By Jose Rodriguez

Part One

For years, there was the original miniature Unimat metalworking lathe which became a household word to just about every scale model builder. Though one can still find some good used examples of the legendary Unimat, sadly it is no longer made. Lucky for us, there are some very good little machines presently available that seem to have been specifically designed with the model engineer in mind. The Taig and Sherline are without question the most popular and versatile of the 4" swing and smaller category of lathes and as such, they are both excellent machines for the money. Specially the Taig with its overall greater workpiece capacity and spindle speed range.

I recently had a great need for a slightly larger capacity lathe, one that would allow me to machine materials like 5-6" diameter flywheels in stainless steel and yet, be small enough to move to other shop locations if I had to. The 4" swing and smaller machines will accept riser blocks in an effort to increase their turning capacities but in all truth, they really have to work rather hard to be able to take a .050" cut on a stainless steel flywheel larger than 3-4". Chatter becomes a big problem with work of that type with the smaller light weight tools. I had seen, as I'm sure many of you readers have, a small Asian make bench style lathe sold through several mail order companies that I'm sure most are very familiar with. The tool is being described as a 7"x10" bench mini lathe with electronic variable speed control. Although I have seen several short comments on the metalworking FAQ about it, no one has gone into any great detail about the lathe itself. Often chastising it rather than giving it a fair chance to prove itself. The weight of 89 pounds from all the cast iron, immediately got my interest and it seemed like I had found exactly what I needed for my medium size steam engine projects. Here was a small machine that not only outweighed my loaded Taig nearly 7 fold but could cut the type of materials that would cause my smaller and lighter weight machines to growl like a bear. I decided to take the plunge even after reading some of the rather "negative" reports volunteered by some of the more "experienced " home shop machinists out in the Internet world. Some didn't even own one but somehwo seemed to "know" all about it! I obtained the machine on sale for around $399 and that included shipping by truck. You all know from whom.

The tool arrived in good physical condition even though the packaging showed all the sings of wear from its long original trip from Asia. In about 30 minutes I had the tool set up and running although I still had a lot of packing grease to rub off of the milled surfaces. A set of little rubber anti skid feet had to be screwed to the under side of the bottom pan and the gibs on both the cross and compound slides were adjusted to a snug but not tight condition. That wasn't any more difficult than on any other tool I've owned. It's just that I was a bit shocked at how loose they were. The lathe is made in China but the three jaw chuck provided with it is Japanese and of very good quality. Right off the box it could repeatedly center unsupported work to within .002" which is pretty darn good for most low to middle of ball park three jaw chucks. With a little work on the jaw faces I'm quite sure you can get it down to a lot less than a couple of thousands. It also came with a set of numbered inside and outside hardened steel jaws. The two basic speed ranges are obtained via a two position gear lever that gives infinitely variable range in a low range from 200 - 1800 rpm and a high one of 440 to 2900 rpm. The lever must never be shifted unless the spindle is completely stopped or you will instantly strip the gear box. But then again, that would make perfect sense on any machine. I find that the lathe will allow me to easily cut even the toughest grade of stainless steel and 1018 CRS specially when the speed lever is set for the low range. More torque to the spindle that way. The tool holder is of the four tool type and can be rotated 360 degrees. It takes 5/16 square bits and I use HSS bits which I mail order in bulk for as little as 70 cents each and grind them to fit my machining needs with perfectly fine results on the majority of metals. With the most basic of care I can produce very intricate parts, that is those with bores, steps, shoulders, grooves, tapers, chamfers and the like that are within .0005" or better.

The lathe has auto carriage advance that can be run in both left or right handed feed directions. The spindle rotation can be also reversed by flipping a reverse switch. Again, don't try this on the fly! Why care about the fact that the spindle can made to run backwards? Well, for one, you can cut short tapers or chamfers on the edges of work without having to rotate the compound beyond center toward the rear of the bed. You could just leave the compound set at the customary 29.5 degrees used for threading and just cut on the back of the work turning backwards. Very handy little trick. Reversing a tailstock held tap out of a hole is made easy with a flip of the reverse switch. With the carriage moving from left to right, you are able to cut left handed threads as those found on cross slide lead screws. A nice feature when you need to make one of those babies from scratch. Threading can be done to any tpi from 12 to 52 by rearranging the included change gears that connect the spindle to carriage feed screw. A chart is provided with the lathe along with the set of change gears. The gears are indeed made out of plastic but not just any kind of plastic. Whatever this stuff is, it's a very tough slippery material. They also run very quietly when they are meshed and running. I tried the metal set that the lathe used to come with and it produced a lot more noise.So far in more than a year of almost constant work, I have not detected any wear on them whatsoever. Threading anything coarser than 16 tpi can be a problem as even with the lowest available factory spindle speed of 200 rpm, it can still get away from you pretty quickly specially when cutting a thread against a shoulder. There is a way to further slow down the electronic speed controller but it does require a bit of now how and maybe a bit or nerve. I have slowed mine down to 30 rpm ( low lever setting ) with enough torque so as to make it extremely hard to even slow the chuck down with my hand.

How well aligned was the spindle, cross slide, tail stock spindle ram, etc? I have to admit that I had to spend some time fiddling with the tail stock to get it aligned to the spindle axis so it would give a parallel cylinder on work supported by the live center. Once I was able to produce a 8" long, between centers held cylinder that was within .0005", I called it quits and left the shop well satisfied. The adjustments for the tail stock were not very well designed. Not at all like that on a Southbend but you get what you pay for. The spindle axis is indeed perfectly aligned to the lathe bed and the cross slide, as far as I can detect. Maybe I got a good one! I turned 3" long unsupported steam engine cylinder that was parallel to less than a couple of tenths along its entire length straight out of the box. The chuck can be removed via three nuts from behind the spindle backplate which is all in one piece. The back of the chuck has a machined tapered recess that self aligns it to the matching back plate and stud holes. Three threaded studs in back of the chuck lock it to the plate. Once the chuck has been removed, you can insert a #3 mt dead center or any other #3 mt size tooling. The overall spindle diameter is about 1-1/4" in diameter with a 3/4" through hole. Much heftier than those found on other so called miniature lathes.

Although this lathe in definitely not a beauty contest winner, with its typical ugly green paint job, it's not so ugly that it would cause me to reject it as a very good low cost medium capacity machine tool capable of just about anything I have asked it to perform.

In the next installment I will discuss the many adaptations, modifications and special tooling I have made with it, for it. Many or these modifications were done on the smaller Taig lathe. Which by the way, once the second and final segment of this article is finished, several Taig article will follow describing modifications, tooling projects specific for it as well as many other goodies for the miniature machine tool fan.

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