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7x10, 7x12, 7x14 Mini-Lathe Information

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Q. What size belt should I use if I know the two pitch diameters of the pulleys and the center to center distance between them?
A. Use our timing belt calculator. Works for MXL, XL, and L sized belts.

Q. How do I setup the "steps per inch" numbers so that I can get the X, Y, Z motors tuned?
A. Use our Mach "Steps per unit" calculator. Currently works for screw and nut setups only. Other setups coming soon.

Q. My drill bit keeps wandering and my holes are "off". What do I do?
A. Use the following (in this order): 1. transfer punch to locate the hole 2. center punch to make an indent 3. use a center drill 4. use a machine screw drill bit (these are stiffer and shorter than jobber bits) or undersize the bit and then use a reamer to get a nicely rounded hole.

Q. I have two identical pieces to machine. How do I save time?
A. Use a piece of paper or index card (thicker than paper) to allow for that thousandth difference between the two pieces. Mount in vise. You can also use clamps (such as the Kant-Twist) brand (excellent!) to hold the two pieces together while in the vise, then when you remove them for another operation (say you flipped them around).

Q. I just bought the mini-mill. How do I make sure it's square to the table?
A. Click here

Q. I just bought the lathe and/or mill. What tools should I buy?
A. Click here

Q. How come whenever I turn the handwheel the other direction there's play and slop before the table/carriage finally engages and moves?
A. This is backlash (aka "axial lash" or "lash") - the axial gap between the screw thread and nut thread. This translates to (in a rotation to linear motion scenario) additional rotations of the screw before the nut and screw engage positively. In a manual machine and coupled with a DRO (digital readout) to determine table position, backlash can be annoying, but is not much of an issue since you no longer have to keep track of handwheel turns and re-zeroing, etc. In a CNC system (computer numerically controlled), backlash is of huge importance. What is sometimes forgotten however is the lead screw accuracy when overall machine accuracy is considered in a CNC machine. Here's why: even if you have a zero-backlash system with the use of some form of anti-backlash nut, this only means that reverse rotations from one direction to its reverse axial direction won't include any additional rotation causing more machine positional error. However, perhaps you have a leadscrew with lead accuracy of 0.004 in./ft. (this means that the leadscrew could be off by as much as .004" by the end of a 12" travel), this translates to 11.996" of travel with full error. Imagine this combined WITH backlash!. In order to get a truly accurate system you'll need both a highly accurate leadscrew (or ballscrew) and some way of addressing backlash at the mechanical level (not the software level - i.e. backlash compensation). Perhaps the most important question to ask is HOW accurate you want the machine to be? If you're making wooden parts with tolerances of +/-0.05", almost any CNC system can accommodate. If you want to get to +/-0.001", you'll have a lot to work on. Click here to read more on this topic.

Q. I've heard about these "er collets" or "er spring collets". What are they and how do I use them?
A. Let's start with the basics. Collets are used to hold cutting tools. There many different types ranging from your most basic of R8, 5C whereby each diameter requires its own sized collet to spring collets whereby they grip ranges of diameters for each size of collet. In a Z-axis limited machine such as the mini and small mills, the use of a drill chuck can reduce travel by 2" or more. This is a huge advantage of using a spring collet. Since the spring collets can grip drill bits of most common sizes ranging from ~1/8" to ~1" shanks (they usually have .040" of gripping range for each size collet), you no longer need to use a drill chuck. Plus, even the inexpensive import er collets usually offer 0.0006" concentricity. With ER collets alone, you have a handful of sizes to choose from ranging from ER-11 to ER-50. Each of these numbers indicate the range of holding they accommodate. For example, an ER-32 size has a gripping range of .080"-.787". But before you go off buying er collets or other types of spring collets, it's a good idea to know the different types of spring collets. Click here to read more on this topic.


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