Radial adjusted drilling is only possible using indexable insert drills.
Radial adjustment of the diameter of an indexable insert drill extends the working area and makes it possible to:
- Achieve a closer hole tolerance by pre-setting the exact drill diameter, which eliminates manufacturing tolerances of drill and insert
- Make a hole larger than the drill diameter and avoid the need to stock other sizes
- Produce stepped and chamfered holes with a standard drill, which is possible in a non-rotating drill application
Note: Adjusting the drill to a smaller diameter than the nominal diameter is not recommended because it can cause the drill body to scratch against the hole wall.
Producing a hole larger than the drill
Maximum adjustment for radial drilling depends on the central and peripheral insert overlap. Radial adjustment influences the cutting force; choose the lower feed in the recommended range.
Non-rotating application for radial drilling
- Holes can be drilled larger than the nominal size of the drill
- Can be used to generate tapered holes
- Chamfers and reliefs can be machined
- A hole which is to be threaded can be prepared in one pass along with chamfering
Pre-setting in a lathe
By pre-setting the drill, and thereby eliminating the manufacturing tolerances of the drill body/tip seat and the insert, a tolerance within ±0.05 mm (0.002 inch) (IT10-11) can be maintained during radial drilling under stable conditions.
Rotating application for radial drilling
This is the most accurate and stable solution for radial adjustment drilling in a rotating drill application. Sleeves are used to adapt various ISO shank sizes to one holder.
- Radial adjustment -0.2 /+0.7 mm (-0.008/+0.028 inch)
- Note that the adjustment range for the drill should not be exceeded
- Hole tolerances down to ± 0.05 mm (0.002 inch)
Settings are done by turning the scale ring surrounding the holder, marked in increments of 0.05 mm (0.002 inch), indicating a diametrical movement of the tool.
It may be necessary to reduce the feed/rev (fn) due to longer tool overhang and less balanced cutting forces created by the offsetting.
Eccentric sleeve for radial drilling
An eccentric sleeve can be used with indexable insert drills with cylindrical ISO 9766 shanks. It should only be used for pre-setting to reach a closer hole tolerance.
When using the sleeve, you will need to use a holder that is one size larger, i.e. drill shank diameter 25 mm + sleeve means that the holder for 32 mm diameter should be used.
- Radial adjustment range is approx. -0.1/+0.3 mm (-0.004/+0.012 inch)
- Adjustment below nominal diameter is not recommended
- One dot increases/decreases hole diameter by roughly 0.10 mm (0.004 inch)
- Turn anticlockwise to decrease the diameter
- Turn clockwise to increase the diameter
- Use both screws to clamp the drill in the fixture and make sure the bolts in the holder are long enough