Author Topic: Farm Boy o-ring sizing  (Read 1983 times)

Offline sshire

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Farm Boy o-ring sizing
« on: November 29, 2014, 01:25:39 PM »
In Jerry Howell's drawings for the Farm Boy, he specs this for the piston o-ring

"piston ring groove .105" wide by .110" deep for a .094" section by 1" diameter Buna-N "O" ring."

I've checked all of the usual suspects (McMaster, Grainger, O-rings-R-Us, etc) and no one has an.094 O-ring.

I got these two sizes from McMaster:

.070 thickness, .864 ID, 1.004 OD
and
.103 thickness, .799 ID, 1.005 OD

Any reason to use one over the other? I've held off machining the o-ring groove until the general wisdom here has been heard from.

BTW, if anyone needs either of these sizes, I now have 100 of each. Just ask.
Best,
Stan

Offline Brian Rupnow

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Re: Farm Boy o-ring sizing
« Reply #1 on: November 29, 2014, 03:55:55 PM »
Use the .070" cross section ring, cut the groove in the piston .057" deep x .093" wide.----Brian

Offline sshire

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Re: Farm Boy o-ring sizing
« Reply #2 on: November 29, 2014, 04:00:54 PM »
Brian
Thanks so much. I'll do it. Just so I understand, why did you choose the .070?
Best,
Stan

Online Jasonb

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Re: Farm Boy o-ring sizing
« Reply #3 on: November 29, 2014, 04:13:34 PM »
No use the larger one, the 0.094" or 3/32" is a nominal size but the actual ring section of these rings is 0.103 so readily available and will fit the specified groove sizes
« Last Edit: November 29, 2014, 04:19:31 PM by Jasonb »

Offline sshire

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Re: Farm Boy o-ring sizing
« Reply #4 on: November 29, 2014, 05:46:35 PM »
And that was my confusion. I did order the 3/32" but the actual size on the McMaster website is .103.
If I had thought of the decimal measure of 3/32 all would have been correct to the drawings.
Still interested to know Brian's thinking on the thinner o-ring.
Best,
Stan

 

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