Turnbuckles

[higgs]

I have some damaged threads on my rigging that I need to take care of. They are big - I am not sure of theri size, but they are bigger than half inch. Purchasing a set up at a chandlery is going to cost over $100 per assembly. Problem is that I only need the stud going from the deck fitting to the turnbuckle barrel. Anyone know of a source for just the threaded stud?

 

[ggrizzard]

SAILING SERVICES in Miami, FL.
1-800-458-1074
sailingservices.com
They will sell just the pieces you need.
You might want to check your rigging with a magnifing glass for hairline cracks and the turnbuckles for damaged threads as well. Any dealer will need the specs, so remove the parts and take them to a local bolt distributor (maybe even Ace Hdw.) and get the number of threads per inch and the thread orientation (left or right hand turn).

 

[sailingdog]

You could also try Rigging Only in Fairhaven, Massachusetts. www.riggingonly.com

Contact Information
Telephone
508-992-0434
FAX
508-992-0488
Hours
M-F 7:30 AM to 4:30 PM Eastern Standard Time
Postal address
PO. Box 264, Fairhaven, MA. 02719
Shipping address
50 Fort St., Fairhaven, MA. 02719
Electronic mail sail@riggingonly.com

 

[Ross]

Higgs, Is it just the mangled threads that are a problem? If that is the case then run a die on them and chase the threads and use them .

http://www.mcmaster.com/#thread-restoring-tools/=1c9lsv

 

[sailingdog]

Ross—

Given the loads on them and the importance of turnbuckles, and the fact that stainless steel doesn't deal with mechanical fatigue very well, I would highly recommend replacing, rather than running a die on any turnbuckle that had damaged threads, unless that was your only option.

 

[Ross]

Like everything in this business it would depend on where and how badly the damage was located sometimes it doesn't take much to ruin a screw thread. If they are damaged because they galled under load then they are shot, but if a lever slipped and bruised the thread they can be saved.
I once saw a 3/8 bronze turnbuckle that failed because it had been bent about 60 degrees.

 

[higgs]

Thanks for the help. I just had a guy look them over. The threads on a casual glance look fine, yet there are spots that a good nut won't thread through. The guy said that the threads actually can get bent down or up - if you look at them from a cross section. he says running a dye over them won't help. The guy does have a good rep around here.

Anyways, these puppies are way bigger than they need to be for my 34. Threads appear to be 9/16. Problem is the boat was built in Taiwan. I will give the places you reccomend a call and see what they can tell me.

 

[jibes138]

Threads

A thread derives most of its' strength from the section below the pitch diameter. For "J" thread fasteners for instance the minor diameter of the female thread is relieved so that the peaks of the thread don't dig into the root radius of the male piece. "J" threads are very common in aerospace where fatigue strength is a concern, you don't want sharp corners to concentrate stresses at the root of the threads. If only the tips of the thread are damaged by some impact, running a die over them will likely solve the problem. If they are more seriously damaged by being bent or severely distorted then replacement is recommended. in this case the material of the base of the thread is now questionable. Stainless by being bent will work harden effecting its' strength especially in fatigue. A thread with only 75% of the thread height will still have over 90% of its' strength as the strength provided by the tips of the thread are minimal.
You can study this information in articles on thread strength. You can also check you rig for indication by using dye check or bring them to a shop with zyglo (FPI) capability. Another option is give them to a student to do x-ray diffraction on them to check for states of residual stress at the local university metallurgy lab.