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IRWIN Left-Hand Mechanic's Length Cobalt High Speed Steel Drill Bit Set, 5-Bits Item # 833854
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- 8% Cobalt for higher heat and abrasion resistance
- Heavy-duty web construction for strength and durability
- 135º split joint begins drilling immediately, minimizing bit "walk"
- Tough metal drilliing, including heavy-duty abrasive alloy metal drilling on hardened steel (heat-treated)
|Cutting Diam||5/64 in, 7/64 in, 5/32 in, 1/4 in, 19/64 in|
|Cutting Edge Material||HSS|
|Tool Type||drilling tool|
|Type||HSS Drill Bit Set|
IRWIN Left-Hand Mechanic's Length Cobalt High Speed Steel Drill Bit Set, 5-Bits is rated out of 5 by 1.
Rated 5 out of 5 by SoManyFIsh from High quality bits saved my minivan's crankshaft! While repairing my minivan, I sheared off the harmonic balancer bolt in the crankshaft. It was a 10 mm grade 10.9 bolt recessed over 20 mm (~3/4") from the crankshaft end. I have never had to extract a bolt of this hardness from such a difficult location. I bought two packages of Irwin #30520 5-piece cobalt bit sets (assuming that I would break a few of them) and a matching 5-piece set of spiral flute extractors (Irwin #53535). With a variable-speed cordless drill at low-speed in reverse, I used the 5/32" bit to drill a pilot hole. I stopped every 15-20 seconds to let the bit cool, clean off shavings and spray in some cutting oil. Once I got the pilot hole about 12-13 mm deep (~ 1/2") I switched to a 1/4" bit (i.e., fits the Irwin EX-4 extractor from the #53535 set). Again, I stopped periodically to cool, clean and lubricate. When the 1/4" bit was about 7-8 mm deep (~ 5/16") I could feel it catching the broken bolt so I slowed down the drill and the bit rotated out the bolt! (I didn't even need to use the extractor.) Not only did no bits break during the job but after cleaning the two drills bits I used I see no indication of wear on them. Wow. These left-hand twist, cobalt alloy drill bits saved me from what would otherwise have been a *very* costly repair to my vehicle's engine.
Date published: 2015-12-14