When drilling holes in sheet metal processing,it is important to ensure that the size and shape of rivet holes are correct and free of burrs.Assuming that the hole is too small,when the rivet is put into the hole,the maintenance layer of the rivet will be scratched;Assuming that the hole is too large,the rivet cannot completely fill the nail hole.When the rivet is stressed,the joint can not exert its full strength,and the structural damage may occur here.

When the damaged skin is exchanged with a new skin,the holes in the AC plate or patch should be drilled to be different from those in the structure.These holes can be positioned with the hole replicator.The clevis pin on the bottom strut of the replicator is inserted into the existing rivet hole.The hole in the new part is made by the sleeve through the top strut.Assuming that the replicator is manufactured to meet the requirements,the holes drilled by this method will be perfectly aligned.

The corresponding replicator must be used for rivets of each diameter.If it is necessary to process countersunk holes,the thickness of metal plate should be considered and the recommended method for processing countersunk holes should be selected.If dimpling is required,the number of hammer blows or the pressure of countersink should be minimized to avoid excessive work hardening around the dimple.In order to make a rivet hole of accurate size,first drill a hole of slightly smaller size.This is called pre-drilling,and the pre-drilled hole is called pilot hole.

Enlarge the hole with a fried dough twist drill of suitable size to obtain the hole of the requested size.The size of pilot hole and reamer is shown in Table 3-1.The recommended rivet hole gap is to inches.When drilling hard metal,the fried dough twist drill should have an included angle of 1180 and should run at a low speed,but for soft metal,the fried dough twist drill with an included angle of 900 can be used and can run at a high speed.Use a fried dough twist drill with an included angle of 1180 to drill aluminum alloy thin plates,which can obtain high-precision drilling.Because the large included angle of the drill can reduce the possibility of tearing or making the hole out of round.