1. Make sketches with typical dimensions showing “forward extrusion”. Make one of the “forced extrusion” type and one of the “open type”.
See sketch
2. Make a sketch with typical dimensions showing “backward extrusion”.
See sketch
3. Make a sketch of a cone tool impression and list the rules that determine the shape of the cone for:
a – a solid cone tool
b – a sliding cone tool
See sketch
4. In cold forming how many diameters of stock can be upset in one blow?
2-1/4 diameters
5. In cold forming how many diameters of stock can be upset in 2 blows with a solid cone?
4-1/2 diameters
6. In cold forming how many diameters of stock can be upset in 2 blows with a sliding cone?
6-1/2 diameters of stock
7. List 3 reasons for using a sliding cone tool
– Over 4-1/2 diameter upset
– provide stock support
– controlled upset
8. List 2 reasons for using a sliding pin in a cone tool
1) To transfer a short blank
2) To assist in ejecting a blank from the tool
9. List 2 reasons for using a sliding die
1) To backward extrude a blank in the die
2) To pierce a blank with the piercing pin in the die
10. What is a supported knockout pin?
A knockout pin with a sliding guide bushing which is positioned in the center of the unsupported length during the heading stroke
11. When do you use a supported knockout pin?
When the unsupported length exceeds 10 or 12 times the diameter of the knockout pin or when heading pressures are extremely heavy or when knockout pressures are extremely heavy
12. Why was the 3 blow 2 die header developed?
To provide extrusion and trim capability on a 2 die machine plus more versatility
13. What is a Phillips impression?
Cross recess with wide center opening, steep walls, blunt conical bottom and tapered wings
14. What is a Frearson impression?
The original cross recess – two intersecting slots with parallel sides, shape bottom (requires only one size driver)
15. What is a Torx impression?
See sketch
16. In cold forming what are 6 or 8 different ways to make a bolt on a Boltmaker?
Standard operations for making standard bolts:
(3 DIE BOLTMAKER)
a. Single extrusion method
A – Single extrusion wire diameter
1 – thread to head bolts
a) Extrude pitch diameter and cone
b) Upset head
c) Trim
B – Body size wire diameter
1 – thread to head bolts
a) Extrude pitch diameter and cone
b) Upset head
c) Trim
2 – long bolts
a) Cone
b) Extrude pitch diameter and upset head
c) Trim
b. Double extrusion method
A – Double extrusion wire diameter
1 – long bolts
a) Extrude body diameter and cone
b) Extrude pitch diameter and upset head
c) Trim
(4 DIE BOLTMAKER)
c. Single extrusion method
A – Single extrusion wire diameter
1 – thread to head bolts
a) Extrude pitch diameter
b) Cone
c) Upset head
d) Trim
B – Body size wire diameter
1 – thread to head bolts
a) Extrude pitch diameter
b) Cone
c) Upset head
d) Trim
2 – long bolts
a) Cone
b) Upset head
c) Extrude pitch diameter
d) Trim
d. Double extrusion method
A – Double extrusion wire diameter
1 – thread to head bolts
a) Extrude body diameter
b) Extrude pitch diameter and cone
c) Upset head
d) Trim
2 – long bolts
a) Extrude body diameter and cone
b) Upset head
c) Extrude pitch diameter
d) Trim
17. At what point do you change from an open type forward extrusion to the forced extrusion method?
Approx. 30% to 35% reduction-in-area
18. What advantage does the solid cutter have over the open type cutter?
It provides a more even end on the cutoff which is very important for short blanks
19. What purpose does the relief in the face of the Cold Nut Former cutter and quill serve?
Shearing between a flat faced cutter and quill presents two problems. If they are close together, the end of the cutoff blank is very rough with high and low spots where the excessive pressure has torn away the material. If they are set further apart so that there is clearance for a material rupture, the blank becomes oblong from the squeezing affect forcing metal into the clearance between the cutter and quill. The contour impression in the face of the Cold Nut Former cutter and quill causes an inward pressure during cutoff which prevents the blank from becoming oblong when the clearance is correct for a natural rupture, which is necessary for a good cutoff blank.
20. Describe the difference between the Boltmaker and Cold Nut Former transfer as far as the motion of the transfer fingers is concerned
The fingers on a Cold Nut Former transfer travel in a semi-circular arc away from one die to another. The fingers can be converted to rotate the blank 180º between any two dies or to transfer the blank without rotation. The fingers can be spread by the use of a special finger opening mechanism or sometimes by the punch itself.
