HSS Left-Hand Drill Bits
Round-shank jobber drills in fractional-inch, metric and numbered sizes, with uncoated, black-oxide and gold-oxide series for different assortment requirements.
Compare HSS Sizes
INDUSTRIAL REPAIR TOOL SUPPLY
Left Hand Drill Bits
Source HSS and cobalt left-hand drill bits for maintenance distributors and industrial buyers, with individual replacements and drill-only sets selected by diameter, length, point and shank.
- Metric, fractional-inch and numbered individual sizes.
- HSS and cobalt steel with series-specific finishes.
- Six HSS drill-only assortments in metal cases.
Match the Drill to Your Repair Range
Choose the cutting tool your customers need by comparing the complete drill configuration, not diameter alone. Material, point geometry, working reach and holding interface distinguish replacement requirements within your repair-tool assortment.
- Jobber and maintenance lengths for different access requirements.
- Round shanks and a separate specialist 7/16-inch hex series.
- Standard or split points matched to the selected series.
Choose Your Left-Hand Drill Material
Cobalt Left-Hand Drill Bits
Metric jobber and fractional maintenance drills, plus specialist short hex-shank sizes, give you distinct length and connection choices within cobalt steel.
Compare Cobalt Configurations
Specify Your Left-Hand Drill Series
The individual range covers several combinations of material, size system and length. Start with the series that fits your customer's existing tools or application, then select the exact diameter. Fractional, numbered and metric designations remain separate ordering references, even where decimal dimensions are close. The table shows the range boundary for each series; selected-size ranges contain listed diameters rather than every possible increment. Finishes and point forms belong to their respective series. For a fixed replacement requirement, compare the complete configuration instead of assuming that another drill with the same diameter will have the same length or geometry.
| Material and Length | Finish | Individual Size Coverage | Point and Connection |
|---|---|---|---|
| HSS jobber | Uncoated | 1/32–1/2 inch, every 1/64 inch | Split point; round shank |
| HSS jobber | Uncoated | Selected metric sizes, 1.0–2.9 mm | Standard point; round shank |
| HSS jobber | Uncoated | No. 60–No. 1 | Standard point; round shank |
| HSS jobber | Black oxide | Selected metric sizes, 3.0–12.0 mm | Standard point; round shank |
| HSS jobber | Gold oxide | Selected fractional sizes, 1/16–1/2 inch | Split point; round shank |
| Cobalt steel jobber | Uncoated | 1.5–13.0 mm, every 0.5 mm | Split point; round shank |
| Cobalt steel maintenance | Uncoated | Selected fractional sizes, 5/64–1/2 inch | Split point; round shank |
| Cobalt steel maintenance | TiN | Selected fractional sizes, 5/64–3/8 inch | Split point; round shank |
| Cobalt steel maintenance | TiAlN | Selected fractional sizes, 5/64–3/8 inch | Split point; round shank |
| Cobalt steel specialist short | TiAlN | 4, 6, 7 and 10 mm | 135-degree split point; specialist 7/16-inch hex shank |
The TiN and TiAlN maintenance series each include 5/64, 7/64, 1/8, 5/32, 3/16, 7/32, 1/4, 5/16 and 3/8 inch. The uncoated maintenance series also includes 9/32, 19/64, 11/32, 13/32, 7/16, 15/32 and 1/2 inch. These differences matter when you want the same size coverage across several finish options: the larger uncoated sizes are a separate selection.
For metric HSS replenishment, the black-oxide series includes 3.0, 3.2, 3.3, 3.5, 3.8, 4.0, 4.2, 4.5, 4.8, 5.0, 5.1, 5.2, 5.5, 6.0, 6.5, 7.0, 8.0, 8.5, 9.0, 10.0 and 12.0 mm. Below that range, the uncoated HSS series provides selected sizes including 1.0, 1.25, 1.5, 2.0, 2.5 and 2.9 mm. Your requested diameter list determines which series belongs in the quotation.
