How accurate are Sherline tools?
When someone asks what is the accuracy of a machine, it is a rather loaded question. The more you know about the subject, the more difficult it becomes to answer. I can easily turn a diameter close to the chuck on the lathe within .0002″ (2 tenths of a thousandth of an inch). Does this mean the machine is built to that tolerance? No, but it does mean the lead screw is accurate*, the cutting tool is sharp and properly shaped, and the diameter I am cutting is large enough not to deflect. In many cases, the accuracy of your method of measuring has as much to do with the accuracy of your parts as the machine you are working on.
* NOTE: Sherline’s leadscrews are precision rolled and are accurate to within 99.97%. Rolled threads are much more accurate center to center than those cut with a die or single-pointed tool.
The tools we make are as accurate as you can build them without expensive grinding and heat treating. We have well over a million dollars invested in state-of-the-art CNC machine tools and tooling to mass produce accurate parts. To increase the accuracy less than 1% would increase the cost by a factor of 10. This simply wouldn’t be cost-effective for the average consumer of our products. The jump from our $600 lathe to a $5000-$8000 lathe of similar size yields only a minor increase in accuracy and could result in a loss in versatility, as few other machines offer the combination of features and complete system of accessories available from Sherline.
When asking about the accuracy of the machines, what is really being asked is, “what kind of accuracy can I expect to achieve in the parts I make on these machines?” When you look in our new catalog at some of the examples of the parts made on Sherline machines, you can see that, in the hands of a good craftsman who knows his or her machine, the parts that can be produced are as accurate as you will ever need. You will find that most problems associated with making very tight tolerance parts are not caused by the machines but rather are the result of the level of craftsmanship of the operator. As your technique improves, you’ll find your machine keeps making better and better parts.
Even if the machine were “perfect,” other things can affect accuracy. For example, the “spring” or deflection of the part you are making and the deflection of the cutter also affect accuracy. Taking all this into account, it is still not uncommon for a good machinist to be able to make parts accurate to within a thousandth of an inch (0.001″) or less on our tools. Keep in mind our lathe is a small engine lathe, not a jeweler’s lathe. If you are a hobbyist, the Sherline lathe for under $500 will be plenty accurate and many times more useful than the most expensive jeweler’s lathe made, as they are designed for different purposes.
Keep in mind also that while you need a big machine to make big parts, it is much easier to make accurate small parts on a small machine. In addition to the advantages of being able to sit down and get close to your work, the smaller machine will give you a much better “feel” for delicate work than a large machine. For example, it is very easy to break extremely small drills if you don’t have some feel for how fast to feed them. A large machine simply cannot give you the “touch” you need for doing delicate work.
How about the alignment of the lathe headstock and tailstock?
The biggest enemy of accuracy here is the versatility of the machine. Because the head rotates to allow taper turning, returning it to a perfectly straight position is dependent on the alignment of the headstock key and keyway. We recently replaced the standard square key stock material with a precision ground key, which has increased the level of accuracy. (New precision ground keys are only $2.00 if you wish to upgrade an older machine.) New assembly procedures in the factory to align the headstock and tailstock have also brought the accuracy of that alignment to even higher levels. (Within less than .003″ or .08mm) We also manufacture adjustable tailstock tool holders, and an adjustable live center, which can help you attain near-perfect alignment should your job require it.
What is “backlash” and how much of it do the leadscrews have?
Backlash is the play in the engagement between the threads of the leadscrew and the nut that drives the axis that allows a few thousandths of an inch to be turned on the handwheel before the slide starts to move when changing directions. This is a fact of life on any machine tool and is accounted for by always making your cuts in the same direction and keeping track of which way you turned the handwheel last. On Sherline tools, backlash is usually set to about .003″ or less to .005″ (.08 mm or less) at the factory. The X-Y leadscrew on the mill has a backlash adjustment, but it is still recommended that it be set to .003″. Sherline CNC machines now also have an adjustable backlash lever on the Z-axis for mills and the leadscrew axis for lathes.
