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  #1  
Old 04-30-2019, 07:23 AM
JwWright57 JwWright57 is offline
 
Join Date: Dec 2016
Location: Charlotte, NC
Posts: 130
Question Elbow too tight in brake master cylinder

Hi all - I've been working on the rudder pedal assembly and hit a snag. I have all the brass elbows in the brake master cylinders except for one set (of course the VERY last one). I can only get the elbows in about 3 threads deep before they get fairly tight. It seems like the threads are a teensy bit undersized or the alodine was too thick.

I'm hesitant to try and force them in fearing the brass elbow might break and then i'm really screwed. I thought about running a tap through the holes but am concerned about metal ending up in the break lines and I doubt i have a tap that big anyway.

Any suggestions?
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  #2  
Old 04-30-2019, 07:52 AM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 4,152
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Quote:
Originally Posted by JwWright57 View Post
Hi all - I've been working on the rudder pedal assembly and hit a snag. I have all the brass elbows in the brake master cylinders except for one set (of course the VERY last one). I can only get the elbows in about 3 threads deep before they get fairly tight. It seems like the threads are a teensy bit undersized or the alodine was too thick.

I'm hesitant to try and force them in fearing the brass elbow might break and then i'm really screwed. I thought about running a tap through the holes but am concerned about metal ending up in the break lines and I doubt i have a tap that big anyway.

Any suggestions?
These are NPT threads and should be more than "fairly" tight. Recommend a good PTFE based sealant and go another turn on it. Concern is not that 3 threads isn't enough to hold it, but that it will leak if not tight enough. Many threads here on leaks from these particular threaded joints. A bit of searching will help.

Larry
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  #3  
Old 04-30-2019, 07:53 AM
Stoo Stoo is offline
 
Join Date: May 2006
Location: LL10, Naperville, IL.
Posts: 60
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Better to screw the fitting into a pipe die, then you can clean off the chips easily. You should have no problem finding the right die at the hardware store.
Stewart Willoughby, 6, paint is next
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  #4  
Old 05-01-2019, 08:19 AM
JwWright57 JwWright57 is offline
 
Join Date: Dec 2016
Location: Charlotte, NC
Posts: 130
Red face NPT fittings

What a great forum! I read all the old posts on NPT fittings, followed the suggestions and BAM everything seems ok. I never would have imagined that you can tighten them down so much OR that you can use the fitting as a semi-tap (tighten/back off/tighten, etc.)
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Rv-12 started!
Tail 99% done
Wings 99% done
12IS fuse kit 99% done
Finish kit coming in a few weeks
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  #5  
Old 05-01-2019, 09:59 AM
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Pilot135pd Pilot135pd is offline
 
Join Date: Jan 2019
Location: Ben Wheeler, TX
Posts: 397
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Quote:
Originally Posted by JwWright57 View Post
What a great forum! I read all the old posts on NPT fittings, followed the suggestions and BAM everything seems ok. I never would have imagined that you can tighten them down so much OR that you can use the fitting as a semi-tap (tighten/back off/tighten, etc.)
And thanks to you bringing it up I learned it today too. Forums are great when you have knowledgeable people like here !!! I help moderate an aviation Facebook page and you get a thousand opinions when a question is asked and more than half are from people who arenít pilots or mechanics and donít know what theyíre talking about.
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