In the process of deep hole machining, problems such as the dimensional accuracy of the workpiece, surface quality and tool life often arise. How to reduce or even avoid the occurrence of these problems is an issue that we urgently need to solve.
Problem: Drilling Diameter Increases, Error Increases
Causes of the Problem
The design value of the reamer outer diameter is too large or the reamer cutting edge has burrs. The cutting speed is too high, and the feed rate is improper or the machining allowance is too large. The main deflection angle of the reamer is too large. The reamer is bent. There is a chip tumor on the reaming cutting edge. The swing difference of the reaming cutting edge is too large during grinding. The cutting fluid is not suitable. When installing the reamer, the oil on the surface of the taper shank is not wiped clean or the taper surface is bumped. The flat tail of the taper shank is offset and the taper shank interferes after being installed in the machine tool spindle. The spindle is bent or the spindle bearing is too loose or damaged. The reamer is not flexible in floating. The reamer is not coaxial with the workpiece and the force of both hands is uneven when reaming by hand, causing the reamer to shake left and right.
Problem Solving Measures
Reduce the outer diameter of the reamer appropriately according to the specific situation. Reduce the cutting speed. Appropriately adjust the feed rate or reduce the machining allowance. Appropriately reduce the main deflection angle. Straighten or scrap the bent and unusable reamer. Use an oilstone to trim it to a qualified level carefully. Control the swing error within the allowable range. Choose a cutting fluid with good cooling performance. Before installing the reamer, the reamer taper shank and the inside of the machine tool spindle taper hole must be wiped clean of oil stains, and the taper surface must be polished with an oilstone. Grind the flat tail of the reamer. Adjust or replace the spindle bearing. Re-adjust the floating chuck and adjust the coaxiality. Pay attention to correct operation.
Problem: Reaming Hole Diameter is Reduced
Causes of the Problem
The design value of the reamer outer diameter is too small. The cutting speed is too low and the feed rate is too large. The main deflection angle of the reamer is too small. The cutting fluid is not suitable. The worn part of the reamer is not ground off during sharpening, and the elastic recovery reduces the hole diameter. When reaming steel parts, the excess is too large or the reamer is not sharp, which is easy to cause elastic recovery. The hole diameter is reduced and the inner hole is not round, and the hole diameter is unqualified.
Problem Solving Measures
Change the outer diameter of the reamer. Increase the cutting speed and reduce the feed rate appropriately. Increase the main deflection angle appropriately. Choose an oily cutting fluid with good lubrication performance. Exchange the reamers regularly and sharpen the cutting part of the reamer correctly. When designing the reamer size, the above factors should be considered. Or select the value according to the actual situation. Make a test cut, take the appropriate allowance, and sharpen the reamer.
Problem: The Reamed Inner Hole is not Round
Causes of the Problem
The reamer is too long and not rigid enough, causing vibration during reaming. The main deflection angle of the reamer is too small. The reaming cutting edge is narrow. The reaming allowance is biased. There are gaps and cross holes on the inner hole surface. There are sand holes and air holes on the hole surface. The spindle bearing is loose and there is no guide sleeve. Or the clearance between the reamer and the guide sleeve is too large, and the thin-walled workpiece is clamped too tightly, causing the workpiece to deform after removal.
Problem Solving Measures
Reamers with insufficient rigidity can use unequal pitch reamers. The installation of the reamer should be rigidly connected to increase the main deflection angle. Select qualified reamers to control the hole position tolerance of the pre-processing process. Use unequal pitch reamers and use longer and more precise guide sleeves. Select qualified blanks. When using equal pitch reamers to ream more precise holes, the machine tool spindle clearance should be adjusted. The matching clearance of the guide sleeve should be higher or an appropriate clamping method should be used to reduce the clamping force.
Problem: High Surface Roughness of Inner Hole
Causes of the Problem
The cutting speed is too high. The cutting fluid is not suitable. The main deflection angle of the reamer is too large, and the reaming cutting edges are not on the same circumference. The reaming allowance is too large. The reaming allowance is uneven or too small, and some surfaces are not reamed. The swing difference of the reamer cutting part is too large, the cutting edge is not sharp, and the surface is rough. The reaming cutting edge is too wide. The chip removal is not smooth when reaming. The reamer is excessively worn. The reamer is bruised, and there are burrs or chipping on the cutting edge. There is a built-up edge on the cutting edge. Due to material reasons, it is not suitable for zero-degree rake angle or negative rake angle reamers.
Problem Solving Measures
Reduce cutting speed. Select cutting fluid according to the material being processed. Appropriately reduce the main deflection angle and correctly sharpen the reaming cutting edge. Appropriately reduce the reaming allowance. Improve the position accuracy and quality of the bottom hole before reaming or increase the reaming allowance. Select qualified reamer. Grind the width of the blade. Reduce the number of reamer teeth according to the specific situation, increase the chip groove space or use a reamer with a blade inclination angle to facilitate chip removal. Replace the reamer regularly and remove the grinding area during sharpening. Protective measures should be taken to avoid bruises during sharpening, use and transportation of the reamer. For bruised reamers, use a very fine oilstone to repair the bruised reamer or replace the reamer. Use an oilstone to trim to a qualified level and use a reamer with a front angle of 5°~10°.
Problem: The Center Line of the Hole is not Straight After Reaming
Causes of the Problem
The drill hole is deflected before reaming, especially when the hole diameter is small. The reamer has poor rigidity and cannot correct the original curvature. The main deflection angle of the reamer is too large. The guide is poor, which makes the reamer easily deviate from the direction during reaming. The back taper of the cutting part is too large. The reamer is displaced in the gap in the middle of the intermittent hole. When reaming by hand, too much force is applied in one direction, forcing the reamer to deflect to one end, destroying the verticality of the reaming hole.
Problem Solving Measures
Add expansion or boring process to correct the hole. Reduce the main deflection angle. Adjust the appropriate reamer. Replace the reamer with a guide part or an extended cutting part. Pay attention to correct operation.
