 rpm, I tried this with a four-flute, TiN-coated, US-made endmill. I was pleasantly surprised to find out that the mini-mill would take a .025" cut in CRS like a sharp knife through bread, with no chatter or column flexing or banging and bouncing around. I eventually tried cuts clear up to .100" deep, which the mill could do. However, that depth is impractical, since four .025" cuts take less time.

Finally came the discovery that it's really, really important to lock any axis that must not change during the cut. On the mini-mill it's particularly important to lock the z-axis, since the rack-and-pinion design of the mini-mill's vertical movement mechanism easily creeps down under the combined effects of gravity, vibration and cutting forces. This results in an increasinly deep cut, leading to, you guessed it, column flexing, jamming cutters, and a general banging and bouncing about. LOCK THE Z-AXIS BEFORE TAKING A CUT!!

As far as the breaking plastic drive gear is concerned, that has happened to me twice, but both times while fly-cutting in excess of the manufacturer's stated limits. With gears, this machine doesn't like flycutting. I've seen some belt drive conversions, and am planning on implementing the one described in the June/July 2002 issue of Machinist's Workshop. I've also read about other HSM's replacing the accursed, cheapo plastic gears with good old, durable, American-as-apple-pie metal ones. Bad idea, I think. The external drive gear is easy to replace, and while not terribly cheap at $11.00US (2004 price), takes only two or three minutes to change if a replacement gear available. I suspect a plastic gear was chosen in the first place at least partly to provide a controlled failure point in the drive mechanism, where the inevitable breakage by a novice user would be easy to for the user to fix, without serious disassembly or expense. I'm sticking with plastic gears until I do a belt conversion.

Over all, the X2 is a nice little machine, "little" being the operative word here. The most challenging size limitation is the width of the table, at a little less than four inches. It's difficult to work some pieces, which would otherwise be within the machines envelope, simply because the shape of the workpiece and narrow table conspire to make it impossible to hold the work solidly enough to mill. But with appropriately-sized work and 1/2" or smaller endmills running at the correctly calculated speed, it's does great work in all the materials I've tried (including brass, CRS, hot-rolled steel, stainless, and cast iron).

• Spring, 2004 - Remilled table way bearing surfaces - The cupped table ways were corrected by remilling them on a Bridgeport at school, using a reground carbide 3/8" lathe bit in a fly cutter. No need for an expensive dovetail cutter! I milled a maximum of .008" from the ways. After this was done, the table easily glides from end to end, with no binding.
• Fall, 2003 - Deburred all way edges in all three planes - The edges of the dovetails, as well as all gibs, had sharp, burred edges as delivered. I broke all of these edges with fine sandpaper. I also manually sanded the rough flats of the gibs. The ways are silky smooth now. The gibs can be tightened to a proper pressure, and everything still moves smoothly, which was definitely not the case when it was purchased.