How much pressure can steel take before it twists?

Question

I was drilling a hole and the drill bit got stuck. I held on to the drill and the steel bit acutally twisted 1/4 inch before it twisted out of my hand and sprained my wrist. Co-workers have broken their wrists and arms from doing the same thing.

Answer 1

I'm not sure I understand what you are saying. What do you mean by twist? Are you asking how much force is require to make a piece of steel buckle (bow out)? If so, it depends on the shape and length of the piece of steel. The actual material involved is not as large of a factor as shape and length.

If you restate your question, I'll be able to answer it far more completely. Are you trying to solve a specific problem, or just curious?

Okay for that specific problem. What is going on is that you are applying nearly pure shear into the bit. Steel fails in shear, so it is a particularly nasty situation.

What happens is that the steel actually starts twisting as soon as you start applying the force, but it isn't noticeable until it is taking so much force that it hits its elastic limit. At that point, the steel is like rubber and will stretch or twist with barely any additional force. For steel that limit could be anywhere from 35 to 70 ksi (ksi = 1000lb/square in). So you have quite a range.

How to transform that into your situation, depends. The shape of the bit will make the stress non-uniform. Also, that elastic limit is for tension or compression more than torsion. The amount of downward pressure you place on the drill also has an effect. Also, steel can be damaged from repeated loadings, so it is a well used bit, it will take less to twist it.

The general rule I'd give is this. Once the bit starts twisting, don't continue. Applying more force will only twist the bit more. I'd try to reverse directions and try to drill the bit out and then start drilling again.

Answer 2

For steel cylinders it will burst if the positive pressure is applied from inside, crumple when a negative pressure is applied inside.

For solid objects, (say a piece of rod) there is a different approach. It will be dependent on torque, that is the amount of force you exerted to a possible perpendicular distance from its center. That is for the twisting effect.

It may also differ for the type of steel that is at pressure.

You can also look for the chart of different steels having their yield and ultimate strength. (Forged steel, mild steel, with their ASTM number)

Mathematically it is: Pressure (P) = Force (F) / Area (A)
P = F/A
Where: F is force applied to it, A is the area affected

units may also be in English and metric units

Answer 3

the hole must be big for the steel area isnt it?
you should start with small size then get gigger
there is tow things for strength of materials
modulous of rigidity and modulous of elasticity
steel have a high mod of elasticity but not that much in regidity
E=200000 mega pascal
it will twist fasty so try to start with small size holes first

Answer 4

depends on what type steel, how thick it is, and where the pressure is concentrated. But i do kno that depending on the type it can take 200 - 400 kN/m^2 before breaking