The standard specification of a grinding wheel is A-46-M-6-V-21. It means a wheel of
If in a turning operation both the feed rate and the nose radius are doubled the surface finish value will be
High of surface roughness be doubled means surface finished hill be decreased by 50%
The ideal cutting fluid for low speed machining of metals should be one which
Function of cutting fluid
(4) Save from external contamination.
Cutting speed in grinding is set to a high value to
Pure metal pose machinability problem in turning operations. The reason is the
Pure metals are ductile, produces long & continuous chip
If the longitudinal feed in centreless grinding is expressed by Vf = πDN sinα, D stands for
For cutting double start screw threads of pitch 1.0 mm on a lathe, the thread cutting tool should have a feed rate of
Pitch = 1mm
Start = Double Start
Feed rate = 2 × 1 = 2 mm/res.
A milling cutter having 10 teeth is rotating at 100 rpm. The table feed is set at 50-mm per minute. The feed per tooth in mm is
ft = 0.05 mm
A milling cutter having 8 teeth is rotating at 150 rpm. If the feed per tooth is 0.1 mm, the speed in mm per minute is
F = ft ZN
= 0.1 × 8 × 150
F = 120mm/min
A grinding wheel A 27 K 7 V is specified for finish grinding of a HSS cutting tool. What do you understand about the wheel from the above code.
Is this an appropriate choice?
Grain size is given for rough cut.
27 → rough cut
Cutting power consumption in turning can be significantly reduced by
By increasing the back rake angle the drag between chip & tool decreased hence cutting power consumption decreased.
Among the conventional machining processes, maximum specific energy is consumed in
Grinding because of smaller chips, large cutting area.
Plain milling of mild steel plates produces
Abrasive material used in grinding wheel selected for grinding ferrous alloys is
Less chance of wheel wear. Other wise all other to ferrous material.
A conventional lathe and a CNC lathe are under consideration for machining a given part. The relevant data are shown below:
The machine preferred for producing 100 pieces is
The hardness of a grinding wheel is determined by the
Bond strength gives the hardness of wheel for soft material strong bond material is used for hard material soft bond material is used.
The time taken to drill a hole through a 25 mm thick plate with the drill rotating at 300 rpm and moving at a feed rate of 0.25 mm/rev is
T = 20 sec
Cutting tool is much harder than the workpiece.Yet the tool wears out during the tool-work interaction, because
Metal cutting takes place in plastic deformation zone where work hardening takes place as chip get strained.
Better surface finish is obtained with a large rake angle because
As rake angle increase shear plane decreases so smaller force one required so smooth machining operation
The length, width and thickness of a steel sample are 400 mm, 410 mm, 40 mm and 20 mm, respectively. Its thickness needs to be uniformly reduced by 2 mm in a single pass by using horizontal slab miling. The miling cutter (diameter : 100 mm, width ; 50 mm) has 20 teeth and rotates at 1200 rpm. The feed per tooth is 0.05 mm. The feed direction is along the length of the sample. If the over-travel distance is the same as the approach distance, the approach distance and time taken to complete the required machining task are :
Depth of cut ⇒ (d = 2 mm) Milling cutter,
D = 100 mm
W = 50 mm
Z = 20 tooth,
N = 1200 rpm
ft = 0.05 mm/tooth rev
f = z x ft
= 20 x 0.05 mm/rev
= 1 mm/rev
Over travel = Approach (A)
Total length covered by tool
L + 2A = 400 + 2 x 14 = 428 mm
Time for one pass,
= 21.4 second
Assertion (A): Single start threads are used for fastening purposes.
Reason (R): Single start threads are easier to produce in a lathe.
Single start thread on be made by single point cutting tool.
A drilling machine has to be designed with 8 spindle speeds ranging approximately between 120 to 1200 rpm. The 5th spindle speed is
Nmin = 120 Nmax = 1200
N = 8
In a grinding wheel marked with AA-48-L-7-V25, L refers to
Find the speed range ratio for the drilling machine spindle if the minimum and maximum diameters of drills used are 5 mm and 25 mm respectively and if the machinability indices for the work materials are 120 (brass) and 40 (alloy steel)
If the index crank of a dividing head is turned through one complete revolution and 10 holes in a 30 hole Circle plate, the workpiece turns through (in degrees)
By one complete revolution of indexing crank the work piece turned through = 360/40 = 9
and by 1/3 Rotation 9/3 = 9
total rotation or turn of workpiece = 9 + 3 = 12°
A grinding wheel is said to be glazed if
Glazing is when hard material is grounded by hard wheel.
A side and face cutter 125 mm diameter has 10 teeth. If operates at a cutting speed of 14 m/ min with a table traverse 100 mm/min the feed per tooth of the cutter is
D = 125 mm Z = 10 teeth V = 14 m/min
F = 100 m/min
ft = 0.25 mm/tooth
During turning of a low carbon steel bar with TiN coated carbide insert, one needs to improve surface finish without sacrificing material removal rate. The achieve improved surface finish one should
By increasing nose radius, surface finish increases.
The binding material used in cemented carbide cutting tools is
Cobalt used as a binding agent in cemented carbide tool. which increases the grain size transverse rapture strength increases & hot hardness decreases.
Grinding ratio is defined as Volume of wheel wear