HSS BSW & BSF Spiral Flute Taps for Blind Holes
Product Specifications
*Confirm the HSS spiral flute blind-hole tool specification for each requested thread size. The supplied model list is labeled straight flute.
Consistent Quality
Consistent geometry across repeat orders.
Flexible Orders
Small batches and mixed sizes available.
OEM Support
Custom marking, labels and packaging.
Standard & Custom
Standard sizes and custom configurations.
HSS BSW & BSF Spiral Flute Taps for Blind Holes
These HSS spiral flute taps are specified for British Standard Whitworth (BSW) and British Standard Fine (BSF) blind-hole threading. The supplied model list includes 12 BSW designations from 1/8-40 to 1-8, plus 3/8-20 BSF. Select the complete thread designation and check the nominal diameter, pitch and pilot-hole reference in the size chart. Spiral flutes help carry chips back toward the hole entrance; the required full-thread depth, cutting lead and bottom clearance must be checked for each application. Confirm the spiral flute tool configuration and tool dimensions for the selected size before ordering.
Key Configuration
For blind-hole tapping, spiral flutes direct chips toward the hole entrance. Confirm the actual flute geometry for each ordered model.
Twelve listed BSW designations cover nominal diameters from 1/8 to 1 in, each with its own threads-per-inch value.
The supplied model list includes 3/8-20 BSF. Its detailed thread dimensions must be confirmed separately.
Key Product Advantages
BSW Size Selection
Twelve BSW model designations support coarse Whitworth thread selection.
BSF Model
A 3/8-20 BSF fine-thread designation is included in the supplied list.
Thread Dimensions
The BSW reference chart lists major diameter, pitch and pilot-hole values by size.
Blind-Hole Chip Control*
An application-matched spiral flute design helps move chips out of a blind hole.
Tapping Applications
Use the selected BSW or BSF thread designation when it matches the part drawing. For a blind hole, confirm the actual spiral flute model, cutting lead, required full-thread depth and bottom clearance. Select cutting conditions according to the workpiece material and chip behavior.
Workpiece Material Selection
The supplied tables do not specify workpiece grades, hardness limits or material-specific cutting speeds. Provide the material grade, hole depth, required full-thread depth and production conditions when requesting a tool recommendation.
Product Details & Available Configurations
The table in Specifications & Sizes gives thread dimensions for the listed BSW models. Thread major diameter and minor diameter describe the thread profile; they are not the tap’s shank diameter or flute diameter. Confirm tap shank size, square size, flute length, overall length, cutting lead, HSS grade and thread tolerance for the selected spiral flute model.
*Spiral flute geometry and blind-hole configuration require confirmation against the actual product specification.
Size Chart & Specifications
The model list contains 12 BSW thread designations and one 3/8-20 BSF designation. The dimensional reference supplies BSW thread major diameter, pitch, effective diameter, minor diameter and pilot-hole values. These are thread dimensions, not tap body dimensions. Values marked “—” need confirmation.
| Thread Designation | Major Ø (mm) | Pitch (mm) | Effective Ø (mm) | Minor Ø (mm) | Pilot Hole* (mm) |
|---|---|---|---|---|---|
| 1/8-40 BSW | 3.18 | 0.635 | 2.768 | 2.362 | 2.5 |
| 3/16-24 BSW | 4.76 | 1.058 | 4.084 | 3.407 | 3.7 |
| 1/4-20 BSW | 6.35 | 1.270 | 5.537 | 4.724 | 5.1 |
| 5/16-18 BSW | 7.94 | 1.411 | 7.304 | 6.131 | 6.6 |
| 3/8-16 BSW | 9.53 | 1.588 | 8.509 | 7.492 | 8.0 |
| 7/16-14 BSW | 11.1 | 1.814 | 9.951 | 8.789 | 9.2 |
| 1/2-12 BSW | 12.7 | 2.117 | 11.35 | 9.99 | 10.5 |
| 9/16-12 BSW† | 14.3 | 2.117 | — | — | 12.2† |
| 5/8-11 BSW | 15.9 | 2.309 | 14.397 | 12.92 | 13.6 |
| 3/4-10 BSW | 19.1 | 2.540 | 17.424 | 15.8 | 16.5 |
| 7/8-9 BSW | 22.2 | 2.822 | 20.419 | 18.61 | 19.2 |
| 1-8 BSW | 25.4 | 3.175 | 23.368 | 21.34 | 22.2 |
| 3/8-20 BSF‡ | 9.53 | 1.270 | — | — | — |
Tool specification confirmation: This is a thread-dimension reference, not a tap-dimension chart. Confirm spiral flute geometry, HSS grade, shank diameter, square size, flute length, overall length, cutting lead and tap tolerance for each ordered size. The earlier supplied model list is labeled straight flute.