What kind of materials can I machine?
There are almost no limits to the kind of materials you can machine. Anything from wood or plastic to exotic materials like stainless steel can be cut as long as the part can be safely and firmly held and the proper cutting tool and cutting speed are used. To view short video clips of various materials from Delrin to Inconel being cut, CLICK HERE.
How big a part can I work on?
The Lathe is capable of turning a 3.5″ (90mm) part over the bed. The fact that the lathe will turn to 3.5″ does not mean you can turn a 3.5″ diameter between centers because the crosslide would be in the way. The lathe will turn a part 1.875″ (48mm) over the crosslide. A 1.25″ riser block kit increases that to over 5.5″ (140mm) over the bed or 4.3″ (109mm) over the crosslide. A .405″ (10mm) diameter hole through the headstock allows long material of up to that size to be fed through and worked on. The standard lathe has 8″ between centers, and the long bed lathe has 17″ between centers.
That gives you the physical limitations of the machine, but what does the hardness of the material you wish to turn do to those numbers in the real world? A good rule to remember when it comes to purchasing any lathe is to take the average diameter you plan to work with and multiply that times three for free machining materials and times four for tough materials like stainless steel. If the materials you plan to work with are free machining (aluminum, brass, and free machining steel), you will be pleased with a Sherline lathe if the average part you make is approximately 1″ (25mm) in diameter. Wood and plastic are so easy to machine that only size limitations need be considered. I don’t mean to imply that you can’t machine a 3″ flywheel, but if you are planning to consistently make parts of that size, you will probably be happier with a larger machine and more horsepower. Removing large amounts of metal on a small machine takes time. If you have lots of time, the size of the part is less critical. Users of any machine are happier with its performance when they are not consistently pushing the limits of its capabilities. If you usually make small parts well within the capabilities of the Sherline lathe and every once in a while need to turn a part sized near the machine’s limits, you will be very satisfied with its performance.
The vertical milling machine is capable of holding larger parts than the lathe because the part is held and only the tool turns. It also has a much longer table throw (“X” axis). A deluxe version is available which offers an additional 2″ of “Y” axis travel compared to the standard mill. It also includes a mill headstock spacer block which adds 1-1/4″ to the throat distance (clearance between the tool and the vertical column). With the addition of the horizontal milling conversion, surfaces up to 6″ x 9″ can be machined without moving the part. This is a very large machinable area for a tool of this compact size.
How powerful is the motor and what is the speed range?
The 90 Volt DC motor offers far more torque than the 1/2 HP AC/DC motors we used to use. (It is also much smoother and quieter.) The electronic speed control adjusts automatically for any voltage worldwide from 100 to 240 volts, 50 or 60 Hz. (For more details, see complete motor specifications and torque curve chart in the file on Sherline tool dimensions.) An electronic circuit in the new speed control unit also compensates for load, keeping the RPM more constant during cuts. Everyone is impressed by how powerful the motor actually is when they use it. The electronically controlled speed range of 70 to 2800 RPM requires no changes of gears or belts to achieve. Just turn the speed control knob for any speed in that range. For example, half-speed is about 1400 RPM. (It is not necessary to know the RPM exactly because your initial approximate speed setting will be adjusted by looking at the chips and listening to the cut as you become more experienced.) For even higher torque at low speeds when turning large parts, a second drive belt position is available on the motor drive and headstock pulleys. (By the way, to buy just a DC motor and speed control of this quality elsewhere could cost you more than the entire model 4000 lathe!)
Introduced in September 2001 was a new pulley set that allows the motor to turn the spindle shaft at 10,000 RPM. This kit (P/N 4335) can be added to any existing Sherline (DC motor) machine or a complete headstock, motor and speed control with the 10,000 RPM pulley set already installed can be purchased as P/N 33070. A second pulley position on the same set allows the speed range to be set for a maximum of 2200 RPM for greater torque. Higher speeds are helpful when turning very small shafts or using very small cutting tools.
