Poł. czopowe - Square Blockings.pdf - Kucie stali - Kowalstwo - Noże etc - rudyrpg

Square Blockings

Mark Aspery

School of Blacksmithing

Springville, California

This article is intended to continue the upsetting article (or perhaps

that should read the article about upsetting!) that appeared in the Fall

2004 issue of The Hammer’s Blow entitled ‘Farriers Style Tongs’.

That article dealt with an upset at the end of the bar, this article

focuses upon putting an upset somewhere along the length of the

bar. I thought that it would be good if we could do something useful

with the upset and so I chose the subject of square and rectangular

blockings. These blockings are used when you want a square or

rectangular bar to pass through another bar.

Both styles of blockings are formed by upsetting a slot-punched hole

and then drifting it to the desired size and shape.

First the math. Each different size of hole requires a different size of slot punch. This mathematical

formula will allow you to complete the blocking without changing the width of the stock at the sides

of the blocking post slotting. Lets work through the math that will help us calculate the dimensions

of the slot punch needed for a 3/4-inch square hole. By the way, if my high school math teacher ever

sees this article, he will die laughing.

You must irst start from the desired outcome, in this case a 3/4-inch square. Circumscribe a circle

inside a 3/4-inch square. That would give you a 3/4-inch diameter circle. The perimeter of the

slot punch is equal to the circumference of that circle. Work out the circumference of the 3/4-inch

diameter circle.

4 = 4 = 2 4 inches

Where C is the circumference and π is equal to 3 and d is equal to the diameter of the circle,

which in this case is 3/4-inch.

C =π d = 1 x

From here you have to work backwards from the inal tool. I know from experience that a slotting

punch made from 4130 will need to be about 1/8 th -inch thick to work well; in that it will stand up to

the rigors of regular use and yet is small enough not to drag material into the eye when punching.

What I do not know is the required length of the punch for this size of square blocking. We do know

that the slotting punch will need rounded edges or sides so as not to cause cracking around the upset

hole. If you call each side a half circle, when both of these halves are added together they must make

a whole (circle) and knowing the diameter because the tool is 1/8 th -inch thick we can work out the

circumference.

C =π d = 1 x

8 = 8 inches

You have a 1/8 th -inch diameter circle that has a 3/8th-inch circumference.

When you take this 3/8 th -inch circumference away from the circumference of the larger circle (2 1/4-

inches) that will leave you with the combined length of both sides of the slotting punch From there

you have to divide the result in half to give the length of one side.

Before you commit to making an actual piece

for a gate or the like, you irst need to conduct

a test piece to determine if the bar will stretch,

shrink or remain unchanged during the slot

and drift process. You know that you will put

in a 1 1/16 th -inch long slot and that you will

eventually make a 3/4-inch square hole with it.

The ends of the slot have to be coaxed in to the

centre by 5/16ths-inch. So the overall bar length

should shrink by at least that much, plus a little

more lost to the upsetting action on either side

of the blocking. This test piece will allow you

to determine the extra length required in a bar.

4 or 1 8 − 8 = 1 8

inches

Divide the result in two to get the length of

each side;

8 ÷ 2 = 1 8

2 = 1 16 each side

So now lets add all that together to get the total

length of the tool. Add the diameter of the 3/8 th -

inch circle (or both of the radii) to the length of

one side for a total length of the slotting punch.

The formula will look something like this;

Step 1: Measuring the test piece before

and after making the blocking.

16 + 16 r + 16 r = 1

16 inches

So, the slotting punch will be 1/8 th -inch thick

by 1 1/16 th -inch long. As this slot will be upset,

it does not matter that the length of the punch

exceeds the dimensions of the drift as it would

do in non-upset slotted holes.

Make two punch marks along the center line

of the bar, one at the one inch mark (a datum).

And one (for example) at the 4 inch mark.

This marks the edge of the intended slot punch.

Using a pair of dividers, set the legs at the

distance between the two marks. I know that it

should be 4-inches, but the dividers will be a

more accurate way of determining the change in

measurement. You can offer this pair of dividers

up to 1-inch mark and the edge of the hole after

you have completed your test to ind out how

much they did move. You will be conducting

this test taking measurements from one side

of the hole only as the stock will be quenched

from this side only. In other procedures, you

might take a measurement including both sides

of a forging, to calculate the average.

NOTE: As you start, you will be working

on what is in effect the end of the bar, I am

presuming that you will be placing the other

end on a work-stand that is on your side of the

anvil and an equal height to it. These next steps

rest on that premise.