HSS Tap Speeds & Feed Settings
The dimension chart does not give cutting speeds. Select a starting speed after confirming the tap grade and geometry, workpiece grade, hole depth and lubrication.
Setting Speed & Feed
Spindle speed: n = (1000 × Vc) / (π × D), where n is RPM, Vc is cutting speed in m/min and D is nominal thread diameter in mm.
Tapping feed: For a single-start BSW or BSF thread, feed per revolution is 25.4 / TPI in mm/rev. When programming in mm/min, F = n × 25.4 / TPI.
Calculation example: For 1/4-20 BSW at 200 RPM, synchronized feed is 254 mm/min, or 1.27 mm/rev. This is a feed calculation, not a recommended cutting speed.
For general reference, see our HSS cutting tools speeds & feeds guide. Confirm that its values apply to the selected BSW or BSF tap and workpiece.
View HY Taps Catalog — confirm the relevant tool series and actual tap dimensions before ordering.
HSS Tap Customization
For requirements beyond the standard range, send your tap drawing or application details. Custom HSS cutting and forming taps can be reviewed for the following specifications.
| PARAMETER | CUSTOMIZATION OPTIONS |
|---|---|
| Thread Specification | Metric, UNC/UNF and pipe threads; special diameters, pitches and left-hand threads. |
| Thread Accuracy | Tap limits and oversize allowances to suit the required internal-thread tolerance and gauging requirements. |
| Tap Geometry | Straight flute, spiral flute, spiral point or forming design; chamfer and working geometry matched to the application. |
| Length & Reach | Overall length, threaded-section length and neck clearance to suit thread depth and component access. |
| Shank & Drive Square | Shank diameter, square dimensions and holding length to match the tapping holder. |
| Material & Surface Finish | HSS or cobalt HSS grades; uncoated, TiN or TiCN options, depending on the tap design and workpiece material. |
Options depend on tap type and size. Final specifications, minimum order quantity and lead time are confirmed with the quotation.
OEM & Private Label
Customer branding and packaging can be specified for distributor and tooling-brand orders.
Laser marking: Logo, thread size, product code and batch identification, subject to available shank space. Labels & packaging: Protective tubes, product labels and branded packaging to the approved artwork.
For a quotation: Send a drawing or thread specification, required tolerance, workpiece material and hardness, blind or through-hole details, thread depth and quantity. Include machine, holder and lubrication details for application-specific requests.
HSS Tap Quality & Inspection
HSS cutting and forming taps are checked against the confirmed product specification or approved drawing. Material verification, in-process dimensional checks and final inspection focus on thread accuracy, tool geometry and consistent identification before packing.
Key Inspection Points
Inspection items and acceptance criteria depend on the tap type, size and agreed requirements.
| INSPECTION ITEM | CHECK POINTS |
|---|---|
| Material & Hardness | HSS or cobalt HSS grade and material records; hardness requirements and verification agreed for the selected grade. |
| Thread Form & Accuracy | Thread size, pitch, profile and specified tap limits against the confirmed specification or drawing. |
| Working Geometry | Flutes, spiral point and cutting edges for cutting taps; forming lobes and lubrication grooves, where present, for forming taps. Chamfer geometry checked for each design. |
| Tool Dimensions | Threaded-section length, overall length, shank diameter and drive-square dimensions. |
| Runout & Surface Condition | Specified runout, burrs, chipped edges and visible defects on cutting or forming surfaces. |
| Coating & Identification | Specified surface finish or coating, visible condition, tool marking and label accuracy. |
Inspection documentation: Specify any required material records, dimensional reports or sample-thread validation before ordering. Availability and inspection scope are confirmed with the quotation.
