Keys and Couplings Flashcards
What would we use a set screw collar for?
To locate objects on a shaft. It is cheap and easy to install but has low transmission capability, and the hardened end of the set screw can damage the shaft, but it will also push the shaft against one side of the bore causing eccentricity.
What is an Anaerobic Adhesive?
It is made from methacrylates, monomers related to acrylics. They can become active and cure in the absence of oxygen.
They lock all types of fasteners and are used to retain bearings, pulleys and gears to shafts.
What are retaining pins?
Use them to keep objects on the shaft. It is cheap, and is simple to make, but the hole that has to be made through the shaft will weaken it. They are good for light duties.
What are keys?
They are a cost effective method of locking. Damaged keys can easily be replaced and they are easy to install. We can use it as a fuse so that it will break first before the component that it is locking onto the shaft.
How do we eliminate axial movement of the key?
use a set screw.
When would we use square keys as opposed to rectangular keys?
Use a square key for shafts that don’t have a large diameter. Rectangular keys are general components where their width will exceed their height allowing them to transmit greater torque without adding any depth to their hole.
What are tapered keys?
They are designed to be inserted into the hub of the component once it is on the shaft. It will impart a compressive contact on the hub and shaft. Does not require a set screw to prevent axial movement.
What is a feather key?
It has a radius at either end.The oval shape will prevent movement axially and holds the key in place.
What are the advantages of feather keys?
They are easily to insert into the shaft, don’t require setscrews, they won’t move axially but can adjust their axial position.
What is a broach
It is the tool used to cut keyways in hubs. It can roughcut, semi finish, and finish in one pass. It looks like a wood rasp.
What is a pin key?
It is a cylinder shape, but has low torque transmission and is complex to machine.
What are the Problems with keys?
Cutting key ways creates stress concentrations. We radius the corners to reduce this. Backlash can occur due to the clearance between the key way and the slot.
Rolled keys, this will happen if the key is loose and can cause shearing of the key.
Chamfers can reduce the surface contact
Key proportion: If it is too big then can prevent proper mating of the components.
Where along a key are the forces most concentrated?
At the torque input end. Get non uniform distribution of forces due to the twisting of the hub.
When we design a key what do we assume?
That the distribution of forces along the key are uniform.
What are the two modes of failure of a key?>
Crushing and shear
