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Antique Gas Engine Discussion

Strange Gibb Keys?


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  #1  
Old 09-01-2005, 08:46:54 AM
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Jebaroni Jebaroni is offline
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Unhappy Strange Gibb Keys?

Hey guys. I'm a little confused. I am almost done restoring my Taylor Vacuum engine. I ordered 2 3/8" gibb keys from Hit and Miss Ent. When I got them, they were the correct width, but were too tall. As in the distance from the flat on the bottom of the keyway in the shaft to the flat in the flywheel is almost 3/16" shorter than the smallest end of the gibb key. Can gibb keys be ordered in different "heights"? The flywheels and crank are correct for the taylor engine (carry correct casting numbers). Looks like i'll have to do some serious grinding to get them to fit unless I can find some that are correct. Anyone else run into this problem and know how I can fix it? The gibb keys I took out were destroyed so I can't reuse them. Thanks for the help.

Jeb
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Old 09-01-2005, 10:16:36 AM
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Jim Sherman Jim Sherman is offline
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Default Re: Strange Gibb Keys?

I have had this same problem with my Foos and an Ottawa. The standard gib keys you get from hit & miss or starbolt are just that, standard. If you check the machinist handbook the sizes they sell are exactly as they are supposed to be. For some reason some of these engine builders used their own sizing. I had to mill off the standard keys to make them fit.


Be careful grinding them, you want as flat of an area as you can get at the correct angle so you are not just relying on a small portion of the key. Milling them at the correct angle is a much better option if you have access to a mill or know someone who can do it for you. If there is anything left of your old key's you can probably get the correct angle off from them to copy.
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Old 09-01-2005, 10:16:57 AM
SteveJ SteveJ is offline
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Default Re: Strange Gibb Keys?

Jeb,
I also have a similar issue with gib keys, on a Stover KA: the two keys that secure the flywheels are 3/8" width, but are only about 1/4" (nominal) in "height", so a std. 3/8" square key will not work. Fortunately, I think I can clean up and re-use the old keys that I have removed along with the wheels.

I would be interested in some contact info re: a source for these gib keys which have a rectangular cross-section. I have looked at H&M, and also at McMaster-Carr...no luck so far.

SteveJ
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Old 09-01-2005, 04:55:14 PM
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Default Re: Strange Gibb Keys?

Fairmont keys are that way also.
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Old 09-01-2005, 06:26:21 PM
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Default Re: Strange Gibb Keys?

Remember these keys do need fitted , they should be blued and filed in for a full contact fit
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Old 09-01-2005, 07:35:41 PM
MHirst121 MHirst121 is offline
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Default Re: Strange Gibb Keys?

All gib keys come this way, unless they have been machined to roughly the right size for final fitting. I always blue mine to get a good fit as not all keyways in the shafts are square.

Martin H
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Old 09-01-2005, 09:16:37 PM
Chip Watford Chip Watford is offline
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Default Re: Strange Gibb Keys?

Gib keys have a standard rate of taper for the size of the key.If you need a key with a shorter verticle diminsion ,mill the material off the flat bottom side.This should be done slowly and check the fit often as you don't want to go too far.As was stated earlier,you can then do the final fitting with a file and some bluing. Chip
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Old 09-02-2005, 05:46:16 PM
Rob Charles Rob Charles is offline
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Default Re: Strange Gibb Keys?

Another thing comes to mind.Most keyways in fws and crankshafts are parallel.The tapered gib key only tightens at the outside edge.The taper is usaully a std found in Machinerys handbook I think it's 8 degrees but I could be remembering wrong. A simple angle block for the mill vise will keep the taper while letting you sneak up the right size.You can also use a small adjustable parallel or dial calipers to measure the total height of the key ways.You can than mill the gib key to that size around a 1/2 " from the head.That will allow room to tighten it and still get somwthing behind it to pull it out.Your mileage may vary Rob
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Old 09-02-2005, 10:12:06 PM
Chip Watford Chip Watford is offline
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Default Re: Strange Gibb Keys?

Rob,After I posted my last reply I went and looked up the standard Gib key taper and it is 1/8" per 12".I didn't figure what degree that would be. Chip
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