If my experience is anything to go by you are unlikely to get an answer to your question, so you'll have to measure it yourself. I have two Makita routers, a 3612 with 20mm x 1mm thread pitch and a RP2301fc with 22mm x 1.5mm thread pitch. A Chinese compact router I have is 17mm x 1mm thread pitch. I'd suggest that the thread on your router will almost certainly be metric. Hope this helps.