Packaging & Batch Identification
Individual protective packaging helps prevent damage to tap threads and working surfaces. Labels identify the tool specification and order or batch reference. Models, quantities and packing details are checked before dispatch.
Export Packing & Delivery
Outer cartons, cushioning and export packing are selected for the order quantity and shipping method. Dispatch dates, freight and payment terms are confirmed with the order.
FAQ & Technical Support
Thread selection, blind-hole preparation and ordering guidance for HSS BSW and BSF spiral flute taps.
Product & Application FAQs
What is the difference between BSW and BSF?
BSW is the British Standard Whitworth coarse-thread series; BSF is the British Standard Fine series. Select the exact series, nominal diameter and threads per inch (TPI) stated on the part drawing. A BSW tap and a BSF tap of the same nominal diameter are not automatically interchangeable.
Which thread sizes are shown in the supplied references?
The model list shows 12 BSW designations: 1/8-40, 3/16-24, 1/4-20, 5/16-18, 3/8-16, 7/16-14, 1/2-12, 9/16-12, 5/8-11, 3/4-10, 7/8-9 and 1-8. It also lists 3/8-20 BSF. Confirm which of these designations are available with the requested HSS spiral flute geometry.
Why use a spiral flute tap for a blind hole?
Spiral flutes help carry cutting chips back toward the hole entrance. This chip-flow direction can be useful in a blind hole, where chips cannot exit through the bottom. Confirm the actual flute design, workpiece material, required thread depth and available chip clearance for the selected tap.
Are the major, effective and minor diameters tap dimensions?
No. These values describe the thread profile. They do not give the tap's shank diameter, square size, flute length or overall length. Request the tool drawing or size-specific tap dimensions when checking holder fit and tool reach.
How should I use the pilot-hole values?
Treat the BSW pilot-hole values as references, then confirm the drill diameter against the workpiece and required finished-thread tolerance. The supplied dimensional chart does not provide a pilot-hole value for 3/8-20 BSF. Its 9/16-12 BSW row also requires a dimension check before production.
How do I check the required blind-hole thread depth?
Provide the drilled-hole depth and required full-thread depth. The cutting lead does not produce a full-profile thread along its entire length, and the tap needs clearance below the required thread. The supplied charts do not specify cutting-lead length or guaranteed full-thread depth.
How is tapping feed calculated for BSW and BSF threads?
For a single-start thread, feed per revolution in millimeters is 25.4 divided by TPI. For example, a 20 TPI thread requires 1.27 mm/rev synchronized feed. Select spindle speed separately according to the actual tap and workpiece; the thread-size chart does not provide cutting-speed recommendations.
Ordering & Customization FAQs
What information is needed for a quotation?
Provide the full BSW or BSF designation, quantity, workpiece grade, drilled-hole depth, required full-thread depth and finished-thread tolerance. Specify spiral flute and blind-hole use, and include holder dimensions or a part drawing if available.
Can dimensions, coating and OEM branding be customized?
Custom shank dimensions, tool length, thread tolerance, coating, marking and packaging requests can be reviewed against the required size and quantity. Confirm the final configuration and inspection requirements before production.
Are samples and mixed-size orders available?
Sample and mixed-size requests can be reviewed. Availability, minimum order quantity and dispatch timing depend on the confirmed spiral flute models and any customization. Send a size-and-quantity list for quotation.
Selection Guides
How to Choose HSS Cutting Tools
Thread Milling vs Tapping: Tool Selection
How to Choose a Thread Mill: Thread, Pitch & Tool Guide
Thread milling guides provide an alternative-process comparison. Confirm the BSW or BSF thread form when selecting any threading tool.
Catalog & Technical Downloads
General tap series reference. Confirm the BSW or BSF spiral flute model and its tool dimensions for your order.
HSS Cutting Tools Speeds & Feeds Guide (PDF)
General HSS reference. Confirm tool-specific cutting speed and match synchronized tapping feed to the selected thread's TPI.
Need Sizes, Pricing or Custom Options?
Send us the required tool type, sizes, quantities, workpiece material and any OEM or custom requirements. We will confirm suitable specifications, availability, lead time and quotation details.
Drawings, size lists and reference photos are welcome.
