In Fahrenheit 451 there is a Mechanical Hound. Do the people think about making more?

If I understand your question correctly, you're asking if there is more than one mechanical hound?

There definitely are two hounds referred to in the text. The first hound belongs to Montag's fire house and it's the hound that is described during Part 1. At the beginning of Part 3, Montag pulls up to his house in the Salamander (fire truck) with Captain Beatty to burn the books in his home. After watching Mildred leave,...

If I understand your question correctly, you're asking if there is more than one mechanical hound?

There definitely are two hounds referred to in the text. The first hound belongs to Montag's fire house and it's the hound that is described during Part 1. At the beginning of Part 3, Montag pulls up to his house in the Salamander (fire truck) with Captain Beatty to burn the books in his home. After watching Mildred leave, bags packed, Beatty begins to taunt Montag, reminding him that the Hound is somewhere in the neighborhood. Beatty suspects the ear bullet and strikes Montag, knocking it free. After Beatty continues to antagonize Montag, in a final act of desperation, Montag turns the flame thrower onto Beatty. The first mechanical hound attacks Montag, managing to prick him in the leg with the needle before exploding from the flame thrower. As a result, Montag's leg is numb, but the full dose of poison wasn't given to Montag. 

The second Hound is brought in from another district to hunt Montag, leading readers to believe that each district has at least one. That Hound loses Montag's scent once he gets to the river, but kills and chases the fake Montag for the people's benefit. That Hound is presumably destroyed with the rest of the city during the war.