Mini Lathe Features

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Table of Contents


Bed and Ways

The bed is the main body of the lathe, made from rough but sturdy cast iron. The ways are the ground surfaces on the top side of the bed on which the carriage and tailstock ride.

Bed_y.jpg (45410 bytes)

The ways have a inverted V-shaped ridge on the front side and are flat on the back side. A matching groove on the underside of the saddle rides along this ridge. The headstock casting also has a V-groove which aligns it with the ways. The ways are not hardened so you must be careful not to drop tools or the chuck on them or you will create dents and gouges.

Bed end.jpg (29112 bytes)


Carriage and Saddle

The carriage supports the cross-slide, compound and tool post and moves along the ways under manual or power feed. It comprises the saddle, a casting that rides across the top of the ways, and the apron, a casting which extends down from the saddle in front of the lathe and supports the carriage handwheel, half nut assembly and threading dial.   The lever to the right of the carriage handwheel is the half-nut lever. It engages and disengages the power feed to the lead screw as described in a later section.

Carriage2_y.jpg (35925 bytes)

The carriage handwheel moves the carriage along the ways by means of a rack and pinion drive.   The rack teeth are visible just below the ways in the photo above. The next picture shows the back side of the apron. The pinion is driven by a reduction gear connected to the handwheel.

Carriage pinion_y.jpg (47920 bytes)

For short cuts, it is often more convenient to just use the carriage handwheel to advance the carriage, but it is hard to get a nice even finish like you get with power feed.


Cross Slide and Compound

The cross slide consists of a dovetailed slide that moves at a right angle to the ways. The compound  is mounted on top of the cross slide. In the following picture the compound has been removed, showing the cross-slide mounted on the saddle. The compound bolts into the disk in the cross-slide which enables the compound to be rotated.

X_slide.jpg (26748 bytes)

The cross feed advances the cutting tool into the work at a right angle to the workpiece by means of a leadscrew and handwheel. More expensive lathes have power feed capability on the cross feed but this lathe does not. It's not a big limitation, though, given the small diameter of typical workpieces.

The compound sits on top of the cross slide and can be rotated to set the tool to advance at an angle to the workpiece. For example, by setting the compound at a 4 degree angle, you can cut shallow tapers suitable for making handwheels. An angle of 30 degrees is sometimes used so that advancing the compound handwheel by .001" actually advances the tool by .0005" (since sine of 30 = .500).

Compound2_y.jpg (39997 bytes)

One particulary inconvenient feature of the lathe is the location of the locking screws for the compound. They are underneath the compound slide and to get to them you must crank the compound slide back almost to the end of its travel. Partly because of this, I find that I don't change the angle of the compound very often. (Note: around 11/03 I came up with a nice modification to solve this problem) Here's a picture showing the compound cranked back to reveal the screws:

Compound_screws_y.jpg (39526 bytes)

A coarse but still useful protractor scale is attached to the front of the compound as an aid to setting angles. Since the divisions are about 1 degree wide you won't get a lot of precision but, most of the time, not much is needed. Older versions of the lathe and the SKU# 39916 version do not have this feature.

Protractor_y.jpg (34722 bytes)

Three adjustable gib screws are visible along the side of the compound. Each consists of a set screw and lock nut. The set screws press against a steel gib strip on one side of the dovetail, enabling you to minimize any play between the sliding surfaces. A similar set of four screws (not visible in the picture) adjusts the cross slide.

Here's a picture of the underside of the cross slide showing the lead screw. The metal gib strip is  visible just above the leadscrew.

cf_screw_y.jpg (30978 bytes)

Chromed handwheels with a ball on one end and a crank handle on the other are used to move the cross feed and compound. They work pretty well, allowing you to crank quickly or make small precise movements as needed. Unfortunately, the screw head that holds them in place tends to scrape your knuckles when you are cranking. Also, on my lathe, at least, if the cross feed crank was at the low end of its swing, it could be hit by the handwheel handle of the carriage feed - thus shifting its setting and possibly driving the tool into the workpiece (not good). For these reasons, I replaced the stock handles on my lathe with aluminum handwheels I made on the lathe.

cf_handle_x.jpg (14867 bytes)

The cross feed and compound are marked with 40 divisions of .001" which on newer models are a satin finish with nicely etched divisions and numbers. While accurate enough for most work, the divisions are not truly exactly .001". This is because the leadscrews for the cross feed and compound are actually 1mm thread pitch. Therefore, each rotation of the handwheel is actually .03937 inches instead of .04000 inches and a single division is thus .000984 inches rather than .00100 inches. Note: (10/01) Micro Mark sells a 7x12 version of the lathe with true inch leadscrews and divisions.

