2.007 Lecture on Shop Practices

Professor of Mechanical Engineering

Massachusetts Institute of Technology

Mill

Spray coolant on cutting tool if you are cutting steel or cutting aluminum fast.

Milling slots in sheet can be tricky- here 1/16th

Aluminum sheet is clamped directly to the table of the mill.

Increments on Lathe axes may be in units of Radius or Diameter-check with a controlled measurement to find out what convention your lathe uses.

Use the center drill to start any precision hole.

Lathe

The lathe makes a good aid for threading rod.

Drill Press

Workpiece clamped, with wood underneath. Good Technique.

UNSAFE way to hold sheet while drilling. If drill binds, sheet spins clockwise and may cause injury.

MUCH BETTER Way to hold sheet-If drill binds, sheet doesn’t spin.

Using the Fence to achieve a nice straight cut. Adjust the blade guide so only the necessary amount of the blade is exposed

Bad way to bandsaw U-channel (thin edge hanging in space—noisy, hard to control)

Bandsaw

Better way—saw force doesn’t vibrate egdes. To ensure a square cut, the crosscut fence should be used (make sure it really is square before you trust it)

Cutting Delrin using bandsaw— This demonstrates a safe method for sawing this type of geometry. Note that the Delrin rod has large residual stresses from manufacturing which are released by the cutting. Here the cut closed in on itself, preventing the blade from being removed once the cut was complete. The part was redesigned for a milled slot.

Sander

Two people working on the same machine is dangerous

Punch

Various punches are available in the shop, with different shapes and sizes of dies. This is the safest and quickest way to put holes in the sheet metal in your kit.

Shear or Notcher

The brake (sheet bender) Allows controlled uniform bends to be mad ein sheet metal. It should not be used for single pieces of round stock (high contact stresses)

Note that the radius of the bend, thickness of sheet, and location of the "fingers" can be adjusted. Moving the fingers in the top edge can allow you to create clearance for existing bends as you make a perpendicular bend, for example.

Use the wire bender for single pieces of round stock:

Brake

This tool allows you to make smooth circular bends in sheet stock. The radius of the bend can be adjusted by changing the location of the rollers.

Arbor Press

Roller

The perfect tool for pressing Square shaft flanges onto square shafts, wheels onto flanges, pulleys onto shafts, etc.

Spot Welder

Clamping parts before spot welding can be very effective.

An overwelded joint—Weak because of squashed connection between melted and solid steel. A good joint should show evidence of flow, and the parts should "intersect" by around 30-50% of diameter.

Punch or drill holes for (1/8") rivets, then insert rivet form one side, and use rivet tool to cinch parts together. "Nail" portion of rivet will snap off in tool.

Riveting

To insure a good solder joint, the JOINT (i.e wire, connector) should be hot enough to melt the solder thoroughly. Applying molten solder to a cold wire makes a cold solder joint--indicated by dull finish and brittle behavior- poor strength and conductivity. Steps

1. Clean the tip by wiping it over the moist sponge

2. Hold the tip of the iron against the wire to be soldered. (Just a little solder on the iron to aid heat transfer is ok)

3. Touch fresh solder to the wire near the soldering iron tip, but not to the soldering iron itself. The wire, heated by the iron, will melt the solder and it will flow easily to create a strong joint.

Soldering

Die in handle, tap in handle and tapping fuild. Tapping fluid is a lubricant and greatly reduces the cutting forces. In order to avoid breaking the tap, you should follow this method to break the chip: Turn the tap forward (clockwise) ½ turn, then back ¼ turn, then forward ½ turn, etc…

Threading a piece of welding rod See also threading with a lathe in lathe section.

Taps and Dies

In the 2.007 Shop it is easy to forget that the best tool for a certain job may not be a power tool or machine.

Hacksaw

The Hacksaw is great for small steel and aluminum. Piano hinges, ¼" rods and square shafts are all best cut using a hacksaw.

File Sometimes a file will take rough edges off better and quicker than a power sander

Deburring Tools These are located between the mills and lathes and are an easy way to clean up drilled holes.

Rod Cutter

Hand Tools

The best way to cut welding rod and screws in 2.007. Thread a nut or 2 onto a screw before cutting it, then as you remove the nut it will reshape any threads damaged by the cutting.

Other Methods Alcohol Cleaning of Rubber

Alcohol is the only solvent to use in 2.007. It is suggested that rubber gloves be worn when working with solvents.

Jigs and Fixtures

An effective fixture for welding many "rungs" of a "ladder" at the same angle. Truss was formed by bending the "ladder" with the brake.