CNC Knowledge: 10 Common Questions About Deep Hole Treatment

In the process of deep hole processing, problems such as dimensional accuracy, surface quality and tool life of the workpiece often occur. How to reduce or even avoid these problems is a problem we urgently need to address. The following summarizes common issues in depth. hole treatment. 10 problems and solutions.

1

The larger the aperture, the greater the error.

1) 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 amount is inappropriate or the machining allowance is too large; is too big; the reamer is bent; the cutting edge of the bore is stuck. Fixed cutting edge; excessive deviation of the cutting edge from the bore during improper installation of cutting fluid; The oil on the surface of the taper shank is not wiped off or the taper surface is struck when cutting; the flat tail of the taper shank is offset and the taper of the taper shank interferes after being installed in the spindle of the machine tool; or the spindle bearing is too loose or damaged; the reamer is not flexible while floating; and the workpiece is not axial, and the force exerted by the two hands is uneven when reaming by hand, causing the reamer to shake left and right.

2) Solutions

Appropriately reduce the outer diameter of the reamer according to the specific situation; reduce the cutting speed appropriately; appropriately adjust the feed amount or appropriately reduce the main deviation angle; straighten or discard the bent reamer that cannot be used carefully; with a whetstone Successful; control the swing difference within the allowed range to select cooling; Cutting fluid with better performance; Before installing the reamer, the oil inside the taper shank of the reamer and the taper hole of the machine tool spindle should be wiped off, and any bumps on the taper surface should be polished with a whetstone; the shank of the reamer must be ground; adjust or replace the spindle bearing; Readjust the floating chuck and adjust the coaxiality; pay attention to proper operation;

2

reduction in pore size

1) Causes

The design value of the outer diameter of the reamer is too small; the cutting speed is too low; the feed speed is too high; the main deviation angle of the reamer is too small; the cutting fluid is inappropriate; the reamer is not ground during sharpening and elastic recovery reduces the opening. Shrinkage; when reaming steel parts, the margin is too large or the reamer is not sharp, which is prone to elastic recovery, causing the hole diameter to shrink, the interior The hole is not not round and the hole diameter is not qualified.

2) Solutions

Change the outer diameter of the reamer; increase the cutting speed appropriately; reduce the feed speed appropriately; increase the main deviation angle appropriately; choose oily cutting fluid with good lubrication performance, regularly exchange the cutting part of the reamer; Design the reamer When selecting the size of the knife, the above factors should be considered, or the value should be determined according to the actual situation, carry out experimental cutting, take an appropriate margin, and sharpen the reamer. reamer.

3

Inner reamed hole is not round

1) Causes

The reamer is too long and has insufficient rigidity, causing vibration during reaming; the main deviation angle of the reamer is too small; the cutting edge of the bore is narrow; there are notches and transverse holes on the surface; inner hole; there are blisters and pores on the surface of the hole; the spindle bearing is loose, there is no guide sleeve, or the corresponding gap between the reamer and the guide sleeve is too large, or the thin-walled workpiece is tight. too tight, causing the part to distort after removal.

2) Solutions

Reamers with insufficient rigidity may use reamers with unequal tooth pitches. Reamers should be installed with rigid connections to increase the main deflection angle; select qualified reamers to control the hole position tolerance in the pre-machining process; , 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 corresponding clearance of the guide sleeves should be higher or used appropriately. This method reduces the clamping force.

4

The inner surface of the hole has obvious edges

1) Causes

Bore tolerance is too large; the clearance angle of the cutting part of the reamer is too large; the bore cutting edge is too wide; There are pores and blisters on the surface of the workpiece, and the spindle swing is too large.

