"button_to" for custom action not working

Rails
1

First thing is I’m no using form_for or any other form tags.

I have a Model
class Modelname < ActiveRecord::Base
def self.methodfirst #Class method
:

Some code

:
end

def methodsecond #Instance method
:

Some code

:
end
end

a controller
class SomenamesController < ApplicationController

def new
@variable = Modelname.new
end

def create
Modelname.methodfirst # calling class method methodfirst
redirect_to(new_somename_path)
end

def deduction
Modelname.new.methodsecond # calling instance method
methodsecond
end

end

a partial file _form.html.erb rendered from new.html.erb

<%= button_to "create action", somenames_path, :class => "btn btn-primary" %> 
<div class="actions">
  <%= button_to "deduction", action: "deduction", :class => "btn

btn-primary", method: “post” %>

new.html.erb
<%= render ‘form’ %>

Problem is: First button is working fine but not the second
<%= button_to “Start recovery printing”, recoveries_path, :class => “btn
btn-primary” %>

is working fine. Since it calls “create” action inside Somenames

But the second button is not working but throwing an error message

No route matches {:action=>“deduction”, :class=>“btn btn-primary”,
:controller=>“recoveries”, :method=>“post”}

Now how can I call custom action “deduction” written inside Somenames
controller so that it will call instance method “methodsecond”