keyway question

I need to design a gear on a shaft for class. I have one question though. The gear will be affixed to the shaft via keyway and then
washers one one side and a shoulder on the other to prevent lateral movement. My question is, how far does they keyway have to go through the gear?
The gear has a facewidth of 15mm and a shoulder width of 10mm.
The shaft has a shoulder on one side of it to prevent lateral movement in one direction.
Thanks, Ryan
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Normaly, they go through completely. If you have a key with round ends, the radiused part is outside the gear. With straight ends, it is enough if the key has the width of the gear.
HTH, Nick
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snipped-for-privacy@gmail.com wrote in

You can use a woodruff key for this application, but your shoulder needs to be shallow enough not to interfere with the key cutter diameter. You do not want to cut into the shoulder as it could create a stress point for failure to start.
--
Anthony

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wrote:

True enough. In which case you use a smaller diameter woodruff key..depending on the load. If its highly loaded..often times a roll pin or taper pin is also used, right through the gear and shaft.
Gunner
"If I'm going to reach out to the the Democrats then I need a third hand.There's no way I'm letting go of my wallet or my gun while they're around."
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On 22 Sep 2006 00:53:41 -0700, snipped-for-privacy@gmail.com wrote:

Two kinds of keys..a square key, usually full width of the gear..and a Woodruff key..which is a half a circle (usally a bit less)
Google woodruff key. Typically..woodroof keys are used if there is a shoulder in the way of a regular square key being cut by a horizontal miller <G> Square keys are stronger.. The keyway should go all the way through the gear. Really hard not to make a keyway all the way in fact, if you are broaching the keyway.
Gunner
"If I'm going to reach out to the the Democrats then I need a third hand.There's no way I'm letting go of my wallet or my gun while they're around."
"Democrat. In the dictionary it's right after demobilize and right before demode` (out of fashion). -Buddy Jordan 2001
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snipped-for-privacy@gmail.com wrote: My question is, how far does they keyway have to go through

I have never seen a keyway in a gear that did not go all the way through the gear. Think about how you are going to create the keyway. With the keyway going all the way through, it can be done by a shaper or a broach. The only way I can think of to make a gear with the keyway only going part way thru the gear would be to precision cast the gear or use EDM to create the keyway.
Dan
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On 22 Sep 2006 00:53:41 -0700, snipped-for-privacy@gmail.com wrote:

========================When designing a part, always try to carry a feature such as a hole or slot through the part. This eliminates the need for close depth control and greatly eases fabrication (chips) and reduced cost.
There is a reason that motorcyclists used to refer to Woodruff keys as "wood rough" keys. Unless you have top quality keys they are more prone to shear that the standard square key, because less area is engaged with the usual sizes. Woodruff keys also cost more, and a special cutter is required for the shaft.
The rounded end keyway in many European designed shafts may eliminate some stress risers by eliminating one set of sharp corners, but the bottom edge is still sharp. It appears to be mainly due to using an end mill to cut the slot, which generates a radius/circular end automatically. While the radius-ended keys are neater looking, a piece of standard key stock with the ends chamfered with a file seems to work as well.
From a manufacturing standpoint, a round ended keyway in the shaft, to within a few thousandths of the face of the flange, plunge cut with an end mill with a square key. possibly 5 or 6 mm, would seem adequate. Pick a standard,widely available size. see: http://www.roymech.co.uk/Useful_Tables/Keyways/keyways.htm http://www.alliedbearings.com/downloads/falk_metric_key_keyway.pdf#search=%22%20%22metric%20keys%22%22 http://www.eng-tips.com/viewthread.cfm?qid 1991&page=5
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Thanks for all the replies!!! still confused tho
Here's a picture of what im trying to come up with... <a
http://img74.imageshack.us/my.php?image=shaftut2.jpg
Bascially is this design possible... to have the shoulder of the gear rest against the shoulder of the shaft while having a keyway there?. I'm very confused as to how to design this becuase what you're saying is the keyway has/shoudl go through the whole gear, yet if the gear is to rest against the shoulder there is no way to have the keyway go through the whole gear. Furthermore, if the keyway sticks out of the gear on the other end, putting a spacer there would require a spacer cut with a groove. Please help, very confused.
Thanks, Ryan
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sorry about the link, use this one
http://img74.imageshack.us/my.php?image=shaftut2.jpg
snipped-for-privacy@gmail.com wrote:

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snipped-for-privacy@gmail.com says...

The keyway cut in the *gear hub* should go all the thru. If the oblong in your pic represents the keyway in the shaft, it's fine as-is.
Ned Simmons
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snipped-for-privacy@gmail.com wrote:

The keyway can go all the way through the gear. The key does not have to be as long an the keyway. So if the gear is two inches wide, you could still use a key that is only one inch long. There would just be some air at the ends of the key.
Dan
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On 22 Sep 2006 16:28:32 -0700, snipped-for-privacy@gmail.com wrote:

===================In any event, the through keyway in the gear against the shoulder will not cause any problems. Make the key slot the full width of the gear.
Most likely yuu will also want to include a threaded holde for a set/grubb screw in the shoulder over the keyslot.
From your earlier post

Your sketch does not appear to be to scale, but the shaft is far larger than necessary to provide a shoulder. With a straight cut gear there will be little end thrust. circlips/e-clips should be adequate to position the gear and will eliminate the need for a big shaft which must be machined away just to provide a shoulder.
I would also consider several alternatives to a shoulder/keyway. This works well but it is expensive, and may be the best choice for a one off or prototype.
The newer anarobic compounds [locktite] will provide good retention at much lower costs, and allow the use of a smaller diameter [cheaper] shaft.
In order: Most expensive to least expensive.
1) As you have it sketched, with key slot through gear, and round end slot cut in small shaft diameter to within a few thousandths of the shoulder. You could cut into the shouder for a full gear length key but with the sholder on the gear, the teath will most likely fail before the key does, even without a full [gear+hub] length key.
2) Reduced diameter shaft, with two slots for circlips/e-clips to retain gear. End mill round end key slot in shaft. shaft key slot does not have to go to end of shaft.
3) reduced diameter shaft, retain gear with loctite, possibly with light [hand arbor] press fit onto shaft for fixturing/positioning while loctite is setting up.
see: http://www.qtcgears.com/RFQ/SpurGears.htm http://www.sdp-si.com/D785/D785Cat.htm
http://www.circlips.com.au/clip.htm#axial http://www.smalley.com /
http://www.3dhobbyshop.com/detail.aspx?ID 7 http://www.smallparts.com/products/descriptions/al.cfm
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There is one thing worth adding: Woodruff keys are more intended for maintaining an index. Like on motorcycles with the Motoplat-ignitions. They are not good for transmitting torque and this is the reason why they should be used on a conical shaft.
Nick
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