21. What is meant when someone says “single extruded” bolt?
A bolt that is made from body size wire so that only the pitch diameter must be forward extruded
22. What is meant when someone says “double extruded” bolt?
A bolt that is made from wire which is larger in diameter than the body of the bolt thus requiring one forward extrusion to body diameter size and a second forward extrusion to pitch diameter size
23. Give a step by step explanation of the operation of the slug discharge assembly of a Cold Nut Former
As the nut blank is pushed into the die, the spring actuated die insert is pushed back until it bottoms against another tool and stops. The die insert carries a steel ball which is held flush with the outside surface of the die insert by the mating surface of the die. The ball also protrudes into the center hole of the die insert by a predetermined amount. As the nut forces the die insert back, the steel ball is allowed to move out of the center hole because of a conically tapered surface in the die. When the die insert has stopped against the filler, the piercing takes place. When the slug breaks free of the nut, the spring behind the die insert drives it forward around the punch and moves the pierced nut blank up on the piercing punch shank. As the die insert is moving forward, the steel ball is forced back into the center hole by the conically tapered surface of the die thus gripping the pierced slug until the next stroke.
24. Why are the transfer fingers on the Cold Nut Former and Boltmaker made from soft steel and case hardened? Why not use tool steel so they would wear longer?
In case of an accident the inexpensive transfer fingers can deform without breaking the tools
25. Why are feed boxes on Cold Headers mounted on the machine with such heavy and strong bolts?
The knockout pin adjustment screw absorbs any heading force that is against the knockout pin and is mounted in the feed box. These feed box screws must be strong enough to absorb these forces and maintain the correct shank length on the blank with variations in wire hardness and other variables.
26. List and explain the advantages of the “over-arm heading slide” used on all National headers
1.) Keeps the heading slide from bouncing when the crankshaft is on the rise at B.D.C.
2.) Prevents the heading slide from binding sideways when the punches contact the work
3.) Allows the crankshaft to be pressing down during heading, thus keeping the slide firmly down on the liners without fear of the face of the slide rising up due to the lever action involved
4.) Allows functional massive construction rather than bulk weight construction
5.) Allows the trouble-free floating pitman since all alignment is done by the liners
27. Why should we not forward or backward extrude in the first die on a Cold Nut Former?
Since the stock gage punch pin is pulled out of the first die with a spring, the entrance into the die must be held to a minimum so that there is no chance of the punch sticking in the die. The extra amount of punch entrance required to forward extrude would increase the chances of the cutoff slide being stuck in the upward position because the punch would tend to stick in the die. Backward extrusion is not possible because there is no way to remove the blank from the punch or slide the first die.
28. When standing at the operator’s position of a National header, which direction is the crankshaft rotating? Why?
Clockwise so that the crankshaft and pitman are coming down during the heading stroke thus holding the slide down on the liners for more dependable operation and alignment
29. What is the general rule to follow when determining the minimum length of a die case which should be used?
A line projected along the centerline of the holdback screw in the die block cap should cross the opposite side of the die block bore within the length of the die case
30. Explain the operation and timing of the trim station on a Boltmaker
The trim-die which is carried in the heading slide, pushes the blank into the trim tool which is located in the die block. As the head of the bank stops against the trim tool, the trim-die shears into the head of the blank to within approx. 1/32 of an inch of the surface of the trim tool. At this time the trim cam advances the trim station knockout rod forcing the blank into the trim-die and pinching off the trim flash. When the flash breaks free, a spring in the trim station knockout rod pushes the blank far enough into the trim-die to be held in place by the ratchet type holder which is located behind the trim-die.
31. All National Cold Headers will operate with the maximum length of cutoff listed in the specs for each machine. What problem arises when using a sliding cone tool with the maximum cutoff length?
The punch rocker will be in position for heading at a distance from the face of the dies greater than the maximum length of cutoff. When using a sliding cone tool, the tool is extended and reaches the blank sooner. There is danger that the cone tool may reach the maximum cutoff length blank before the punch rocker is in position. Usually the length of slide in the cone tool must be subtracted from the maximum length that can be cut off.
32. List 5 advantages of a tapered die insert which is put in from the back of the die case and held in with a threaded filler?
1.) Less chance of the die insert jacking forward out of the die case through the front
2.) Can achieve more interference fit due to the taper angle
3.) Easier to index a die insert shape due to the short stroke required to press it into place
4.) Less wear in the die case bore due to the short stroke required to press the insert into place
5.) The wall thickness of the die insert at the open end of the case can be less than normal, allowing better die case to insert relationship at the face which is the weakest point of the case
6.) Shorter front die inserts can be used because the angle will hold them in place
7.) Since the die inserts are between the angle at the front and the threaded filler in the back, there is a pressure holding the inserts against one another equal to the pressure required to assemble the inserts
33. Why does a carriage bolt head require so much pressure to form?
Due to the shape of the head near the circumference of the diameter – very small cross sectional area (sharp, shallow angle)
34. In cold forming how do you determine what specials and on what machine a part could be made?
The first task is to draw a proposed forming sequence. This should allow you to determine the wire size, number of dies, machine size and specials required. At times it may be necessary to draw a complete or partial die assembly layout to determine these facts. Extreme care should be taken while making and analyzing these drawings.
