Tensile strength Vs Shear-pin Material type?
Tensile strength Vs Shear-pin Material type?
(OP)
I have been asked to manufacture a shear pin out of some form of steel or iron. It will be used to break off, when a touch probe over travels its safe area on a CNC machine tool. I need a material that is brittle, so it will break when needed. And i need a material that will be strong enough to function as part of the touch probe option.
Does anyone know what kind of material that i could machine that would react the way that i need.
Does anyone know what kind of material that i could machine that would react the way that i need.





RE: Tensile strength Vs Shear-pin Material type?
You might incorporate a shear line (small cut) when using thicker pins...
RE: Tensile strength Vs Shear-pin Material type?
How fast will the probe be traveling?
Single shear or double shear?
What over-travel will be permitted as the pin is sheared?
What reaction do you need? Lots of questions.
Ted
RE: Tensile strength Vs Shear-pin Material type?
Tobalcane
"If you avoid failure, you also avoid success."
RE: Tensile strength Vs Shear-pin Material type?
RE: Tensile strength Vs Shear-pin Material type?
RE: Tensile strength Vs Shear-pin Material type?
Tobalcane
"If you avoid failure, you also avoid success."
RE: Tensile strength Vs Shear-pin Material type?
Ted
RE: Tensile strength Vs Shear-pin Material type?
RE: Tensile strength Vs Shear-pin Material type?
RE: Tensile strength Vs Shear-pin Material type?
Ceramic
AISI 1095, harden by water quench, do not temper.
Ted
RE: Tensile strength Vs Shear-pin Material type?
Look for material with a yield strength very close to its ultimate strength. Most high-quality/high-strength bolts meet this. Also, you can get similar performance out of certain mild carbon steels which have been extensively cold worked -- just verify that the yield strength is very close to its ultimate strength.
Also, you can get drill blanks made of tool steel from any catalog. Obtain the W-type (water quench) or 1095 stock as hydtools mentions. This is very easy to quench and temper after you machine it to the needed shape, just don't temper it. Since you're not looking for any extraordinary or exacting properties, just heat it with a torch - propane, MAPP or acetylene and keep it white hot for a minute or so, then dip it into a coffee can of water and leave it there until it's below 900F. Dip it in with the axis vertical so that you can reduce (not eliminate) the tendency for cracking. Now you have an extremely brittle pin. But be careful -- do not overtighten when you put it into your fixture. You may have a problem trying to retrieve it if you break it off inside your tapped hole.
Engineering is not the science behind building. It is the science behind not building.
RE: Tensile strength Vs Shear-pin Material type?
untempered state. We used 1095 drill rod to make small shear pins for our metering pump drives. Unless you have absolute control of the HT for the 1095 there is normally quite a bit variability in the quench. By tempering you take the majority of the variability seen as quenched version out of play. I don't know about you size but in
the smaller sizes a good number will crack longitudinally (die crack) if left untempered.
For Aluminum Pins we used various alloys, non that would age harden at RT, wire or rod. Our shear area was an undercut in the middle of the pin. The depth would be determine by shearing a few with an undercut of about 90% of nominal and from these values we would calculate the the require depth for this particular lot of material.
The key for getting a precise shear in any material is having a holding fixture harder than the pin, parallel faces with the gap as narrow as practical to prevent any bending with the resultant tensile stress.
RE: Tensile strength Vs Shear-pin Material type?
Any material can be made to work. Designing and manufacturing a fuse pin that reliably shears at a consistent load point under possibly varying conditions is actually quite difficult. Surface finish, assembly tolerances, metallurgy, heat treatment, temperature, corrosion, number and type of load cycles the pin will see during its life before shearing, etc., all will have an impact on the reliability of your fuse pin design.
If you want a pin that fractures and breaks away, then you probably want a material that has a low elongation rate. If you want a fuse pin that fails more gradually and stretches before shearing, then you want a material with higher elongation.
Regardless, the key to getting consistent performance from your fuse pin is careful control of the pin's manufacture and assembly.
Good luck.
Terry