Why is my keyway width so small? what am I doing wrong here?
Why is my keyway width so small? what am I doing wrong here?
(OP)
Hello All,
I am calculating the width of a keyway to use a key for a hub and a shaft. The key will fit half in the hub and half in the shaft to prevent the rotation of the hub inside the shaft.
Here are the values
Hub diameter=1.5"
which is about same as the ID of the shaft.
r=.75"
Length=5"
b=width=?
max Torque, which I am going to apply= 1800 in.lb
material SS316, yield = 42100 psi
shear stress= yield/FOS = 42100/1.5= 28066 psi
Now,
As we know
shear stress= Force/bL = T/bLr
b=T/shear stress*L*r= 1800/28066*5*.75= 0.0171 "
This looks too small compare to what I thought.
could you please help
thanks
Torque=
I am calculating the width of a keyway to use a key for a hub and a shaft. The key will fit half in the hub and half in the shaft to prevent the rotation of the hub inside the shaft.
Here are the values
Hub diameter=1.5"
which is about same as the ID of the shaft.
r=.75"
Length=5"
b=width=?
max Torque, which I am going to apply= 1800 in.lb
material SS316, yield = 42100 psi
shear stress= yield/FOS = 42100/1.5= 28066 psi
Now,
As we know
shear stress= Force/bL = T/bLr
b=T/shear stress*L*r= 1800/28066*5*.75= 0.0171 "
This looks too small compare to what I thought.
could you please help
thanks
Torque=





RE: Why is my keyway width so small? what am I doing wrong here?
RE: Why is my keyway width so small? what am I doing wrong here?
I want to make sure the key goes over the whole surface of the shaft.
just for increase strength and symmetry.
So you are saying everything is good with these calculations, the width is very small because the length is big??
RE: Why is my keyway width so small? what am I doing wrong here?
RE: Why is my keyway width so small? what am I doing wrong here?
RE: Why is my keyway width so small? what am I doing wrong here?
A more typical approach would be to pick a common size key for your shaft size and calculate the length that you need to transmit your torque.
RE: Why is my keyway width so small? what am I doing wrong here?
RE: Why is my keyway width so small? what am I doing wrong here?
There are standard key and key way sizes to select from see this link:-
http://www.roymech.co.uk/Useful_Tables/Keyways/key...
RE: Why is my keyway width so small? what am I doing wrong here?
don't I need calculations to see which standard size key to pick based on the dimensions and the material(SS) I have?
RE: Why is my keyway width so small? what am I doing wrong here?
Sorry i forgot to mention I am in US. We use inches not millimeters, Do you know something like this in inches.
RE: Why is my keyway width so small? what am I doing wrong here?
http://www.hercus.com.au/uploads/29161/ufiles/Keys...
This link is from the links on the bottom of the first link I posted.
RE: Why is my keyway width so small? what am I doing wrong here?
Thanks for providing this chart. Now I have a question here. What I want to have 2 or 4 keys on the entire circumference of the hub. How would that effect these height and width. Do I divide the height and width by 2, If I want to have 2 on the opposite sides?
RE: Why is my keyway width so small? what am I doing wrong here?
No you keep the sizes as they are, why would you want four keys? The most I have seen is two.
If you use two keys its recommended that they are placed at 180 degrees apart.
It seems pointless having multiple keys because it's unlikely that the keys will all act to transfer the load simultaneously and in addition assembling four keys could be quite difficult.
If you can tell us exactly what it is your trying to do we might be able to help further but pleased give as much information in a single post as possible,otherwise we end up with extremely long threads and information is scattered over lots of posts when it could easily fit into one or two.
RE: Why is my keyway width so small? what am I doing wrong here?