Revolving Centres are Frictionless. Used for supporting heavy jobs and jobs revolving with high speeds. A high-speed steel inserted centre is supported by two bearings housed in a body. It is also called the revolving dead centre.
22) A dead centre is the lathe centre fixed in
Tail stock
Related ISRO Technician-B Fitter Question Paper - 2016 (Set - 4) with Answer Key
Bastard, Second cut, Smooth and Dead smooth
The grade of file tool is listed below
1. Rough
2. Bastard
3. Second Cut
4. Smooth
5. Dead Smooth
1) Rough File : A rough file is used for removing rapidly a larger quantity of metal. It is mostly used for trimming the rough edges of soft metal castings.
2) Bastard File: A bastard file is used in cases where there is a heavy reduction of material.
3) Second Cut File: A second cut file is used to give a good finish on metals. It is excellent to file hard metals. It is useful for bringing the jobs close to the finishing size.
4) Somooth File: A smooth file is used to remove small quantity of material and to give a good finish.
5) Dead Smooth File: A dead smooth file is used to bring the material to accurate size with a high degree of finish.
60 degree Prick Punch
This punch is used for making witness marks is 60 Degree Prick Punch.
0.8 mm
Pitch selection for Hacksaw Blade:
For soft materials such as bronze, brass, soft steel, cast iron, heavy angles etc. use a 1.8 mm pitch blade.
For tool steel, high carbon, high speed steel etc. use a 1.4 mm pitch. For angle iron, brass tubing, copper, iron pipe etc. use a 1 mm pitch blade.
For conduit and other thin tubing, sheet metal work etc. use a 0.8 mm pitch.