Compare Actual Individual Configurations
These examples show how diameter, length and maximum drilling depth vary within the collection. Maximum drilling depth is the listed depth specification, separate from flute length. Overall length includes the whole tool. Keeping both dimensions in a replacement specification makes the required reach and holding arrangement clear.
| Individual Configuration | Overall Length | Maximum Drilling Depth | Shank and Point |
|---|---|---|---|
| 6 mm HSS jobber, black oxide | 93 mm | 48 mm | 6 mm round; standard point |
| 6 mm cobalt jobber, uncoated | 102 mm | 70 mm | 6 mm round; split point |
| 1/4-inch HSS jobber, uncoated | 4 inches | 2.25 inches | 1/4-inch round; split point |
| 1/4-inch HSS jobber, gold oxide | 4 inches | 2.63 inches | 1/4-inch round; split point |
| 1/4-inch cobalt maintenance, uncoated | 3.5 inches | 1.63 inches | 1/4-inch round; split point |
| 1/4-inch cobalt maintenance, TiN or TiAlN | 3.375 inches | 1.63 inches | 1/4-inch round; split point |
| 6 mm cobalt specialist short, TiAlN | 3 27/64 inches | 1 27/32 inches | 7/16-inch specialist hex; 135-degree split point |
The two 6 mm jobber drills have different material, point form, overall length and listed depth. The two 1/4-inch HSS jobber examples share an overall length but have different depth specifications. A distributor replacing an established item therefore needs the original configuration as well as the nominal size. Use these examples to shortlist a series, then send the sizes and quantities required.
Six Details That Define the Drill
Counterclockwise Cutting
Left-hand cutting geometry drills in reverse, turning in the loosening direction of conventional right-hand threaded fasteners.
Standard and Split Points
Point form varies by series, giving buyers a defined geometry to match when selecting individual replacements.
Jobber and Maintenance Lengths
Actual tool dimensions distinguish the available reach and projection, even where two drills share a nominal diameter.
Round-Shank Configurations
Most individual series use round shanks, with shank dimensions listed alongside the selected cutting diameter.
Specialist Hex Connection
Four short cobalt sizes use a dedicated 7/16-inch hex shank, separate from common 1/4-inch hex connections.
Series-Specific Surfaces
Uncoated, oxide, TiN and TiAlN options identify different configurations; material and finish remain separate specifications.
Keep Size-Based Replenishment Exact
Individual left-hand drills let you replenish selected diameters without buying another complete assortment. Preserve the original inch, metric or numbered designation when matching stock: No. 60 is 0.040 inch, while No. 1 is 0.228 inch in the HSS numbered series. A nearby metric equivalent serves as a dimensional comparison, rather than an automatic substitute for an extractor's specified pilot size or an established customer item.
Select the Length Your Customers Need
For a compact repair assortment, compare cobalt maintenance lengths with the corresponding jobber dimensions. A 1/4-inch uncoated cobalt maintenance drill is 3.5 inches overall; the 1/4-inch uncoated HSS jobber is 4 inches. The shorter drill offers a different reach and projection. When sourcing left-hand stub drill bits, use the actual overall length, depth and connection as the purchasing reference, since length-category names alone do not specify those dimensions.
Match the Point and Holder
Specify a standard or split point when replacing an existing drill. The specialist short cobalt series has a stated 135-degree split point; the round-shank split-point series does not inherit that angle. Its 7/16-inch hex connection also needs the corresponding holder. A 7/16-inch round-shank drill instead describes a cutting diameter and round connection. The Drill Point Angle Guide explains the geometry terms used in technical purchasing specifications.
Separate Material From Surface
HSS and cobalt steel describe the drill material. Black oxide, gold oxide, TiN and TiAlN describe the surface configuration. For cobalt left-hand drill bits, choose the required length and diameter before comparing the finishes available in that series. A gold appearance does not identify cobalt content or a particular coating. The cobalt and titanium drill comparison provides further context for buyers comparing material descriptions with coating names.
Supply the Right Drill for Each Repair Requirement
Broken-Fastener Repair Supply
For steel fastener repairs requiring a counterclockwise pilot hole, source the drill diameter specified by the repair procedure or paired extractor. Fractional and metric individual drills cover different tool pairings, while a drill-only set provides several pilot options. Left-hand cutting sometimes loosens a conventional right-hand threaded fastener during drilling; it does not guarantee removal. The broken-bolt extraction guide covers the repair sequence beyond product selection.
Workshop Assortments and Replacement Stock
A repair-tool distributor can compare fractional HSS sets by the largest diameter and interval, then select individual sizes for replacement inquiries. A 13-piece assortment serves 1/16–1/4-inch requirements; a 29-piece assortment extends to 1/2 inch with the same 1/64-inch interval. Where workshops consume certain pilot sizes more often, the individual range provides a separate ordering route. Match point form and length when the replacement must retain the kit's configuration.
Repairs With Restricted Access or Known Material Requirements
An assembly with limited clearance may call for a maintenance-length drill, provided its reach suits the fastener position. A deeper target may require a jobber configuration instead. For stainless steel or hardened fasteners, include the known workpiece grade, hardness or fastener specification with your application inquiry. HSS or cobalt identifies a material category; neither label establishes suitability for every hardened workpiece. Select the configuration against the actual repair requirement.
