Gun Drill Lifecycle Management: Tracking, Regrind Scheduling, and Retirement

Gun Drill Lifecycle Management

A production deep hole drilling shop may manage dozens to hundreds of gun drills across multiple machines, diameters, and materials. Without a systematic lifecycle management system, drills are lost, reground too early or too late, and cost tracking is impossible.

This guide covers the practical elements of a gun drill lifecycle management system — from drill identification through retirement.

Drill Identification and Tracking

Minimum Identification

Every gun drill should have a unique ID. Three practical methods:

Method	Implementation	Durability	Cost	Best For
Laser engraving on shank	Laser-marked ID near the shank end	Excellent	$$	Production drills, permanent ID
Etched number	Chemical etch on shank	Good	$	Smaller shops
Colored bands	Paint rings near the connection	Poor (coolant strips paint)	$	Quick visual sorting
RFID tag	Embedded tag in shank or holder	Excellent	$$$	Automated tracking, large shops

Information Linked to Drill ID

Data Field	Why It Matters
Diameter	Identification for setup
Drill type (brazed, solid carbide, indexable)	Expected regrind life
Original length	Remaining length tracking
Nose grind type	Regrind geometry specification
Manufacturer	Quality tracking
Purchase date	Age tracking
Purchase price	Cost per hole calculation

Database Structure

Recommended Table Design

A simple database or spreadsheet should track:

Drill ID:
  - Diameter, type, manufacturer, purchase date, purchase price
  - Shank length, flute length, tip type, coating

Usage Log:
  - Date, machine, part number, holes drilled
  - Parameters used (speed, feed, pressure)
  - Quality results (diameter, Ra, straightness)

Regrind Log:
  - Date reground, regrind number
  - Material removed (mm)
  - Remaining tip length
  - Regrind cost
  - Regrind service provider

Event Log:
  - Breakages, damage, abnormal wear
  - Root cause (if known)
  - Corrective action

Retirement:
  - Retirement date
  - Reason (reached life limit, damaged beyond repair, worn out)
  - Total holes achieved
  - Total regrind cost

Tracking Tool Life Per Regrind Cycle

Drill ID: GD-412 (Brazed, Ø8.5 mm)
Date        Holes Since  Total Holes   VB (mm)   Tip Remaining    Action
2026-01-15  —            0             0.00      5.0 mm          New
2026-02-20  320          320           0.18      4.8 mm          Regrind #1 ($35)
2026-03-18  310          630           0.20      4.6 mm          Regrind #2 ($35)
2026-04-22  305          935           0.19      4.4 mm          Regrind #3 ($35)
2026-05-25  290          1,225         0.22      4.2 mm          Regrind #4 ($35)
2026-06-28  280          1,505         0.18      4.0 mm          Regrind #5 ($35)
2026-07-30  270          1,775         0.32      3.7 mm          Replace — tip insufficient

Regrind Scheduling

Just-in-Time vs Batch Regrind

Approach	Advantages	Disadvantages	Best For
Just-in-time (regrind each drill individually as needed)	No waiting for batching; drills always available	Higher per-regrind cost	Small shops, low volume
Batch regrind (collect 10–20 drills, ship together)	Lower per-regrind cost (volume discounts); less shipping per drill	Drills may wait for batch to fill	High volume, multiple drills
Exchange program (send dull drills, receive reground drills)	No downtime waiting for regrind	Must maintain pool of exchange drills	Production shops

Regrind Trigger Criteria

Criterion	Description	Set At
Flank wear (VB)	Primary indicator	0.15–0.20 mm
Holes per cycle	Expected life per regrind	Tracking data
Surface finish degradation	Quality-based trigger	Ra > 2× baseline
Diameter drift	Process control trigger	+0.02 mm from baseline

Automated Regrind Scheduling Algorithm

IF (current_holes >= holes_before_regrind × 0.9) THEN
  Flag for regrind at next opportunity

