| 释义 |
▪ I. counterbore, n.|ˈkaʊntəbɔə(r)|
[counter- 8 b: see note at countersink v.]
= countersink n. 1, 2.
a1884Knight Dict. Mech. Suppl., Counter-bore, a cylindrical counter-sink, usually made with a pin-drill. 1939C. B. Cole Tool Making 97 In emergency, another form of counterbore is used. 1948A. P. Morgan Tools xii. 209 Counterbores are end-cutting tools used to enlarge a drill hole for a portion of its length. 1967O. Almeida Metalworking xii. 192 Counterbores..may be turned in the workshop from silver steel or plain carbon steel, and the flutes filled. 1977Reader's Digest Bk. Do-it-Yourself Skills & Techniques v. 152 Drill the counter bore before drilling clearance holes for the threads.
▪ II. counterbore, v.|ˈkaʊntəˌbɔə(r)|
[See prec.]
trans. To enlarge (the upper part of a cylindrical hole or cavity) to take the head of a screw. Also absol. Cf. countersink v.1
1890in Webster. 1939C. B. Cole Tool Making 95 To counterbore a hole previously machined by drilling or reaming is to enlarge the hole to the required diameter and depth. Ibid. 96 The pilot diameter determines the size of the hole that can be counterbored. 1975R. A. Salaman Dict. Tools 38/1 The adjustable L-shaped cutter bar..enlarges or counterbores the hub to the required depth. 1984E. P. DeGarmo et al. Materials & Processes in Manuf. (ed. 6) xxi. 594 Special combination drills are made that can drill two or more diameters, or drill and countersink and/or counterbore, in a single operation.
Hence ˈcounterbored ppl. a., ˈcounterboring vbl. n.
1905J. Horner Tools for Engineers & Woodworkers xi. 125 Every one knows the trouble of counterboring in wood. 1909Cent. Dict. Suppl. Counterbored, counterboring. 1920Engin. & Mining Jrnl. 7 Feb. 405/2 They run on hardened tool-steel shafts set in counterbored sockets open at the top only. 1948A. P. Morgan Tools xii. 209 Counterboring of small diameter can be done by hand power. 1984E. P. DeGarmo et al. Materials & Processes in Manuf. (ed. 6) xxi. 599 Counterboring provides an enlarged, cylindrical hole with a flat bottom so that a bolt head, or a nut, will have a smooth bearing surface that is normal to the axis of the hole. |