Saturday, February 20, 2016

Yet Another Special Tool

It's still rather inconvenient outside, so as the engine cylinder is waiting to be painted, I decided to make use of my time working on yet another "special tool".
This time, it's for unscrewing the awkwardly shaped "crown nut" that holds the transmission output flange on its shaft. Crown nuts are suitable for tight places where you don't have enough room for a spanner or similar. There is actually even an international standard for the crown nuts, but the standard ones are with six arms. This one has only four, probably manufactured before that standardization and only for this purpose. Consequently, you can not simply buy a tool in the market to unscrew this.

I bought a long 16mm socket to sacrifice, which fits the inner diameter and thickness of the nut quite well. I am going to cut its edges to align with the nut. Once removed, perhaps I should consider replacing it with a regular/standard one.

The socket has to be long to avoid hitting the tip of the shaft. Its excess is a bit more than two centimeters long, plus the tips on the nut, so I need more or less three centimeters inside. This one looks pretty promising.

Here's the fun stuff again. I fitted the grinder on a universal bench tool. It is not really a must have, but this time all I need is another hand. Without it, I would hold the machine with a hand, holding the socket with the other, and would have needed yet another hand for the precise alignment during cutting. No, I don't fancy an angry and heavy angle grinder running on my lap...

Luckily, the socket turned out to be relatively soft. One eye on the crown nut, I started cutting the dents.

Doesn't it look awesome?

I managed to make pretty decent dents. So I even did some finer work on the side edges of the tips to fit better onto the nut.

Not bad at all. It is not a perfect fit, to be honest, but obviously the nut itself is not brand new anyway. I'm sure it has never been removed with a proper tool, but only using the hammer and chisel method. It is not good for the old and tired metal.

Here comes the good old friend WD-40. The nut is almost covered with filth and oil, which is a great combination to jam the nut no matter how hard you try to unscrew it. The cleaner the better.

The output shaft is free to rotate, and obviously I can't unscrew a nut on a freely rotating shaft. So this very simple L-shaped "special tool" aims to hold the output flange onto the transmission body.

I support the spanner with a long thick iron pipe as a lever and literally sit on the transmission body with my entire weight. Let give it a try...

And here comes the moment: Failure... The nut is so stubborn in its place. The socket seems to fit well, but when you apply the force it slides out of the crown right away. I think I should have made it a better fit. Luckily the socket itself is long enough to allow me a second try. But later... So today's score: 0-1.

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