Compare Drill-Only Sets and Extraction Kits
Left-hand twist drill bits cut the pilot hole. Screw extractors grip the remaining fastener to apply turning force. An industrial supplier purchasing both needs the drill diameters and extractor capacities identified separately. The extractor's stated fastener capacity is a different dimension from its companion drill's cutting diameter.
| Purchase Requirement | Suitable Order Scope | What to Compare |
|---|---|---|
| Several pilot-drill sizes for workshop repair | Drill-only assortment | Material, included diameters, intervals, point form and case |
| Replacement of frequently used pilot drills | Individual sizes | Original size designation, geometry, length, finish and quantity by size |
| Pilot drilling followed by a gripping tool | Drill-and-extractor combination | Separate drill and extractor lists, their pairing and total tool count |
| A dedicated machine connection | Specified individual configuration | Shank type, shank size, holder reference and required cutting diameter |
A mixed ten-piece kit containing five drills and five extractors supplies five drilling tools. A drill-only set contains drilling tools throughout. Compare the number of usable drill sizes before comparing case prices or setting a reseller assortment. Repeated sizes within a set create another difference: fifteen tools need not mean fifteen unique diameters. For the companion gripping tools, see our screw extractor collection.
View related tool reference images
Configure Your Drill-Only Assortment
The six HSS sets below use jobber-length, uncoated drills with standard points and metal cases. Select the size system first, then compare the covered diameter span and interval. The fractional sets suit different coverage requirements; letter and numbered sets serve their own nominal size systems. The set count describes the tools included, rather than a universal measure of assortment coverage.
| HSS Set | Included Sizes | Size System | Configuration |
|---|---|---|---|
| 13 pieces | 1/16–1/4 inch, every 1/64 inch | Fractional inch | Jobber; standard point; uncoated; metal case |
| 15 pieces | 1/16–1/2 inch, every 1/32 inch | Fractional inch | Jobber; standard point; uncoated; metal case |
| 21 pieces | 1/16–3/8 inch, every 1/64 inch | Fractional inch | Jobber; standard point; uncoated; metal case |
| 26 pieces | A–Z | Letter | Jobber; standard point; uncoated; metal case |
| 29 pieces | 1/16–1/2 inch, every 1/64 inch | Fractional inch | Jobber; standard point; uncoated; metal case |
| 60 pieces | No. 60–No. 1 | Numbered | Jobber; standard point; uncoated; metal case |
Choose Coverage Before Piece Count
The 15-piece HSS set and 29-piece HSS set both reach 1/2 inch. The 29-piece version includes the intermediate 1/64-inch positions, while the 15-piece version uses 1/32-inch steps. A buyer serving customers who specify those intermediate pilots has a different requirement from one sourcing wider size intervals. The 21-piece set retains 1/64-inch increments and stops at 3/8 inch; it offers another defined coverage boundary.
Letter and numbered assortments deserve separate consideration. A 26-piece A–Z set is not a fractional set with two or three sizes removed. The 60-piece numbered set covers No. 60–No. 1 rather than sixty fractional diameters. Use the nominal size system required by your customer's procedure, maintenance specification or established stock when comparing these cases.
Keep the Two 15-Piece Sets Separate
The separate 15-piece cobalt set covers 1/16–3/8 inch and includes repeated sizes. The 15-piece HSS set covers 1/16–1/2 inch in 1/32-inch increments. Their material, upper diameter and assortment pattern differ. Specify which set you need by its contents as well as its count. This keeps a cobalt repair assortment with repeated positions distinct from a fractional HSS set covering fifteen sizes.
Compare Set Contents for My Order
Match Samples and Replacements to the Selected Configuration
For an initial order or replacement program, the configuration you approve should identify material category, cutting direction, nominal diameter, overall length, maximum drilling depth, point, shank and finish. The individual examples above provide concrete comparisons. A retained reference sample is useful when several purchasing or technical staff need to evaluate the same proposed item.
The HSS fractional drill-only sets use standard points. The uncoated HSS fractional individual series uses split points. This is an important replacement distinction: a matching diameter from the individual series is a different point configuration. If your customer requires an identical kit replacement, send the original kit reference or its complete specification. If an alternative point form is acceptable, state that separately so the quotation addresses the intended scope.
For cutting evaluation, identify the workpiece and machine arrangement relevant to the order. A sample result on one material does not establish suitability for another fastener grade or heat treatment. Buyers requiring dimensional acceptance criteria, material documentation or a defined cutting assessment can include those requirements with the selected configuration. Photographs help identify visible connections and geometry; alloy grade and hardness require their own evidence.
