29-240 case with stubborn threads

Alright, so I used my 29-240 case that I got from 3stoogesrocketry on here. I assembled it at Freedom Launch with an H250G, and then flew it, put it in the car because we had to leave right then (long story) and I did not get to disassemble it until that night (about 6 hours later). It disassembles easily. I clean it out, and try and thread the closure back in. Fore closure goes in easily, after closure spins about 2 turns, and then it is too tight to thread anymore. I switch closures. Same issue. I assume it is a case issue. I clean out the threads again, and still no joy. I tried the freezer/boiling water trick, and that didn't work either.


Any suggestions? For any wondering, the case was made in '93 (serial number in the 200-low 300's).



I would really like to keep the case in operation. I never dropped it.

Matt you using lube or doing it dry ?


if dry AT grease might get it past the buggered up thread

I basically drowned it with WD-40.

WD-40 is a good solvent/cleaner. Hit the threads with a toothbrush, put some Vaseline on it, and try again?

Post pictures of the case threads.

Any luck?

I have several and found some couldn't be swapped. Matched to the right case, it was fine. If you only have one, this isn't the issue.

Another thing to try is soaking the case in vinegar to loosen the crud. Then toothbrush, rag whatever, to clean out the threads. You might want to look in there with a flashlight to see if they aren't dorked in some way.

If worse comes to worst, buy a die for that thread/opening size and rethread it. Yeah, I know, PITA.

You (or a previous owner) may have bumped or dropped the case while cleaning and slightly dented the one end. I suppose this could happen upon hard landing, but it most likely happened when the closure wasn't in the case.

It should be possible with plenty of grease (not WD-40) to get the closure to thread back into the case.

--Lance.

Hey BB, what is the diagnosis?

I have been nonstop working on history the past few days, so I haven't had a chance to get to it yet.

OK, so I took a toothbrush, and scrubbed the closure and threads for about 10 minutes. Then I soaked it in hot water, scrubbed it, dried it, and no joy. Bummer. I don't think it is a crud issue. Why would it go in like halfway and then get really really tight though?

Did you apply grease?

Adrian

Matt sounds like you cross threaded the clouser . Check the threads . Look at the 2nd and 3rd thread for damage . If no joy mail the case and clouser back to me and ill fix it for you .

Eric

blackbrandt said:

OK, so I took a toothbrush, and scrubbed the closure and threads for about 10 minutes. Then I soaked it in hot water, scrubbed it, dried it, and no joy. Bummer. I don't think it is a crud issue. Why would it go in like halfway and then get really really tight though?

Click to expand...

Matt- I'm going to assume you have good eyesight for as young as you are. Is the case concentric? Are the threads evenly spaced and landed? If all appears to be good, here is a machinist trick you can use: Use a bit of powdered graphite from a locksmith or Wallyworld (sporting section where they make keys-comes on a carded tube.) Burnish some in on both pieces using firm finger pressure (yeah your going to get your finger dirty!) Polish this in and work the threads together a bit,but DON'T force it. Now you need to find some Clover Lapping Compound-check any metal working supply house or your local gear head Speed Shop. Tell them you are lapping in valves seats-they may have a different brand. I'd recommend anything from 320 thru 600 grit. Dip a bit on the case threads and work your closure in-tightening and backing off a little deeper each time. Ultimately you'll 'match machine' these threads together. Carefully examine the threads for witness marks to make sure you haven't weakened the threads in bearing and they still have sealing strength. Look at the top of the thread for polishing. This may take repeated trials and you'll have to clean off the threads each time to verify your progress. Re-apply graphite as needed. This will remove some of the anodizing on the threads and hopefully not much more. The anodizing should be taken into account when machining these, but there is a min/max tolerance you may have wound up on the wrong side of. (To explain: if the tolerance is +/-.005 and both parts are at +.005, you may have an interference fit.)

(or send it to Eric! He posted while I had to figure where they moved all the keys around the board today...)