II I I I I ~
Y =W D (cotg a+ 1)
2
Vi dv: ck co kich thu&c cua W la 50mm, goc o la 50°, trong do ta SU d\lllg con Ian co kich thu&c la 10mm. Kich thu&c do dugc cua Y phai la:
Y = 50 - 10 (cotg 50+1) = 50. 8 (2.415 + 1) = 18.55mm.
2
Trong truong hc;rp nay chung ta SU dvng hai chi tiSt Hip ghep v6i nhau thi g6c cua ranh khong th@ siftc nh9n duqc, nen trong truong hc;rp nay chung ta phai tiSn hanh lam ngU<)i. Ngoai ra dS su dvng thu~n lqi cho vi~c kiSm tra ta c6 thS su dvng cac t§.m phiSn (c6 cac kich thu6c khac nhau hinh 28.4.3), dS do va d9c kich thu6c va tfnh kich thu6c th~t chiSu r(mg cua ranh.
Hinh 28.4.2.Su dvng 2 loi sftt trcm d@ ki@m tra kich thu6c ranh
3.2. PhrrO'ng phap bao ch6t duoi en.
3.2.1. Bao hai mijt hie.
a} Ki~m tra phoi va 1,y d,u SO' b(>.
Ki@m tra cac yeu c§.u ky thu~t cua phoi nhu: D9 song song, d9 vuong g6c, hay cac yeu c§.u ky thu~t khac. NSu cac ySu t6 ky thu~t dam bao m6i tiSn hanh cac bu6c tiSp theo. Cach 1§.y d§.u (v~ch d§.u va ch§.m d§.u) ta phai thµc hi~n m9t each nghiem tuc b~ng cac nguyen tiftc da duqc h9c a cac bai t~p tru6c (luu y khi kich thu6c ngoai d6i xung v6i ch6t duoi en).
b} Ga va kf p chijt phoi
Ch6t duoi en duqc dung tren cac b9 truySn d9ng, cac chi tiSt may, ban may ho~c cac xa ngang, vi~c dinh vi va kyp ch~t nen su dvng ban may b~ng cac d6 ga chuyen dung nhu: Cac lo~i v§.u kyp, bich ga, bulong kyp, .. D6i v6i cac chi tiSt nho, nhy hay cac bai t~p CO' ban khi thi;rc hanh (J xuang duqc SU dvng cac lo~i eto v~ nang, bai n6 SU dvng dS dang va c6 a cac phan xuang thvc hanh.
c} Ti~n hanh bao (xem bai 27.4)
3.1.2. Bao ch6t duoi en