Charlie's Metalworking Page

2/28/07 Yanked some dead links and general cleanup.
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Atlas Lathes

Wood Steel Aluminum Filing
Accessories- Reversing Switches Toolpost Grinding Troubleshooting

I purchased an Atlas 12"x36" lathe a couple of years ago. Here is what I've learned.

Atlas Press started out making presses in the early 1900's. They eventually moved into lathes, milling machines and drill presses. Clausing also made lathes. Atlas Press company bought out Clausing and adopted the Clausing name. Atlas "Clausing" still supports their old products. You can buy parts from either clausing or Sears Online. Sears has more parts, but they generally charge more. There were earlier models, some made by Atlas and some made by AA Engineering. The Atlas Lathes are preferred because of their heavy construction.

You can turn wood with a metal lathe, provided you

1. can obtain a high enough spindle speed for the diameter which you are turning.

2. use the proper tools, dogs/centers or faceplate and toolrest.

Atlas printed an excellent book titled "Lathe Operation Manual." Clausing sells it. It describes turning wood with the 12"x36" lathe.

What kind of steel are you using? Mild steel most commonly sold is low carbon AISI/SAE 1018 or 1020. This is horrible for cutting threads. There is a property called "machinability" and this is one of the worst, rated around 60 percent. 1018 can be improved by a process known as "spheroidizing". Heat the steel to just below the critical point, hold there for at least 1 hour, then slowly cool. The longer the steel is held near the critical point, the greater the degree of spheroidization. I turned a mild steel crucible used in a Dave Gingery charcoal furnace and it had an excellent surface finish. I am certain this was due to the spheroidization which occurred when I was melting the aluminum (1 hour or so) and the resulting slow cooling once I put the crucible back in the furnace and let it cool down slowly.

The preferred type of aluminum is 6061, high in silicon. This machines quite well. A metal polish available from McMasters will give you a mirror-like finish- unbelievable!

Metal Polish- Haven't tried this yet.

You can use any metal file on a lathe, but special files are made for lathes, with different angles on the teeth.

Toolpost Grinding-

Tip- Use a "dremel" tool and a rubberized abrasive wheel for polishing steel- It does an incredible job.  The "Dremel" is not sufficient for grinding, as it is not rigid nor powerful enough.  You can make a toolpost grinder, or you can buy one for $1000-1400.

Cutting threads and they gall or tear.- Mild steel will do this. Make sure your tool is sharp. Take small cuts. Use "free maching type steel instead.

Reversing Switches

It is entirely O.K. to reverse the direction of a lathe with a threaded spindle. On the 12x36" lathe, there is a dowel pin which is used to lock the spindle when attaching the chuck or faceplate, call it a "spindle lock". Another method to lock the spindle is by using the back gear. The chuck must be tightened adequately to prevent it from coming off. Make sure you release spindle lock before starting the lathe. The challenge is to avoid tweaking anything out of alignment. Read Page 75 of "manual of lathe operation and machinists tables".

Remember, torque= force x distance. Think about how much force a cutting tool is able to place on the work before failing. Multiply that by the diameter of the work which you are turning. The result is the minimum torque which the chuck must be tightened. This only applies if you are operating in reverse, but why would you operate a cutting tool in reverse?? If you are sanding a wood turning, a better finish is obtained if you reverse the direction occasionally. Sanding requires minimal torque. Another application for reverse is threading. During the reverse portion of a threading operation, since the tool is not cutting, there is zero torque on the spindle. With a toolpost grinder, reverse is required- Page 191 of "manual of lathe operation and machinists tables".

What usually happens instead is loosening due to the rotational inertia of the chuck. When a single phase motor starts, the angular accelleration is quite high. Since chucks are usually pretty massive, with a large diameter, which equates to a high rotational inertia, a high startup torque is encountered. Torque= rotational inertia X angular accelleration. Another way to tighten the chuck is to use the the inertia of the chuck itself while spinning it on.

**** DISCLAIMER** *******************************************************
The following is for informative purposes only and is not intended to be a substitute for electrician's school. High voltages are involved which could cause injury or death. Before attempting any wiring, a licensed electrician should be consulted.
As far as wiring up the switch, there are basically 2 wires coming in on a 120V single phase service- hot and neutral. On a 240V service, there is an additional hot lead which is 180 degrees out of phase with the other. A single phase motor usually has 2 windings, main and auxilary. Main is to provide a field which is, well, single phase. A single phase field does not rotate in space, it can only change direction in a linear fashion. In order to get a rotating magnetic field, you must have a second winding which is perpendicular to the main winding. This is called the auxilary winding. The current fed to the auxiliary winding must be out of phase with the current to the main winding, ideally 90 degrees. Different methods are used to achieve this- capacitive, reactive(split phase). The capacitive motors are easy to recognize by the big semi-cylindrical protrusion from the side of the motor. That's the capacitor.

