"that" and "so that" - usage in compound sentences

[Pierce111]

I am thinking about sentences such as:
"We did this so that he do something."
1) First question:
Do "that" and "so that" mean exactly the same and can be used as replacement for each other?

2) What tenses should I use in second part of these sentences (examples below, are they correct?)? Is there a tense shift?
For example:
a) "We bought those parts so that he checked them" (He should have check them in the past, just after we purchased those parts )
b) "We bought those parts so that he will check them" (He is expected to check those parts in the future. He hasn't done it up till now when we say this sentence)

3) Can I use "that" or "so that" with "want", e.g.:
"I want so that he do it." (or "he will do it")

Thanks in advance.

[Barb_D]

Hello,
None of your sentences are grammatical.
1) As a general rule, any question that asks whether two phrases are "exactly the same" will usually be answered with "no."

2) Here is how you use this: I want Thing B to happen. To allow Thing B to happen, I do Thing A. I do A so (that) B.

I moved to this town so my children could be in a better school system.
Could you move to your left a little so I can see the stage?

3) No. I want him to do it. I hope he will do it. I order that it be done.

[Pierce111]

So to make it more clear.
2) How should my examples a) and b) look like to express my intentions?

3) I am interested in examples that you submitted. As I see, in sentence "I hope he will do it." the future tense is allowed and in second one there is some kind of tense shift "I order that it be done."
To make it more clear:
I hope it will be done.
I order that it be done.
So "order that" requires further a verb in infinitive form ("be")?

[Barb_D]

We bought the parts after he checked them.
He has bought the parts and he will check them soon.

[Pierce111]

Thanks, but now they don't exactly express my meaning. I will try to describe you a hypothetical situation to give you more informations about my intents.
a) We (e.g. me and my brother) bought some car parts earlier then it was necessary. Then comes my friend, sees those parts and ask me why I bought them so soon becasue he knows that I am going to "tune" my car in a few months. And then I answer that I bought them so early so that my mechanic could check them. And he (mechanic) did it (for example a few days ago), they are checked while I am talking to my friend about it.

b) Almost the same situation. We (e.g. me and my brother) bought some car parts earlier then it was necessary. Then comes my friend, sees those parts and ask me why I bought them so soon becasue he knows that I am going to "tune" my car in a few months. And then I answer that I bought them so early so that my mechanic could check them. And he (mechanic) will do it in the future (for example tomorrow), they are not checked while I am talking to my friend about it.

Maybe I am expecting too much. In my language it possible to create such sentences that represent this meaning. But I thought that phrase "so that" would allow me that.

[5jj]

I bought these parts early so that a mechanic could check them.

[Barb_D]

Unfortunately, there is no way to tell from "I bought them early so that our mechanic could check them" will tell you whether this check has taken place yet.

You have to add that as extra information. (He said they are fine. or It's a good thing we did, because he found a problem with one. or He's going to do that soon, and even if there's a problem, I still have plenty of time.)