Does this drive you crazy? Here again, you have to recognize the limitations of the machine and work around them. In practice, I find that much of the work I do requires precision of less than .005 anyway. When I need more accuracy I use a dial indicator and/or frequently check the diameter of the workpiece (with the lathe stopped!) using a dial caliper. Or, if you are handy with a calculator, you can just calculate the number of divisions you need to move the handwheel to get the true distance you want.


Toolpost and Tools

The toolpost can hold up to four tools at once, each locked in place by hex-head cap screws. The newer model lathes (1999 and later) use 5/16" tools, but some older models and the Homier 7x12 use 3/8" tools. Strictly speaking, these lathes were presumably designed to use metric tool blanks, so imperial size tools will probably not align exactly with the centerline.  You can use shims or an adjustable tool holder to solve this problem.

Tools can be ready-made carbide tipped tools of various types or high speed steel (HSS) ground to shape by the user from commonly available tool blanks. 5/16" tool blanks can be obtained from most machine tool suppliers such as Enco, J&L, Grizzly, etc., for around $1.00 each.

Toolpost_y.jpg (42899 bytes)

The toolpost rotates around a large bolt on top of the compound slide and is locked in place by a clamping lever. You can set it to any convenient angle. Underneath the toolpost is a spring-loaded indexing pin which engages with detents in the base of the tool holder. I, and some others, did not find this useful and removed the indexing pin.

No cutting tools are provided with the lathe and you can't do much without them, so be sure to order about 5-10 blanks or premade tools when you order your lathe! Of course, if you intend to grind your own HSS tools, you will need a bench grinder. Suitable 6" grinders are available for under $50 from many sources. I bought an Ohio Forge brand from Home Depot and have been pretty happy with it. Here's a link to my tool grinding info.

Harbor Freight sells a 'quick change tool set' for about $79 which seems to be intended for use with the 7x10 lathe. You do not need it, since the lathe does come with a tool holder. Reviews on the quick change holder have been mixed: some users have returned them and those who have kept them have found it to be of limited value but useful for boring and knurling. More recently, HF started selling a QC toolpost for $99.  This one seems to be OK, but I don't have much feedback on it yet. JW Early has modified several 7x10's to use a commercially available QC toolpost. If you're interested, check out JW Early's QC toolpost mod.

You can make your own toolholders for holding boring tools, knurling tools and other special purpose tools. I will add info on this later.


Leadscrew, Power Feed

Extending from the gear drive train on the left side of the headstock, through the speed control box and out to a pillow block supporting the right end, the leadscrew can be driven under power to advance the carriage in either direction for turning or threading.

Leadscrew2_y.jpg (39941 bytes)  Pillow block_y.jpg (34361 bytes)

The rotational speed of the leadscrew relative to the spindle speed can be adjusted by manually adding and removing gears to and from the gear train. These adjustable gearing ratios also, of course, determine the number of threads per inch during threading operations.


Half-Nut and Threading Dial

A standard feature on all lathes that have power feed, the half-nut consists of two parts threaded to mate with the leadscrew which are engaged from above and below the leadscrew by turning the half-nut lever. The lever engages or disengages the carriage from the turning leadscrew to advance or stop motion of the carriage along the ways.

Half nut lever_y.jpg (46973 bytes)  Half-nut_y.jpg (45567 bytes)

On the 7x10 the half-nut pieces are cast iron and ride in a crude dovetail to engage the leadscrew. Adjusting screws, accessible from the right side of the apron, can tighten or loosen the grip of the half-nut on the leadscrew. . When the half nut lever is in the up position it is disengaged; in the down position, engaged. If the leadscrew is turning when the half nut is engaged the carriage will move towards the headstock or tailstock depending on the direction of leadscrew rotation as determined by the leadscrew direction lever on the back of the headstock.

Most often the carriage is advanced towards the headstock when making "long" (a relative term on this lathe) turning cuts. Of course you must pay attention when cutting under power and disengage the half nut as the cutting tool approaches the chuck. You can reduce this risk in some cases by reversing the leadscrew direction so that you are cutting away from the chuck. This is especially handy for short threading cuts where the carriage is moving fast compared to the chuck speed.