Will continuous running at high speed ruin my spindle motor?
Normally, machining operations have a built-in cycle time when the machinist does an operation and then turns off the machine while a part is measured or changed. The advent of software-generated 3D CNC programs that are thousands of lines long has brought a different type of use to Sherline machines, because some of these programs may take several hours to run. The DC motor used on a Sherline machine was chosen because it is the only package that meets the requirements for size, cost, RPM range, torque, torque at low RPM’s, noise level and weight. AC motors are gigantic by comparison. The Sherline DC motor is also totally enclosed to prevent unwanted debris from internally contaminating the windings and commutator and causing damage. The disadvantage of this type of design is less cooling; however, we believe that you will also see the benefits outweigh the drawbacks.
Although the motor is rated as a continues-use motor and has built-in thermal protection that will automatically shut off power if the sensor reaches 170° F, it would be unwise to use this as an indication of when you are overloading the motor. Be aware that your motor has a given life that is determined by load and time. It doesn’t take a rocket scientist to figure out that if you run your motor 8-12 hours a day under a high load, you are going to shorten the amount of motor life faster than a machinist who uses it for only a few hours a day. The high-speed operation will also shorten life compared to running at lower RPM’s. That is why the warranty has never been extended for production use.
The first thing to wear out on a motor is usually the brushes. A few years ago we switched to a motor designed to allow the brushes to be changed from the outside without taking the motor apart. We recommend checking for wear every six months or so. In doing so, you’ll help assure you’ll get maximum life from your motor. When checking your brushes for wear, keep these precautions in mind:
- Unplug the machine before attempting to remove the brushes.
- Remove only one brush at a time when checking them so you can’t accidentally switch them.
- Make sure you replace the brush in the holder in the same direction it was facing when you took it out. (Turning it will establish a new wear point and substantially shorten brush life.)
- New brushes are 5/8″ long (15 mm) and should be replaced when they are 1/4″ (6 mm) long. If the brush is allowed to wear down to the spring, the copper commutator surface will be ruined, and the motor will have to be replaced.
If you keep these factors in mind when operating your Sherline machine, you can maximize the life of your spindle motor.
How heavy a cut can I make on the lathe?
This depends mostly on the diameter and type of material you are attempting to cut. It is also dependent on the sharpness of your cutter and the firmness of your setup. The high torque DC motor we use is very powerful for its size. In fact, it is more common for people to underestimate its abilities and feed the cutting tools too slowly causing the tool to “chatter.” For aluminum, you could expect to be able to take cuts of up to .060″ on 3/4″ diameter stock, while stainless steel would require taking no more than .015″ with each pass. (In another example, on free machining steel, you could take that same .015″ cut on a 3″ diameter piece.) Heavy cuts at high RPM will also cause the tool to “chatter.” Metal must be cut with enough feed to keep the cut continuous (keep the tool biting into the metal). Rule #1 in any machining operation is: “If the tool chatters, reduce speed (RPM), reduce the depth of cut and increase the rate of feed.”
To see a video demonstration of chatter and how to eliminate it, go to the Video page and view the “Eliminating Tool Chatter” demonstration video.
Can the lathe cut threads and what kind?
With the addition of the optional Thread Cutting Attachment (P/N 3100), the Sherline lathe is capable of cutting almost any size thread. It will cut 31 different unified thread pitches from 80 to 10 threads per inch and 28 different metric pitches from .25 to 2.0mm. You can also cut any of those as right or left-hand threads. Inch threads can be cut on a metric machine, and metric threads can be cut on an inch machine. You never need be limited to threads available in standard tap and die sets again!
What is the difference between a “3-axis” mill and an “eight direction” mill?