35. What purpose does the safety block behind the “stock gage punch pin” serve on a Cold Nut Former?
After the cutoff blank is carried up to the first die and upset, the stock gage punch pin is pulled back into the cutter so that the cutoff slide can return down. Since a spring is used to pull back the stock gage punch pin, there is the danger of it jumping back more than the required amount. When this happens, the stock gage punch pin will come down on top of the stock gage and adjusting screw thus breaking something or preventing the cutter slide from returning to its down position.
36. What purpose does the spring loaded ball against the intermediate knockout pin in the first die of a Cold Nut Former serve?
When the first die blank is kicked out of the die it must be held flush with the die face until the cutoff slide comes up again. This is so that the cutter holder will kick the blank out of the way should the transfer fingers fail to pick it up. A short feed will cause a short cutoff and the blank may not fill out against the die when it is squared up. The transfer fingers may not grip this undersize blank thus leaving it on the end of the knockout pin. This pin must be held forward so that it does not go back with the big knockout rod in the bed pulling the blank back into the die with it. This would cause a double header and broken tooling.
37. Describe 3 ways which are used to remove pierced slugs from the piercing punch and discharge them from the machine
The Cold Nut Former type is one as described with the answer to question number 23.
A second method is the restricted-hole method. It is based on the fact that a pierced slug expands slightly after it is free of the part. By pushing this slug through a sleeve with a hole very near in diameter to the piercing punch the slug will be tight in the hole and will remain there as the punch retracts.
A third method is an air discharge method. A small hole is drilled through the center of the piercing punch through which a timed air blast is released during the actual piercing operation. This is sufficient to remove the slug from the end of the piercing punch and discharge it out of the machine.
38. How many turns are needed to roll a Class 2 thread?
Varies with size of thread – approx. 5-6 revolutions
39. How many turns for a spaced thread such as Type A?
Type A = 5-6 revolutions
40. How many turns for a lag?
Lag = 7-8 revolutions
41. How does a thread form?
The thread dies penetrate the surface of the blank to form the thread roots – metal is displaced radially outward to form thread crests
42. In cold forming what is the forming sequence for a nut?
a.) Shear and square up cutoff blank
b.) Reduce height and start filling hex
c.) Fill hex by penetrating center of blank
d.) Form ends and form start for pierce punch
e.) Pierce ID and separate slug
43. How is the clearance – quill to cutter formed?
Quill to cutter clearance = wire diameter x .020 (can vary somewhat with differing materials)
44. In cold forming how do you calculate the wire size for forming a standard nut?
Max. flats of nut x 92.5%
45. How is the slug separated from the nut on a standard Cold Nut Former?
Slug is pierced through the part and into the die past a spring loaded ball which prevents the slug from moving back toward nut – slug is ejected through rear of die case
46. What are 3 or 4 other ways of separating the slug from a nut or other part?
Slug separation: timed air through punch – forcing past eccentric diameters – forcing past spline – force past stationary pointed pin – force past slight reduction or taper
47. What is a TKO?
Timed kick out in tool – insures that the part is ejected from the tool – roller that kick-out lever works upon is timed to allow kick out only on backward stroke of heading slide
48. What is a safety KO?
Safety K.O. – a stationary pin or rod that forces the part from the tool as heading slide approaches rear dead center
49. What is a Modified TKO?
Modified T.K.O. – performs same function as T.K.O. except that the kick-out lever moves twice per stroke since no timed roller is utilized. Kick-out lever acts against stationary cam
50. What is RKO?
Relieving kick out – insures filling of die cavity by withdrawing kick out pin slightly at the heading blow
51. What are the 2 basic methods for trimming?
Trimming may be done in the punch or die, the punch being more popular
52. Where is carbide used?
Tungsten carbide is used for extrusion inserts (ND-20) and for heading inserts (ND-25)
53. What is a forward extrusion?
Reduction in area by flowing metal in the same direction as the punch movement
54. What is a backward extrusion?
Reduction in area by flowing metal in the opposite direction as the punch movement (around the punch)
55. What is a Hooker extrusion?
A hollow forward extrusion
56. What is normalizing?
Heating metal approx. 100º F above upper critical temperature (about 1700º F for .20% carbon steel) and cooling in still air to room temperature – produces harder and stronger steel than full anneal, refine grain and improve machinability
57. What is spheroidizing?
Spheroidizing is a type of annealing that allows carbide in the metal to assume the form of round particles instead of plate shape thereby providing both good machinability and ductility
58. What is drawing?
Drawing equals tempering: heating to a below critical temperature – relieves residual stresses and improves steel ductility and toughness
59. Is the stationary or moving roll thread die the longer and how much do they overlap in the pickup position?
The moving die is the longest. The amount of overlap of the dies when picking up a blank is approx. 1/2 of the machine size. This will vary from one machine size to another.