Combination Dies

Double dies for blanking and perforating are extensively used in the manufacture of washers, key blanks, electrical instruments, hardware, etc. The blanking and perforating punches act simultaneously.

At a single stroke of the press

The perforating and blanking punches act simultaneously in such a manner that the holes are punched first, whereupon the strip or sheet being fed forward, the blank is cut out around them and the holes for the next blank perforated at the same stroke. In this manner a blank is completely perforated at every stroke of the press.

The same principle may be extended so as to punch a number of perforated blanks at a time.

one punch perforates the holes and the other punch cuts out the metal between the holes punched at the previous stroke. These dies are usually so arranged that the finished article is automatically pushed out from the dies by the action of the springs. An expert operator can punch many thousands of pieces in a day.

EXAMPLE.

How much metal will be required for 2000 blacking box covers, 6" in diameter, and 3" deep?

6" + 3" + 3" = 7", diameter of one cover.

7.5 x 7.5 44.1786 sq. in., area.

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1. How large must the blank be cut for a pail cover that is to be (a) 5" in diameter and 3" deep? (b) 7" in diameter and 14" deep? (e) 6" in diameter and 1" deep? (d) 8" in diameter and 11" deep?

2. How large must the blank be cut for the pail bottom in each of the above examples (a, b, c, and d)?

The blank must be 1" larger in diameter than the diameter of the part in order to allow 1' all around for forming into the sides.

3. How large must the piece be to form the sides of the pail in each of the above examples? Pail (a) to be 6" high, (b) 9′′ high, (c) 8" high, and (d) 10′′ high.

Allow ' in height, and for the lock seam allow 3" in circumference.

4. How much metal will be necessary for 850 complete pails in example (a) above?

5. How much metal will be necessary for 1500 complete pails in example (b) above?

6. How much metal will be necessary for 840 complete pails in example (c) above?

7. How much metal will be necessary for 1000 complete pails in example (d) above?

8. How many square feet of sheet copper will be required to make a rectangular tank 7' long, 3' wide, 1 deep, allowing 10% extra for waste? The tank is to be open on top.

9. If the sheet copper weighs 12 lb. per sq. ft. and costs 25 cents per lb., what will be the cost of the material used?

10. Find the amount of material in a straight piece of copper pipe 24" diameter and 8' long. The pipe is formed from sheet copper weighing 15.4 lb. per sq. ft. What does it weigh? Allowance for seam, 11".

11. If the cost of copper in Example 10 is 27 cents per lb. and the amount of copper wasted in making the pipe is equal to the finished weight of the pipe, what is the total cost of material used?

12. What is the cost per pound of finished pipe for the material used in Examples 10 and 11?

13. If the labor to make the pipe in Example 10 costs $ 36, what is the cost per lb. for labor?

14. What will be the total cost in Example 10 of all material and labor per pound of finished pipe?

Circles

Review the paragraphs on the Circle on pages 62 and 63, and on the Cylinder, page 72.

EXAMPLES

To find circumference of a cylindrical tank, when the diameter is given.

1. What is the circumference of a tin plate (a) 8′′ in diameter? (b) 14" in diameter? (c) 1′ 6′′ in diameter? (d) 2′ 3′′ in diameter? (e) 1' 9" in diameter ?

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2. What is the diameter of a copper plate containing (a) sq. in.? (b) 43 sq. ft.? (c) 349 sq. in.? (d) 8840 sq. in.? (e) 616 sq. in.? (f) 340 sq. in.?

3. What is the diameter of an iron tank (a) 6′ high, containing 40 gallons? (b) 5 high, containing 360 gallons? (c) 6' high, containing 120 gallons? (d) 12' high, containing 141 gal

lons? (e) 8' high, containing 181 gallons? (f) 4' high, containing 241 gallons? (231 cu. in. = 1 gal.)

Two circles are formed by a plane passing through a hollow cylinder of metal, as it has an outside and an inside circumference, due to the thickness of the metal. A circle the circumference of which is midway between these two circumferences is said to be the neutral circle or ring, and its diameter is the neutral diameter.

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To illustrate the neutral diameter of a ring 8" outside diameter and 6" inside diameter is 7.

4. What is the length of a smoke arch ring whose outside diameter is 60" and a section of which measures 21" x 21"? The length of the ring is the length or circumference of a circle whose diameter is the neutral diameter of the ring.

5. A smoke stack 32" inside diameter is made from 3" iron sheet stock. What would be the length of the sheet, allowing 2" for lapping?

Use the neutral diameter.

6. If we desire to make a close fit over the above sheet and allow 2" for overlapping, what size sheet will we use?

7. A blacksmith desires to place a band around a hub that is 17" in diameter. If the band is 2" square and if no allowance is made for shrinking, how long a piece of iron is necessary to do the job?

8. If the above band averages lb. per cu. in., what is the weight of the band?

9. A flat iron ring casting has the following dimensions: 18" outside diameter, and 9" inside diameter, and 3" thick. What will it cost at 3 cents a pound? What is the cost of a cubic foot of the iron? (1 cu. in. iron = .26 lb.)

10. The neutral diameter of an engine wheel tire is 76". If the steel weighs .28 lb. per cu. in., what would be the weight of the foregoing, if its section was a trapezoid whose dimensions were 6′′ wide on the face, 33′′ thick on one side, and 47′′ on the other?