Most milling machines are three-axis machines; that is, there are handwheels to move the part in the “X” axis (left/right), the “Y” axis (in/out) and the “Z” axis (up/down). In addition to this, the standard Sherline mill has a headstock that can be rotated for angled milling. This is a direction of movement for the cutter, but it is not an “axis” of movement for the part. The Model 2000 mill has a ram/column arrangement that also allows the headstock to be moved in and out, pivoted side to side, swung back and forth and rotated side to side. These additional four directions of movement make a total of eight possible directions either the part or headstock can be moved. As far as part movement, however, even the Model 2000 mill is still considered a 3-axis machine. A “4th axis” of movement is usually a rotary motion, and this can be added to any Sherline machine with the addition of a rotary table. (This is referred to as the “A” axis.)
By definition, then, the Model 5000 and 5400 mills are 3-axis machines with one additional direction of possible headstock movement. The Model 2000 mill is a 3-axis machine with an additional five directions of possible headstock movement. Obviously, the potential setups on a machine with more directions of movement are more diverse. The tradeoff to this greater versatility is that squaring up that many axes requires more setup time.
Do I need all those directions of movement?
Both your skill level and the nature of the jobs you intend to take on will determine the level of sophistication of the mill you need. Most beginners simply do not need an 8-direction mill. Each time one of the directions of movement is taken out of square, it must be “indicated” back to square when the job is done. This is a fact of life with a full-size machine like a Bridgeport® mill, and every machinist must become familiar with squaring up his mill. However, on the standard Sherline mills, since there are fewer ways to get it out of square, less time must be spent putting it back into square. This is one of those engineering trade-offs we always speak about where any change usually brings both an advantage and a disadvantage. Often, setups that require a part be machined from several angles at once can be achieved with the use of a tilting angle table that holds the part at an angle rather than angling the headstock. The capability of angled drilling can also be added to a standard mill either by tilting the part on a tilting angle table or by adding a rotary column attachment (P/N 3500). These methods work well on small parts; however, some castings, may be too large to be attached to a tilting angle table and the more versatile mill is the best solution.
There are many things to learn when first using a mill. A new machinist can become discouraged by trying to use a machine that is more complicated than he needs, however, a machinist with some experience will immediately appreciate the outstanding versatility of a sophisticated, multi-adjustable machine. If you are not sure you need the many levels of movement available on an 8-direction machine, we would suggest you start with a 5000 or 5400 mill. At any time you decide you need more sophistication, your machine can be upgraded to the full capability of the 8-direction machine by installing a column conversion (P/N 5650/5660). The difference in price between a Model 2000 mill and a Model 5400 mill plus an 8-direction conversion kit is about $60.00 ($1045.00 vs. $1103.25, respectively), so there is little disadvantage to putting off that decision until you are sure you need it. If money is no object and you simply want “the best,” and are willing to take the time to learn to use the extra capabilities, then, by all means, dive in headfirst and start with a Model 2000.
Is the Model 2000 mill as rigid as the Model 5000 or 5400?
The column and ram components used in the Model 2000 mill allow several more directions of movement than are available on the standard models. When the prototype was tested, we ran the table out to the end of its travel and extended the ram to its maximum overhang to fly cut a part held out on the end of the table. This is a very extreme setup that you would probably never use, but the machine had to work even in this configuration, or it wasn’t worth making. Just as on a full-size mill, the size of the cut you make must be scaled back somewhat when moving away from the center of the machine, but the cut was quite acceptable. The cross-section of the components on all the machines are designed to be appropriate for the loads that can be applied by the motor supplied with the machine. Keep in mind that we are talking about relatively low horsepower here, not the higher power motors used on a full-size mill, so the column and ram are more than sufficiently rigid.
What does “CNC-ready” mean?
All Sherline lathes and mills are now offered as “CNC-ready” machines as an option, or any existing Sherline machine can be converted to CNC-ready status with a conversion kit. This means the handwheels are removed and a stepper motor mount is installed. CNC stands for “Computer Numeric Control,” which means the movement of the leadscrews is controlled by a computer that drives a stepper motor to rotate them. “CNC-ready” means the machine is ready for you to bolt on stepper motors. You must also supply your own computer, stepper motors, motor drivers, and software. The Sherline conversions do include the handwheels that would normally come with any given machine. When using a dual-shaft stepper motor, this means you can still turn the handwheels for manual control if you so desire. (NOTE: the stepper motor should be disconnected before you do so to keep it from acting as a generator and possibly damaging your computer.) High-quality stepper motors are available from Sherline as an additional option.