Most motors have a centrifugal switch that bypasses the auxiliary winding once the motor is up to speed. On some motors, you can hear it click in and out. If the motor is running without the aux and you switch directions, the field is not rotating, just reversing.... So the motor just keeps going round and round... Kind of like a piston and a crankshaft.

There are different kinds of reversing switches, but most of them reverse the phasing to the auxiliary winding. The main winding can remain the same, since it does not affect the direction of rotation of the magnetic field. Follow the directions which come with the switch and motor. Also, your local library has many titles on electric motors. It would be well worth the trip.

With a three phase motor, the order of phases is reversed ABC to ACB.

The ultimate solution is a variable speed AC drive, which uses a three-phase motor. Better torque is obtainable, and you can reverse the motor in a smooth spin-down fashion. Finer speed control is capable than with the pulleys and countershafts. I plan on converting my lathe to one of these systems in the distant future. CNC lathes usually have some kind of AC drive.

Accessories -  Just a list of things I plan on listing drawings or links for

Toolpost Grinder
Dremel Toolpost Grinder
Spherical Cutter
Clamp Knurler
Thread Rolling Wheels
Centerless Grinding Setup
Draw-in Collet Chuck
Woodturning Toolrest
Boring Bar Holder
Surface Grinding Setup
Dividing Head
Milling Attachmnt

Drilling a backplate with 3 holes.

I've done a lot of drilling/tapping of panels for electrical installations and mounting printed circuit cards. Without a CNC mill or indexing head, you can still obtain very precise results. A template is hard to line up with the workpiece. Better to use the workpiece itself as your canvas.

Some tips-

1. Get a spring-loaded center punch.
2. Get an etched steel rule with 100ths, 1Oths, 64ths and 32nds. Get a thin one.
3. Get a small x-acto knife for use as a scribe.
4. Consider a head-mounted magnifying glass.
5. Get some layout paint, red and blue. Helps to see the marks.
6. an engineer's square is good to have for square pieces.
7. Numbered drill set. Precision Twist drill makes a nice cobalt set.
8. drill press
9. drill press clamp

Now for the backplate-

1. Find out what the bolt hole radius is.

2. The most critical part of drilling those holes is to make sure they are concentric. Mount the backplate on the spindle. Put a dead ctr in the spindle. Mount a scribe tool in the toolholder and orient it perpendicular to the spindle. You can use a narrow pointed tool. Get the scribe as close as you can to the center of the spindle, using the dead center as a reference. Zero out your cross slide indicator dial. Move the scribe tool out by bolt hole radius, making sure to account for leadscrew backlash. Run the tool up to the backplate and lightly scribe a circle with the same radius as the bolt holes.

3. Take the backplate off the spindle and take to a well-lit workbench. Check the radius for accuracy. A pair of dividers comes in handy.
4. Scribe a reference point for the first hole. Call this point "A".
5. Imagine a equilateral triangle inscribed within the circle you just scribed. To find the length of each side, using the radius, calculate r * 1.7321 (note- this is a 30/60/90 triangle and the ratios of the sides are hypotenuse=2, opposite=1 and adjacent= sqrt(3))

This is the length of each side of the triangle, and the distance from one bolt hole to any other.

6. Measure from the reference point the distance calculated in 3. Call this point "B". Mark the spot with your x-acto knife. The etch marks on the rule come in real handy for this. Also, since calculators usually output in decimal, the 100th's of an inch feature on the rule comes in real handy.
7. repeat #4, going in the opposite direction. Call this point "C".
8. Check your work by measuring from point B to Point C.
9. Center punch at each mark.
10. Drill a pilot hole with a small bit. Use the drill press clamp.
11. Drill to final size.
12. Depending upon the fasteners you are using, you may need to countersink/counterbore.

This technique can only get you to within a couple of hundredths of accuracy, which is why the fit of the recess step is so important.

I've made templates with Autocad and sometimes the plotter/printer isn't very accurate when it comes to linear measurements... If you CAD it out, use an accurate rule to verify your printer is accurate.

Other Processes
Laser Diodes-furnace controllers Anodization
CO2 Laser Cutting
CNC setups
Laser Measuring
Laser Leveling