7x10 VARIABLE SPEED

MINI LATHE

 

 

I recently added a mid size Taiwan built 7x10 variable speed lathe to my shop to help augment my smaller 4-1/2" x 9-3/4" TAIG micro lathe. I have had friends tell me that I really did not need the larger lathe as all of my projects are small enough to be easily handled by my TAIG. The little TAIG when assisted by some of its many extra attachments ( many of them homemade ), is one of most versatile little machines I have ever used. So at first glance it seemed that the addition of a bigger machine may have been money wasted, but then you have to consider that because every component of the lathe is about eight times as massive, you get an incredible increase in rigidity when one compares it to the TAIG. The TAIG weighs about ten pounds without the motor compared to about 89 pounds ( with motor and basic cutting accessories) for the 7"x10". The extra weight alone will contribute toward the extra rigidity, not to mention the solid cast iron construction of all its components. Right from the onset, it became apparent that I would be able to machine grades of steel that I would never even consider cutting on the TAIG. The tool bit size is also bigger from 1/4" to 5/16". That extra 1/16" seems insignificant at first glance but it actually adds much more stiffness to the tool bit. The tool post is a 2" square multi - tool type instead of the 1" square size used on the TAIG. Don't get me wrong, I am not in the least thinking of retiring my TAIG out to tool pasture. It is still the workhorse of my model making shop as it is simply a pleasure for me to use for all the basic machining operations and even some of the more exotic ones. Features of the 7" x 10" are a two position variable speed control from 200-2900 rpm, reversible motor - great for tapering and boring on the back side of the workpiece, multi-directional auto longitudinal feed, very solid cross and compound slides, 12 to 56 pitch threading capability, #2 morse tail stock with live center which by the way, can be offset laterally for cutting long tapers in work held between centers. A #3 morse tapered head spindle after the three jaw chuck is removed. A four inch capacity three jaw chuck with inside and outside jaws, and a 3/4" spindle bore made it all a very attractive machine. What really cinched the deal for me was being able to buy it on sale for only $449 from Harbor Freight Tools in Camarillo, California with free freight included to boot! I had seen the same identical machine under various other importer's brand names and the cheapest price at this writing was $995 plus freight. Quite a mark up I must say. It can now be purchased for as little as $349 from Harbor Freight so you can almost consider buying to lathes and have each one set up for specific functions. This little lathe is really nice, really, but even with the variable speed motor, auto feed and all of the other features, it still falls short in total versatility when compared to the Taig as it comes out of the box. Accessories are needed, but none seem to be commercially available except for your normal drill chuck and #2 and #3 morse centers. To counter this, I have begun to design and build a series of home made accessories for the lathe to alloy cutting off, grooving, tapping, thread cutting with dies / taps and lathe, boring, milling work and generally increase its capabilities somewhat.

First thing I did was to acquire a 2 morse taper / 33 Jacobs taper arbor so I could use my 1/2" capacity Jacobs drill chuck on the tail stock to immediately bring drilling capabilities to the lathe. The next thing I did was to build a boring bar / cut off tool holder. Now I can bore to perfect diameters and part off parts from bar stock or cut grooved slots or fins in cylinders for hot air or gas powered model engines. I only had the three jaw chuck that came with the lathe and I really needed to be able to use a four jaw chuck for square stock or to truly center or purposely set up a workpiece off center such as when machining an eccentric for a steam engine. I took my four jaw chuck that has a 3/4-16 threaded mounting hole (for the TAIG) and a flat plain back and machined it to fit the tapered flanged mounting plate of the mini lathe. The mounting plate on the lathe is a little bigger than 3" in diameter with a raised centering flange for which a matching female recess has to be made to the back of the chuck. Three equally spaced, matching mounting holes finish the job. The stud holes are threaded 1/4-20 and three short lengths of threaded rod with the ends nicely finished are screwed as studs into the holes. I would have set them in permanently with CA glue or epoxy but since I only have this single four jaw chuck I left the studs removable so it could be interchanged between the TAIG and the 7x10. I will have to purchase a separate one so I could dedicate a chuck for each lathe. The modified chuck. as with the one furnished with the lathe, is inserted through the three mounting holes, seated on the centering flange on the back plate and secured with three nuts from behind. I just recently finished a face plate with slots and several threaded clamping holes to accommodate an adjustable driving dog to be used with a #3 morse taper center on the head spindle to drive work pieces between centers. To provide milling capabilities, a Palmgreen brand vertical milling vice / slide is all that is needed. It sells for about $170. but it is a fine piece of equipment of superior quality and well worth every dollar. It attaches to the tool post to provide the "Z" or vertical movement except this one also provide angular movement to truly provide the capability to set up work at a compound angle. A smaller version can be made from a TAIG milling slide but two holes will have to be drilled on top of the cross slide to accept the milling slide. Several of the attachments I have already made for the TAIG, which use the one inch diameter blank arbors sold by the TAIG manufacturer could also be used to make a slitting blade, milling bit, or spur drive arbors. These can be directly chucked into the three jaw chuck and used in the same manner as before. For the highest degree in accuracy, I would first chuck the blank arbor and take a light turning cut on the outside to true it up. Flip it end for end and true the untouched portion to the same diameter. Now all you have to do is to put a punch mark on one side so it lines up with jaw #1. Then you have to always mount the arbor so the mark is against the #1 jaw. Of course, you would have to machine the arbor for the intended purpose at the same time you are marking it.

There will also be other little gadgets, single purpose items and special fixtures that will be built for the mini lathe in the future or as the needs arise to further increase its versatility.

One of the disadvantages of this mid size machine is that when a workpiece is held in the three jaw chuck you loose about 2-1/2" of operating room, reducing the already narrow 10" of center to center distance. Using the drill chuck in the tail stock, reduces the distance even further, you won't be able to insert a regular jobbers length 1/2" drill bit into the chuck unless you almost slide the tail stock completely off the lathe bed. The solution here is to use so called "screw machine" length bits which are almost one half the regular length of so called "jobbers" style drill bits. The shorter length provides more stiffness than the longer bits but somewhat reduce the drilling capacity due to their shorter flutes. They are available only through the larger tool supply houses as individual bits or in complete sets of fractional - letter and numbered size bits and off course, cost more per bit than the longer ones. It reminds me of diet foods that end up costing you more for less food. If you are on a limited budget as I am, I would suggest only purchasing the sizes needed most. I do own a full set of all the types mentioned only because I was able to purchase them on sale but realistically, I only use a few of the many sizes included in the set for most of my work. Most of the smaller holes meant to receive threads are for the smaller machine screw sizes. My most frequent needs are for 10-32 threads which require a #21 bit for the tapping hole and a #11 for the clearance hole for the screw itself. 4-40 threads need a #43 / tap and #33 / clearance, 2-56 needs a #50 / tap and #44 / clearance. Other than the occasional need for a #5 or #6 series thread, the above six bit sizes should suffice for quite a while. Since these six sizes will be used all the time I would spend a bit more and get cobalt steel bits for the most popular sizes, latter getting any other sizes I might need in regular M2 grade high speed steel. The cobalt steel bits with outlast the common H.S. steel bits many times over specially when you start drilling into the harder materials. Plenty of the proper kind of lubricant specific for the particular metal you are drilling will do wonders toward extending tool bit life.

The standard live center supplied can also be replaced with one that allows the rotating tips to be exchanged for many types of workpieces like tubing, pipe or small diameter work.

I think that with a few additions to the tooling of my new variable speed 7x10 mini lathes, I will be able to bring it up the same high standards of versatility as my TAIG.