Problems relating to the alignment of vices

Aligning a plain vice parallel to the milling table

This is probably the most common way of holding a workpiece. If it is used for one job it could well be used for others without being setup up again. In general it is always worth doing this to a reasonable standard.

There have been suggestions for special gadgets for doing this. The problems with these is that they usually work for one particular vice in one particular position. All of the methods here will work where the jaw is at any height relative to the table and also wherever the jaw is across the milling table.

Mew no 182 p40

A     Aligning a vice using a DTI

This is the most accurate method but is time consuming.

See  –  using a DTI

B     Using a parallel, angle plate and square method.

      This method is usually good enough but is quicker than using a DTI.

        See  –  Parallel, angle plate, square

C     Using fixed  alignment blocks

      Since this arrangement is very common it could well be that it is worth having one plain vice fitted with alignment blocks so that it can always be mounted on the milling table and will always be aligned properly.

       See   –  fixed alignment blocks

 D     Using just one parallel

Fit a long parallel in the jaws. Check by sight against an edge of a T-slot. Though this might be good enough for one job, it will not be good enough for others that might follow it. It is best if this is only used if it is known that it will not be left like this.

 

PP37

Aligning a plain vice at right angles to the milling table

A     Aligning using a DTI

Most accurate but the most time consuming

Use   TT9   use a DTI

B     Square, angle plate and square method

This method is usually good enough but is quicker than using a DTI.

 

See   MM29  Parallel/square/protractor, angle plate, parallel

 

C     Using fixed alignment blocks

This is accurate and quick but only works if the vice can be fitted and is fitted with alignment blocks. Very few vices have slots for fitting alignment blocks for a vice at right angles. It is not often needed like this and this stops it being used parallel to the milling table.

 

See  MM24  Use of fixed alignment blocks

 

D     By sight

Not recommended

 

See   MM23  setting a vice by sight

 

PP41

Aligning a vice at an angle to the milling table

If it necessary to use a vice at an angle to the milling table it is best to use a swivelling vice for reasons explained later.

A swivel vice can be aligned as a plain vice in order to be parallel or at right angles to the milling table in exactly the same way as a plain vice.

A     Aligning using a DTI

Cannot be done

B     protractor, angle plate and square method

This method is usually good enough and is the only practical method available.

This can be done using a variation of the parallel, angle plate and square method. In this case instead of the parallel a precision protractor is fitted in the jaws of the vice. The other arm is set against one side of the angle plate. The other side of the angle plate is set against the square etc.

 

See  MM29  Parallel/square/protractor, angle plate, parallel

 

C     Using fixed alignment blocks

Not relevant

D     By sight

Not possible

 

PP59

Aligning a tilting vice

A tilting vice can be tilted to an angle using the markings on the vice. The accuracy of these can be limited.

It can be aligned more accurately by fitting a precision protractor in the jaws in a vertical position. The angle will only be correct in the plane at right angles to the jaws of the vice. The protractor must lie in the vertical plane to give an accurate reading. The other arm of the protractor can be tested to be horizontal using a DTI (plunger sort) mounted on the vertical head.

 

Fig. 177 Aligning a tilting vice 586

 

To do this the jaws of the vice have to lie along the x axis. But this is only so the DTI can run along the blade of the protractor. Once the angle of the tilt has been set it would still be the same if the vice was rotated about the z axis.

 

PP95

Setting the angle on a sine vice

The sine vice works like a sine bar. A stack of slip gauges is put underneath it to set the angle. Since the distance from the point about the vice tilts to the point the slip gauges are in contact with is very accurately set, the angle can be computed.

The length between the axis of rotation and the roller is a fixed length. This is the hypotenuse of a right angle triangle. The height of this triangle is the height of the stack of slip gauges. The relationship between these and the angle ? is:

 

Sine (?) = opposite (height of the slip gauges)

Hypotenuse (length from axis to roller)

 

See   TT7   sine bars and slip gauges

 

A sine vice might be metric or imperial. Consider the common one made by Jones and Shipman. To be able to make very small angles would require a stack of slip gauges with a smaller height than that of the thinnest slip gauge. The vice is constructed so the with no slip gauges it tilts slightly below the horizontal. To be horizontal it needs a slip gauge of 0.100 inches thick. It is then easy to make up any size bigger than this. So for whatever height is required 0.100in has to be added to this.

 

PP94

Alignment of the swivel, tilt and swivel vice

All three movements of this vice are calibrated. For many purposes these are good enough.

The alignment problem here is the horizontal tilt axis. It is possible for the jaws of the vice to be lined up vertically and horizontally yet not be correct. In the figure the first swivel is at 20° but the top one is at 20° the other way.

 

Fig. 178 The problem when aligning a swivel, tilt and swivel vice 612

 

It does not appear to be easy to set the vice up so the axis of the tilt is perfectly at right angles to the milling table.

This is further complicated by the nature of the tilt and second swivel joints. They are both made with tapers. They both have a useful feature whereby the taper is forced apart. But the other consequence of his is it is very difficult to adjust these joints precisely by tapping with a soft headed mallet.

 

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