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Automotive: Thread Repair & Broken Bolts
Taps, metric drills and left-hand drills for chasing stripped threads and backing out broken bolts and studs on body and chassis parts.
Chasing threads, clearing bolts
Seized, stripped and snapped fasteners are routine on a repair. This step holds the taps and drills to clear the old thread and cut a clean new one.
- Triumph ThunderTaps in taper, plug and bottoming styles from 1/4" to 3/4", coarse and fine thread, and machine-screw taps from 4-40 up.
- Metric jobber drills from 2 mm to 13 mm, for tap drill sizes and clearance holes.
- ITM left-hand hard steel drill bits with a carbide tip, 1/8" to 1/2", and a 5-piece set. A left-hand bit can back a broken bolt out as it drills.
Drill and tap with care
Drill the right tap drill size for the thread, keep the bit centered in the broken fastener, and use cutting oil on the tap. Back the tap off a half turn every turn or two to break the chip. A tap breaks easily in a blind hole, so go slowly and clear the chips. Torque specifications and repair limits come from the vehicle maker.
Free shipping on orders over $200. Trade accounts can reorder in a click from My Toolbox, or call (833) 438-6657.
Common questions
What tap drill size for an M8 x 1.25 thread?
6.8 mm. In general, subtract the thread pitch from the nominal diameter: M6 x 1.0 takes 5.0 mm, M10 x 1.5 takes 8.5 mm. Confirm against a tap drill chart.
How does a left-hand drill help with a broken bolt?
A left-hand bit turns counterclockwise, so as it bites the broken bolt it can catch and back it out. Drill straight and centered, and go slowly.
Taper, plug or bottoming tap?
A taper tap starts easiest and suits through holes. A plug tap is the general choice. A bottoming tap cuts to the bottom of a blind hole, after the thread is started with a plug tap.
Buying for a crew?
Call 833-438-6657, 8 AM to 4 PM MST. We know the parts, not just the part numbers.