troubleshooting
Mag Drill Making Rough or Oversize Holes
A hole that looks rough and a hole that measures oversize are not necessarily the same problem. Stop producing further parts until the defect is understood. Keep the failed sample, cutter details and job settings together for a useful diagnosis.
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Define the defect in measurable terms
Record the required diameter and tolerance from the job specification, then record how the finished hole was measured. Note the measuring tool and whether the measurement was taken near the entry, middle or exit. Avoid accepting or rejecting a precision hole from appearance alone.
Photograph the entry and exit separately. A visible burr, an out-of-round opening and a misplaced hole should be described separately even if they occurred in the same operation. For safety-critical fabrication, the responsible inspector or engineer should decide whether a part can be accepted or repaired.
Separate four different defects
A burr at the exit, a tapered or out-of-round bore, a uniformly oversize bore and a misplaced center are different failures. Measure entry, middle and exit where the job's inspection method permits, and record location separately from diameter. That gives the cutter or machine supplier useful evidence without guessing at a cause.
Use the manufacturer manual to establish which user inspections are permitted before attempting adjustments. Do not tighten random slide screws until the machine feels stiff. Likewise, an arbor that appears loose needs an appropriate inspection, not an improvised shim.
- Keep an acceptable sample for comparison if one exists.
- Record whether the issue affects every hole or a particular location.
- Separate measured diameter from positional error on the drawing.
Match the next action to the measured defect
If diameter changes through the bore, send the measurements and cutter, arbor and pilot IDs to the cutter or machine supplier. If diameter is acceptable but location is not, the setup and job-control question belongs with the responsible inspector. A cleaner edge does not prove that either dimension is acceptable.
The Milwaukee 2787/2788 manual supplies maintenance and service boundaries for those models, not a universal runout diagnosis. Resume production only after the applicable inspection method and setup are accepted for the job.
Questions, answered
Does a clean-looking hole prove the size is correct?
No. Check the required dimension and tolerance with an appropriate measurement method.
Can I enlarge a bad hole to repair the part?
Only if the job's responsible authority approves the revised hole and repair method. Do not assume enlargement preserves the part's suitability.