MODEL ENGINEER TAPPING DRILL SIZES If you have been pointed directly to this page by a search engine, please also see:- http://homews.co.uk/page29.html and http://homews.co.uk/ SIZE OUT CORE PIT TAP DEP DIA. DIA. CH DRILL TH in. in. TPI mm % 40 TPI SERIES 1/8 0.1250 0.093 40 2.70 58 1/8 0.1250 0.093 40 2.65 65 1/8 0.1250 0.093 40 2.60 71 5/32 0.1562 0.124 40 3.50 57 5/32 0.1562 0.124 40 3.45 64 5/32 0.1562 0.124 40 3.40 70 3/16 0.1875 0.155 40 4.30 57 3/16 0.1875 0.155 40 4.25 63 3/16 0.1875 0.155 40 4.20 69 7/32 0.2188 0.187 40 5.10 56 7/32 0.2188 0.187 40 5.00 68 7/32 0.2188 0.187 40 4.90 81 1/4 0.2500 0.218 40 5.90 55 1/4 0.2500 0.218 40 5.80 68 1/4 0.2500 0.218 40 5.70 80 5/16 0.3125 0.280 40 7.50 54 5/16 0.3125 0.280 40 7.40 66 5/16 0.3125 0.280 40 7.30 78 3/8 0.3750 0.343 40 9.10 52 3/8 0.3750 0.343 40 9.00 65 3/8 0.3750 0.343 40 8.90 77 32 TPI SERIES 1/4 0.2500 0.210 32 5.80 54 1/4 0.2500 0.210 32 5.70 64 1/4 0.2500 0.210 32 5.60 74 9/32 0.2813 0.241 32 6.60 53 9/32 0.2813 0.241 32 6.50 63 9/32 0.2813 0.241 32 6.40 73 5/16 0.3125 0.272 32 7.40 53 5/16 0.3125 0.272 32 7.30 63 5/16 0.3125 0.272 32 7.20 73 3/8 0.3750 0.335 32 9.00 52 3/8 0.3750 0.335 32 8.90 61 3/8 0.3750 0.335 32 8.80 71 7/16 0.4375 0.397 32 10.60 50 7/16 0.4375 0.397 32 10.50 60 7/16 0.4375 0.397 32 10.40 70