Sherline now also offers complete CNC machine packages. This means all the components you need for complete CNC operation are supplied along with the machine including the motor mounts, stepper motors, driver box, cables, computer, keyboard, mouse, etc. You supply only the monitor. For more on complete CNC systems see the next question.
Who supplies complete Sherline CNC machines?
SHERLINE FACTORY DIRECT CNC SYSTEMS: Sherline now supplies a complete CNC system that even includes a new computer with operating system and software already loaded. Both mill and lathe systems are available as well as complete CNC shop packages. See our CNC menu for more details. Sherline’s system utilizes Linux as the operating system and EMC (Enhanced Machine Controller) as the software. It runs industry-standard G- and M-code. Upgrades are also available to turn manual Sherline machines into complete CNC systems. Because of software support issues, complete CNC systems including the computer are available only factory direct from Sherline.
CNC SYSTEMS FROM SHERLINE DEALERS: In addition to systems from Sherline, many aftermarket suppliers can provide the parts to turn your “CNC-ready” machine into a complete CNC system. These suppliers are listed on our “dealers” page under “CNC Dealers.” Just about any configuration you need is available, from retrofit kits to complete turn-key systems. Most require a separate computer, but the computing power required is not high, and a Pentium III (or equivalent 800 Mz) or better computer will usually work. Most of us have an old computer sitting around somewhere that will work, or used computers of sufficient capacity are available at very low cost. Sherline does not recommend one system over the others because each has its own strengths. We recommend you look up the website of each supplier and see which one best suits your needs. A link to each supplier’s site is provided from the list.
Sherline’s standard 1-year warranty still applies to CNC-ready machines, whether purchased from Sherline or from one of our suppliers. However, we do not warranty the software or other non-Sherline components that may be supplied by these aftermarket companies, so warranty service on those items must be obtained from the supplier. Technical support on the software must also be obtained from the supplier, not from Sherline.
By the way, Sherline also offers a single-axis CNC controller that can be used to drive a stepper motor attached to any CNC-ready axis of a Sherline machine. This hand-held controller is completely self-contained and can be programmed with simple commands via the built-in keypad. One controller is required for each axis, but they can be “daisy-chained” together to signal each other, allowing you to automate some fairly sophisticated tasks with very little effort. There is also a controller for the rotary table that allows you to program indexing tasks. By daisy-chaining a rotary controller and a linear controller, for example, complete gears can be cut with only five input commands and the push of one button to start the sequence. While this is not a full CNC setup, it may be sufficient for your job and is very easy to learn to use compared to learning to operate a full CNC system. To find out more, see information on P/N 8700 and 8850.
Are accessories available to do special jobs on the lathe and mill?
Yes. Over the past four decades, we have added accessories each year to make this the most complete line available from any single machine tool manufacturer in the world, regardless of size. Any machine shop job you might attempt can be achieved in miniature on Sherline tools. Accessories include attachments for thread cutting, knurling, indexing, boring and fly cutting. We have a 4″ rotary table, mill vise, power feed, wood tool rests, and a large selection of 3-and 4-jaw chucks and tool posts. High-speed steel and carbide cutting tools can be ordered as well as center drills, end mills, and collet sets. We also make special tools for watch and clockmakers.
Do I have to be an expert machinist to run Sherline equipment?
No. In fact, a good craftsman will often do better than a professional machinist on small tools. Machinists work all day with big machines that cost thousands of dollars, and will often tend to push a smaller machine too hard. It’s sort of like a race car driver going to the airport in a 4-cylinder rental car…he’ll have his foot pushed to the floor the whole time and wear the car out in a hurry!
