Pouzi stupnovity vrtak
https://www.google.sk/search?hl=sk&q=vykruzovaky&bpcl=35466521&ion=1&bav=on.2,or.r_gc.r_pw.r_cp.r_qf.&biw=1366&bih=679&um=1&ie=UTF-8&tbm=isch&source=og&sa=N&tab=wi&ei=aByBUMiwM8SytAaty4CoDg#um=1&hl=sk&tbm=isch&sa=1&q=stupnovity+vrtak&oq=stupnovity+vrtak&gs_l=img.3..0i24.29942.33644.0.33809.16.16.0.0.0.0.346.3693.0j4j7j4.15.0...0.0...1c.1.aqQ-Ke9JIqg&pbx=1&bav=on.2,or.r_gc.r_pw.r_qf.&fp=1a424d8a581ac739&bpcl=36601534&biw=1252&bih=596

alebo Kruhovy dierovac plechu - neviem este ako by sa to malo volat. Takato sranda.
http://www.dovavanik.cz/eshop/foto/491/491943_o_0.jpg

Pripadne uplne DIY sposob. Najvacsim vrtakom aky najdes a dorobit okruhlim pilnikom.