Time‑Sert Size Chart: How to Match Inserts, Drills, and Taps
Time‑Sert size charts map an original fastener specification to the exact drill, installation tap, and solid insert dimensions needed for a threaded‑insert repair. Repairers and parts buyers use the chart to convert a damaged thread (for example M10×1.5 or 3/8‑16) into the drill designation, the Time‑Sert installer tap, the external OD of the insert, and the recommended insert length and kit. The following covers naming conventions, a step‑by‑step lookup workflow, how to read a cross‑reference table, tooling compatibility notes, common fitment checks, and a compact checklist for confirming the correct insert and tooling before ordering or installing.
Naming and sizing conventions for original threads and inserts
Start with the fastener specification printed on the bolt or in the parts manual. Metric entries appear as M[major diameter]×[pitch] (for example M8×1.25); imperial entries use nominal diameter and threads per inch (for example 5/16‑18). The chart translates that specification into three measurable items: the repair drill (given as a number, fractional inch, or millimeter), the installer tap (a Time‑Sert tap code or size that matches the insert’s external thread), and the insert internal thread (which matches the original fastener size).
Insert dimensions are expressed as external outer diameter (OD) for pilot/drill clearance and length (short/standard/long). Installer taps are often proprietary to maintain correct thread form and depth for the solid insert. Charts also note whether a countersink, pilot drill, or special spacer is required for blind holes or thin material.
Step‑by‑step sizing lookup process
Begin by confirming the original thread specification visually and with basic measuring tools. Measure major diameter with calipers and confirm thread pitch with a pitch gauge or by counting threads per inch. If the thread marking is unclear, measure both diameter and pitch before proceeding.
Next, locate the manufacturer cross‑reference for Time‑Sert inserts. Identify the row that matches the original thread. Read across to find the drill designation (this is the hole you will enlarge to accept the installer tap and insert), the installer tap code (use the specific Time‑Sert tap supplied in the kit or listed), the insert outer diameter, and recommended insert length. Note any special instructions such as countersink diameter, pilot use, or insert orientation in through versus blind holes.
Finally, confirm tool compatibility. Match the tap shank and driver socket sizes to the tools included in the kit or to replacement tools from suppliers. Verify whether the kit contains a drill, tap, insert(s), and driver; some buyers will purchase taps and inserts separately. Confirm the insert length against the workpiece wall thickness to ensure enough engagement on both internal and external threads.
Cross‑reference table layout and how to interpret each column
| Original Thread | Thread Spec | Drill Designation | Installer Tap | Insert OD / Length | Notes |
|---|---|---|---|---|---|
| Example: 3/8‑16 | UNF, 3/8″ × 16 TPI | Drill listed by fraction or jobber size | Time‑Sert tap code for 3/8‑16 insert | OD value / standard or long (mm or inch) | Through‑hole vs blind‑hole note |
| Example: M8×1.25 | Metric, M8 × 1.25 mm | Drill listed in mm | Metric installer tap code | OD value / length class | Countersink / pilot requirements |
The table above shows a typical cross‑reference structure: the first column is the fastener you’re repairing, the next columns list the drill and tap designations you will use, and the insert OD and length describe the physical replacement. The Notes column flags anything that affects fit: required countersink, pilot drills for thin walls, or when a special bottoming tap is needed for blind holes.
Tooling and kit compatibility considerations
Time‑Sert kits commonly bundle the drill, installer tap, solid insert(s), driver, and sometimes a countersink or pilot. Kits are organized by original thread size and insert length. Verify that the kit’s tap and driver shank match the shop’s tap holder or hand‑driver; some taps have proprietary shanks intended for the installer. If ordering inserts separately, confirm the insert part code, OD, and length match the chart entry for the original specification.
Consider hole access and workpiece material. Thin castings or flanges may need short inserts or spacers; thicker sections can accept standard or long inserts for improved pullout resistance. For blind holes, ensure the kit includes a bottoming installer tap or follow the manufacturer’s installation sequence to avoid incomplete seating.
Common fitment pitfalls and verification checks
Confirm actual thread condition before committing to a size. Damaged threads can mask the true pitch or diameter; use a thread gauge and calipers to verify. Avoid relying on visual match alone when fasteners vary between production batches or model years.
Check hole straightness and bore concentricity. An off‑axis hole can cause premature thread engagement issues even when sizes match the chart. Inspect for cracking or missing boss material that would prevent full insert seating. Clean all debris and chamfer edges to the drill and countersink specifications in the chart before tapping and inserting.
Trade‑offs, tolerances, and verification requirements
Manufacturers publish drill and tap designations based on nominal thread geometry and material assumptions. Real components introduce variation: cast aluminum may flex under cutting, hardened steel may require different tooling, and older parts can have stretched or corroded bores. These factors affect drill choice and whether a standard installer tap will form the correct pocket for the insert. Tolerances on insert OD, tap pitch, and seating depth are finite; verify dimensions with calipers and confirm that wall thickness supports the chosen insert length before ordering. For thin walls or borderline conditions, choose shorter inserts or different repair methods per engineering practice rather than forcing a longer insert into inadequate material.
Which Time‑Sert kit fits my thread?
How to choose thread repair insert size?
What tap and drill bit sizes apply?
Summarize the selection process by returning to measured facts: identify the original thread size and pitch, consult the manufacturer’s Time‑Sert cross‑reference to read drill and installer tap designations, confirm insert OD and length against workpiece thickness, and match tools in the kit to shop equipment. Before ordering, verify part codes and physical dimensions, confirm whether the repair is through or blind hole, and ensure the kit includes the correct installer tap and driver. A final checklist: measure diameter and pitch, confirm drill and tap codes, verify insert length vs wall thickness, inspect for alignment or damage that prevents seating, and confirm tool shank compatibility with shop holders. Following these steps reduces fitment surprises and helps select the right insert and tooling for reliable threaded repairs.
