niku wo kiru toki ha, yoku kireru naihu wo tukaimasu.

Before とき, the form of the verb shows the time relationship.

• 肉を切るとき = when cutting meat / when you cut meat
• The dictionary form 切る is used because the action is viewed as something that happens at that time, or just before it.

Compare:

• 日本へ行くとき = when going to Japan / before going to Japan
• 日本へ行ったとき = when I went to Japan / when I had gone to Japan

So 肉を切るとき is the natural way to say when cutting meat.

とき means time or when, and は marks that whole phrase as the topic.

So:

• 肉を切るとき = when cutting meat
• 肉を切るときは = as for when cutting meat / when cutting meat, ...

The は gives a sense like:

• When it comes to cutting meat, ...
• As for when you cut meat, ...

It is very common to put は after a time phrase to set the scene or introduce a general rule.

Each を belongs to a different verb.

1. 肉を切る

   • 肉 is the thing being cut
   • so it takes を

2. ナイフを使います

   • ナイフ is the thing being used
   • so it also takes を

So the sentence contains two separate verb phrases:

• 肉を切る = cut meat
• ナイフを使います = use a knife

That is why you see を twice.

Yes, that is a good way to think about it.

切れる is the potential form of 切る, so it can mean:

• can cut
• is able to cut

But with tools like knives, よく切れる often means:

• cuts well
• is sharp
• works well for cutting

So よく切れるナイフ means:

• a knife that cuts well
• more naturally in English: a sharp knife

This is a very common Japanese way to describe tools by what they are able to do.

It is the same word, but here it means well, not often.

よく can have different meanings depending on context:

• よく行きます = I go often
• よく切れる = cuts well
• よくできました = well done

In this sentence, よく modifies 切れる, so it means well.

So:

• よく切れるナイフ = a knife that cuts well

You could describe a knife as sharp in other ways, but よく切れるナイフ is a very natural Japanese expression.

It focuses on function rather than appearance:

• よく切れるナイフ = a knife that cuts well
• 鋭いナイフ = a sharp knife, but this can sound more like describing the blade itself
• シャープなナイフ is less natural in many ordinary situations

Japanese often prefers expressions like よく切れる for tools because they emphasize usefulness and performance.

Yes. The subject is omitted because Japanese often leaves it out when it is obvious or general.

This sentence could mean things like:

• When cutting meat, use a sharp knife.
• When you cut meat, you use a sharp knife.
• When cutting meat, we use a sharp knife.

The exact subject depends on context. Without context, it sounds like a general statement or instruction.

Because 切る is inside a modifying phrase, while 使います is the main verb of the sentence.

Japanese often uses plain forms inside subordinate clauses, including before nouns like とき:

• 肉を切るとき = when cutting meat

But the main sentence can still be polite:

• ナイフを使います = use a knife / will use a knife

This combination is completely normal:

• subordinate part: plain form
• main sentence: polite form

It can cover when cutting meat in a broad sense, and the exact nuance depends on context.

With dictionary form + とき, it often refers to:

• the time when you are about to do it
• the time when you do it

So here it naturally means:

• when cutting meat
• when you cut meat

In practical English, when cutting meat, use a sharp knife is the best translation.

Because Japanese puts modifiers before the noun they modify.

Here:

• よく切れる modifies ナイフ

So the full noun phrase is:

• よく切れるナイフ = a knife that cuts well

Then that whole noun phrase becomes the object of 使います:

• よく切れるナイフを使います = use a sharp knife

This is very common in Japanese:

• 日本で買った本 = the book I bought in Japan
• よく切れるナイフ = a knife that cuts well

It can be understood as a general rule or recommendation.

Because the sentence uses 使います rather than a command form like 使ってください or 使いなさい, it sounds calmer and more neutral. Depending on context, it may mean:

• When cutting meat, use a sharp knife.
• When cutting meat, one uses a sharp knife.
• We use a sharp knife when cutting meat.

So it often has the feel of a general fact, instruction, or advice rather than a direct command.