Cutting Screw Threads

With the supplied gears, the lathe can cut a variety of threads - many more, in fact, than are listed on the chart on the gear cover. Metric threads can also be cut within reasonable accuracy, using the appropiate combinations of gears. Check out Varmint Al's site for good info on these ratios and gear cutting. For a detailed tutorial on thread cutting, you may wish to subscribe to the  Premium Content Threading page.

Quite some time ago, Varmint Al created a BASIC program to calculate the required gears needed to cut a specified thread pitch. Paul Bussières has created a much more sophisticated version that you really have to see to fully appreciate. Click here to download a zip file containing the program and support files.  It is pretty small and downloads quickly.

Jose Rodriguez sells several excellent videos describing the 7x10, including explanation and demonstrations of threading and the use of the threading dial. Here's a close-up of the threading dial

Thread_dial_y.jpg (17707 bytes)

The threading dial is used to engage the half-nut lever at exactly the right time when cutting threads. A chart on the front of the gear cover shows the thread dial engagement settings for various thread pitches. If the leadscrew is rotatating but the half-nut is not engaged, the thread dial turns slowly. Once the half-nut is engaged, the thread dial does not turn.

Update 05/13/02

Gary Giddings posted an excellent explanation of how the threading dial works:

The main function of the threading dial is to act as an "advisor" on when to close the half-nuts onto the leadscrew. On the Homier 7x12, the threading dial (called the "indicator" there) has 8 divisions, with the odd divisions marked 1, 3, 5, and 7. So, the unmarked divisions can be thought of as 2, 4, 6, and 8. The gear on the threading dial shaft (that mates with the leadscrew) is a 16-tooth gear. Thus (with the half-nuts open and moving the carriage back and forth), the threading dial revolves once for each 16 leadscrew-threads that pass by. Or, one revolution for each inch of carriage travel.

One can try to close the half-nuts at any time. At some locations the thread ridges on the half-nut will be aligned with the grooves on the leadscrew and the nut will close smoothly, as it should. However, at other times, the nut will not be aligned properly with the leadscrew, and the nut ridges will ride on the top of the leadscrew ridges, and the nut will not close properly. With the lathe off, but just moving the carriage, one can easily try this (gently) and feel the difference. So, there are 16 places in each inch of carriage travel where the nuts will close properly ... sixteen can-close (properly) positions. The threading dial divisions line up with the index mark for every other one of these 16 can-close positions, showing us visually that we are properly located to close the half-nut and properly mesh with the leadscrew.

Call these can-close positions the "marked" positions. So, if one (again gently) tries to close the half-nuts just before a division passes the index mark, one should be able to feel the nuts drop into place just as the division reaches the index mark - at one of the "marked" positions on the leadscrew. In a similar manner, one can find and feel the eight can-close positions that lie exactly half-way between each of the marked threading dial divisions. Call these the "un-marked" positions. Try to gently close the half-nuts about one third of the way between divisions, and the closure into the "un-marked" leadscrew position should happen exactly between the index marks. So, the threading dial is, at least, acting as a visible "can-close" indicator for the half-nuts.

Using the half-nut during threading: Think of (or sketch to scale) the threaded rod that one wants to make and the leadscrew placed side by side. Start with a 16 track per inch (tpi) rod. Notice (in your mind) that every groove on the rod lines up with a groove on the leadscrew. In cutting this thread, one could close the half-nut in any groove of the leadscrew and the tool would still follow the same path down the rod while cutting the thread Next, think of a 32 tpi rod ... where two grooves of the rod are spanned by one groove of the leadscrew. Again, any closing position of the half-nut will work. This is true for any multiple of the leadscrew pitch (like 16, 32, 48, or 64). Now, think of an 8 tpi rod next to the leadscrew and notice that the rod grooves only line up with every other groove on the leadscrew (call these the "marked" grooves on the leadscrew).

Now, making repeated cuts on this rod is easily done if the half-nuts are consistently closed at any of the "marked" positions, avoiding the "un-marked" closure positions. This is true for any multiple of 8 tpi (8, 16, 24, etc.) Next, take 12 tpi (an odd multiple of 4). Here, the threads line up at the start and at each half-inch along the leadscrew (each 6 threads on the rod, and 8 threads on the leadscrew). So, the opposite indicator marks, like 1 and 5 (or 3 and 7) would work. Next to last, take a 9 tpi rod next to the leadscrew (an odd whole number of threads per inch). Here, the threads line up only at the start of each inch along the leadscrew (9 threads on the rod, and 16 threads on the leadscrew). So, any one indicator mark, like 1 only (or 3 only, etc.) would work.

