10 common problems and solutions in deep hole machining!

1. What is a deep hole

In the machinery manufacturing industry, a cylindrical hole whose hole depth exceeds 5 times the diameter of the hole is generally called a deep hole. According to the ratio of hole depth to diameter (L/D), deep holes can be divided into general deep holes, medium deep holes and special deep holes. (The larger the ratio of ps:L/D, the more difficult it is to process.)

1. L/D>5, belongs to the general deep hole, which is often processed by the extension twist drill on the drilling machine or lathe.

2. L/D=20–30, which belongs to medium deep hole and is often processed on lathe.

3. L/D=30–100, belongs to special deep hole, must use deep hole drill to process on deep hole drilling machine or special equipment. According to the chip removal method, deep hole drilling is divided into two types: external chip removal and internal chip removal: external chip removal includes gun drill and integral alloy deep hole drill (can be divided into two types with cooling holes and no cooling holes); It is divided into three types: BTA deep hole drill, jet suction drill and DF system deep hole drill.
2. Common problems and solutions in processing

1. Aperture reduction

Causes: The design value of the outer diameter of the reamer is too small; the cutting speed is too low; the feed is too large; the main declination angle of the reamer is too small; Recovery reduces the aperture; when reaming steel parts, if the allowance is too large or the reamer is not sharp, it is easy to produce elastic recovery, which reduces the aperture and the inner hole is not round, and the aperture is unqualified.

Solutions: replace the outer diameter of the reamer; appropriately increase the cutting speed; appropriately reduce the feed rate; appropriately increase the main declination angle; choose an oily cutting fluid with good lubricating performance; ; When designing the size of the reamer, the above factors should be considered, or the value should be selected according to the actual situation; for experimental cutting, take an appropriate allowance and sharpen the reamer.

2, the aperture increases

Causes: The design value of the outer diameter of the reamer is too large or there are burrs on the cutting edge of the reamer; the cutting speed is too high; the feed rate is improper or the machining allowance is too large; The chip edge is adhered to the mouth; the swing of the reaming cutting edge is out of tolerance during sharpening; the selection of cutting fluid is inappropriate; the oil stain on the surface of the taper shank is not wiped clean or the taper surface is damaged when the reamer is installed; the flat tail of the taper shank is out of position After being loaded into the machine tool spindle, the taper shank and cone interfere; the spindle is bent or the spindle bearing is too loose or damaged; the reamer is inflexible; it is not on the same axis as the workpiece and the force of both hands is uneven when reaming by hand, causing the reamer to shake left and right.

Solution: Appropriately reduce the outer diameter of the reamer according to the specific situation; reduce the cutting speed and adjust the feed amount or reduce the machining allowance appropriately; appropriately reduce the main declination angle to straighten or scrap the bent unusable reamer; carefully trim with oil stone Control the swing difference within the allowable range; choose a cutting fluid with better cooling performance; before installing the reamer, the reamer taper shank and the inside of the taper hole of the machine tool must be wiped clean, and the taper surface is polished with oil stone ; Grinding the flat tail of the reamer to adjust or replace the main shaft bearing; re-adjust the floating chuck and adjust the coaxiality; pay attention to correct operation.

3. The reamed inner hole is not round

Causes: The reamer is too long, the rigidity is insufficient, and vibration occurs during reaming; the main declination 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; , Air holes; the spindle bearing is loose, there is no guide sleeve, or the clearance between the reamer and the guide sleeve is too large, and the workpiece is deformed after unloading due to the thin-walled workpiece being clamped too tightly.

Solution: The reamer with insufficient rigidity can use the reamer with unequal pitch, and the installation of the reamer should use rigid connection to increase the leading angle; select the qualified reamer, and control the hole position tolerance of the pre-processing process; Equal pitch reamers use longer and more precise guide sleeves; select qualified blanks; when using equal pitch reamers to ream more precise holes, the clearance of the machine tool spindle should be adjusted, and the matching clearance of the guide sleeves should be higher Or use an appropriate clamping method to reduce the clamping force.

4. The position accuracy of the reamed hole is out of tolerance

Causes: wear of the guide sleeve; the bottom end of the guide sleeve is too far from the workpiece; the length of the guide sleeve is short, the accuracy is poor, and the spindle bearing is loose.

