Lo svaso è più difficile della tacca.

Because svaso starts with s + consonant (sv). In Italian, masculine singular nouns beginning with this kind of sound usually take lo, not il.

Examples:

• lo svaso
• lo studente
• lo spazio

So lo svaso is the correct form.

Useful related forms:

• indefinite: uno svaso
• plural definite: gli svasi

È means is. It is the 3rd person singular of essere (to be).

The accent matters because:

• è = is
• e = and

So in this sentence, è must have the accent.

Più difficile means more difficult.

Italian normally forms the comparative of an adjective with:

più + adjective

So:

• difficile = difficult
• più difficile = more difficult

Unlike English, Italian usually does not add an ending like -er to the adjective. It uses più instead.

Because after a comparative like più difficile, Italian often uses di where English uses than.

Here, the second noun is la tacca.
When di comes before la, they combine:

di + la = della

So:

• la tacca = the notch
• più difficile della tacca = more difficult than the notch

Literally, della can look like of the, but in this comparative structure it corresponds to English than the.

Because in this kind of comparison, Italian normally uses di (or a combined form like del, della, dei, delle) before a noun.

Here you are comparing one thing with another thing:

• lo svaso
• la tacca

So di is the normal choice:

• più difficile della tacca

Che is used in other comparison patterns, especially when comparing:

• two qualities: più utile che bello
• two actions: studia più che lavorare
• elements with the same preposition in some structures

So in this sentence, della is the standard form, not che.

It agrees with svaso, because it describes the subject:

Lo svaso è più difficile...

So the sentence says that the flare/chamfer/etc. is more difficult.

However, in the singular, difficile has the same form for both masculine and feminine:

• il lavoro difficile
• la prova difficile

That is why you do not see a visible change here.

In the plural, it becomes:

• difficili

For example:

• Gli svasi sono più difficili...
• Le tacche sono più difficili...

Usually, yes.

Italian uses definite articles more often than English does. In a normal full sentence, lo svaso and la tacca sound natural and standard.

If you removed the articles, the sentence would sound unnatural in ordinary Italian, unless it were some kind of note, label, or very telegraphic technical style.

So:

• natural: Lo svaso è più difficile della tacca.
• not normal in standard prose/speech: Svaso è più difficile di tacca.

Because più is the standard spelling of the word meaning more.

The accent shows the stressed vowel and is part of the normal written form. So you should always write:

• più

not

• piu

It is pronounced roughly like pyoo, in one syllable.

The sentence follows a very common Italian pattern:

subject + verb + comparative + second term of comparison

So here you have:

• Lo svaso = subject
• è = verb
• più difficile = comparative adjective phrase
• della tacca = second term of comparison

This is the neutral, standard word order: Lo svaso è più difficile della tacca.

Italian can sometimes change word order for emphasis, but this is the most straightforward version.