Turnbuckle Jam

[russb]

I was changing out my old tubular SS turnbuckles for bronze open style and had an interesting problem. After cleaning up the threads (1/2 20 LH) on a jaw toggle with the proper die, a jam nut would spin on the full length of the toggle threads, as would the die. The new turnbuckle, however would only run to about half the length and freeze tight. Visually the threads looked fine. I am replacing the jaw toggle. Does anyone have experience with this sort of problem?

Russ Baney
1979 S2 Auslese
Rogers City MI

[osirissail]

Stainless steel has a characteristic known as "spalling." The threads generate microscopic heat as they are screwed together which is enough to cause "flakes" to separate and jam the threads. Tuf-gel and Lan-a-cote are two anhydrous lanolin products which are wiped onto the threads to prevent spalling.

[Minggat]

I may be wrong, but I believe you mean "galling". Spalling is another thing all together.

russb-there is some damage there that may or may not mean the hardware is salvagable. The microscopic flakes are the culprit.

http://www.estainlesssteel.com/gallingofstainless.html
Thread galling seems to be the most prevalent with fasteners made of stainless steel, aluminum, titanium, and other alloys which self-generate an oxide surface film for corrosion protection. During fastener tightening, as pressure builds between the contacting and sliding thread surfaces, protective oxides are broken, possibly wiped off, and interface metal high points shear or lock together. This cumulative clogging-shearing-locking action causes increasing adhesion. In the extreme, galling leads to seizing - the actual freezing together of the threads. If tightening is continued, the fastener can be twisted off or its threads ripped out.

[osirissail]

Yes, "galling" - too many technical words - - but anyway the use of Tuf-Gel or Lan-a-Cote anhydrous lanolin products on any ss screw or bolt - especially if going into a dissimilar metal like aluminum. This will allow you to remove that screw/bolt many years later.
- - On the subject of ss screws/bolts - these days they are super mass produced in factories (guess the country) and there is - no - quality control anymore. It is very, very common for the head of ss screws/bolts to simply fall off due to microfractures caused when the rod was pressed to form the head. Sources for "316" stainless screws/bolts are becoming as scarce as hen's teeth. So only the lower grade 304/308 type alloys are available in the screw/bolt section of your stores.

[Minggat]

Originally Posted by osirissail

hen's teeth..

"Hens teeth". Typically made from unobtainium.
(I've been so patient while waiting for my turn to use that word)

[russb]

Guys,

I am aware of galling. Part of the reason for the switch of turnbuckle bodies was to go with bronze, to avoid the stainless on stainless potential to gall. The stainless body unscrewed OK (I had used Tef-Gel). I cleaned up the threads with a 1/2 20 LH die. Nuts spun on just fine. The new bronze body screwed on fine right to a point (about half way) and then stopped like the threads were bad. It would loosen and unscrew just fine. I am quite puzzled.

[sigmasailor]

Originally Posted by russb

Guys,

I am aware of galling. Part of the reason for the switch of turnbuckle bodies was to go with bronze, to avoid the stainless on stainless potential to gall. The stainless body unscrewed OK (I had used Tef-Gel). I cleaned up the threads with a 1/2 20 LH die. Nuts spun on just fine. The new bronze body screwed on fine right to a point (about half way) and then stopped like the threads were bad. It would loosen and unscrew just fine. I am quite puzzled.

I do not think galling is your problem. Maybe the SS part has stretched a little. So little that the tolerances allow a nut to pass (may be using 5 threads) but big enough to cause problems with the longer bronze parts (using 20 or more threads). To make sure find some fresh thread of the same size or a thread comb and compare for pitch.

Why do you keep the old SS part and not change out the whole lot?

[osirissail]

Originally Posted by russb

Guys,

I am aware of galling. Part of the reason for the switch of turnbuckle bodies was to go with bronze, to avoid the stainless on stainless potential to gall. The stainless body unscrewed OK (I had used Tef-Gel). I cleaned up the threads with a 1/2 20 LH die. Nuts spun on just fine. The new bronze body screwed on fine right to a point (about half way) and then stopped like the threads were bad. It would loosen and unscrew just fine. I am quite puzzled.

Your having covered just about all the proper bases for a problem leaves only the obvious answer that the new bronze body is defective. This is not at all uncommon. Being in the rigging business for many years I have a box full of rejects with manufacturing defects. I have the box because the cost of returning the item exceeds the value of the item. I always purchase one or two extra's with the initial order as I know it is likely that maybe one will be defective.
- - If you can find the proper size "tap" of sufficient length you might be able to fix the internal problem in the bronze body. Or if you have a surplus SS bolt that is the same thread and long enough you might be able to put some cutting oil on it and use it as improvised "tap." But that is unlikely and you might have to just return the bronze body for a replacement.