Best Left Hand Drill Bit Set

An Easy Guide to Help you Select the Best Left Hand Drill Bit Set!

If you happen to be a maintenance machinist, auto mechanic, or an automobile restorer sooner or later you will find yourself faced with removing a broken stud or screw.  The best solution in many cases is to drill the broken fastener with a left hand drill bit and allow the counterclockwise torque and friction remove it.  Consequently, you just never know in advance what size drill bit you will need. That’s why it’s a good idea to have the best left hand drill bit set available when the challenge presents itself.

Unfortunately, some left hand drill bit sets are made from high carbon steel. Although these lower quality bits work OK for some applications, they can become dull quickly when drilling into a Class 8 screw fastener. Keep in mind, Class 8 fasteners are made from heat treated Chrome Moly steel which typically have a core hardness of Rockwell C33 to C39. Furthermore, a high carbon bit can easily break off while drilling through the fastener, destroying almost any hope of removing it.

A better choice would be to select a left-hand drill set made from HSS (High Speed Steel) which will stay sharp for many applications if used correctly. Additionally, they are much stronger and less likely to break while drilling through a broken stud.

What Are the Best Left Hand Drill Bit Sets?

RECOMMENDATIONS

Here are some high quality sets for you to consider.  Each set will perform at the highest level, and help you accomplish the task as fast and easy as possible.  Based upon my years of experience as a precision machinist, I believe these are the 5 best left hand drill bit sets.

NOTE:  Make certain to ONLY use these bits in a reversing drill motor rotating in a counterclockwise direction.

 

#1  Drill Hog 13 Pc NIOBIUM Left Hand Drill Bit Set

Features:

• Series: Fractional
• Sizes: 1/16 to 1/4 by 1/64ths increments
• Material: Niobium HSS
• Coating: None
• Recommended for: Grade 8 Bolts, Spring Steel, Stainless, and low and high carbon steel
• Special Features: N/A
• Case: Metal hinged index

Overview

The Drill Hog 13 Pc NIOBIUM Left Hand Drill Bit Set is designed especially for removing broken screws and studs. The bits are made from an enhanced grade of HSS that has a melting point of 4,475 degrees Fahrenheit.

Starting at 1/16″ up to 1/4″ in 1/64″ inch increments this left hand drill set will work for broken screws and studs up to 5/16″ inch.

Because of the hardness and toughness this left hand drill bit set is ideal for drilling through Grade 8 Bolts, Stainless, Spring Steel, Auto and Farm equipment frames.

 

 

#2   Neiko 10037A 15 Piece Left Hand Drill Bit Set

Features:

• Series: Fractional
• Sizes: 1/16″ to 1/2″ by 1/32″ increments
• Material: M2 HSS (high speed steel)
• Coating: TiN (titanium nitride)
• Recommended for: Grade 8 Bolts, Spring Steel, Stainless, and low and high carbon steel
• Special Features: Split Point
• Case: Metal, hinged index

Overview

The Neiko 10037A 15 Piece Left Hand Drill Bit Set is ideal to keep on hand in the machine shop or auto repair or restoration garage.

Made from M2 grade HSS (high speed steel) these left hand drill bits will drill through tough truck frames and leaf springs. Stainless and annealed high carbon steel are no problem if you happen to be in the machining business. A TiN coating is applied to the flutes and cutting surfaces for increased hardness up to 80 Rockwell “C” Scale.

These bits feature a Split Point which prevents “walking” and they drill more efficiently with less feed pressure than standard bits.

The bits included in this set are 1/16, 3/32, 1/8, 5/32, 3/16, 7/32, 1/4, 9/32, 5/16, 11/32, 3/8, 13/32, 7/16, 15/32 and 1/2. This range of sizes will allow you to drill broken off bolts and studs up to 7/16″ for removal with a screw extractor.

 

 

#3 COMOWARE Left Hand Drill Bit Set, 13 Piece

Features:

• Series: Fractional
• Sizes: 1/16″ to 1/4″ by 1/64″ increments
• Material: M2 HSS (high speed steel)
• Coating: TiN (Titanium Nitride)
• Recommended for: low & high carbon steel, stainless, spring steel, Grade 8 screws, auto and farm maintenance
• Special Features: 135 degree split point prevents skating and improves cutting
• Case: Steel hinged index

Overview

The COMOWARE Left Hand 13 Piece Drill Bit Set is ideal for removing broken screws up to 3/8″ diameter. Made from M2 High Speed Steel these left hand bits will cut through tough Grade 8 screws, truck frames, leaf springs, and other metals.

Each bit is coated with TiN Titanium Nitride which increases the hardness and wear resistance by a whopping 30% for even longer life.

This inexpensive set is an excellent choice for the HVAC service person to keep in his/her tool box for those on-site emergencies.

 

 

#4   29 Piece, Left Hand Industrial Black & Gold Drill Bit Set

Features:

• Series: Fractional
• Sizes: 1/16″ to 1/2″ in 1/64″ increments
• Material: HSS (high speed steel)
• Coating: Black and Gold Titanium Finish
• Recommended for: Drilling Grade 8 fasteners, low & high carbon steel, stainless, spring steel, truck frames.
• Special Features: 135 degree split point for faster penetration
• Case: Metal, hinged indexes

Overview

The VCT 29 Piece, Left Hand Industrial Black & Gold Drill Bit Set is an excellent choice for farm equipment maintenance, automobile restoration, machine shop, fab shop, and mill wright on-site applications.  The large size range will enable you to remove broken bolts and studs up to 3/4″ diameter.

The flutes and cutting edges are precision ground for more precise cutting and improved performance. A 35° Split Point design eliminates skating, improves, penetration, and decreases the likelihood of breakage.

High Speed Steel material will survive the high wear and heat typically encountered in commercial applications.  The Titanium coating improves chip flow and increases the hardness for longer tool life.

The VCT 29 Piece, Left Hand Industrial Black & Gold Drill Bit Set is one of the best full-size Left Hand Drill Bit Sets for professional use at a very moderate price.

 

 

#5   DRILL MASTER 13 Piece Left-Hand Drill Bit Set HSS Double Flute

Features:

• Series: Fractional
• Sizes: 1/16″ to 1/4″ by 1/64″ increments
• Material: HSS (high speed steel)
• Coating: Titanium coating
• Recommended for: G-8 Screws, low and high carbon steel, spring steel, truck and auto frames, farm machinery maintenance, and service applications
• Special Features: 135 degree split point eliminates skating and improves penetration
• Case: Steel, hinged index

Overview

The DRILL MASTER 13 Piece Left-Hand Drill Bit Set is a budget-priced set that will perform as well as the more expensive sets.

Heat and wear resistant HSS material assures long wear, even when drilling through tough Grade 8 screw material.  The Titanium coating protects these bits from corrosion and improves chip flow.

Each bit is ground with a 135° Split Point which improves penetration and eliminates skating.
SEE:  The Anatomy of a Twist Drill

This set is a good choice for the auto mechanic, auto restorer, HVAC residential or commercial service person.

How to Remove a Broken Screw or Stud With a Left Hand Drill Bit!

As a toolmaker and precision machinist I have had many occasions to remove broken screws and studs from machined parts.  But before we address the proper steps for removing a broken off fastener, its helpful to consider why it broke in the first place.

Reasons Why Studs and Screws Break Off in Tapped Holes!

Reason #1:  In the auto repair business the most common reason for a stud or screw to break off is rust or metal dissimilarity. A steel stud can become frozen in a threaded hole tapped into a cast iron part such as an engine block. If the part or engine block is made of a dissimilar metal such as Aluminum a cathodic effect can cause the fastener to become frozen.

Reason #2:  The second reason for a threaded stud or bolt to become frozen in a tapped hole is because it is too long or the tapped hole isn’t deep enough.  This can cause galling of the two metals making the threaded bolt extremely difficult to remove.

When torque is applied to remove the frozen threaded fastener it usually breaks off flush just above the part surface or slightly below. If you’re lucky there might be just enough sticking up to grab with a pair of Vice Grips, but don’t try it. That will almost certainly fail and make the job even more difficult.

Reason #3:  Another reason threaded fasteners break off in tapped holes is because of excessive shear or tension forces.  This is often the case with automobiles and farm equipment involved with collisions or accidents.  Fortunately, this scenario is often easier to deal with than with a frozen or seized fastener.

Reason #4:  The last but very common reason  studs and screws break is from over torquing a faster beyond its specified limit when installing, causing it to break.  This type of broken faster is usually easy to remove with a left hand drill bit.

Procedure for Removing a Broken Stud or Screw!

Here are some step-by-step instructions for removing a broken stud or screw.  If you follow them carefully there is a very good chance you will have success.

The tools and items you will need to remove a broken stud or screw are:

• Electric Drill Motor:  Its always best to use a drill press if possible but a good corded/cordless drill motor will work just fine.  Just make sure to run it in a COUNTERCLOCKWISE direction to avoid ruining the drill bit.
• Penetrating Oil:  A good quality Penetrating Oil can mean the difference is success or failure.  The best industrial grade Penetrating Oil is Kano Kroil which is available at Amazon.  Or, an excellent substitute would be to mix some Acetone which is available at any big box store and some PSF (power steering fluid) in a 50% mixture.  This home brew is the best penetrating oil you can use.  Just be very careful of the Acetone because its very volatile.
• Single-Cut Mill Flat File:  Every machine shop or auto repair garage should have a sharp Single-Cut Mill Flat File on hand.
• Center Punch:  Since its impossible to know in advance what size Center Punch you will need its a good idea to keep a Center Punch Set around the shop.

Step #1:  The first step for removing a  broken stud or screw is to apply some good quality Penetrating Oil and let it soak for at least 15 minutes.  I can’t over stress this step!   It will greatly increase your chances of success without damaging the tapped hole in the removal process.

Step #2:  The next step is to grab a flat file and file the end of the stud flat and parallel with the part.  This may be difficult, depending on the accessibility of the broken off stud. It might be easier to grind it flat.  If the break is below-flush you will need to deal with it as-is.

Step #3:  Now, using a Center Punch, carefully punch the exact center of the stud. This step can be tricky because the threads make it difficult to see the true center.  Make a small punch mark at first to see how it looks.  If off center adjust it by angling the center punch and make the mark deeper until its in the center.  The closer to dead center you center punch the hole the greater your chances are for success.

Step #4:  For the next operation select a left hand drill bit approximately the same diameter as the punch mark.  The reason for this is to create a core or pilot hole for a larger drill to follow.  Now carefully drill a hole a hole in the broken off threaded shaft.  Make sure the drill is aligned with the center punch mark.  As you are drilling be prepared for the screw to loosen and start unscrewing.   If this happens you can count yourself very lucky.

Step #5:  Select a drill bit approximately 60% the diameter of the screw diameter.  For example, for a 1/2″ diameter screw use a 5/16″ left hand drill bit.   Now, carefully drill into the broken off stud or screw.  Once the drill point has penetrated full depth increase the feed pressure momentarily.  If you are lucky the broken screw will break loose from the left handed torque action of the drill bit and come unscrewed.

After removing the broken fastener its a good idea to clean up the threaded hole with the appropriate size tap.

Optional:  If you were unsuccessful at removing the broken bolt or stud with just the left hand drill bit, your next best option is to use a Screw Extractor.