IF (current_holes >= holes_before_regrind) THEN
  Remove from active inventory
  Add to regrind queue

IF (drill in regrind queue AND batch_size >= min_batch) THEN
  Ship to regrind service

Retirement Criteria

Criterion	Brazed Tip	Solid Carbide	Indexable
Tip length remaining	< 3.0 mm	< 2.0 mm	N/A (replace insert)
Total regrinds used	5–7	7–10	N/A
Holes per regrind decline	< 60% of first cycle	< 60% of first cycle	N/A
Shank diameter wear	> 0.5% of nominal	> 0.5% of nominal	> 0.5% of nominal
Shank bent or damaged	Immediately	Immediately	Immediately
Flute damage	If chip flow affected	If chip flow affected	Replace

Retirement Decision Matrix

Is the drill damaged beyond repair?
  └─ Yes → Retire (record root cause)
  └─ No → Continue

Has it reached maximum regrind count?
  └─ Yes → Retire (reached design life)
  └─ No → Continue

Is the remaining tip length sufficient for at least one more regrind?
  └─ Yes → Schedule regrind
  └─ No → Retire (insufficient tip material)

Is the cost per hole of the next regrind cycle still economical?
  └─ Yes → Schedule regrind
  └─ No → Retire (diminishing returns)

Cost Tracking

Cost per Hole by Regrind Cycle

Cycle	Regrind Cost	Holes	Cost per Hole	Cumulative Cost	Cumulative $/hole
New (no regrind)	$180 (purchase)	320	$0.563	$180	$0.563
Regrind 1	$35	310	$0.113	$215	$0.341
Regrind 2	$35	305	$0.115	$250	$0.267
Regrind 3	$35	290	$0.121	$285	$0.228
Regrind 4	$35	280	$0.125	$320	$0.205
Regrind 5	$35	270	$0.130	$355	$0.196

Warning: Diminishing Returns

If holes per regrind decline significantly:

New:    320 holes @ $0.563/hole
R1:     310 holes @ $0.113/hole
R2:     280 holes @ $0.125/hole
R3:     220 holes @ $0.159/hole  ⚠️ Declining
R4:     150 holes @ $0.233/hole  ⚠️ Below 50% of new life
R5:     80 holes  @ $0.438/hole  ⚠️ Almost as expensive as new

When holes per regrind drops below 50% of the first cycle, retirement should be considered.

Implementation for Different Shop Sizes

Small Shop (< 20 Drills)

Tool	Spreadsheet (Excel, Google Sheets)
Setup time	1–2 hours initial setup
Tracking	Manual entry after each regrind
Complexity	Low — suitable for any operator
Cost	Free
Limitation	No automatic alerts; prone to data entry errors

Medium Shop (20–100 Drills)

Tool	Simple tool management database (Access, Airtable)
Setup time	4–8 hours
Tracking	Manual entry + barcode scanning
Complexity	Moderate
Cost	Low ($0–$50/month)
Features	Automated alerts at regrind threshold, basic cost reporting

Large Shop (> 100 Drills)

Tool	Commercial tool management system (CribMaster, E2)
Setup time	20–80 hours
Tracking	Barcode/RFID scanning, automated data collection
Complexity	High
Cost	$5K–$50K + annual maintenance
Features	Full lifecycle tracking, automated reordering, integration with ERP/MES, advanced analytics, usage forecasting

Summary

An effective gun drill lifecycle management system tracks each drill from purchase through retirement, recording regrind history, usage data, and cost per hole. Minimum viable system: a spreadsheet with drill ID, regrind dates, hole counts, and cost. A drill should be retired when it reaches maximum regrind count (5–7 for brazed, 7–10 for solid carbide), remaining tip length is below 3 mm, or cost per hole of the next regrind approaches the cost of a new tool. For single-shift production with 50 drills, a spreadsheet system saves approximately 30% in tooling costs compared to informal management. For regrind best practices, see gun drill regrinding guide. For cost analysis, see gun drilling cost per hole.