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close this bookFundamentals of Fitting - Course: Techniques of Fitting and Assembling Component Parts to Produce Simple Units. Instruction Examples for Practical Vocational Training
View the document(introduction...)
View the documentPreliminary Remarks
View the documentInstruction Example 31.1. Mitre Angle Gauge
View the documentInstruction Example 31.2. Square Bolt for Three-jaw Chuck Wrench
View the documentInstruction Example 31.3. Locking handle for Three-jaw Chuck Wrench
View the documentInstruction Example 31.4. Keyed Joint of Pulley and Shaft

Instruction Example 31.2. Square Bolt for Three-jaw Chuck Wrench

Practising of the shift-fitting of broad plane surfaces by manual filing.



Round stock made of steel (600 MPa)

diameter: 16 mm
length: 105 mm


Steel scriber, finishing file and bastard file 200 mm (flat), hand hacksaw

Measuring and testing means

Steel rule, vernier caliper, small bevelled edge square, feeler gauge 0.1 mm

Auxiliary accessories

Vice, square bush of a small three-jaw chuck (by the example of a wrench opening of 12 mm)

Necessary previous knowledge

Manual working of materials - measuring, testing, marking, sawing, filing

Sequence of operations


1. Prepare the workplace, make the working material available

- Check for completeness

2. Saw the square bolt to the required length, mark the square and pre-file it with an over-dimension of 0.4 mm for interference

3. Take a surface as reference surface and file an adjacent surface angularly

- Take care that the surfaces are even

4. Angularly file the second surface contiguous to the reference surface; overdimension only 0.2 mm

5. File the last surface opposite to the reference surface evenly, always check its angularity to the other surfaces

6. Finish the square to fit size; square has to touch the square bush slightly

7. Drive the square with your finger slightly into the bush and determine the pressure points (points of contact)

8. File off of the pressure points (points of contact)

9. Repeat operations 7 and 8 until the square can be inserted in the bush in any rotation

- Clearance shall not exceed 0.1 mm

10. Test the shift-fitting and the clearance