Keyway design

[TyVan07]

Hi all,
I am designing a keyway to fit a 7.625" Shaft. I sized the key and keyseat and everything looks good from a stress point of view, however, I am more curious about the positioning of the key.

The key is 1.75" W X 1.5" H and 10" Long with radius equal to half the width of the key on the ends. The key is positioned in the middle of the shaft, so it drops into a slot.

The corresponding hub butts up to a shoulder in the shaft, at one end of the key, my question is, how far away from the mating face of the hub/shoulder should the closest edge of the keyseat radius be?

Let me know if I need to describe this clearer...

Thanks,
Tyler

 

[Cockroach]

Sounds good, rectangular key (1 3/4 X 1 1/2) of length 10.0 inches should handle quite the load.

As far as mating, you need to maximize the length of contact in order to obtain key functionality, so you can come close to that shoulder assuming no stress risers such as sharp fillet or such. Probably a sketch would be better to comment upon.

But good luck with it.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

 

[electricpete]

According to Shigley's Mechanical Design

The sled-runner keyseat can only be used when definite longitudinal key positioning is not necessary. It is also not as suitable near a shoulder. Keeping the end of a keyseat at least a distance of d/10 from the start of the shoulder fillet will prevent the two stress concentrations
from combining with each other [Note 9]...
9 Ibid p 381

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(2B)+(2B)' ?

 

[electricpete]

Actually that quote doesn't tell what d is. From the context, I believe it is shaft diameter. For more context, see page 35/49 here.

https://highered.mcgraw-hill.com/sites/dl/free/0073121932/365766/chapter07.pdf

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(2B)+(2B)' ?

 

[JohnRBaker]

Depending on how 'high' the shoulder is, the real trick will be how close can you get the mill the keyway slot to the face of the shoulder. If the height of the shoulder was such that you could get an end-mill to reach the bottom of the slot without the tool-holder hitting the top of the shoulder, theoretically you could run the keyway slot until the end was all but tangent with the face of the shoulder, as this would give you the maximum contact area between the side of the key and the keyway slot in the hub.

John R. Baker, P.E.
Product 'Evangelist'
Product Design Solutions
Siemens PLM Software Inc.
Industry Sector
Cypress, CA

http://www.siemens.com/plm

http://www.plmworld.org/museum/

To an Engineer, the glass is twice as big as it needs to be.

 

[TyVan07]

Thanks for all the replies..I think I'll leave the keyseat radius a distance from the shoulder face. Another question for discussion, I have read that the key must protrude past the hub to avoid any stresses from the key corners 'digging in' to the hub material. Is this true for keys with rounded edges as well?

 

[MikeHalloran]

The round-end key and seat is intended for use in the middle of a plain lineshaft.

Your shoulder makes things more complicated.

I think the answer is that you have to decide what you want to fail first, and how.



Mike Halloran
Pembroke Pines, FL, USA

 

[electricpete]

I think there are a number of reasons that the keyway typically extends all the way through the hub:
1 - The keyway needs to extend all the way past the hub in at least one direction... otherwise you can't assemble it.
2 - as mentioned by Cockroach... to extend the effective length of the key within the hub.


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(2B)+(2B)' ?