What is a twist bit
Twist drill is a tool used to drill round holes of workpiece by rotating cutting of its relative fixed axis. Because of its capacity chip groove into spiral shape and shape like hemp and named. Spiral grooves have 2, 3 or more grooves, but 2 grooves are the most common. Twist drill can be clamped on manual, electric hand-held drilling tools or drilling machines, milling machines, lathes and machining centers. Drill material is usually high - speed tool steel or carbide.
How to operate twist bit
1, twist drill should be installed in a special packaging box, to avoid vibration collision.
2. Non-contact measuring instrument (such as tool microscope, etc.) should be used to measure the diameter of drill bit, so as to avoid the cutting edge being bruised by contacting with the mechanical measuring instrument.
3, when using, take out the drill from the box should be installed into the spring chuck of the spindle or automatically replace the tool bank of the drill.
4, often check the spindle and spring collet concentricity and spring collet clamping force, concentricity is not good will cause small diameter drill break and large aperture, clamping force is not good will cause the actual speed and set speed does not conform to, collet and twist between the slip.
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5, the use of positioning ring CNC machine tools when the depth of the installation positioning must be accurate, such as the use of positioning ring drill installed on the spindle length to adjust the same, more spindle drilling machine should pay attention to this, to make each spindle drilling depth should be consistent. If inconsistent, it may cause the drill to drill to the table or unable to drill through the circuit board, resulting in obsolescence.
6, can use 40 times stereo microscope to check the wear of the cutting edge of the drill.
7. Check the spindle press foot frequently. Press foot contact surface should be horizontal and vertical with the main shaft can not shake, to prevent drilling and offset hole.
8. The clamping length of fixed handle twist bit on the spring chuck is 4 -- 5 times the diameter of drill handle.
9, the substrate lamination includes the upper and lower plate to be fixed and flattened in a hole and groove positioning system on the workbench of the drilling machine. When using adhesive tape, it is necessary to prevent the bit from sticking to the tape and cutting chips, resulting in chip removal difficulty and drilling break.
10. The suction effect of drilling machine is good. The suction air can reduce the temperature of drill bit and take away dust to reduce friction and produce high temperature.
11, timely regrinding can increase the use of twist bit and regrinding times, prolong the life of the bit, reduce production costs and expenses.
How to grind twist bit
"Less grinding" is the first "no grinding", get the drill in a hurry to grind, is certainly blind grinding. It is very important to position yourself well before grinding to lay a solid foundation for the next step of "good grinding".
Here with four formula to guide the grinding process, the effect is better.
Formula one: "edge to balance the wheel surface."
This is the first step of the relative position between the drill bit and the grinding wheel. Often, some students lean on the grinding wheel to start grinding before the edge is balanced. This is definitely not going to grind well. The "edge" here is the main cutting edge, and the "leveling" means that the main cutting edge of the part being ground is in a horizontal position. "Wheel surface" means the surface of the grinding wheel. "Lean" means to draw closer slowly. At this point, the drill can not contact the grinding wheel.
Formula two: "drill shaft oblique release front Angle."
Here refers to the position relationship between the bit axis line and the grinding wheel surface. "Edge Angle" is half of the tip Angle 118°± 2O, about 60° This position is very important, directly affects the size of the tip Angle and the shape of the main cutting edge and the bevel Angle of the edge. Students should be reminded of the common 30°, 60°, 90° triangle board in the 60° Angle, students easy to master. Formula 1 and formula 2 are the relative position of the drill before grinding, both should be taken into consideration, not to balance the edge and ignore the bevel Angle, or to balance the oblique axis and ignore the edge. These errors are often made in practice. At this point, the drill bit is ready to contact the grinding wheel in the correct position.
Tip 3: "from the blade to the back grinding back."
In this case, grinding is done slowly from the edge of the bit along the entire back surface. This facilitates heat dissipation and grinding. On the basis of stable consolidation of tips 1 and 2, the bit can gently contact the grinding wheel for a small amount of grinding. During grinding, the uniformity of spark should be observed, the pressure should be adjusted in time, and the bit cooling should be paid attention to. When cooling back to grinding, to continue to set the position of formula one and two, which is often not easy to master in the beginning, often can not help but change the accuracy of its position.
Formula four: "up and down swing tail do not become warped."
This action is also very important in the process of bit grinding, often students in the grinding "swing up and down" to "turn up and down", so that the other main blade of the bit was destroyed. At the same time, the tail of the drill bit should not be tilted above the horizontal center line of the grinding wheel, otherwise the edge will be blunt and unable to cut.
Twist drill maintenance method
1. Twist drill when in use, first insert the bolt joint of the horizontal handle part into the directional slot of the movable connecting nut of the drill bar, tighten the connecting nut counterclockwise, and then insert the predetermined drilling area into the soil by hand pressure. Every rotation of about 200~250 mm, the drilling hole is lifted up (if it is too deep, it will be difficult and inconvenient), and the soil in the drill screw is removed, which is the soil sample from the lot.
2, successive reciprocating work to 1 meter drilled just need to move on, should be clockwise unscrew bit of connection parts of cross coupling nut off, connect additional drill rod bolt head part in the second quarter insert bit parts activity connecting screw clockwise tighten connection nut, then cross the parts with the drill pipe is better than by continue to work, three, four, five up until finished work.
3. Twist drill pipe is made of cattle-wall seamless steel pipe, so it is not suitable for use in hard soil areas.
4, after each use should be washed, dry, coated with anti-rust grease, to prevent rust.