Solutions: Regularly replace the guide sleeve; lengthen the guide sleeve to improve the matching accuracy of the guide sleeve and the reamer gap; repair the machine tool in time and adjust the spindle bearing gap.

5. High surface roughness value of inner hole

Causes: too high cutting speed; inappropriate selection of cutting fluid; too large main declination angle of reamer, reaming cutting edges are not on the same circumference; reaming allowance is too large; reaming allowance is not uniform or too small, local surface Not reamed; the cutting part of the reamer is out of tolerance, the cutting edge is not sharp, and the surface is rough; the reaming cutting edge is too wide; the chip removal during reaming is not smooth; the reamer is excessively worn; the reamer is damaged, and the cutting edge remains Burrs or chipping; built-up edge on the cutting edge; not suitable for zero or negative rake reamers due to material.

Solutions: reduce the cutting speed; select the cutting fluid according to the deep hole processing material; appropriately reduce the main declination angle, 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 a qualified reamer; sharpen the width of the margin; reduce the number of reamer teeth according to the specific situation, increase the space of the chip groove or use a reamer with an inclination angle to make the chip removal smooth; replace the reamer regularly, When sharpening, the grinding area should be removed; during sharpening, use and transportation, protective measures should be taken to avoid bumps; Repair it, or replace the reamer; trim it with whetstone to pass, and use a reamer with a front angle of 5°-10°.

6. The inner surface of the hole has obvious facets

Causes: The reaming allowance is too large; the clearance angle of the cutting part of the reamer is too large; the reaming cutting edge is too wide; the surface of the workpiece has pores, sand holes and the spindle swing is too large.

Solutions: reduce the reaming allowance; reduce the clearance angle of the cutting part; sharpen the width of the margin; select a qualified blank; adjust the machine tool spindle.

7. The center line of the hole after reaming is not straight

Causes: The drilling before reaming is skewed, especially when the hole diameter is small, due to the poor rigidity of the reamer, the original curvature cannot be corrected; the main declination angle of the reamer is too large; poor guidance makes the reamer in reaming It is easy to deviate from the direction in the middle; the reverse taper of the cutting part is too large; the reamer is displaced at the gap in the middle of the interrupted hole; when reaming by hand, the force in one direction is too large, forcing the reamer to deflect to one end, destroying the verticality of the reaming hole Spend.

Solutions: increase the reaming or boring process to correct the hole; reduce the main declination angle; adjust the appropriate reamer; replace the reamer with the guide part or lengthen the cutting part; pay attention to correct operation.

8. The service life of the reamer is low

Causes: The material of the reamer is not suitable; the reamer is burned during sharpening; the selection of cutting fluid is not suitable, the cutting fluid cannot flow smoothly, and the surface roughness value of the cutting part and after grinding of the reaming cutting edge is too high.

Solutions: Select the reamer material according to the processing material, and can use a carbide reamer or a coated reamer; strictly control the amount of sharpening and cutting to avoid burns; often choose the correct cutting fluid according to the processing material; often remove the chips in the chip groove , with sufficient pressure of cutting fluid, after fine grinding or grinding to meet the requirements.

9. Reamer tooth chipping

Causes: The reaming allowance is too large; the hardness of the workpiece material is too high; the swing of the cutting edge is too large, and the cutting load is uneven; the main angle of the reamer is too small, which increases the cutting width; when reaming deep or blind holes, There are too many chips, which are not removed in time, and the teeth have been cracked during sharpening.

Solutions: Modify the pre-machined aperture size; reduce the hardness of the material or use a negative rake angle reamer or a cemented carbide reamer; control the swing within the qualified range; increase the main declination angle; pay attention to timely removal of chips or use belt blades Inclined reamer; pay attention to sharpening quality.

10. The reamer handle is broken

Causes: The reaming allowance is too large; when reaming taper holes, the allocation of rough and fine reaming allowances and the selection of cutting amount are not appropriate; the chip space of the reamer teeth is small, and the chips are blocked.

Solution: Modify the pre-machined aperture size; modify the allowance distribution, and select the cutting amount reasonably; reduce the number of reamer teeth, increase the chip space or grind the gap between the cutter teeth by one tooth.