What a good craftsman will find is a whole new world in which to express their creativity. Things that were impossible to do before now become simple operations. Sherline tools were designed to be operated by people with a good, “common sense” knowledge of mechanics. We provide the most complete instructions in the industry. With our tools, accessories, and instructions plus a willingness to take the time to make good parts, you have everything you need to enjoy the world of miniature machining.
If I don’t know anything about machining, how can I learn what I need to know to get started?
Unlike the instructions that come with most machine tools, your Sherline lathe and mill come with an illustrated color instruction book that goes far beyond just the setup and operation of the machine. In it, you will find all the basic machining knowledge you need to start making parts right away. If you want to read it before you buy it, it’s all available on our website. See the pdf instructions for Setting Up and Using a Sherline Lathe or Mill called “Assembly and Instruction Guide.”
To really go into depth on miniature machining and using Sherline tools, I wrote a book called Tabletop Machining. This allowed me to go into a much greater level of detail than I could do with the instructions that are provided free with the machine. This book will give you all the knowledge you need to get started in machining. It includes many color photos of tools, setups and finished projects by other machinists. It would be useful for anyone getting into machining, whether they are using Sherline tools or not, although it will be particularly useful for the Sherline machinist. If you desire more information than that, we also offer a book by Doug Briney called The Home Shop Machinist’s Handbook, which is another excellent introduction to the world of miniature machining. In fact, Sherline tools are used in all the setups throughout the book, and it covers all aspects of machine shop work. Both my book and Doug’s book give plans for simple but useful projects you can try to get started.
The ultimate book for any serious machinist’s bookshelf is Machinery’s Handbook. The 25th Edition contains 2560 pages of charts, formulas, articles, and information related to machining and metalworking processes. If the answer to your machining question can’t be found there, you’re probably asking the wrong question. This book has been published and updated since 1914 and is based on an information database that goes back to the 1880s. It is the largest and most informative collection of metalworking information available anywhere, bar none.
I have an older Sherline lathe. If I buy a new Sherline lathe will my old accessories still work?
Yes. Part of the design criteria for any change or advancement made on Sherline tools is that they still work with all the accessories we have made in the past. This also means that if you buy a used Sherline tool from a friend, all our new accessories will work on it, no matter when it was made. The only exception would be when an advancement eliminates the need for a particular accessory, such as the new DC motor’s greater torque and speed range eliminating the need for the slow speed attachment or the new tailstock design eliminating the need for a tailstock spindle extender.
NOTE: Our brass leadscrew cover will not work with the old-style column base.
Will my Sherline tools ever become obsolete?
No. We have been making tools since 1974, and all our accessories will still fit any of the tools we have ever made, and we plan to keep it that way. Though we will continue to strive to improve our tools and add to our accessory line as the years go by, you never need to worry that the machine you buy today will be outdated. A good lathe from the 1950s is still a good lathe today because the job of a lathe has never changed. We look at the functionality of our tools the way you might look at a pair of high-quality needle-nose pliers. It does its job so well there is no need to redesign it, and properly maintained it will still be doing its job 100 years from now.
Where are Sherline tools made?
We make all Sherline tools and accessories in our own factory in Vista, California, USA. We are a true manufacturing facility, turning raw bar stock and extrusions into finished machines and accessories using well over a million dollars worth of modern CNC machining centers, lathes, grinders, and other tooling in our own 66,000 square foot building. We even do our own plastic injection molding and laser engraving. Since we are in total control of our own production and do not import our machines from overseas, we are in a position to make sure we always have enough on hand to fill orders promptly. Orders are normally shipped the day after they are received and always within 48 hours.
