Friends. Thread damage. Need to replace this part (see photo) the lower threaded eye toggle of my older Unit 0 Harken roller furling. Harken cost exorbitant. Need your expert opinion on purchasing 5/16 pin hole size and jaw width and 1/2 in threaded eye rod. Have pin pressed on locally by career machinist friend. Or if you have alternate suggestion. I assume part threads cannot be rethreaded.
Replace Toggle Part
- Thread starter DockH
- Start date
I would try running a threading unit down it just for thread clean up to see if it would correct the problem. In this case you are not trying to do new threads in stainless, just cleanup of threads. Chief
Ok, I'm normally the one who would agree to fix and repair if at all possible. I know I'm running a furler that has a bad foil but is patched together with some splints for this season due to a serious lack of boat bucks.
However, I'll throw a grain of salt at the above discussion about trying to repair rather than replace. As you mention this is the lower toggle for the roller furling. If you repair the part and it fails what are the consequences, does the entire rig come down? Is it catastrophic or will you just lose the use of the furler. If it fails and it happens during a blow will you be able to recover or will you lose the entire rig or worse.
Just a word of caution, if it can be repaired with minimal loss of functionality and is still safe do it. But, don't bet the whole boat on the failure to spend a few bucks.
Victor
However, I'll throw a grain of salt at the above discussion about trying to repair rather than replace. As you mention this is the lower toggle for the roller furling. If you repair the part and it fails what are the consequences, does the entire rig come down? Is it catastrophic or will you just lose the use of the furler. If it fails and it happens during a blow will you be able to recover or will you lose the entire rig or worse.
Just a word of caution, if it can be repaired with minimal loss of functionality and is still safe do it. But, don't bet the whole boat on the failure to spend a few bucks.
Victor
If I can repair the one thread enough so that it does not inhibit tension adjustment then I should be good to go. If the one damaged thread would be right at the optimum tension point then I might compensate with a spacer. Otherwise the end of the bolt that is threaded into the body of the furling drum is good and would not be at risk to come loose.
Thanks for your wise warning.
Thanks for your wise warning.
Spacer can work but woodster does not think I should clean up the threads because he believes they are machine rolled, not die cut, and therefore will not be as tight as the machine rolled threads. Since the bolt threads into the body of the furling drum the threads have to be compatible. I have a bud who is an expert machinist. I will seek his opinion. Thanks
What does rolled mean ? On a CNC lathe ? I have an expert machinist bud. Is this something he could do ? Threads have to be compatible with the internal female threads of the drum assembly. Would they also be rolled ? FYI normally I would cough up but they want about $170 for just the replacement on special order and no returns.
What Woody is talking about is that rolled threads are cold worked and impart strength to the unit by flowing the material and having the grains in the metal aligned with the stresses. In addition a rolled thread might be what is known as a "J" thread where there is a root radius at the bottom of the thread that further helps with stress reduction. For a male "J" thread the female thread has the I.D. relieved a little so the sharp points of the thread don't dig into the root radius of the male part. A die will cut the thread all the way to the bottom so it will make a sharp pointed "V." There can sometimes be a disadvantage to a rolled thread in that as the material flows from both sides into the "V" of the thread rolling die it tends to create a notch where the material flows together. In high stress high cycle fatigue this can lead to fracturing at the root of this notch. I have seen this in fatigue testing on aircraft products. For low cycle fatigue like this unit that is probably not a serious concern but stress corrosion of that notch might be a concern. Another option is to use a polishing jack and some lapping compound to clean up the thread. It is hard to see from the picture just what is wrong. Loss of a mast could be catastrophic if it landed on you or a passenger, or holed the boat that then sank. Seems like the right advice is replacement if it shows sings of corrosion or is significantly damaged. Your machinist buddy might be able to cut off the damaged section on a lathe down to the root diameter of the thread then use the good thread section as previously noted. I you have access to a visual comparator at 50X power you will be able to see and measure much of the thread like the root radius.