Tsakami Precision Automatic Lathe: BM163-II, BM164-II and BM165-II

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  What a Tsakami precision automatic lathe actually does
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  How the BM163-II, BM164-II and BM165-II differ
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  Cycle design: cams, guide bushing and tool sequencing
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  Where the cam design stops being the right answer
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  Holding size: inspection and process control on small parts
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  When each machine type fits the job

A Tsakami precision automatic lathe is a sliding-headstock machine driven by cams rather than servo axes. The bar sits in a spindle that moves along the Z axis, and the cutting tools sit close to a guide bushing. Because the tool never moves far from the bushing, a long, thin part stays supported right where the cut happens. That is the whole reason the layout exists: rigidity comes from the guide bushing, not from the tool holder.

The BM163-II, BM164-II and BM165-II follow the same idea with different sizes and spindle counts. A camshaft rotates, followers move the tool slides, and the cycle repeats exactly as many times per hour as the cam allows. There is no controller interpolating a path. The shape of the cam is the program.

That difference matters when you quote a job. A cam machine is fast and repeatable, but a design change means a new cam, not a new line of G-code. For a part that will run for years without change, that trade is good. For a part that may be revised next month, it is not.

One more point that engineers often miss: the guide bushing sets the practical minimum diameter. Below roughly Ø0.3 mm the bar can whip or buckle before it reaches the tool, so the bushing support stops helping and the process becomes unstable.

The three models share a family design, so the differences are mostly about work envelope and how many operations can run at once. A single-spindle layout cuts one part per cycle and is easier to set up. A multi-spindle layout cuts several parts per cycle and multiplies output, but it also multiplies setup time and the cost of a mistake.

Bar capacity is the first thing to check against your drawing. If the finished diameter sits close to the bar size, you lose the radial clearance that the guide bushing needs, and the last few tenths of a millimeter get hard to hold. A machine that is one size up from the part is usually the better fit.

Spindle count decides the hourly rate more than spindle speed does. Two spindles at moderate speed often beat one spindle pushed to its limit, because the second spindle keeps cutting while the first one indexes. This is the main reason shops keep these machines for high-volume small parts.

Tool positions vary between the models as well. Front and rear slides can hold turning, grooving, threading and cutoff tools, and some setups add a drilling or milling station on the sub side. If your drawing needs a cross hole or a milled flat, check that the chosen model has a driven station free before you commit.

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  Single spindleOne part per cycle, faster setup, lower hourly output
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  Multi spindleSeveral parts per cycle, higher output, longer setup
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  Bar sizePick one size above the finished diameter for bushing clearance

A cycle is a sequence of overlapping motions. The headstock feeds the bar forward, the front slide turns the outside diameter, a rear slide may groove or form, a drill advances on the face, and the cutoff tool separates the part. Each motion is tied to a cam angle, so overlapping two motions in time is how the cycle gets short.

Overlapping has a limit. Two tools cutting at once push the part from two directions, and a slender part will deflect. The usual answer is to split the overlap: let the heavier cut run alone, then overlap the lighter finishing and drilling motions. That keeps cycle time low without losing size.

Guide bushing clearance is the single biggest factor in size control on this type of machine. Too loose and the bar rattles, which shows up as a lobed or tapered diameter. Too tight and the bar can seize or scuff. A clearance in the low hundredths of a millimeter is typical, and it must be rechecked every time you change bar stock lot.

Coolant and chip evacuation deserve attention on small parts. A chip that wraps around a Ø2 mm part will mark the surface or break the tool. High-pressure coolant aimed at the cutting zone and a short, sharp peck on deep holes solve most of these problems.

These machines are built for a narrow band of work: small, round, high-volume parts that do not change. Step outside that band and the economics flip quickly. A part with a complicated profile, several milled features and a two-week design freeze belongs on a CNC Swiss-type or a 5-axis mill-turn center, not on a cam machine.

Material matters too. Free-machining brass and low-carbon steel cut cleanly at the speeds these machines like. Stainless 316 and 17-4PH work, but tool wear rises and the cam timing may need to be gentler to avoid chipping. Titanium and nickel alloys are usually a poor match unless the volume is very high and the geometry is simple.

Deburring is another boundary. A cam machine can break an edge with a form tool, but it cannot follow a complex blend. If the drawing calls for a radius on a curved intersection, plan a secondary operation or move the job to a machine that can interpolate.

Finally, consider what happens when the part is done. These machines run best when they run continuously. A job that fills two days a month will sit idle the rest of the month, and the setup cost never pays back. Match the machine to the annual volume, not to the first order.

On a Ø2 mm part, a 0.005 mm error is a quarter of a percent of the diameter. You cannot see that with a shop caliper. Measurement has to match the tolerance: a micrometer with a proper anvil, or better, an optical comparator or a vision system for form and burr checks.

In-process sampling matters more here than on a large part. The usual pattern is to check the first part, then sample at fixed intervals through the run. If the diameter starts to drift, it is almost always one of three things: bar lot variation, guide bushing wear, or a dull tool. Each has a different fix, and the sample tells you which one.

For a production run, ask for first-article inspection plus a final inspection report. On the parts we machine for Swiss-type work, we run raw material verification, in-process monitoring and a full check before shipment, and we can supply reports on request. A 100% inspection before shipment is standard on our side.

Surface finish follows the same logic. A turned small part usually lands in the Ra 0.8–1.6 μm range as machined, with finer finishes down to Ra 0.2–0.8 μm when the customer needs a sealing face or a bearing seat.