Plan Your Bulk Order Around the Supply Requirement
Your order may be a drill-only set range for resale, selected individual sizes for industrial customers, or a combination of cases and replacement stock. List quantities for each size or set separately. A total quantity without the size mix does not define the assortment, especially when different materials, lengths and finishes share the same nominal diameter.
For a new distributor line, identify the size system and case coverage you intend to carry. For a repeat requirement, provide the existing item or approved sample reference and any fixed dimensional criteria. For application-led sourcing, describe the workpiece, required pilot diameter, available reach and holding arrangement. Each route gives AXIMET a clear starting point for a product-specific quotation.
If the project requires private-label markings, barcodes or a particular presentation, include the requested artwork and packaging requirements for review. Keep those requirements alongside the drill specification so that the proposed product and presentation can be assessed together. The listed HSS drill-only assortments use metal cases; individual packing requirements and requested changes belong in the commercial discussion.
Add the destination country, requested order schedule and any required purchasing documents. Where you have a target packing quantity or acceptance standard, state it with the inquiry. Pricing, order quantities, sample arrangements and shipment timing depend on the selected order scope and belong in the quotation. You can also compare the wider HSS and cobalt drill range when your purchase includes other drilling requirements.
Purchasing Priorities
Compare application fit, equipment compatibility and the supply configuration when preparing your purchasing requirement.
Build the Required Size Range
Select individual replacement diameters and drill-only sets around the sizes your customers use. Keep metric, fractional-inch and numbered requirements identified separately.
Compare the Complete Drill
Match the material, point, working length and shank to the repair setup. A matching diameter alone does not define an interchangeable replacement.
Keep Reorders Specific
Record the selected series, sizes and quantities in your inquiry. Use the same configuration details when specifying samples and repeat orders.
Left-Hand Drill Bit Buying Questions
01Do Left-Hand Drill Bits Need to Run in Reverse?
Yes. Conventional left-hand twist drills cut counterclockwise. For procurement, identify equipment that accepts the selected shank and holds it securely in that direction. Round-shank drills and the specialist 7/16-inch hex series have different connection requirements. A reverse setting alone does not establish holder compatibility, and a specialist hex shank should not be ordered as a common 1/4-inch hex bit.
02How Do I Choose the Drill Size for a Broken Bolt?
Use the pilot diameter specified by the repair procedure or companion extractor. The bolt's nominal diameter and screw-head diameter do not define one universal pilot size. Include the required size system and drilling reach in your inquiry. If you are sourcing drills and extractors together, send both tool specifications or the existing kit reference so their intended pairing is clear.
03Should I Source Jobber or Maintenance-Length Left-Hand Drills?
Choose by the required reach, clearance and connection. Compare actual overall length and maximum drilling depth for the selected size. Maintenance and jobber describe length categories, rather than fixed dimensions for every diameter. For a replacement program, retain the original dimensional requirement; for a new application, provide the available access and target position so the proposed drill can be assessed against that requirement.
04Should I Choose HSS or Cobalt Left-Hand Drill Bits?
Start with the workpiece and the required assortment. HSS offers fractional, selected metric and numbered individual series here; cobalt offers metric jobber, fractional maintenance and specialist short configurations. Cobalt steel is a material category rather than a coating. If your purchasing specification requires a particular alloy grade or documentation, include that requirement. Neither category name alone establishes suitability for every hardened fastener.
05Can I Order Individual Replacement Sizes for a Set?
Individual-size drills are available within the listed series. Send the required sizes and quantities with the original set reference where an exact replacement is needed. Pay particular attention to point form: the HSS drill-only sets use standard points, while the uncoated fractional individual series uses split points. Identify whether you require the original configuration or will consider a stated alternative in the quotation.
06What Do You Need for a Bulk or Private-Label Inquiry?
Send sizes or set contents, material category, quantities by item and destination country. Add fixed requirements for finish, point, length and shank, together with any sample or documentation requirements. For a branded project, provide the requested marking, artwork and packaging details for review. This defines the technical and presentation scope before commercial terms are agreed for the selected order.
Request a Left-Hand Drill Bit Quote
Send AXIMET your size list or selected set, quantity by item and delivery country. Include material, finish and connection requirements, plus an existing kit reference when matching replacement stock. For a new repair application, add the workpiece and access constraints. We can then address the configurations and commercial requirements relevant to your inquiry.
Send Your Size List for a Quote