Technical Guidance Basics of Drilling, Drilling Edition
■ Runout Accuracy
(Unit: mm)
For the runout accuracy of web-thinned drills, the runout after thinning (A) is important in addition to the difference in lip height (B).
MDS140MK Carbon Steel v c = 165 SFM f = .0118 IPR
.010
.008
.006
.004
(A)
.002
(B)
0
Centre runout (A) (inch)
N
.0002
.0008
.002
.004
(A): Runout accuracy of thinning point (B): The difference of the lip height
Peripheral runout
.0002 .0008
.004
.002
.0008
.004
(B) (inch)
■ Drill Mounting Peripheral Runout Accuracy
● When the tool rotates The peripheral runout accuracy of the drill mounted
Peripheral runout (inch)
Hole expansion Cutting Force*
.002 (in.)
22 (lbs)
0
0
on the spindle should be controlled within .0012”. If the runout exceeds the limit, the drilled hole will also become large and an increase in the horizontal cutting force, which may result in drill breakage.
.0002
.0035
* Horizontal cutting force. Drill: MDS120MK, part material: Carbon Steel (230HB) Cutting Conditions: v c= 165 SFM, f = .0118 IPR, H = 1.50” Water-soluble Coolant
Runout: Within .0012”
Runout: Within .0012”
● When the part material rotates The peripheral runout at the drill edge (A) and the concentricity at (B) should be controlled within .0012”.
0.03mm
(A)
(B)
■ Work Material Surface and Drill Performance
(Entrance)
(Exit)
● Part material with slanted or uneven surface If the surface of the hole entrance or exit is slanted or uneven, decrease the feed rate to 1/3 to 1/2 of the recommended cutting conditions.
■ How to Use a Long Drill
● Problem When using a long drill (e.g. XHGS Type), SMDH-D Type drill or SMDH-12.5D Type drill at high rotation speeds, the runout of the drill tip may cause a deviation of the entry point as shown on the right, bending the drill hole and resulting in drill breakage. ● Remedies
Hole bend
Position shift
Method 1
Step 1
Step 2
Step 3
2 to 3mm
1xDC prepared hole machining (same diameter)
n=100 to 300min -1
Drilling under recommended conditions
Short drill
Method 2 *Low rotational speed minimises centrifugal forces and prevents the drill from bending.
.079 to .118”
Step 1
Step 2
(n=100 to 300min -1 )
f=.0059 to .0079 IPR
Drilling under recommended conditions
N62
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