2) Solutions

Reduce bore tolerance; reduce the clearance angle of the cutting part; correct the width of the edge; select qualified blanks;

5

The surface roughness value of the inner hole is high

1) Causes

The cutting speed is too high; the selection of cutting fluid is inappropriate; the main deviation angle of the reamer is too large and the reaming cutting edges are not on the same circumference; bore tolerance is too large; too small and part of the surface is not reamed; the oscillation of the cutting part of the reamer is out of tolerance and the cutting edge The surface is not sharp and rough; the cutting edge of the bore is too wide; chip removal is not smooth when the reamer is excessively worn, leaving burrs or scales on the cutting edge; Material, not suitable for zero rake angle or negative rake angle reamers.

2) Solutions

Reduce the cutting speed; select the cutting fluid according to the processing material; appropriately reduce the main deviation angle and properly sharpen the boring cutting edge; improve the position accuracy and quality of the bottom hole before reaming or increasing the value; Bore. ; Select a qualified reamer; reduce the blade width according to the specific situation, increase the chip groove space or use blade tilt; The reamer should be angled to ensure smooth chip removal; replace it regularly and remove the grinding area when sharpening; during the process of sharpening, using and transporting the reamer, protective measures should be taken to avoid bruising if the reamer is; bruised, for reamers, use an extra fine sharpening stone to repair the bruised reamer, or replace the reamer; use the whetstone to cut it until it is qualified, and use a reamer with a cutting angle of 5° to 10°.

6

Reamer life is short

1) Causes

The reamer material is inappropriate; the reamer is burned during sharpening; the cutting fluid is not properly selected, the cutting fluid does not flow properly, and the surface roughness value of the cutting place and the reamer after sharpening is too high.

2) Solutions

Select the reamer material according to the processing material, you can use carbide reamer or coated reamer; strictly control the amount of sharpening cutting to avoid burns; always choose the cutting fluid correctly according to the processing material; frequently remove chips in the chip groove; , and use sufficient pressure cutting, fine grinding or grinding fluid to meet the requirements.

7

The accuracy of the position of the reamed holes is out of tolerance.

1) Causes

The guide sleeve is worn; the lower end of the guide sleeve is too far from the workpiece; the guide sleeve is short, inaccurate, and the spindle bearing is loose.

2) Solutions

Replace the guide sleeve regularly; lengthen the guide sleeve to improve the clearance matching accuracy between the guide sleeve and the reamer; repair the machine tool in time and adjust the spindle bearing clearance.

8

Chipping of reamer teeth

1) Causes

Bore tolerance is too large; the hardness of the part material is too high; the cutting edge oscillation is too large and the cutting load is uneven; the main declination angle of the reamer is too small, which increases the cutting width; chips when reaming deep holes or blind holes, it was not cleaned in time, and the blade teeth were worn and cracked during sharpening.

2) Solutions

Change the size of the pre-machined opening; reduce the hardness of the material or change to a negative rake angle reamer or carbide reamer; control the oscillation error within the acceptable range; pay attention to chip removal in time or use; a blade tilt angle reamer; Pay attention to the quality of the sharpening.

9

Broken reamer handle

1) Causes

Bore tolerance is too large; when reaming a taper hole, the distribution of coarse and fine reaming tolerances and the selection of cutting quantity are inappropriate; the chip space of the reamer teeth is small and the chips are blocked.

2) Solutions

Change the size of the pre-machined opening; change the distribution of excess thickness and reasonably select the cutting quantity; reduce the number of reamer teeth, increase the chip spacing, or grind one tooth from the cutter tooth spacing.

10

The center line of the hole after reaming is not straight

1) Causes

The drill hole before reaming is deflected, especially when the hole diameter is small. Due to the poor rigidity of the reamer, the original curvature cannot be corrected; the main deviation angle of the reamer is too large; the reamer is easy to deflect during reaming direction; the reverse taper of the cutting part is too great; the reamer is moved to the gap in the middle of the interrupted hole, excessive force is applied in one direction, forcing the reamer; to deviate towards one end, destroying the verticality of the reamed hole.

2) Solutions

Increase the hole expansion or reaming process to correct the hole; reduce the main deviation angle; adjust the appropriate reamer; replace the reamer with a guide piece or extended cutting piece;