I am the one that created the table on the C&C Photo Album. It has been
so long ago that I don't remember where I got the raw data. I agree
that the 1/2 nut values seem high. I originally created the table when
I bought Corsair in 1996. One of the survey items was that the keel
bolt backing plates (mild steel) were severely corroded and should be
replaced. I obtained stainless steel backing plates and put together
the chart from one of the C&C documents that I could find. We had
Corsair for 21 years and never had to touch the keel bolts after that.
She was just beginning to develop a noticeable smile last year.
For our 1 inch keel bolts, the clamping force for a dry bolt at 350
ft-lb (4200 in-lb) is 21,000 lbs (coefficient of friction of steel on
steel ranges from .15 - .25 dry, I used .2). This equates to a tensile
stress across the coarse thread minor diameter of 37,300 psi (29,900 for
fine thread). For an Austenitic Stainless Steel (300 Series), this is
right at the yield strength. Once again, this used the mid range
nominal dry friction and nominal SS yield strengths. This does become a
problem if you lubricate the threads. The coefficient of friction goes
to a range of .11 - .17, steel on steel. The coarse thread stress
becomes 49,300 psi, well above the yield strength of 300 Series SS.
We had lots of broken bolts at work when assemblers didn't know if the
torque specified was dry or lubed. We finally went to lubed
torques,exclusively, since we were building hydraulic pumps.
All that said, we haven't had a rash of broken keel bolts. Does anyone
know what material Mars uses on their keel bolts?
Neil Schiller
BSME, Michigan Tech, 1977
1983 C&C 35-3, #028
"Grace"
Whitehall, Michigan
Retired after 37 years in Aerospace and Defense Engineering
On 1/3/2018 12:21 PM, Dennis C. via CnC-List wrote:
Don't think you did. I was just offering some clarification for
anyone who might be technically challenged.
I be an engineer. It's what I do, er, did.
That's what's great about this list, with our combined intellect and
experience, we stand a good chance of doing something right. :) Then
again, even a blind squirrel finds a nut every now and then.
Dennis C.
On Wed, Jan 3, 2018 at 10:17 AM, Josh Muckley via CnC-List
<cnc-list@cnc-list.com <mailto:cnc-list@cnc-list.com>> wrote:
Follow my links and tell me if I'm missing something. I assumed
316 stainless, Course thread, and lubed with tef-gel.
Josh
On Wed, Jan 3, 2018, 10:44 AM Dennis C. via CnC-List
<cnc-list@cnc-list.com <mailto:cnc-list@cnc-list.com>> wrote:
Torque specs are affected by, as a minimum, the following:
Bolt size
Grade of bolt
Material, SS or steel
Thread pitch
Lubed vs dry
Make sure you're comparing apples to apples.
Dennis C.
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Thanks everyone for supporting this list with your contributions. Each and
every one is greatly appreciated. If you want to support the list - use PayPal
to send contribution -- https://www.paypal.me/stumurray
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Thanks everyone for supporting this list with your contributions. Each and
every one is greatly appreciated. If you want to support the list - use PayPal
to send contribution -- https://www.paypal.me/stumurray