Finally, take a 25.4 tpi thread next to the leadscrew. The only place the threads match is at the start point. At one inch, at two inches, etc. - no match (they do match at 5 inches, but that does not do us any good here) So, best to keep the half-nuts always closed in these cases, and reverse back to the start point for the next pass.

Reading the chart "Indicator Table" on the Homier: The numbers punctuated with periods (like 1.3.5.7 or 1.5) should be read as if they are written with commas and spaces (as 1, 3, 5, 7 or 1, 5) and they mean use any of the mentioned settings. The designation "1~8" means 1 through 8 - use any of the settings (1, 2, 3, 4, 5, 6, 7, or 8). There are only 4 designations in the chart: Any (1~8): for any multiple of 8 tpi (8, 16, 24, 32, 40, 48 tpi) Odd Number (1.3.5.7): for any odd multiple of 4 (12, 20, 28, 36, 44, 52 tpi) One or Five (1.5): for an even tpi not covered above (14, 18, 22, 26, 38) One Only (1): for all odd tpi (13, 19, and others) The simple answer - always use "1". (Note that this really means always use the SAME number to re-start each new cut pass). Sketching the leadscrew and rod threads has helped me to understand the threading dial. I hope this helps somebody else.


Change Gears and Tumbler Gears

On the left side of the lathe is a plastic cover which conceals the gear train that drives the leadscrew. This cover is held in place by two 4mm bolts. Removing the cover gives access to the gear train.

    Left_side_y.jpg (63709 bytes)   Gears_y.jpg (54618 bytes)

The small white nylon gears are the tumbler gears which are controlled by the leadscrew direction lever to determine the rotational direction of the leadscrew. In the neutral position neither gear should be touching the metal gear on the spindle shaft.

Additional gears (not shown) are provided and together allow the lathe to cut a wide variety of inch and metric threads. Expensive lathes have gear sets attached to quick change levers to quickly and conveniently select the desired thread. On this lathe you must manually remove and add the proper gears each time you need a different thread pitch. This is a pain, but for most users, threadcutting is done infrequently, so the invconvenience is tolerable. For normal power feed operation, the gear train is set to 256TPI. Some of the possible thread pitches and gear combinations are shown on a chart on the left end of the lathe:

Threads_y.jpg (49605 bytes)


Tailstock, Centers and Drill Chuck

The tailstock casting rides on the ways and is locked in place by means of a nut and 17mm wrench. A handwheel advances the tailstock spindle for drilling and tapping operations. The spindle bore is a #2 Morse Taper and a #2MT ball-bearing live center and a dead center are supplied with the lathe.

Tailstock_y.jpg (37739 bytes)

A tailstock chuck is not supplied and is an essential accessory for drilling, so be sure you order one when you order your lathe. A 1/2" chuck is a good choice to start with but you may find that you want a 3/8" or 1/4" chuck later on. The chuck is mounted in the tailstock spindle using a #2MT arbor, so you will also need to purchase the arbor. The back of the chuck will either be threaded or will have its own taper - usually a Jacobs taper - so you must get an arbor that also matches the chuck. I got my 1/2" chuck from Grizzly (P/N G1649, $16.95) along with an arbor (P/N G1434, $7.95) that is #6 JT to #2 MT.

#2 MT arbors often have a flat tang on the end and are too long to fit in the shaft of the tailstock spindle. Therefore the tang must be removed. This can be done by cutting with a 'chop saw', a diamond or carbide tool in a Dremel or similar tool. I used a fiber cutoff blade in my 10" radial arm saw and clamped the arbor between two pieces of wood in my drill press vise. Check the back postings on the 7x10 interest group for much discussion on this topic.


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Mini-Lathe    Mini-Mill    Bandsaw   Grinder  Anodizing   Lapping    Links   Safety     Premium Content

Mini-lathe:  Accessories   Adjustments   Capabilities    Chucks    Dial Indicators   Features   Getting Started   Glossary     Introduction   Materials    Modifications   My Shop   Operation    Reviews    Sieg Factory    Tool Grinding    Troubleshooting   Tuning     Versions