Author Topic: 950 mm long socket extension bar from 3/4" to 1/2" mount size  (Read 265 times)

Offline PekkaNF

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I had some frigging rusted and tight high tension bolts to remove. M14 thread size, nominally 175 Nm, glued and rusted from 2006 underside of a Ford vehicle.....marinated in glorious finnish short summers and long winters with some salt on the roads....

Tried with a rachet....not wuite has space to coax all that it needs....breaker bar does not fit....possibility to put three extensions and then 3/4" T-bar comes out of car body and straight line to turn. Straight line is great. Three 1/2" extensions provides incredible amount of flex and it hard to keep it stable.

I had one chopped off 3/4" socket to start, some DN20 pipe (OD27 mm, about 2,6 mm wall) and 75 mm long 1/2" extension. Online calculator promised around 300 Nm of torque before failing....marginal, but that is what I had in hand.

Some lathe work to make tight fit fits to help welding. I did not have the right welding rods to weld tool steel and such...There is real danger of hardening the ends and make them brittle. Closest to proper rod was CromaRod 316L 3,2 mm thick that was just the right for the thick end with 100A, but thin end even 80A was getting way too fluid. I had to preheat the parts to about 200C to prevent nasty habits of the ready made tools to show up. Weld on the thin and critical end came out ugly, but looked solid.

To my surprice the extension worked like a charm. Other bolt came out with simple 3/4" T-bar. The other end was resisting really good: The bushing over the bolt had rusted up and rubber thingy was acting up like a powerful spring. It need nearly two rounds with 1,5 m long extension pipe over the 3/4" T-bar before breaking free....and came out a one piece!


Offline russ57

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Well done...

-Russ


Offline PekkaNF

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Re: 950 mm long socket extension bar from 3/4" to 1/2" mount size
« Reply #2 on: May 23, 2020, 04:44:00 AM »
Thank you Russ,

I felt iffy about this, online calculator showed that I sould have gone up least one size, but that would have left a cap that small end socket extension. Would have been more difficut to fit. I was not sure how tha cable would have played out. Plan "B" would have been to use 3/4" to 1/2" adapter and turn it dow to fit into the pipe, but that would have left very little wall thickness over the 3/4" square part....should have pushed the pipe very front of that and then HAZ of the weld would have gone very close to 1/2" square that is inherently weakest point of this system.

Therefore I allready got 3/4" 250 mm long extension and 40 mm OD 3mm wall pipe that would give over 1000Nm with a good certainty. But both plan "B" and "C" would have needed a short additional 1/2" extension or slender long socket (not standards in 3/4" and 17 mm AF) that would have been more extensions to pin together. pretty much same as buying two 400 mm long 3/4" extensions, adaper and a long 1/2" 17 mm AF socket, wobbly too and how often do you need two 400 extensions.

I had to to try. And it worked. And I learned a thing or two of welding tool steel....I am not too confident on welding tempering steel ot tool steel, because I have not other good heat reatment option than use gas tortch to preheat parts. It would have been a bit dangerous to have this snap while leaning it big time.

Offline WeldingRod

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TIG brazing or silver soldering wont ruin the temper on really tough quenched and tempered stuff like 4340. 

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Offline PekkaNF

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TIG brazing or silver soldering wont ruin the temper on really tough quenched and tempered stuff like 4340. 

Sent from my SM-G892A using Tapatalk

It is true. But I am not familiar with TIG brazing and the silver soldering temeperature would affect on existing tool-steel tolls.

There is less problem with the "big end" I.E.  square drive end.

I think that the small end is the problem: Where the some lenght extension shaft should be joined to pipe shaft. This relatively thin shaft and shaft transition to square drive seems to be the inherently weakest part of the structure.

I think that one possible solution would be to use a bushing that would have a press fit to extension shaft, some distance to avoid exsessive heat ransfer and then decent weld between the bushing and the pipe shaft. This is something I am considering if I need to make another one.