FitCheck: Hole Sizes & Fits

"What size hole do I need?" That's the question FitCheck answers — for screws, bearings, and hex nuts. Enter a size — M5-0.8, #8-32, 1/4-20, or a 608 bearing - and you get the hole or pocket to model, whether you're drilling, tapping, boring a bearing seat, or printing the part. For makers, hobbyists, and anyone who designs and builds: • Clearance holes and tap-drill sizes for every screw and bolt in the catalog • Bearing pockets: press, slip and loose fits for machined and 3D printed seats • Hex-nut pockets in three clearances (snug / normal / loose) • 3D-printed screw holes in three grades (close / normal / free) • Heat-set insert holes, with pocket depths matched to your insert length • An inch-to-mm converter and fraction ruler for caliper readings • Cross-section diagrams that show the fit The part a chart can't do: your machine. Calibrate each printer or mill once, and every size — screw, bearing, or nut — comes out corrected for that machine's measured error. Less re-printing and re-milling to get a fit right. It works completely offline. No accounts, no ads, and no tracking — all reference data lives on your device. Machine calibration is free to try. FitCheck Pro — a one-time purchase, no subscription — keeps your calibrated machines saved, so every lookup comes out corrected without redoing setup. This app is a reference only — always check against your own test parts before you cut.