OK, we are ready to go to work. Make a

slotting punch to the above dimensions. I use

a piece of 3/4-inch 4130 for this. By choosing

a bar size that is smaller than the dimensions

of the business end of the punch, I make sure

that the slotting punch tapers away from the

business end on two edges, ensuring that there

is less friction when punching and, when the

bar bends during punching, that the sides of

the hole will not be galled. I am using a piece

of 1 1/4-inches by 1/2-inch material in which

to make the blocking. A convenient length is

needed for handling purposes while upsetting

on a loor anvil (about 40-inches)

Figure 1 below shows the business end of

the punch together with the initial stages of

punching the hole.

Step 1b

Chamfer the end of the bar. As found in

the Farrier style tongs article printed in the

Hammer’s Blow, Fall 2004, the closer you can

keep the force to the center of the bar, the less

it will want to wiggle and bend during the upset

process!

Step 2 a

Take a heat around the slot and quench out the

end of the bar to a point equal to the dimension

of the material left on one side of the hole. In

this case 9/16ths-inch. Why cool to within

this 9/16ths-inch? You will be upsetting the

material around the slot and eventually turning

the slot into a circle. The sides of the slot need

to be able to move and they need somewhere

to go. They need at least their own width to do

that. As the bar is 1 1/4-inches wide and you

have taken a 1/8 th -inch slug out for the slot that

should leave you with 9/16-inch on each side.

Try to keep the heat to just around the slot.

Don’t get it too hot further up the bar or it will

upset at the same time as the slot. If you are

working in a gas forge, you will have to quench

both above and below the slot (to within 9/16ths

or so) before upsetting the slot.

If this is a production job, I would use a rose

bud on an Oxy/fuel system and get the heat that

way.

If, per chance, the slot is off to one side or the

other of the bar, mark the thin side on the edge

of the bar somewhere away from the hole. You

will be referring to this mark later so make sure

that it is somewhat permanent.

Turn the bar 180º after each time that you throw

it into the loor anvil. I say throw because it

relects the effort needed and in order to throw,

you must release hold of the bar . Do not hold

tightly onto the bar at the moment of impact.

Turning 180˚ will help to keep the upset even.

Upset the hole until it becomes round.

Step 1c & d

Take a light welding heat at the 4 to 5-inch

mark and slot punch the hole. The side of the

slot punch furthest from you should rest on the

center punch mark made at 4-inches. So the slot

starts 4-inches from the end of the bar and is

incised towards the longer end of the bar.

Step 1 d shows the result. The slug has been left

in for show and tell purposes. Remove the slug!

Step 1 ‘c’ above and ‘d’ below

Quench

Step 2 a. Left showing slot punch and right

showing the upset underway

Take care as you approach the round stage as

the hole will tend to collapse rather than upset.

One side of the hole will look signiicantly

better that the other. This is due to the slot

punching process pushing material to the back

side of the bar.

Now you are ready to apply the square drift.

If your slot was off to one side, place the thick

side of the hole down in the coals. By leaving

the thin side up and uncovered by coals there

will be a difference in heat between the two

sides.

If you work quickly with the drift, the thicker,

now hotter, side will now stretch more than the

thin cooler side. If you are working in a gas

forge, you will have to quench the thin side to

achieve the same effect. The disadvantage of

quenching is that the cold side now acts as a

heat sink and sucks heat away from the rest of

the eye. This will cut down your forging time

on the anvil per heat.

Drive the drift in from both sides over the hardy

hole. Move the piece around the hardy hole so

that the material gets support on all sides.

Figure 4 a, b, c.

Step 2 b. At left original slot and

right after upsetting.

At this stage the bar may not be straight or

level. If you leave the bar in this condition and

you apply the square drift, which side of the bar

will you align the side of the drift to?

Lock the bar in the vice and using a straight

edge, align the bar on either side of the hole.

Shown in steps 3 a (adjusting the stock) &

3 b (checking with a straight edge) below.

I like to have lat sides to the blockings. In

order to get the lat sides I need to forge them

in. I don’t want to stretch the eye so I forge

them in lightly (so as not to penetrate the whole

of the bar) and I start to latten the sides quite

early on in the drifting process, certainly before

I have driven the drift fully through the hole.

When you have inished with the drift, use your

dividers, check to see what happened to the

length of the stock between your center-punch

marks.

Knowing this alteration in length, you can apply

it to the layout as you mark each hole.

Result of the blocking shown above and

applied below.

Hopefully you have made all your mistakes

on the test piece and you can go on to making

trouble free square blockings on you own gate

or railing project.

I usually start from the hinge style with the

quality of each blocking tending to improve as

you reach the latch style.

Mark Aspery owns and operates a school for

artist blacksmiths, teaching week long classes

for business and ABANA associates in the

Western United States.

Step 4 c, d, & e above.

Poł. czopowe - Square Blockings.pdf

Plik z chomika:

Inne pliki z tego folderu:

Inne foldery tego chomika: