{"product_id":"300lh-11-pc-set","title":"300LH 11 PC Set","description":"\u003ch2\u003eDRILLCO 300LH 11-Piece Left-Hand Cobalt Screw Machine Drill Bit Set — Engineered for Broken Bolt Extraction\u003c\/h2\u003e\n\u003cp\u003eThe DRILLCO 300LH11 is an 11-piece left-hand cobalt screw machine drill bit set designed for counterclockwise drilling to facilitate the removal of broken bolts, screws, and other hardened fasteners. Constructed from M42 Cobalt High Speed Steel (HSS), these bits deliver superior abrasion resistance and heat tolerance compared to standard HSS drills, making them suitable for use in tough metals. The set is intended for use in left-hand screw machines and in conjunction with screw extractors, and is packaged in a rollup pouch for organized jobsite storage. Targeted at machinists, maintenance departments, contractors, mechanics, and installation crews who regularly encounter seized or broken fasteners.\u003c\/p\u003e\n\u003ch3\u003eTechnical Specifications\u003c\/h3\u003e\n\u003ctable\u003e\n\u003cthead\u003e\u003ctr\u003e\n\u003cth\u003eSpecification\u003c\/th\u003e\n\u003cth\u003eDetails\u003c\/th\u003e\n\u003c\/tr\u003e\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eBrand\u003c\/td\u003e\n\u003ctd\u003eDRILLCO\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eItem #\u003c\/td\u003e\n\u003ctd\u003e300LH11\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eUPC\u003c\/td\u003e\n\u003ctd\u003e045997492711\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCountry of Origin\u003c\/td\u003e\n\u003ctd\u003eUnited States\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMaterial\u003c\/td\u003e\n\u003ctd\u003eM42 Cobalt High Speed Steel (HSS)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePoint Angle\u003c\/td\u003e\n\u003ctd\u003e135° split-point\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFlute Direction\u003c\/td\u003e\n\u003ctd\u003eLeft-hand\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eShank\u003c\/td\u003e\n\u003ctd\u003e3-flats (sizes 3\/16\" and above)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSurface Treatment\u003c\/td\u003e\n\u003ctd\u003eBronze (high lubricity)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eLength Type\u003c\/td\u003e\n\u003ctd\u003eScrew machine length\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePieces\u003c\/td\u003e\n\u003ctd\u003e11\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePackaging\u003c\/td\u003e\n\u003ctd\u003eRollup pouch\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eApplications\u003c\/td\u003e\n\u003ctd\u003eCounterclockwise drilling for easy removal of broken bolts\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTechnical Tips\u003c\/td\u003e\n\u003ctd\u003eSpeed, feed, and lube are all critical to cutting tool performance\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003ch3\u003eAvailable Sizes\u003c\/h3\u003e\n\u003ctable\u003e\n\u003cthead\u003e\u003ctr\u003e\u003cth\u003eSize\u003c\/th\u003e\u003c\/tr\u003e\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\u003ctd\u003e1\/16\"\u003c\/td\u003e\u003c\/tr\u003e\n\u003ctr\u003e\u003ctd\u003e3\/32\"\u003c\/td\u003e\u003c\/tr\u003e\n\u003ctr\u003e\u003ctd\u003e1\/8\"\u003c\/td\u003e\u003c\/tr\u003e\n\u003ctr\u003e\u003ctd\u003e5\/32\"\u003c\/td\u003e\u003c\/tr\u003e\n\u003ctr\u003e\u003ctd\u003e3\/16\"\u003c\/td\u003e\u003c\/tr\u003e\n\u003ctr\u003e\u003ctd\u003e7\/32\"\u003c\/td\u003e\u003c\/tr\u003e\n\u003ctr\u003e\u003ctd\u003e1\/4\"\u003c\/td\u003e\u003c\/tr\u003e\n\u003ctr\u003e\u003ctd\u003e9\/32\"\u003c\/td\u003e\u003c\/tr\u003e\n\u003ctr\u003e\u003ctd\u003e5\/16\"\u003c\/td\u003e\u003c\/tr\u003e\n\u003ctr\u003e\u003ctd\u003e11\/32\"\u003c\/td\u003e\u003c\/tr\u003e\n\u003ctr\u003e\u003ctd\u003e3\/8\"\u003c\/td\u003e\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003cp\u003eUnlike standard right-hand HSS drill sets, the 300LH11 combines left-hand flute geometry with M42 cobalt steel construction and a bronze surface treatment — a combination that addresses both the directional requirement for fastener extraction and the hardness demands of drilling into seized or hardened materials. The screw machine length adds rigidity that reduces deflection and breakage compared to jobber-length alternatives, and the 3-flat shank minimizes chuck slippage during high-torque counterclockwise operation.\u003c\/p\u003e\n\u003ch3\u003eKey Features \u0026amp; Benefits\u003c\/h3\u003e\n\u003ch4\u003eM42 Cobalt High Speed Steel Construction\u003c\/h4\u003e\n\u003cp\u003eM42 Cobalt HSS provides superior hardness and wear resistance compared to standard HSS, enabling the bits to drill into hardened fasteners and tough metals where conventional drills would dull prematurely. Cobalt drills can drill approximately 30% faster than HSS drills, reducing cycle time on extraction jobs. Longer tool life means fewer bit replacements and lower cost per hole on demanding applications.\u003c\/p\u003e\n\u003ch4\u003eLeft-Hand Flute and Cutting Edge Geometry\u003c\/h4\u003e\n\u003cp\u003eLeft-handed flutes and cutting edges allow for counterclockwise drilling, which is the critical design feature for broken bolt and fastener removal. As the bit engages a broken fastener, the counterclockwise rotation can cause the fastener to back out on its own without requiring a separate extractor. This geometry makes the set directly compatible with left-hand screw machines and screw extractor workflows.\u003c\/p\u003e\n\u003ch4\u003e135° Self-Centering Split-Point\u003c\/h4\u003e\n\u003cp\u003eThe 135° split-point is self-centering, which reduces walking when starting a hole on a flat or curved surface and minimizes the thrust force required to begin cutting. For extraction work where precise hole placement over a broken fastener is essential, this point geometry improves accuracy and reduces the risk of damaging the surrounding material.\u003c\/p\u003e\n\u003ch4\u003eBronze Surface Treatment\u003c\/h4\u003e\n\u003cp\u003eThe bronze surface treatment increases lubricity at the cutting interface, reducing friction and heat buildup during drilling. This protective layer extends tool life and helps manage chip buildup, which is particularly important when drilling into harder metals and stainless steel. Reduced heat at the cutting edge also helps preserve the cobalt steel's hardness over repeated use.\u003c\/p\u003e\n\u003ch4\u003eScrew Machine Length for Added Rigidity\u003c\/h4\u003e\n\u003cp\u003eThe shorter screw machine length increases the rigidity of each bit compared to jobber or taper length drills, directly reducing the risk of deflection and breakage during high-torque extraction operations. Greater rigidity also improves hole accuracy, which is important when drilling concentrically over a broken fastener stub.\u003c\/p\u003e\n\u003ch4\u003e3-Flat Shank for Reduced Chuck Slippage\u003c\/h4\u003e\n\u003cp\u003eThe 3-flat shank design (on sizes 3\/16\" and above) provides positive engagement in the drill chuck, preventing the bit from rotating within the chuck under the high torque loads typical of counterclockwise extraction drilling. This reduces operator frustration and prevents damage to both the chuck and the shank.\u003c\/p\u003e\n\u003ch3\u003eCommon Applications\u003c\/h3\u003e\n\u003ch4\u003eBroken Bolt Removal\u003c\/h4\u003e\n\u003cp\u003eThe primary application for this set is drilling out broken bolts using counterclockwise rotation, which can cause the fastener to back out as the bit engages it. The cobalt construction handles the hardened steel typically found in seized or heat-affected fasteners.\u003c\/p\u003e\n\u003ch4\u003eUse with Screw Extractors\u003c\/h4\u003e\n\u003cp\u003eThe 300LH11 is designed for use in conjunction with screw extractors, where the left-hand drill first creates a pilot hole in the broken fastener before the extractor is applied. The 11 sizes cover the most frequently encountered fastener diameters in this workflow.\u003c\/p\u003e\n\u003ch4\u003eLeft-Hand Screw Machine Operations\u003c\/h4\u003e\n\u003cp\u003eThese bits are suited for use in left-hand screw machines where counterclockwise spindle rotation is standard. The screw machine length and 3-flat shank are optimized for this type of equipment.\u003c\/p\u003e\n\u003ch4\u003eDrilling Hardened Fasteners and Tough Metals\u003c\/h4\u003e\n\u003cp\u003eThe M42 cobalt HSS material makes these bits capable of drilling into hardened materials that would quickly dull standard HSS bits, including high-tensile fasteners and hard alloy steels encountered in maintenance and repair work.\u003c\/p\u003e\n\u003ch4\u003eMaintenance and Repair Applications\u003c\/h4\u003e\n\u003cp\u003eMaintenance departments, mechanics, and installation crews use this set for field and shop repair situations where broken or seized fasteners must be removed without damaging the surrounding workpiece. The rollup pouch keeps all 11 sizes organized and accessible on the job.\u003c\/p\u003e\n\u003ch3\u003eCompatible Materials\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eHardened metals\u003c\/li\u003e\n\u003cli\u003eTough metals (general)\u003c\/li\u003e\n\u003cli\u003eHardened fasteners (broken bolts, screws)\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eProduct Documents\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\u003ca href=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0551\/8396\/6382\/files\/zdthzlg6jaigvlhnd5ps_a5673136-c60f-45e7-9672-ebd18389c6db.pdf?v=1793375166\" target=\"_blank\" rel=\"noopener\"\u003eSafety Data Sheet (SDS)\u003c\/a\u003e\u003c\/li\u003e\n\u003cli\u003e\u003ca href=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0551\/8396\/6382\/files\/lbgzq52ysoyqwhpchtwf.pdf?v=1793375167\" target=\"_blank\" rel=\"noopener\"\u003eProduct Sheet\u003c\/a\u003e\u003c\/li\u003e\n\u003cli\u003e\u003ca href=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0551\/8396\/6382\/files\/cinakvujelpexceens0b_46c63d35-9dcb-429c-b39b-c8fed6ec9471.pdf?v=1793375167\" target=\"_blank\" rel=\"noopener\"\u003eLinecard\u003c\/a\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eSafety Data Summary\u003c\/h3\u003e\n\u003ch4\u003eHazard Information\u003c\/h4\u003e\n\u003cul\u003e\n\u003cli\u003eDuring normal operation, cobalt cutting tools do not present inhalation, ingestion, or other chemical hazards.\u003c\/li\u003e\n\u003cli\u003eGrinding, cutting, machining, burning, or welding may release dusts, fumes, or vapors that present health hazards if exposure limits are exceeded.\u003c\/li\u003e\n\u003cli\u003eExcessive inhalation of metallic fumes and dusts may cause irritation of eyes, nose, and throat.\u003c\/li\u003e\n\u003cli\u003eHigh concentrations of fumes and dusts of iron oxide, manganese, copper, zinc, and lead may result in metal fume fever (metallic taste, throat irritation, chills, fever — symptoms may persist 12 to 48 hours).\u003c\/li\u003e\n\u003cli\u003eCobalt is listed as a Group 2B carcinogen by IARC (possibly carcinogenic to humans). Chromium and Nickel are listed as carcinogens by NTP and OSHA.\u003c\/li\u003e\n\u003cli\u003eChronic exposure to cobalt dusts, fumes, and mists may cause permanent respiratory diseases including occupational asthma, interstitial pneumonitis and fibrosis (hard-metal disease), and emphysema.\u003c\/li\u003e\n\u003cli\u003eSkin sensitization to cobalt is noted in a small percentage of cases.\u003c\/li\u003e\n\u003cli\u003eFine metal particles produced when ground or sawed can burn; high concentrations in air may present an explosion hazard.\u003c\/li\u003e\n\u003cli\u003eNFPA Hazard Rating: Health 1; Flammability 0; Reactivity 0.\u003c\/li\u003e\n\u003cli\u003eCalifornia Proposition 65 Warning: This product can expose you to chemicals including Cobalt, which is known to the State of California to cause cancer. For more information go to www.P65Warnings.ca.gov.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch4\u003ePersonal Protective Equipment\u003c\/h4\u003e\n\u003cul\u003e\n\u003cli\u003eWear safety glasses or goggles with side shields; do not wear contact lenses when handling.\u003c\/li\u003e\n\u003cli\u003eCloth or leather gloves recommended when contact with dust or mist is likely.\u003c\/li\u003e\n\u003cli\u003eUse an appropriate NIOSH-approved respirator if airborne dust concentration exceeds the applicable PEL or TLV.\u003c\/li\u003e\n\u003cli\u003eHearing protection may be required.\u003c\/li\u003e\n\u003cli\u003eAlways use machine guards and wear protective clothing to prevent injury in the event of tool breakage.\u003c\/li\u003e\n\u003cli\u003eEmployer should provide an eye wash station within the immediate work area.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch4\u003eSafe Handling\u003c\/h4\u003e\n\u003cul\u003e\n\u003cli\u003eUse only with local exhaust ventilation adequate to limit personal exposure to airborne dust below PEL or TLV levels.\u003c\/li\u003e\n\u003cli\u003eAll grinding, welding, or fume-generating operations should be performed in well-ventilated areas.\u003c\/li\u003e\n\u003cli\u003eClean up using methods that avoid dust generation: vacuum with appropriate filters, wet dust mop, or wet clean-up.\u003c\/li\u003e\n\u003cli\u003eWash hands thoroughly after handling and before eating or smoking; wash exposed skin at end of work shift.\u003c\/li\u003e\n\u003cli\u003eDo not shake clothing, rags, or other items to remove dust — remove dust by washing or vacuuming with appropriate filters.\u003c\/li\u003e\n\u003cli\u003eStore in a dry place in a manner that prevents accidental environmental contamination from traces of industrial lubricants or wetting oils.\u003c\/li\u003e\n\u003cli\u003eSoiled clothing should be laundered separately.\u003c\/li\u003e\n\u003cli\u003eIncompatible with strong acids and strong oxidizers.\u003c\/li\u003e\n\u003cli\u003eFor powder fires: smother with dry sand, dry dolomite, ABC-type fire extinguisher, or flood with water.\u003c\/li\u003e\n\u003cli\u003eEmergency phone: CHEM-TEL INC 1-800-255-3924.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eFrequently Asked Questions\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eQ: What is the primary purpose of this left-hand drill bit set?\u003c\/strong\u003e\u003cbr\u003eA: The 300LH11 is designed for counterclockwise drilling to facilitate the easy removal of broken bolts, screws, and other hardened fasteners. It is used in left-hand screw machines and in conjunction with screw extractors.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ: Why use cobalt HSS instead of standard HSS for this application?\u003c\/strong\u003e\u003cbr\u003eA: M42 Cobalt HSS provides superior abrasion resistance and hardness compared to standard HSS, making it capable of drilling into hardened materials. Cobalt drills can drill approximately 30% faster than HSS drills, and they offer longer tool life in tough metals.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ: What sizes are included in the 11-piece set?\u003c\/strong\u003e\u003cbr\u003eA: The kit contains the 11 most frequently used sizes: 1\/16\", 3\/32\", 1\/8\", 5\/32\", 3\/16\", 7\/32\", 1\/4\", 9\/32\", 5\/16\", 11\/32\", and 3\/8\".\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ: Does the 3-flat shank apply to all sizes in the set?\u003c\/strong\u003e\u003cbr\u003eA: The 3-flat shank for reduced slippage in the drill chuck applies to sizes 3\/16\" and above. Smaller sizes below 3\/16\" have a standard round shank.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ: Why is screw machine length used instead of jobber length?\u003c\/strong\u003e\u003cbr\u003eA: The shorter screw machine length adds rigidity to the drill bit, which reduces deflection and breakage — particularly important during the high-torque counterclockwise drilling required for fastener extraction.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ: What are the critical factors for getting the best performance from these bits?\u003c\/strong\u003e\u003cbr\u003eA: According to DRILLCO, speed, feed, and lubrication are all critical to cutting tool performance. Proper attention to all three parameters will maximize tool life and cutting efficiency.\u003c\/p\u003e","brand":"Drillco","offers":[{"title":"Default Title","offer_id":67905909227694,"sku":"300LH11","price":83.43,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0551\/8396\/6382\/files\/eaasutrj6yo5zc2y7eze.jpg?v=1793375170","url":"https:\/\/www.diamondtoolstore.com\/products\/300lh-11-pc-set","provider":"Diamond Tool Store","version":"1.0","type":"link"}