Jack is a tough nut to crack.

[alpacinou]

Given the context of each sentence, have I used 'tough nut to crack' correctly? Are these okay?

1. Jack is a tough nut to crack. He's humourless and a bit arrogant. Overall, I don't enjoy working with him.
2. Sara is bit of a tough nut to crack. She's not comfortable with expressing her emotions and it takes a long time for her to feel comfortable around someone and let her guard down.
3. Brooke is hard to work for. She's a tough nut to crack and can be exceedingly demanding.
4. My new girlfriend is a tough nut to crack. She's very introverted and always keeps her cards close to her chest. I wish I knew how she really feels about me.
5. To get admission, I need the approval of Dr Mason, but unfortunately she's a tough nut to crack. I would have to work really hard to convince her I deserve a chance.

 

[alpacinou]

And this:

6. Our teacher is a tough nut to crack. He's stingy in handing out marks and I have a feeling he'll fail me.

 

[Tarheel]

I'm not much used to that one. I think it means somebody is hard to figure out. I've been waiting for somebody else to respond, but so far nobody has. I guess we'll both have to be patient.

 

[PeterCW]

I am more used to seeing the expression in terms of hostile questioning or interrogation.

"He confessed in the end but he was a tough nut to crack"

 

[alpacinou]

I am more used to seeing the expression in terms of hostile questioning or interrogation.

"He confessed in the end but he was a tough nut to crack"

This is the definition according to Merriam Webster:
: a person or thing that is difficult to deal with, understand, or influence

Definition of A HARD/TOUGH NUT (TO CRACK)

a person or thing that is difficult to deal with, understand, or influence… See the full definition

www.merriam-webster.com

 

[jutfrank]

We don't need to see dictionary definitions, @alpacinou.

 

[alpacinou]

We don't need to see dictionary definitions, @alpacinou.

What do you think about the sentences in post 1?

 

[jutfrank]

I think 5 is the only one that works well.

Think of the nut as a problem to be solved.