The conduit has to be "reamed" to clean the edges. There are specific tools, though some electricians find other tools that fit inside and can scrape the edges smooth. DEWALT Conduit Reamer, Impact Ready (DWA2600IR) https://www.amazon.com/dp/B00OA02UBS/ref=cm_sw_r_apan_glt_fabc_7BFVEZSBNAH1KDY9X7EZ?_encoding=UTF8&psc=1
DEWALT DWA2600IR Impact Ready Conduit Reamer https://www.amazon.com/dp/B00OA02UBS/ref=cm_sw_r_cp_api_0yMVBbWEH0WGQ