TPC 327 Flashcards
You will probably use the dividing head most often to machine?
Shapes, like gear teeth
What machining method relies on the index holes around the spindle?
Direct indexing
With a gear ratio of 40:1 how many times must you turn the worm gear and spindle to complete one 360 degree rotation?
40 turns
Indexing fractions of a turn formula
T= 40/N
In simple angular indexing one crank turn produces?
360/40 or 9 degrees
For simple angular indexing use any circle in the index plate with a total number of holes that can be divided by?
Nine, for example 27,36,45, or 54
one turn of the crank moves the spindle how many degrees?
9 degrees
In compound indexing, you first turn the crank, as in simple indexing. Next….
You turn the index plate itself to provide the final index
Differential indexing is similar to, but more accurate than?
Compound indexing
How does a universal dividing head differ from a plain dividing head?
The spindle nose can be rotated 90 degrees from parallel with the tabletop to a perpendicular position
Workpieces can be held between the center in the spindle nose and the center in the?
Foot stock
The power flow moves from the dividing head spindle to the driver, from the driver to the dog, and then from the dog to the…?
Workpiece
How do you support a workpiece in a dividing head chuck?
With the footstock center or a steady rest
If you straddle mill a hexagonal bolt head how many cuts are needed?
Only three
How to prevent chips from falling into the spindle while the nose is pointing upward?
By inserting a specifically made cap over the spindle opening
What indexing method does not count for the hole it was in ( the zero hole )
Direct indexing method
How do you use the plain indexing method?
By leaving the worm and worm gear in the engaged position
Make your rough and finish cuts to mill the first side of the hexagon. Retract the pin and turn the crank clockwise six full revolutions and then continue until the pin reaches?
The hole indicated by the second sector arm. This is for plain indexing
Straddle milling a hexagon
You will mill two sides at a time and need only position the workpiece 3 times
When will you find the dividing head useful?
Whenever you must drill or bore a series of holes in a circle
Cutting the teeth in spur gears is a type of form milling. That is the work is done with?
Special profile cutters which form the sides of the teeth in a gear blank
Spur gear OD formula
OD = number of teeth + 2
————————-
Diametral pitch
Several things affect cutter selection when you mill gear teeth, they are?
Diametral pitch of the gear
Number of teeth
Material of the gear blank
The tooth spaces in a small gear have a different size and shape than those in a larger gear with the same?
Diametral pitch
A series of how many cutters has been developed to suit the different number of gear teeth?
Eight cutters
Many gear blanks are too large to be mounted on a dividing head. In such cases they are mounted on a?
Rotary table
Use a micrometer to check?
The dimension over pins
Gear tooth vernier calipers are used to check?
Tooth thickness at the gears pitch circle
The AB line is called?
The lead of the helix
What is pitch?
Pitch is another term used in describing a helix. Pitch is the distance between adjacent helices that are wound on a common cylinder
The milling machine lead determines?
The lead of the helix it will produce
You use a system of gearing called _____ between the lead screw of the milling machine and the worm shaft of the dividing head.
Change gears
Lm = milling machine lead
Lh = lead of the helix to be cut
Tg = number of teeth in the dividing head
Tn = number of teeth in the driven gears
Lm = Tg
— —
Lh Tn
The worm shaft of the dividing head is meant to utilize how many gears?
Four gears
To expand fractions what do you do?
Multiply the numerators and denominators of both fractions by a number which produces figures to match the numbers of teeth on the change gears
Drive systems with three gears can be used to cut both right hand or a left hand helix by reversing the direction of gear rotation of the?
Dividing head spindle
To determine how far apart the 15 teeth are on the circumference of the work piece what do you do?
Divide 360 by 15
You must swivel the table 12 degrees in order to?
Cut the 12 degree helix angle
If you draw the cutter back through the work what could happen?
You could damage the critical features of the tooth surfaces
Normal diametral pitch is a measurement you will use when describing?
The proportions of helical gear teeth. This differs from the circular pitch used to describe tooth dimensions in spur gears
After you mill each tooth why should you lower the table?
So you do not drag the cutter back through the newly cut tooth space
What do cams do?
They change the direction of motion of machine parts
Although the cam forces the follower upward, the system depends on what to bring the follower back down to its starting position.
It depends on gravity, a spring, or some other force
What is cam rise?
Rise is the distance that one lobe moves the follower from its starting point
What is cam lead?
Lead of the cam is the total distance that a lobe on a uniform-rise cam would move the follower if the lobe extended a full 360
How do you mill a uniform rise cam
You do this by holding the workpiece in a dividing head whose spindle is geared to the milling machine lead screw. You must use a vertical milling attachment for this setup
The axis of the dividing head spindle and the axis of the cutter must always be?
Parallel, they must also be at some angle other than horizontal when milling plate cams
Assume the rise of each lobe in the cam is?
.160 in.
L = R x 36
——
C
R = lobe rise
C = degrees of circumference that the lobe occupies
The incremental cut method is most often used to mill cams having?
A non uniform rise
