Cross-Threaded Woe

[GBCues]

Hey Guys,
A customer contacted me this week, he had a cue that he somehow cross-threaded when taking it apart and wanted to see if I could fix it. When I first saw the cue, I gave it a moderate twist in both directions and it does in fact seem pretty locked up. i asked him "Just how hard have you tried to unscrew this cue?" His answer "Well, two of us couldn't get it to come apart." I'm thinking "Geez, this is going to be a challenge." So, unscrewing a cross-threaded screw is generally not a big deal. My thoughts were to try to tighten it back up a little bit, get it on track and then back it out carefully. But it won't move. There is a bit of wiggle in it from the pin only being in part way. I tried wiggling it back and forth while twisting (I tried both directions) but it isn't letting loose. I'm reluctant to put any excessive force on it as I don't want to rip out the pin or the insert. I figure both will probably need replacing anyway, but I'd rather do it in a controlled fashion.
My question is, am I missing any other technique to getting this thing apart? I haven't yet sprayed any WD-40 into the joint, but that is coming soon if I don't get any better suggestions.
Thanks in advance, :thumbup:
Gary

 

[GBCues]

Praise the Lord and Pass the WD-40!

As the title says: Praise the Lord and Pass the WD-40!
A little squirt was enough to break it loose to about 1 turn. Then I simply worked it clockwise and counterclockwise with moderate force until I got past the bump. The pin is pretty chewed up as you can see. I chased out the insert with a 5/14-14 tap - not sure if I'll have to replace it or not.
Anyway the first part of the problem is solved.
Gary

 

[KJ Cues]

Howdy Gary,

Congrats on your separation.
Yeah, you'll be replacing the pin (at least) but I'm thinking that's not a 14 tpi pin.
From the pic I'm counting 15 thrds and that pin doesn't look to be 1" exposed.
Could be wrong, it happened once before. Anyway... just for grins, try a 5/16x18 nut on it.
You very rarely find a 14 pin on an import cue.
The pin is toast. Heat and Vise-Grips would be my tools of choice.
Good Luck.

PS, unless that's a CueTec pin, that would be 14 tpi but not 5/16, more like .360".
The visual perspective of the pin's dia. is tough. Measure it please.
The more I look at your picks, the more I'm convinced it's a CueTec 'type' joint.
This puppy is a prime candidate for a 3/8x10 w/pheno insert.
Again, Good Luck.

KJ

 

[GBCues]

KJ,

Yeah, I wish the separation from the last wife had been so easy!
I am sad to say you are correct about the thread count, but it worked out.
I put a 1/8" aluminum heat shield over the pin to protect the joint, heated it up with a small torch and the pin unscrewed cleanly from the butt.
I feel silly now worrying about such a simple problem, but man, it was REALLY jammed in there and after he told me "Two of us couldn't get it apart" I was wondering how badly it had been further cross-threaded.
Live and learn.
Thanks again,
Gary

 

[whammo57]

I have fixed pins like that with a thread file.... local or Ebay for about $10..... doesn't look pretty after but works just fine.......

Kim

 

[scdiveteam]

Don't think this was cross thread result.

I believe the threads were gulled and were damaged when it was unscrewed.

Was this cue left together for a long period of time?

JMO,

Rick

 

[GBCues]

Rick,
No, he said he breaks it down and stores it in his case after playing. The insert is cheap aluminum at best, but more likely some kind of pot metal, it's junk. Last night I was thinking I might just leave it, but after sleeping on it, I'm either going to replace it with a real brass 5/16-18 insert or follow KJ's suggestion and go with a 3/8-10 and phenolic insert. He doesn't really care which, but I'm leaning toward the 5/16-18 just so it is closer to what he's been playing with. I might should add, that yes, it's a nothing special cue, but it's special to him and he doesn't have a lot of money. He told me he joined the service in 1965 and retired in 1989 and is living on his pension, which isn't much. When asked about cost, I told him that since he volunteered his time and service for me, the least I could do would be to return the favor. It's a pro bono repair, but that's no reason not to do it right. I have a bad tendency to fall back on "it'll do" rather than follow yours' and everyone else's advice in here to not ever let something out of your shop that you can't be proud of. :embarrassed2:
Gary

 

[scdiveteam]

Gary,

Your are a good man and KJ has the right suggestion.

Galling occurs in metal whereby the female and male contacts are the same material code specs. So having dissimilar metals or flat face big pin with insert is the way to go.

The metal on that pin and insert is no doubt very low end for this to happen as you pointed out.

I am sure when your done with his cue it will be able to rock and roll again.

Rick

 

[DaveK]

Rick,
No, he said he breaks it down and stores it in his case after playing. The insert is cheap aluminum at best, but more likely some kind of pot metal, it's junk. ...

Gut feel Rick is right and that is a galled thread. Aluminum is prone to the problem, and my guess is that the aluminum insert galled and a small chunk of aluminum broke free and locked up the cue. The damage to the pin was done by the al chunk when the cue was forcefully unscrewed.

Note that galling can happen anytime there is force applied (screwing the cue together). It doesn't need to be left together for a long time, it just needs to be forceful (and thereby break/wear-throug/abrade the oxidation layer on the aluminum insert). I've been threading aluminum for decades and know the stuff can gall easily ... been there, done that, and sworn a blue streak at the offending parts

Dave

 

[GBCues]

Rick, Dave,
Thanks for the info. I knew the effect of galling, but now I have the correct technical term to describe it.
And Dave, yes, I previously titled one of my responses "Praise the Lord and Pass the WD-40" but a devout Christian would hardly classify the language I was using as "Praise" - LOL :grin:
Gary

 

[3kushn]

As the title says: Praise the Lord and Pass the WD-40!
A little squirt was enough to break it loose to about 1 turn. Then I simply worked it clockwise and counterclockwise with moderate force until I got past the bump. The pin is pretty chewed up as you can see. I chased out the insert with a 5/14-14 tap - not sure if I'll have to replace it or not.
Anyway the first part of the problem is solved.
Gary

Look at the bottom of the first damaged thread. I'll bet the problem started on the way in. I can't imagine how you can cross thread a fastener on removal without there being a really lousy, loose fit.

 

[conetip]

When you have 2 of the same materials joining together, if the thread is too neat a fit, it will pick up at the start of the thread when assembled, ie at the position as shown. This is a common problem in engineering. The solution is to make them of a different hardness or to have dissimilar materials.
The reason it picks up where it has is because the 1st thread pitch on the Nut/Joint face takes the highest percentage of the load, all the others have less load. Small amounts of chalk can be the catalyst for this process to start.
It is also called a Galled thread.
With stainless steel, if it is electro polished, this process seems to help in the reduction of the fastener from galling.Hence a lot of stainless fasteners are electro polished.
Neil