Initial impression about Chinese made equipment and tools.
Most if not all of them are made by the same company. Sieg Industries. They are sold with some rough edges and need some work or tuning before they can be used. The castings are rough in many areas. There is usually residual sand left in the machine that you need to clean. The paint job is shoddy and some parts are made crudely. You need to disassemble, clean, lubricate, file, de-bur and calibrate them for accuracy and repeatability. The mini lathe tailstock is infamous for its poor quality and lack of accuracy. After you go through this religious indoctrination, your piece of equipment is ready for the game. There is an excellent web site that has most of the information to get you started. Sort of mini lathe heaven, which I recommend for the beginner and everyone else. The link is www.mini-lathe.com.
Milling Machine.
This is the Harbor Freight mini mill. This mill is made in China by Sieg Industries. This is their X2 model. Price is around $500.00 which includes a few wrenches (cheap) and a drill chuck. It has a spindle which takes R8 tooling. From what I have heard it is more ubiquitous, cheaper than the MT3 tooling. There are a few other versions of this mill, sold by the usual suspects, Homier, HF, Grizzly and MicroMark. If you ever need parts for these mills, you are very fortunate. Most parts are interchangeable between the mini mills. A good source for these parts and more is LMS The last picture shows a boring head, it accepts 1/2" boring bars.
Adjusting the mini mill.
After receiving the mini mill, the usual disassembly process was undertaken. You have to clean the red grease that is common to all of these units built by Sieg. I removed the X table first. This is done by removing two phillips screws present on the left side. Then you just crank the handle until the lead screw disengages the nut. A gentle pull will release the table into your stretched arms. It is somewhat heavy, so be careful. The rest of the process dictates that you remove the protective accordion pieces of rubber. Two screws are locate at each end. The Y table is removed in a slightly different manner. Remove the handle from the lead screw and turn the lead screw until it disengages the nut. Now you have to loosen the set screw that holds the nut in place. The nut will drop (it did in mine) and then you pull the table out. Watch out for the gib so you don't drop it.
This is the base of the mini mill. The X and Y components have been dismounted. You can see the dovetail. The surface appears with a slight rust discoloration in some small areas. I will focus my attention now to the area where I had most concern due to its large amount of backslash and slop. The Y component of the table. This is somewhat narrow as the following pictures show.
Y component of the table.
This component, though very narrow and short, holds most of the parts that determine the accuracy and repeatability of the overall motion of this table. The first picture shows the gib locking screw in the center and on the side, the two screws that adjust the gib. The locking screw pushes the center of the gib against the dovetail of the table. Next picture shows the underside of the table. It holds the two nuts that the X, Y lead screws fit in. The nut on the left is for the X lead screw, the one located in the middle, for the Y lead screw. Next picture shows the adjusting screws for the gib located inferiorly. On the top, the adjusting screw for the nut. There is only one!. That is the main reason (My humble opinion) why the table has so much slop, backslash, even though it has a very short lead screw . The one for the X nut has two adjusting screws that hold the nut more securely. For comparison this is shown in the last picture.
These last few pictures, show the Y nut, a single dimple caused by the adjusting screw can be seen at the bottom. Next two pictures show the single adjusting screw from the other side. The slot side. Last picture shows a close up of the X table component. My plan to reduce the backslash and improve accuracy is to drill and tap 2 new holes next to and on either side of single adjusting screw. Those new ones would allow a secure and much better adjustment of the nut. Will be reporting on my progress in the near future.
Well, some progress has been made during the last few days... Two new holes were drilled and tapped as previously planned. They were tapped for 10-32 set screws. I observed some more disturbing lack of attention to detail in the construction of my mill.
These few pictures show the changes made to the original Y table. First picture is the original condition with a single setting screw. Next picture, (upside down) two new holes drilled on each side of the original hole. Third picture shows the nut next to the 3 screws. This gives you an idea of how the new set screws will help in securing this nut's position. Compare this picture with the first picture, before the modification was made. The last picture reveals how poorly centered the nut for the X table is!! It looks like the left side screw may not even contact the nut due to the poor nut construction. The hole location in the brass stock, is way shifted to the left of center. I have not tested it altogether, because I am debating wether to make new nuts out of delrin or keep the original ones. The story continues...
Well, I finally decided to put the mini-mill back together. I need it to make the new nuts, etc. As I reassembled the mill, some of my initial impressions were confirmed. I repositioned the y table, and secured the nut with its single screw. As I moved the table back and forth, it was troubling to see that the nut would move up and down like a children's see-saw. I then centered the nut and tightened the two other screws. This stopped the up and down motion, but made it very difficult to move the table. There was a clear misalignment between the lead screw and the nut. After playing with it for a while, I was able to ease the problem. After all was said and done, there is a lot less slop and backlash. The final conclusion. I don't think it is by accident that there is only one screw. This allows the machine to function (somewhat poorly) when there is a lack of alignment between the nut and lead screw. It provides an easy way to let the table move when there is considerable lack of accuracy in the construction and assembly of this machine. I will be making some new nuts in the near future. More to come...
Mini lathe.
Microlux mini lathe. It has some improvements over the other mini lathes sold by Grizzly, HF and Homier. It has a buitl in tachometer, the motor is a little beefier, the TS has a locking mechanism, the bed length is 14 inches, and the lead screws for the compound, cross slide, etc are 20 tpi. So it is the only true inch mini lathe of the whole group. These improvement will set you back around $200.00 extra if compared to the price you pay for the Homier mini mill. The second picture shows a quick change tool post. It allows to use different size tool bits without the need for shims. The 3rd. and 4th. pictures show a dial test indicator and a dial indicator. The indicators allow you to determine if you there is run out in the chuck, stock, etc. In other words it allows you to find if a piece of round stock is perfectly centered in your chuck, or if its surface has irregularities (not perfectly round). Tramming the mill is another use of the indicator. You place the indicator in the spindle and move the table right to left, up and down and check for perfect vertical alignment of the column to the table. On the second row there is a digital caliper.
Tool bits.
Most of your work with a lathe, will be done using high speed steel or HSS tools. Some of them are made with small amounts of cobalt to increase its hardness and resistance to heat. So, you will find 5%, 10 % cobalt HSS in the more expensive tool bit blanks. That brings the whole world of grinding, honing, etc into play. So buy a grinder as soon as you begin this hobby. After grinding, usually you need to hone the edges to make them razor sharp. You can not call yourself a machinist unless you can grind your own bits...Anyways, that is what I was told when I began my hobby. My advise when you begin this swarfing enterprise get yourself a couple of already made bits so you can understand the geometry. There are many angles involved and believe me, a picture is worth ... There are right hand, left hand, parting bits. The right or left handed bits are used depending if you are cutting towards the headstock or the tailstock. The first picture shows two bits. The one to the left is a finishing bit, as you see, it has a rounded nose or tip. The one on the right, has a sharp pointed tip. It allows to cut deeper, and remove more material per cut. So you do most of the metal removal with the roughing bit and create a nice smooth finish with your round nose finishing bit. The second picture is an example of right and left hand indexable tool bits. Looking at the angle you can deduce that the tip of the bit cuts towards the headstock or the tailstock. Last picture is a diamond hone. A must for sharpening the tool bits.
