JButton not displaying properly

hello there,

i have a jtable in which i want to add button in one of the columns.my problem is the button size is very small. i dont know why.i have attached a screen shot.

tabs=new JTabbedPane();
		tabs.addChangeListener(this);
		
		//finishTable=new JTable();
		bulkTable=new JTable();
		packTable=new JTable();
		
//		Init tables models
		finishTableModel=new DefaultTableModel(){
			private static final long serialVersionUID = 1L;
 
			public boolean isCellEditable(int row, int column) {
				if(column==6)
				{
					return true;
				}else
				{
					return false;
				}
			}
		};
		finishTableModel.setColumnIdentifiers(new String[]{"","Cheque No.","Cheque date","Days left","Cheque amount","Comment","Action"});
		
		
		bulkTableModel=new DefaultTableModel(){
			private static final long serialVersionUID = 1L;
 
			public boolean isCellEditable(int row, int column) {
				if(column==5)
				{
					return true;
				}else
				{
					return false;
				}
			}
		};
		bulkTableModel.setColumnIdentifiers(new String[]{"","Cheque No.","Cheque date","Cheque amount","Comment","Action"});
		
		packTableModel=new DefaultTableModel(){
			private static final long serialVersionUID = 1L;
 
			public boolean isCellEditable(int row, int column) {
				return false;
			}
		};
		packTableModel.setColumnIdentifiers(new String[]{"","Cheque No.","Cheque date","Cheque amount","Comment"});
		
		
		
		finishTable=new JTable(finishTableModel);
		finishTable.setDefaultRenderer(Object.class,new CustomeTableCellRenderer()); 
		finishTable.setAutoCreateRowSorter(true);
		ButtonCell buttonCell=new ButtonCell(){
			/**
			 * 
			 */
			private static final long serialVersionUID = 1L;
 
			@Override
			public void actionPerformed(ActionEvent e) {
				super.actionPerformed(e);
				/*JComboBox jcb=new JComboBox(bankNameCBM);
				GUITools.fixFieldsWidth(150,jcb);
				int result = JOptionPane.showOptionDialog(finishTable, 
						jcb, "Deposit the cheque"
						, JOptionPane.OK_CANCEL_OPTION, JOptionPane.PLAIN_MESSAGE, null, null, null); 
		        if(result==JOptionPane.OK_OPTION)
		        {
		        	//moveToDeposit(finishTable.getSelectedRow());
		        }*/
			}
		};
		finishTable.getColumnModel().getColumn(0).setMaxWidth(40);
		finishTable.getColumnModel().getColumn(6).setCellRenderer(buttonCell);
		finishTable.getColumnModel().getColumn(6).setCellEditor(buttonCell);
		finishTable.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
		finishTable.setColumnSelectionAllowed(false);

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1.JPG