A New Mill

I finally did what many have told me I should do, and that is get a bigger mill for my reel work.
IMG_4818
This is a Model 3990 from Little Machine Shop. It is several times heavier, stiffer, and more powerful than the Sherline mill that I have been using. It is too big for the utility room in my house, so I have bolted it to a workbench in the garage. Before next winter, I have to figure out how to heat the space.

For the near future, I intend to continue with the Sherline lathe. For many of the larger parts of a reel, I make an oversize rough part using the mill, then take final light cuts with the lathe. This makes the small size of the lathe less of a problem. And for the many reel parts that are under 3/8 inch diameter, the Sherline lathe is just right.

Update 12 May 2015: I am trying to adjust to the larger scale of this mill. Here is a comparison of the R8 collet that it uses with the MT1 collet of the Sherline mill.
IMG_4826

And here is the 3 inch milling vise compared with the Sherline 2 inch vise.
IMG_4827
The picture does not tell the whole story; the new new vise is steel and the Sherline is aluminum, so the weight ratio is even larger.

I am going to continue with the Sherline rotary tables. At 4 inch diameter, they are good for reel work. I have already made many fixtures that fit these tables. The rotary tables offered by Little Machine Shop are calibrated in minutes rather than tenths of a degree and I think that this adds potential for error to every calculation of angle.
IMG_4825
It looks as if there is enough X direction travel that I will be able to “permanently” bolt down the vise and two rotary tables, saving setup time.

I am still struggling with the issue of the X and Y leadscrews, they are 16 threads per inch. I cannot very well do modulus 62.5 arithmetic in my head, but modulus 50 (for the Sherline 20/inch screws) is quite manageable. Options are:
1. buy the Little Machine Shop kit to change the screws to 20/inch, or
2. buy digital readouts for the two axes and ignore the engraved scales on the crank skirts.

Update 25 May 2015: I bought the conversion kit for 20/inch leadscrews, and have now installed these. LMS provided very good step-by-step instructions for this conversion, and I recommend that anyone who buys this mill go through this tear down and reassembly, even if not making the conversion. It the only way to get at many hidden areas that should be cleaned of the preservation gel, and to lubricate internal parts.
LMS does not provide a rule for the Y axis motion, but it will be easy to add one. The X axis rule that they did provide has 1/16 inch markings, so I will cover it over with a 1/10 inch rule.

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4 Responses to A New Mill

  1. Jeff says:

    Hello,

    Now that you have been using the LMS mill for a while, I would be interested in your experiences having used both the Sherline and LMS mill.

    Some background for my question. I am preparing to purchase a Sherline lathe (4400) and milling machine (5400). I plan on using both for precision, small scale model engineering types of projects (engines, locomotives) in brass, aluminum, and steel. The lathe is an easy decision because even should I later choose to purchase a conventional lathe for larger work, I am confident that I will still favor the Sherline for smaller precision parts.

    The mill is another matter. I see a number of people who were not satisfied with the rigidity and capabilities of the Sherline mill. Some of these individuals migrated to the Taig or Asian Sieg mills (like yours). Like the lathe, I can easily envision later buying a larger milling machine and retaining the Sherline mill as a “house mill” for small precision milling…. however, I am just a bit concerned with the capabilities of the Sherline mill even for the smaller applications. Just looking at it, makes me want to put a stiffener behind the dovetail column!

    Hence, I have actually been considering the LMS 4700 SX1 Micromill. The table size, table travel, and work envelope are not that much smaller than your mill. It has the Z-axis screw like a Sherline, eliminating the need for return springs and resulting in fewer issues with backlash. The spindle is belt driven and the 250 W brushless motor is reported to be quite capable even at low speeds….certainly much more powerful than the Sherline, and it is quite a bit more rigid than the Sherline. Although I have read about issues the the X2 mills, owners of the X1 seem quite satisfied.

    I have two concerns. First I would be giving up the Sherline “system”. This is not a major concern but may require some duplication of tooling/accessories. Some items such as the Sherline rotary table seem to fit this size mill better than the smallest equivalents sold by LMS.

    The main concern is precision and that is my question for you. I do not mind doing some fettling and performing modifications. What I don’t want to deal with serious mis-machined (not parallel, square, etc) components that require re-machining to correct. How would you compare the precision of the LMS mill to your Sherline? Have you done a comparison of machining the same material with the same tooling to compare…say…surface finish? Do you still use the Sherline mill? Do you only use the LMS for parts too big for the Sherline or do you find yourself using the LMS for coarse milling, leaving finishing operations to the Sherline? Any additional observations would be appreciated.

    Thank you,

    Jeff

  2. premodernbloke says:

    Hello again,

    I did read one of your subsequent posts in which you discuss the rigidity issues with the Sherline milling machine and how you are happy with the rigidity and power capabilities of theLMS mill. I would still be interested in your observations regarding precision, and machining surface quality of the LMS mill.

    Also, the idea of a brushless motor for the Sherline is intriguing. But wow…$500 for the 600W. I wonder what LMS charges for the 250W motor and controls as is used on the 4700 mill? Of course, one would have to make one’s own adapter and pulleys. Even that would be a big boost in torque compared to the Sherline motor.

    Thank you,

    Jeff

    • dave49 says:

      Jeff,
      I kept my Sherline mill until I had made one complete reel with the new LMS mill. At that point I could see that there were no operations for which I would prefer the Sherline, so I sold it.

      Points in favor of the Sherline:
      1. It was small enough that I could fit it in an enclosure and contain 98% of the waste chips.
      2. It was lightweight enough that I could stack it over the lathe, thereby fitting all my machining operations onto a built-in desk in my utility room, a heated space. The LMS (X2 size) mill has to go in my garage.

      Points in favor of the LMS mill:
      1. The greater mass, rigidity, and power allow larger cuts while producing a better surface finish. I do not detect that is is less precise in any way.
      2. The rack and pinion Z axis drive (with air spring) is far superior to a simple lead screw. This especially evident when making a plunging cut, because it effectively removes all backlash. I have much better control of the depth of counterbores (which I make with end mills). When plunging with the Sherline, Z motion is a sequence of sudden lurches. When working brass, the cutter is likely to suddenly seize.
      3. An R8 collet has a much bigger cone angle than MT1, so it takes only a light tap to unlock. If I were buying a new Sherline lathe or mill, I would get the ER16 headstock because the MT1 is too difficult to unlock. (Sherline has special chucks that fit the ER16 collet thread.)

      Sherline’s column is secured by four 10-32 screws. The off-center weight of the motor and constant vibration cause the column to work its way to a leaning position, so the mill is normally out of alignment (i.e., the spindle is not square to the table). You can loosen the 4 screws and put it back, but it won’t stay for long.
      I think that LMS has the best X2 mill because it is the only one with a solid column. The X2 mills with the big bolt at the bottom of the column could be worse that the Sherline in maintaining alignment.
      LMS sells T-nuts with 10-32 thread, making it easy for me to mount my Sherline rotary table or milling vise.
      I have not used an SX1 mill, and so cannot comment on it.
      Dave

  3. premodernbloke says:

    Thank you Dave. That was helpful.

    Jeff

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