# Hand tool boundary conditions - Forces determination

• Engineering
• LuigiL
In summary, the forces on the spanner jaws are not equal and the center of rotation for the purple ##O## is not the same as the center of rotation for the other colors.
LuigiL
Homework Statement
Determine the forces acting on the hand tool (magnitude & direction).
Relevant Equations
ΣF = 0, ΣM = 0
Hello,
I' m trying to make a linear static analysis (Finite Element Analysis) on the following hand tool. I want to determine the boundary conditions. In order to do that I have decided to use a force couple to represent the forces that a bolt exerts on the jaws of this spanner.
Despite using force and moment equilibrium, I' m not able to determine the magnitude and direction of the forces.
Should I include any other forces in order to satisfy the equilibrium (maybe a force R in the lower jaw)?

I would be grateful if you can give me some advice. Thank you.

## M_O = F_1 \cdot d, ~ \text{&} ~ F_1=F_2 ##
## \Sigma M_O = 0,~ 144.93 \cdot F_3-M_O = 0,~ M_O = 14493 ~N \cdot mm. ##

## \Sigma F_x = 0,~ F_{3x} - R_x=0,~ R_x = F_3 \cdot sin(14.31^\circ). ##
## \Sigma F_y = 0,~ F_{3y} - R_y=0,~ R_y = F_3 \cdot cos(14.31^\circ). ##

Last edited:
Delta2
Welcome to PF.

I think you are modelling the spanner with the force 3 applied up when it should be down. The reason is that the offset head will tend to slide off a nut if used the way you show it here. That would change the hexagonal nut contact points into the diagonally opposite positions between the jaws, which puts them at more similar distances along the handle.

The offset head allows a hexagonal nut in a confined place, to be advanced in 30° steps, by repeatedly turning over the spanner when access is restricted. But it also allows the more secure orientation when working on a more exposed nut.

The two nut edges that contact the spanner jaws will be deformed by the pressure of the spanner until the area of the contact is sufficient to handle the force applied. When you model the hardened spanner jaws, it is the nut that will deform, not the spanner. Maybe you need to model the soft plastic nut between the hard jaws.

Lnewqban
Hi,

##M_O = F_1 \cdot d, ~ \text{&} ~ F_1=F_2##
How have you determined that those forces are equal ? And what do you use for ##d## ?

I take it the purple ##O## is the center of the nut ?

Then, if the purple ##O## is your center of rotation, shouldn't the 144.63 (144.93 ?) be smaller ?
Like the 137.97 + 4.69
Now it looks as if it is up to the point where ##F_1## acts

The drawing has a lot of measurements that are unexplained.

And how do you determine these to such an accuracy ?

##\ ##

BvU said:
Hi,

How have you determined that those forces are equal ? And what do you use for ##d## ?

I take it the purple ##O## is the center of the nut ?

Then, if the purple ##O## is your center of rotation, shouldn't the 144.63 (144.93 ?) be smaller ?
Like the 137.97 + 4.69
Now it looks as if it is up to the point where ##F_1## acts

The drawing has a lot of measurements that are unexplained.

And how do you determine these to such an accuracy ?

##\ ##
Hello,
I assumed that ##F_1=F_2##.
##d## is the unknown and I want to determine it.
Indeed ##O## is the center of the nut.

##144.93 = 137.97+\frac{13.91}{2}## is the perpendicular distance from point ##O## to point ##3## (Force ##F_3##).

I apologize for the complexity of my drawing. Measurements were taken from the software that I designed this hand tool (with some roundings).

## 1. What are hand tool boundary conditions?

Hand tool boundary conditions refer to the limitations or constraints placed on a hand tool when it is being used. These conditions can include factors such as the type of material being worked on, the strength and dexterity of the user, and the environment in which the tool is being used.

## 2. How are forces determined in hand tool boundary conditions?

Forces in hand tool boundary conditions are determined through a combination of physical measurements and mathematical calculations. The amount of force required to complete a task depends on the type of tool being used, the material being worked on, and the desired outcome. Engineers and scientists use various methods, such as force gauges and simulations, to accurately determine the forces involved.

## 3. What factors affect the determination of forces in hand tool boundary conditions?

There are several factors that can affect the determination of forces in hand tool boundary conditions. These include the type of tool being used, the material properties of the object being worked on, the angle and direction of force application, and the skill and strength of the user. Other environmental factors, such as temperature and humidity, can also play a role in determining forces.

## 4. How do hand tool boundary conditions impact the design of tools?

Hand tool boundary conditions play a crucial role in the design of tools. Engineers and designers must consider the forces involved in different tasks and the limitations of the human hand when creating new tools. The goal is to design tools that are efficient, safe, and comfortable for users to use, while also being able to withstand the forces required for the task at hand.

## 5. How can hand tool boundary conditions be optimized for better performance?

Hand tool boundary conditions can be optimized for better performance by considering the factors that affect force determination and using this information to design tools that are well-suited for the task at hand. This can include making adjustments to the shape, size, and material of the tool, as well as providing ergonomic features to reduce strain and fatigue on the user. Regular maintenance and training can also help optimize hand tool performance in boundary conditions.

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