Using a Vice

Vices use hardened and serrated steel jaws to grip the work-piece. These jaws are removable and can be replaced if worn. In normal use, make sure the jaws are kept tight.

The serrated jaws keep a tight grip on the work-piece but they also inevitably mark it. So in most situations, the jaws are covered with soft metal jaws. The easiest way of making these is to cut some short sections of aluminium angle a little longer than the width of the jaws.

The work-piece is positioned within the jaws of the vice and the vice just nipped-up.

The work is then rechecked for location, keeping in mind that you don’t want your hand tool (eg a file) to touch the hardened jaws of the vice. The vice is then firmly tightened by hand.

Normally the full width of the jaws is employed to hold the work-piece (or the work-piece is centred, as here) but sometimes the item must be positioned at one end of the jaws. Note, however, that doing this frequently over a longer period will distort the jaws – as a result, the clamping force will no longer be even across the jaws’ full width.

Mounting a Vice

Strange as it sounds, mounting the vice is perhaps the most important aspect of vice-use to get right. If the vice is mounted incorrectly, it will be hard to use and may even be dangerous.

Height

A vice must be mounted so that when you are standing next to it, the top surface of its jaws is level with your bent elbow. If the bench top is too low, the vice can be raised with a hardwood block.

If the vice is too high, you can stand on a rubber or timber board. Having the vice at the correct height will allow much more accurate filing and hacksaw cutting – your fore-arm will be able to move back and forth horizontally.

Rigidity

A vice must be very securely mounted. This has implications both for the way in which it is attached to the bench, and how secure the bench itself is.

Some books recommend the use of coach screws to attach a vice to a bench – but don’t! Instead, use heavy-duty bolts, nuts and washers to securely bolt the vice to the bench. Large vices use four bolts, while smaller vices may use only two.

It’s no use attaching the vice securely to a bench if the bench can then ‘walk’! The heavier the bench, the better. If you’re working with a bench that is not bolted down and is lighter than desirable, at least make sure that it has a lower shelf on which weighty objects can be placed. A bench that is not bolted to the floor needs to have a mass of at least 150kg if it isn’t to be easily moved around by objects being manipulated in a 150mm vice. If used to mount a vice, this bench should be bolted to the concrete floor. Note the 'feet' that can be used for this purpose.

Location

As we’ve indicated above, vices are normally mounted on heavy benches. But where on the bench? This is a deceptively tricky question. As shown in this diagram, the parting line of the vice is best positioned so that it very slightly overhangs the edge of the bench. In that way, long items can be vertically mounted in the jaws of the vice – and that’s even more important when mounting a vice with offset jaws.

Bench Vice / Work Vise

In order that work may be held rigidly for the performance of hand operations, the machinist uses what is termed a vise. They are made in a great variety of forms and sizes, but all consists essentially of a fixed jaw, a movable jaw, a screw, a nut fastened to the fixed jaw, and a handle by which the screw is turned in the nut and the movable jaw brought into position. The sectional view, Fig. 43, shows these parts clearly and also a device, present in some form in all vises, by which the movable jaw is separated from the fixed jaw when the screw is backed out of the nut. In the machinist's vise, both jaws are made of cast iron with removable faces of cast steel. These may be checkered to provide a firm grip for heavy work, or may be smooth to avoid marking the surface of the plate operated upon. When holding soft metal, even the smooth steel jaws would mar the surface; and in such cases it is customary to use false jaws of brass or Babbitt metal, or to fasten leather or paper directly to the steel jaws. The screw and handle are made from steel and the nut from malleable iron.

Standard Wire Gauge (SWG)

• lA gauge for measuring the diameter of wire, usually consisting of a disk having variously sized slots in its periphery or a long graduated plate with similar slots along its edge.
• lA standardized system of wire sizes.
• lWires are manufactured to standard sizes and labeled with their SWG.
• lAs the SWG increases the diameter decreases. 

 

How to use Micrometer?

• •Thimble

–The thimble rotates around a cylinder which is marked in millimeters.

–The left-hand side of the thimble has markings all around it.

–The line labeled 0 is the primary pointer.

• •Close the jaws

• •Calculate the least count
• •Place the object between the two jaws
• •Record the position of main scale where the two measuring rods met.
• •Note the position of the circular scale which coincides with main scale 

  

 

Reading of the Instrument

 

 

lReading of the instrument = MS div + (coinciding CS div x L.C)

l= 8+ (12 x 0.01)

l= 8 + 0.120mm

l= 8.120 mm = 8120 µm

 

 •

Micrometer

• lFunction

lMicrometer allows the measurement of the size of the body i.e. thickness, depth, inner/outer diameter.

• lFeatures

lTwo jaws (one fixed, one movable)
lSpring loaded twisting handle
lEasy to use and more précised
lCan measure up to .001cm

Structure of the Micrometer

 

• lJaws

l2 jaws (one fixed, one movable)

• lCircular Scale

lMovable jaw is attached to a screw, scale on this screw is called Circular scale.

lEither 50 or 100 divisions

• lLinear Scale

lHorizontal Scale

• lFrame

lThe C-shaped body that holds the anvil and sleeve in constant relation to each other.

• lAnvil

lThe jaw which remains stationary.

• lSpindle

lThe jaw which moves towards the anvil.

• lLock Nut

lA lever, one can tighten to hold the spindle stationary.

• lSleeve

lThe stationary round part with the linear scale on it. (Main Scale)

• lThimble

lThimble rotates around the sleeve.

• lRatchet Stop

lDevice on end of handle that limits applied pressure by slipping at a calibrated torque.

Pitch of Micrometer
 

l

When the head of the micrometer rotate through one rotation, called pitch of the micrometer.

lThe screw moves forward or backward 0.5mm on the linear scale.

lPitch of Micrometer = distance on linear scale in one rotation

Pitch of Micrometer = 1/2 = 0.5mm 

 

Least Count

• lLeast Count = Pitch of the Micrometer / Total number of circular scale division

• lLeast Count = 0.5 / 50 = 0.01mm           = 0.001cm

How to use Vernier caliper?

• •Close the jaws

• •Calculate the least count

• •Place the object between the two jaws
• Record the position of zero of Vernier scale on the Main scale (3.2cm)

• •Notice the reading of VS which coincides with MS reading (3rd division in this case) 

 

• lReading of the instrument = MS div + (coinciding VS div x L.C)

l= 3.2 + (3 x 0.01)

l= 3.2 + 0.03

l= 3.23 cm

 

One More Sample For Reading 

 

 

• To measure the depth 

 

• lA rod extends from the rear of the caliper and can be used to measure the depth.

• lOpen the jaws of caliper and place the rod inside hole of the object, such as the rod reaches the inner most portion of the object.

• lRead the Vernier caliper. (same procedure as described in previous slides) 

 

 

Vernier caliper

• lFunction

lTo measure smaller distances

lCan measure up to .001 inch or .01mm.

• lFeatures

lLarger, lower jaws are designed to measure outer points e.g. diameter of a rod.

lTop jaws are designed to measure inside points e.g. size of a hole.

lA rod extends from the rear of the caliper and can be used to measure the depth. 

 

• Structure of Vernier caliper

 

   

• Main Scale

lMain scale is graduated in cm and mm.

l

• lVernier Scale

lIt slides on the main scale.

lOn Vernier scale 0.9cm is divided into 10 equal parts.

l

• lJaws

lTwo inside jaws (Upper)

lTwo outside jaws (Lower)

 

• Least Count

lLeast count (L.C) is the smallest reading we can measure with the instrument.

lL.C = one main scale division – one vernier scale division

L.C = 1mm – 0.09mm

L.C = 0.1mm = 0.01cm

lLeast Count = Value of the smallest division on MS/ Total number of division on VS

L.C = 1mm / 10 = 0.1 cm / 10 = 0.01cm

 

 

Measuring Tools

lVernier caliper

lVernier caliper is a measuring device used to measure precise increments between two points. 

 

l

lMicrometer

lMicrometer is a measuring device used for precisely measuring thickness, inner and outer diameter, depth of slots.

l

l 

SWG

lA gauge for measuring the diameter of wire, usually consisting of a long graduated plate with similar slots along its edge.

 

 

Meter and its Multiples

Meter and its Sub-Multiples

Measurement

• lMeasurement means to compare something with standard.lE.g. measuring length of a wire, diameter of a cylinder, depth of any object.

• The SI unit of length is meter (base unit).

• Its multiples and sub-multiples are given in the table. 

Introduction

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