Stemmehammeren brukes ettersom stemmeskruen må justeres.

The ending -en marks the definite singular form of many common-gender nouns in Norwegian.

So:

• en stemmehammer = a tuning hammer
• stemmehammeren = the tuning hammer

and:

• en stemmeskrue = a tuning pin / tuning screw
• stemmeskruen = the tuning pin / screw

In Norwegian, the definite article is usually attached to the end of the noun instead of being a separate word like the in English.

Because Norwegian normally writes compound nouns as one word.

So:

• stemme
  • hammer → stemmehammer
• stemme
  • skrue → stemmeskrue

This is very common in Norwegian. English often separates these into two words, but Norwegian usually combines them.

Here stemme- is related to tuning.

It comes from the verb å stemme, which can mean to tune in musical contexts.

So:

• stemmehammer = a hammer used for tuning
• stemmeskrue = a screw/pin involved in tuning

This kind of first element is very common in Norwegian compounds.

Brukes is a passive form.

• bruker = uses / is using in the active sense
• brukes = is used in the passive sense

So:

• Man bruker stemmehammeren = One uses the tuning hammer
• Stemmehammeren brukes = The tuning hammer is used

The sentence chooses the passive because the focus is on the tool itself, not on who is using it.

Because justeres here is also a passive form.

• å justere = to adjust
• justeres = be adjusted / is adjusted

So:

• stemmeskruen må justeres means the tuning pin/screw must be adjusted

This is a very common Norwegian structure: a modal verb plus an infinitive/passive verb.

Because after modal verbs such as må, kan, skal, vil, and bør, Norwegian normally does not use å.

So you say:

• må justeres
• kan brukes
• skal stemmes

not:

• må å justeres

This is similar to English, where we say must adjust rather than must to adjust.

Here ettersom means since, as, or because.

It introduces the reason:

• Stemmehammeren brukes ettersom stemmeskruen må justeres.
• The tuning hammer is used because the tuning pin must be adjusted.

Compared with other words:

• fordi = because (very common, direct)
• siden = since / because
• ettersom = often a bit more formal or written, but still perfectly normal

In this sentence, ettersom sounds natural and slightly formal.

Because ettersom introduces a subordinate clause, and Norwegian word order changes in subordinate clauses.

In a main clause, Norwegian usually follows the V2 rule: the finite verb tends to come in the second position.

But after a subordinating conjunction like ettersom, the subject usually comes before the finite verb:

• ... ettersom stemmeskruen må justeres

Here:

• stemmeskruen = subject
• må = finite verb
• justeres = infinitive/passive form

That is normal subordinate-clause word order.

Yes. A more active version would be something like:

• Man bruker stemmehammeren ettersom man må justere stemmeskruen.

That means roughly One uses the tuning hammer because one has to adjust the tuning pin.

The original sentence uses passive forms:

• brukes
• justeres

This makes the sentence sound a bit more impersonal and technical, which is very common in instructions or descriptions of processes.

Either is fine.

• must be adjusted
• has to be adjusted

Both match må justeres well in English.

The Norwegian må often covers both must and have to, depending on context. In a technical sentence like this, either translation sounds natural.

Yes, very much so.

The sentence sounds like something from:

• a manual
• a repair guide
• a technical explanation
• a description of piano tuning

That is because of:

• the passive forms brukes and justeres
• the formal connector ettersom
• the specific compound nouns stemmehammeren and stemmeskruen

It is grammatically normal Norwegian, but the style is more technical than conversational.