By the way, we welcome visitors to the factory. Our office hours are Monday through Friday, from 8 AM to 4:30 PM. All of our products are on display in the lobby for you to examine. If you call first and let us know you’re coming, we can be sure someone will be available to take you through the factory and show you how our tools are made. Those interested in miniature machine tools usually find the big factory tools that make them fascinating to watch. These include a high-powered laser engraver and impressive computer-controlled lathes and mills. If you are ever in the North San Diego County area and would like to stop by, we look forward to meeting you. Just down the road from the Sherline plant is the Joe Martin Foundation Museum of Craftsmanship. It is open for your enjoyment Tuesday-Saturday, from 9-4 (Closed Holidays). Admission is free but donations are welcome.
Is there a Sherline dealer near me?
A list of Sherline dealers and distributors is available elsewhere on this site. It includes dealers in the USA, Overseas Distributors, and Reputable Mail Order Sources. It also includes a list of CNC suppliers.
If there isn’t a dealer listed in your hometown, the mail order list is another good place to start. Of course, you can always order directly from Sherline. We do not compete with our dealers by offering discounted prices, but we do ship your order the same or next working day. We provide the same excellent product support whether you buy from a local dealer, a mail-order supplier or directly from us.
What if I have a question that wasn’t answered here?
If you need more information, please call our toll-free number, and we’ll do our best to answer your specific questions. The number is 1-800-541-0735. Outside the USA, call (760) 727-5857 or fax (760) 727-7857. You may also email questions to firstname.lastname@example.org.
What kind of cutting oil should I use for machining processes?
You can purchase a thread-cutting oil at any large home improvement store like Home Depot or Lowe’s, or you can use charcoal lighter fluid, which can be found just about anywhere.
What is the difference between climb milling and conventional milling?
Roughing cuts and cutting hard materials should be done with “Conventional Milling.” Finish cuts can be done with “Climb Milling.” Climb milling is, as the name implies, the cutting edge of the tool that is literally climbing up the side of the part. Conventional milling has the cutting edge of the tool digging into the side of the part. For a detailed explanation of the difference between the two milling procedures, CLICK HERE for instructions.
My pulley is rubbing on the headstock. How do I adjust it?
There is supposed to be a .020″ gap between the pulley and the headstock body. If your pulley is rubbing on the headstock, chances are that the set screw that secures the pulley to the spindle has come loose. You are going to need to remove the V-belt from the pulley. Then turn the pulley until you see the access hole for the set screw (see Figure 1).
Use a 3/32″ Allen wrench and loosen the set screw about six (6) full turns. Pull the pulley back away from the headstock until you see the flat that is machined into the spindle (see Figure 2). If the set screw has come loose, it may have galled the surface of the spindle which will raise a bur. This will make the pulley removal difficult. You may need to tap the pulley with a wood mallet or other soft material. Once the pulley is removed, inspect the spindle area around the set screw flat for burs. These can be filed off easily.
Now push the pulley back on making sure to align the set screw hole with the flat on the spindle. Push the pulley up until it touches the headstock. Then pull it back until there is a .020″ gap. Now slowly tighten the pulley set screw. As it begins to make contact with the flat, turn the pulley slightly back and forth while holding the spindle stationary (use the Tommy bar to hold the spindle in place).
Continue to tighten the set screw while wiggling the pulley. This will ensure that the set screw is perpendicular to the flat. Once the set screw is set, tighten it. Now spin the pulley a full revolution and see if it is rubbing anywhere (there should still be a .020″ gap). If the gap is there, and there is no contact with the headstock, put the V-belt back on and test it out.
Is there a limit to how tight I should tighten my tool post/T-nuts to my lathe crosslide or mill table?
If you are concerned about the torque required to sufficiently tighten T-nuts or tool posts on your Sherline machine, 55 in/lbs is a good number with which to start.
Are there metric equivalents to SAE screw threads?
The 10-32 is actually the only SAE thread that has a metric equivalent. The 10-32 thread is almost the exact same size as a 5 x .8mm thread. The major diameter of the 5mm screw is slightly larger than a 10-32. If you buy a 5 x .8mm screw, you can see if it will thread in. If the fit is too tight, you can retap the 10-32 holes with a 5 x .8mm tap and the new threads should be fine.